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LIBRARY

Michigan State
University

This is to certify that the
thesis entitled
CONTROL OF INTERNAL BREAKDOWN IN
JONATHAN APPLE FRUITS BY PREHARVEST
REGULATION OF SORBITOL CONTENT

presented by

Rafael Amé zqui t a—Gar ci a

has been accepted towards fulfillment
of the requirements for

Ph . D. degree in We

/‘ ,6,
W‘_ . 2. ‘_! _ “ML,“ 1.‘ (“K «~11? (‘_ : '\ L
Major professor /

 

 

0-7639

 

 

 

 

ABSTRACT

CONTROL OF INTERNAL BREAKDOWN IN JONATHAN APPLE FRUITS
BY PREHARVEST REGULATION OF SORBITOL CONTENT

By

RaFael Amézquita-Garcia

The close relationship oF the occurrence oF watercore in
Jonathan apple Fruits at the time oF harvest to the subsequent
development oF internal breakdown during Fruit storage and
marketing indicated that the internal breakdown disorder could
be controlled by preharvest regulation oF the sorbitol content
0F the Fruit. Orchard treatments designed to modiFy the supply
or metabolism 0F sorbitol were applied to replicated 8—year
old Jonathan trees in a commercial orchard beginning in l970.
Fruit samples were taken at several harvest dates, stored in
air or controlled atmosphere at O0 and 20C, and evaluated
For various quality characteristics, sorbitol content, and
incidence OF watercore, internal breakdown and other disorders.
Treatments utilizing calcium as a tree spray or Fruit dip
were extensively examined during the l97l-72 Fruit production
and storage season.

DeFoliation oF the trees approximately one week beFore
Fruit harvest was eFFective in reducing sorbitol and watercore

at harvest and the subsequent development 0F internal breakdown.

RaFael Amézquita-Garcia

Complete defoliation, either chemically or by hand, was more
eFFective than partial deFoliation by pruning 0F the terminal
growth. Since there was a signiFicant positive correlation oF
sorbitol with watercore and of sorbitol with internal breakdown,
it is concluded that deFoliation regulated internal breakdown
as a result oF its eFFect on the sorbitol content oF the Fruit.

Fruit thinning, injection oF sorbitol into the tree and
orchard sprays oF ethephon increased sorbitol and watercore
at harvest and the subsequent development 0F internal breakdown.
Fruits From trees receiving these treatments had higher rates
oF respiration and ethylene evolution than apples From
chemically deFoliated or kinetin-sprayed trees. It is probable
that the signiFicant increase in sorbitol and watercore,
and thereFore internal breakdown, oF ethephon-sprayed trees
was due to acceleration oF Fruit ripening.

Several applications oF calcium chloride and single
applications oF lime sulFur as orchard sprays signiFicantly
reduced sorbitol and watercore, and eventually internal
breakdown during storage. The signiFicant negative corre-
lations oF Fruit sorbitol with Fruit Ca and internal
breakdown with Fruit Ca, when considered with the Findings
oF other investigators, indicate that Ca Facilitates the
metabolism oF sorbitol and its storage as Fructose in the

cells.

 

RaFael Amézquita-Garcia

Fruits sprayed with calcium or lime sulFur solutions
had lower respiration rates and less C2H4 evolution than
nontreated Fruits oF the same chronological age. This lower
metabolism would decrease the possibilities For accumulation
oF toxic compounds that may develop as a result oF watercore.
Apples Free oF watercore wOuld be unlikely to accumulate
toxic quantities oF volatile metabolites because oF good gas
exchange properties oF the Fruit tissues. Tissue porosity,
as measured by gas Flow From the pith outward, decreased
markedly with increases in watercore content at harvest.
Several possibilities For the practical control oF
internal breakdown oF Jonathan apples are suggested by the
results oF these experiments. One is to prevent the
accumulation oF sorbitol in the Fruit by regulation oF its
source oF supply, as accomplished by the preharvest deFoliation
0F the tree. Another is by the Facilitation oF Fruit sorbitol
metabolism with calcium applied as a preharvest spray or post—

harvest dip.

 

 

CONTROL OF INTERNAL BREAKDOWN IN JONATHAN APPLE FRUITS
BY PREHARVEST REGULATION OF SORBITOL CONTENT

By

RaFael Ameéquita-Garcia

A THESIS
Submitted to
Michigan State University

in partial FulFillment 0F the requirements
For the degree oF

DOCTOR OF PHILOSOPHY

Department 0F Horticulture

I972

To My WiFe and Children

 

ACKNOWLEDGMENTS

The author wishes to express his sincere gratitude to
Dr. D. H. Dewey For his constant aid, encouragement, guidance,
and understanding during the course oF these studies and in
preparation oF the manuscript.

The writer is indebted to Drs. D. R. Dilley, C. J.
Pollard, P. Markakis and H. P. Rasmussen who provided technical

assistance, reviewed the manuscript and served as members 0F

the guidance committee.

GrateFul acknowledgment is accorded to Drs. A. A. DeHertogh
and A. L. Kenworthy For the use oF their laboratory Facilities.
Numerous kindnesses, oFten unsolicited, From many members 0F
the Horticulture Department, are also deeply appreciated.

A special debt oF gratitude is owed to Dr. H. J. Carew,
Chairman oF the Department oF Horticulture, and to Drs. D. H.
Dewey and D. R. Dilley For the opportunity oF working as a
member oF the Department during the course oF these studies.

Special appreciation is expressed to my wiFe, Martha,

For her patience and encouragement throughout the course oF

graduate studies.

 

TABLE OF CONTENTS

ACKNOWLEDGMENTS
LIST OF TABLES
LIST OF FIGURES

INTRODUCTION.

REVIEW OF LITERATURE.
MATERIALS AND METHODS
RESULTS

DISCUSSION.

SUMMARY AND CONCLUSIONS
LITERATURE CITED

15
21+
88
96
99

Table

IO

LIST OF TABLES

EFFect oF orchard treatments on watercore
of Jonathan apples at harvest, I970.

EFFect oF orChard treatments on sorbitol oF
Jonathan apples at harvest, I970 .

EFFect oF orchard treatments on internal
breakdown oF Jonathan Fruit aFter 3 months oF
storage at 20C in air, I970.

EFFect oF orchard treatments on internal
breakdown oF Jonathan apples aFter 6 months
oF storage in air at 20C, I970

EFFect 0F orchard treatment on internal
breakdown oF Jonathan Fruit aFter 6 months
oF storage in CA at 00C plus two weeks at
room temperature, I970

EFFect 0F time oF harvest on watercore index,
sorbitol content, internal breakdown, lenticel
spot, Fruit weight, ground color, Firmness, K,
Ca, Mg, K/Ca, Mg/Ca, Mg+K/Ca, as measured at
harvest, I970. . . . . . . . . . . . . . . .

EFFect 0F orchard treatments on mineral content
oF Jonathan apples, I970

SigniFicant correlation coeFFicients For Fruit
mineral content with internal breakdown, core
browning, and brown heart oF Jonathan apples
aFter 6 months of CA storage at 00C + 2 weeks
at room temperature, I970.

SigniFicant correlation coeFFicients oF Fruit
mineral content with watercore, Firmness and
internal breakdown oF Jogathan apples aFter

3 months oF storage at 2 C . . .

Correlation coeFFicients oF Fruit mineral
content with watercore and internal breakdown
oF Jonathan apples aFter 6 months oF storage
at 20C

Page

25

26

27

29

3O

31

A8

A9

50

SI

Table Page

II EFFect oF orchard treatments on leticel spot
oF Jonathan apples aFter 6 months oF air
storage at 2°C and 6 months oF CA storage
at 00C . . . . . . . . . . . . . . . . . . . . . 52

l2 EFFect oF orchard treatments on core
browning and brown heart oF Jonathan apples
aFter 6 months CA storage at 00C plus 2 weeks
at 200C. . . . . . . . . . . . . . . . . . . . . 53

I3 Correlation coeFFicients For ground color,
watercore and sorbitol at harvest and internal
breakdown with Firmness, lenticel spot, core
browning and brown heart oF Jonathan apples
as measured aFter 6 months oF CA storage at
0°C. . . . . . . . . . . . . . . . . . . . . . . 5A

IA EFFect oF treatments on Flesh Firmness oF
Jonathan apples at harvest, and aFter 3 and
6 months oF storage. . . . . . . . . . . . . . . 56

IS EFFect oF orchard treatments on ground color
and Fruit size oF Jonathan apples. . . . . . . . 57

I6 Linear correlation coeFFicients between Fruit
size and incidence oF watercore, internal
breakdown and core browning oF Jonathan apples . 58

I7 EFFect oF orchard treatments on watercore and
sorbitol content Jonathan apples at harvest,

I97l-l972. . . . . . . . . . . . . . . . . . . . 59

I8 EFFect oF orchard treatments and post harvest
dips on the incidence oF internal breakdown oF
Jonathan apples aFter 6 months (A) and aFter
8 months (B) oF air storage at 20C plus 2
weeks at 200C. . . . . . . . . . . . . . . . . . 60

I9 Correlation coeFFicients oF Fruit sorbitol
content and watercore by harvest date to
average Fruit weight and internal breakdown
aFter 6 months air storage at 20C plus 2 weeks
at 200C. . . . . . . . . . . . . . . . . . . . . 62

20 EFFect oF orchard treatments and postharvest
dips on the incidence oF lenticel spot oF
Jonathan apples aFter 6 months (A) and aFter
8 months (8) oF air storage at 20C plus 2
weeks at 200C. . . . . . . . .

68

Table Page

2l EFFect 0F orchard treatments and postharvest
treatments on Jonathan spot and soFt scald oF
Jonathan apples aFter 6 months oF cold
storage at 20C plus 2 weeks at room
temperature. . . . . . . . . . . . . . . . . . . 69

22 EFFect oF orchard and postharvest treatments
on Flesh Firmness oF Jonathan apples at
harvest time and aFter 6 months oF air
storage at 2°C . . . . . . . . . . . . . . . . . 7O

23 EFFect oF orchard treatments on weight oF
Jonathan apples at harvest . . . . . . . . . . . 7I

2A Summary 0F correlations From orchard experi-
ments with Jonathan apples according to
relative time 0F harvest, I970 and l97l. . . . . 72

 

25 Mean internal atmosphere and watercore
development 0F IO McIntosh apples by harvest
date . . . . . . . 7A

26 Mean internal atmosphere oF l5 Jonathan apples
From 3 trees as related to harvest date, water-
core, and subsequent breakdown development
aFter 8 days at 200 C . . . . . . . . . . . . 76

27 Porosity 0F late harvested (October 28)
Johnathan Fruits showing distinct external
breakdown symptoms aFter being two weeks at
200 C, as compared with Fruits now showing
breakdown symptoms . . . . . . . . . . . . . . 82

28 Porosity in ul/min/inch2 oF Jonathan apples
From I2 orchards as related to harvest date. . . 8A

29 Correlation coeFFicients oF porosity to
weight (Fruit size) and watercore by harvest
date. Jonathan apples . . . . . . . . . . . . . 85

30 EFFect oF leaves on the weight, porosity and
watercore development oF Jonathan apples . . . . 86

3I EFFect oF orchard treatment on porosity and

watercore development oF late harvested
(October 28) Jonathan apples . . . . . . . . . . 87

vi

Figure

IO

II

LIST OF FIGURES

Method used For evaluation oF gas Flow
characteristics oF Jonathan apples.

Method used to measure gas Flow through pith
discs oF Jonathan apples. . . . . . .

The correlation oF sorbitol content and water-
core index at harvest . .

The correlation oF sorbitol content at harvest
and internal breakdown index aFter 3 months
oF air storage at 2°C plus 2 weeks at 20°C.

The correlation oF sorbitol content at harvest
and internal breakdown index aFter 6 months
oF air storage at 2°C

The correlation oF sorbitol content at harvest
and internal breakdown index aFter 6 months
oF CA storage at 0°C plus two weeks at 200C

The correlation 0F watercore index at harvest
and internal breakdown index aFter 3 months
oF air storage at 20C plus two weeks at 20 C.

The correlation oF watercore index at harvest
and internal breakdown index aFter 6 months
oF air storage at 2°C

The correlation oF watercore index at harvest
and internal breakdown index aFter 6 months
oF CA storage at 0°C plus two weeks at 20°C

The correlation oF calcium content and internal
breakdown index aFter 6 months oF air storage
at 2°C.

EFFect oF the diFFerent treatments on the
respiration rate 0F Jonathan apples

Page

2l

2I

33

33

35

35

38

38

no

A0

A2

Figure Page

l2 Effect of the diFFerent treatments on the
ethylene evolution oF Jonathan apples . . . . . AA
13 EFFect oF the diFFerent treatments on the

respiration rate oF Jonathan apples aFter
3 months oF air storage at 2°C. . . . . . . . . A6

IA EFFect oF the diFFerent treatments on the
respiration rate oF Jonathan apples . . . . . . 6A

l5 Internal content oF ethylene oF Jonathan
apples as related to treatment and time oF
harvest . . . . . . . . . . . . . . . . . . . . 66

I6 Gas Flow characteristics From the pith
outward 0F watercored and non watercored
Jonathan apples . . . . . . . . . . . . . . . . 77

I7 Gas Flow through characteristics oF pith
discs From watercored and non watercored
Jonathan apples . . . . . . . . . . . . . . . . 79

I8 EFFect oF skin peeling and Flesh removal on
gas Flow characteristics From the pith
outward oF watercorded and non watercored
Jonathan apples . . . . . . . . . . . . . . . . 8]

viii

INTRODUCTION

The Jonathan varietyis 0F great importance to the apple
industry oF Michigan since it accounts For 27% 0F the apples
produced (Michigan Agricultural Statistics, I970) and 29% 0F
the Fruit stored (Michigan Apple Council, I97l). Internal
breakdown is a physiological disorder oF considerable impor-
tance to this variety since its occurrence can cause signiFicant
economic losses during storage and marketing. Numerous
investigators (Brooks g£_al. I920; Palmer, I93]; Kemp e£_§l.
I939; Ceponis and Friedman, I969; Lord and Damon, I966) have
related the incidence 0F internal breakdown to the watercore
content oF the harvested apples. Watercore is a physiological
disorder which occurs mostly in late harvested Fruits. It is
characterized by clear translucent areas 0F tissue in which
the intercellular spaces are Filled with a liquid recently
identiFied by Williams (I966) as containing sorbitol which is
the D-glucitol analog oF glucose. Sorbitol is produced in the
leaves and translocated to the Fruit where it is usually
transFormed to Fructose and stored. Most varieties lose their
capacity to convert sorbitol aFter a given degree 0F ripeness
is attained. They then accumulate sorbitol in the inter-
cellular spaces, Forming the condition known as watercore

(Kollas, I968).

Recent work by Smagula §£_al. (I968) has associated
watercore with abnormal metabolic processes in the cells
leading to the accumulation 0F toxic compounds mainly ethanol,
acetaldehyde and ethylacetate. These workers demonstrated
that these substances alone or together applied exogenously
or developed endogenously, would cause cell damage. and
browning oF the cortical tissue.

The close relationship oF watercore at the time oF Fruit

harvest to the development oF internal breakdown in storage,

 

and CF watercore to sorbitol metabolism suggest that internal
breakdown and watercore could be controlled by regulation oF
the sorbitol content in apples. Accordingly, a study was
undertaken to attempt to modiFy by orchard practices the
sorbitol content oF Jonathan apples beFore harvest and to re-
late such modiFications to the subsequent development oF

internal breakdown.

LITERATURE REVIEW

Some oF the Factors aFFecting internal breakdown, a
serious physiological disorder that develops during the

storage oF Jonathan apples, have been studied in recent years

 

by graduate students at Michigan State University. The
literature has been extensively reviewed by Bunemann (I958),
Chace (I959), Kerawala (I968), Stebbins (I970) and Kilby
(I97l). Additionally, an excellent review on internal break-
down as well as other disorders, including watercore, was

recently published by Faust et al. (I969). The latter authors

 

 

have dealt with these disorders in respect to their relation
to carbohydrate metabolism within the Fruit.

Stebbins (I970) demonstrated a highly signiFicant positive
correlation oF Fruit watercore and susceptibility to the
development oF internal breakdown in Jonathan apples. Similar
results were reported as early as I93l by Palmer (I93I) and
in recent years attempts have been made to reduce the incidence
oF breakdown in Delicious apples by sorting out Fruit with
watercore by light transmittance procedures (Bramlage and
Shipway, I969).

The close correlation 0F watercore symptoms at harvest
and the subsequent development oF internal breakdown suggest

a possible cause—eFFect relationship. And, perhaps controlling
watercore would be a means oF reducing the extent 0F the

internal breakdown disorder.

Watercore, depending on the variety, is usually conFined
to the interior Fruit tissues but occasionally may be visible
externally. When the aFFected Fruit is cut in halF, trans-
versely,circular areas oF translucent tissue associated with
vascular bundles can clearly be distinguished From the
adjacent normal white Flesh. The cells oF aFFected tissue
are highly turgid and the intercellular spaces are Filled
with liquid containing solutes at a higher concentration than
that oF adjacent healthy cells (Williams, I966). Tissues I
being aFFected by watercore are characterized by a rapid
decrease in starch and a corresponding increase in soluble
sugars as compared to unaFFected tissue (Norton, I9Il). 0n
the basis oF these results, Carne (I9A8) proposed that rapid,
premature hydrolysis oF starch raises the osmotic concentration,
and causes a rapid movement 0F sap From the vascular strands
to the adjacent cells, resulting in watercore. However,

Brown (I9A3) measured the starch and soluble solids 0F tissues
with and without watercore and concluded that Factors other
than the conversion oF starch to sugar may be responsible For
its development. He also observed that areas around the
vascular bundles were the last to become Free oF starch and
these were the areas in which watercore First appeared.

Brown also noted that watercored apples upon removal From

the spur, showed an exudation oF liquid From the stem and
cluster base, thereby suggesting that physiological changes

in the tree rather than in the Fruit contributed to watercore

development. Kollas (I968) concluded that watercore was due
to a condition oF the Fruit rather than tree or Foliage
conditions by graFting a branch 0F an early variety onto a
tree oF a late variety. The early variety matured early as
usually and developed watercore.

It is generally accepted that carbohydrates move Freely
within a woody tree or herbaceous plant. Assimilates labelled
with lLIC moved into developing Fruits 0F apples and grapes
From leaves situated either above or below (Hale and Weaver,
I962; Hansen, I969). Fruit thinning and deFoliation experi-
ments have shown that growth oF Fruit can be sustained by
leaves situated a considerable distance away (Haller and
Magness, I925); For apples (Haller, I930) and grapes (Winkler,
I932), Fruit growth was maintained with leaves no closer than
A and lo Feet.

The sugar alcohol, sorbitol (D-glucitol) is known to
be a major constituent oF the leaves and Fruits 0F a number
oF Rosaceae sp, such as apple and plum; For example the
sorbitol content in apple leaves and Fruits is approximately
2.2% and 0.6% oF the Fresh weight, respectively (Anderson
§£_§i. l96l; Whetter and Taper, I963; Taper and Liu, I969).

IA

Following application oF C02 to leaves on an apple shoot,
Webb and Burley (I962) Found three times as much radioactivity
in sorbitol extracted From the bark at distances oF up to

60 cm., as in sucrose.

 

These Findings, together with the observation that
sorbitol and glucose were major constituents oF the sieve
tube exudate 0F apples, led Webb and Burley, (I962) to
conclude that sorbitol was an important transport carbohydrate
in this species. In support oF this view, Williams (I967)

Found that ILIC From 1LIC-sorbitol applied to apple leaves
moved much Faster than From application oF HIC-sucrose.

Williams (I966) Found that watercored Fruits oF Delicious
apples were consistently low in sugars and at least twice as
high in sorbitol as nonwatercored Fruits picked the same day.
Sorbitol levels oF the leaves declined sharply and simul—
taneously with watercore development in the Fruit. The sorbitol
levels in the Fruit increased as severity oF watercore increased.
Since total sugars were not related to the severity oF water-
core, Williams concluded that high sugar contents resulting
From rapid starch hydrolysis could not be responsible For
the development oF watercore. He suggested that the movement
0F sorbitol From the leaves to the Fruits would cause an
accumulation oF sorbitol in the intercellular spaces 0F the
Fruit and development of the watercore symptoms. On the other
hand, Golden Delicious leaves show a decline in sorbitol
levels as the Fruits mature, yet high levels oF sorbitol and
watercore are not Found in the Fruits (Williams, I966). The
Findings 0F Chong and Taper (I97I) and Whetter and Taper
(I963) on daily variations in sorbitol and related carbo-

hydrates in Malus leaves, and oF Bieleski (I969) on

 

accumulation and translocation oF sorbitol in apple phloem,
support the interrelationship oF sorbitol and watercore as
proposed by Williams (I966). The possible relation oF
sorbitol to other physiological disorders oF apples was
reported by Fidler and North (I970). With Cox's Orange Pippin
and Chiver's Delight apples, they Found that an accumulation
oF sorbitol during storage at 0°C was correlated with core
Flush and low temperature breakdown injury, but a causal
relationship was not established. I
The speciFic relationship 0F watercore to internal
breakdown is not clear. Studies by Smagula g£_§l. (I968) on
the eFFect oF watercore on respiration and mitochondrial
activity revealed that watercored tissue consumed 26% less
02 in an aerobic environment that nonwatercored tissue. The
watercored tissue exhibited a respiratory quotient oF I.7I;
For nonwatercored it was l.5l. There was no apparent adverse
eFFect 0F watercore on the mitochondria. Watercored tissue
contained more ethanol, acetaldehyde and ethyl acetate than
nonwatercored tissue and these substances persisted in the
Fruit aFter the watercore symptoms disappeared. All three
0F these substances, individually or in combination injected
into the atmosphere surrounding the Fruit caused cortical
tissue browning. They suggested that watercore alters the
metabolism oF Red Delicious apples to induce Fermentation.
Toxic substances then accumulate and cause browning and

breakdown.

 

Further evidence that the accumulation oF acetaldehyde
is Important to the development of internal breakdown was
reported by Clijsters (I965). He Found that diseased tissue
produced acetaldehyde more readily than ethanol, whereas
the reverse was true For healthy tissues. It was shown that
acetaldehyde accumulation preceded the normal development
of internal breakdown in Jonathan apples, and that injection
oF 30 umol oF acetaldehyde or 50 umol of ethanol produced

browning artificially within one week at 200C. More recently

 

Wills (I970), using the injection technique, Found that
acetate and mevalonate were more effective than acetaldehyde
in producing tissue browning symptomatic of low temperature
breakdown. He further Found that geraniol, a monoterpene
derived From two mevalonate molecules, was the most eFFective
isoprenoid compound in producing breakdown symptoms.

The accumulation of acetate or acetate derived compounds
may be directly involved in creating physiological conditions
leading to breakdown. This may explain Scott and Roberts
observation (I968) that amounts 0F breakdown decreased when
Fruit was stored at low relative humidity. Wills (I968)
Found an increasing loss of acetate in the Form of
n-butylacetate, isoamylacetate and n-hexylacetate with an
increasing rate of waterloss From the Fruit during storage.
Later Wills and McGlasson (I97I) reported that low temperature
breakdown does not occur at intermediate storage temperatures

of 5°C because there is an increased loss oF acetates as

 

esters which results in a reduction oF the amount of acetic
acid available to produce the disorder.

In cork spot, another physiological disorder oF apples,
Faust and Shear (I968) Found acetate to be the major respira-
tory substrate in diseased tissue while glucose catabolism
was dominant in healthy tissue.

The incidence oF some Fruit physiological disorders can
be markedly reduced or eliminated by the application oF
calcium. Noteworthy examples are bitter pit of apples (Garman
and Mathis, I956; Askew e£_al. I960; Drake e£_§l. I966;
Bangerth, I972) and blossom end rot oF tomatoes (Geraldson,
I957; Fisher, I967). It now appears likely that the symptoms
of such disorders result From localized deficiencies of
calcium in developing Fruits, even though such Fruits are
borne on plants with supplies oF calcium considered to be
adequate according to the leaf analysis criterion.

An inverse relationship between Ca content oF the fruit
and susceptibility to internal breakdown has been shown by

Schreven et al. (I963) and Perring(l968). Sharples (I967)

 

and Stebbins (I970) Found a high positive correlation between

K and Mg and internal breakdown and a high negative correlation
between Ca and breakdown incidence. The movement of calcium
into the Fruit occurs primarily during the First Few weeks

oF development (Perring, I968). Apparently some calcium
remains mobile in the later stages oF Fruit development since

Martin (I967) showed that “SCa applied to the Fruit could be

detected in the tree. Wilkinson (I968) demonstrated that as
much as l.0 mg of Ca may move out of the Fruit in seasons
when the weather is dry. This may be of the same order of
magnitude, as shown by fruit analysis, as that contributed
by calcium Sprays (Wilkinson, I968). There is evidence
pointing to Ca involvement in metabolism in the cell walls,
plasma membranes and in enzyme activation (Jones and Lunt,
I967). The Full role oF each to the development of Fruit
physiological disorders is not known.

Information on the sugar uptake mechanisms of Fruit cells
is limited, but there is information on carbohydrate uptake
mechanisms in sugar cane. According to a scheme developed by
Glasziou (I960) and Sacher e£_al. (I963), exogenously supplied
sucrose is hydrolysed by an invertase in the Free space oF
immature storage parenchyma oF sugar cane.

After inversion of sucrose, the glucose and fructose
or their phosphorylated derivatives are transported into the
cellular storage compartment before sucrose is resynthesized
(Bowen and Hunter, I972). Sacher (I966) reported that hexoses
appeared to be converted to sucrose during uptake in bean pod
tissue and the accumulated sucrose is rapidly hydrolysed in
the vacuole. Investigations of sugar uptake in sugar beet
tissue indicate that sucrose could be taken up directly without
hydrolysis (Kursanov §£_§l. I96A). Kollas (I968), working
with Delicious Fruit tissue, concluded that sorbitol trans-

located to the Fruit was rapidly converted to Fructose and

sucrose. This occurred up to a given state of maturation
without watercore development. Upon Further Fruit

maturation, the sorbitol was not as readily converted to
Fructose and sucrose, and watercore then appeared. It was
Found with tissue discs that Fructose and sucrose were
eFFectively retained within the parenchyma cells, whereas
intercellular sorbitol escaped readily to the isotonic

bathing solutions. He concluded that the watercore condition
occurred as a result of sorbitol accumulation in the inter-
cellular spaces oF the Fruit tissue. Recently Bangerth et al.
(I972) Found that the addition of calcium to isotonic
solutions considerably reduced the tissue leakage of previously
infiltrated sorbitol and inhibited the tissue browning that

is characteristic oF internal breakdown.

(Mothes et al. I959; Mothes and Engelbrecht, I96I) suggest

 

that translocation is under some sort of hormonal control.
This may be so in the Fruit. In excised leaves For example,
kinetin will bring about movement oF amino acids and phosphate
to localized areas of application. In intact plants it has
been demonstrated that auxin, (Davies and Wareing, I965),
gibberellin, (Denisova and Lupinovich, l96l), or cytokinin,
(Muller and Leopold, I969), increase the movement oF phosphate
and other inorganic ions. When either cytokinins or
gibberellins were applied to grape shoots or portions of

shoots, the normal pattern oF translocation oF labeled

assimilate was altered so there was increased movement into
the treated areas (Shindly and Weaver, I970). Although these
eFFects are easily explained by the hypothesis that applica-
tion of plant growth substances increases the capacity oF
some tissues to accumulate photosynthetic products, there
is increasing evidence that hormone-directed transport is
important in the normal redistribution of nutrients From
various parts of the plant to growing organs. Crane (I965)
and Crane and Van Overbeck (I965) considered the induction of
parthenocarpic Fruits in figs by growth regulators to be the
result of the movement oF metabolites produced in other parts
of the tree into the developing fruits. They suggest that the
Fertilized ovule or seed synthesize hormones which initiate
a similar metabolic gradient Following normal pollination.
Regulation of aging processes in attached and detached
leaves has been demonstrated For auxins, kinins, and
gibberellins (Osborne, I967). With fruits, considerable
progress has been made in the use oF growth regulators to
accelerate the ripening process (Kidd and West, I933; Burg
and Burg, I962; Maxie and Crane I967; Hansen and Blanpied,
I968, and Iwahori EflLjiLi I968). In some cases ripening Is
retarded, For example, gibberellic acid has been reported to
retard ripening oF tomatoes (Dostal and Leopold, I967; AbdeL
Kader §t_§l. I966; bananas (Russo e£_§i. (I968); oranges

(Coggins and Lewis, I962) and apricots (Abdel-Gawad and

l3

Romani, I967). The latter authors also reported that
benzyladenine applied as a postharvest treatment retarded
the rate of ripening of apricots. Preharvest application
of I00 ppm benzyladenine to Jonathan apples one week prior
to harvest slightly reduced Fruit respiration, but had no
effect on Flesh firmness or soluble solids (Dilley, I969).
N—dimethylamino succinamic acid (SADH) delays ripening of
Lodi and Yellow Newton Transparent apples according to
Edgerton and Hoffman (I965), and of McIntosh according to
Dilley and Austin (I967), and decreases watercore of Winesap
and Delicious apples (Batjer and Williams, I966). No reference
has been made of the possible effects of this growth
regulator on the translocation of solutes From the leaves to
the Fruit.

Applications of exogenous auxins, gibberellins and
cytokinins however, have been shown to influence the distri-
bution of organic compounds within plants or detached plant

parts (Mothes et al. I959; Gunning et al. I963; Morris and

 

Thomas, I968). Of special interest in this respect are the
Findings of Seth and Wareing (I967). Working with bean

plants (Phaseolus vulgaris) they found increased accumulation

 

of 32F and increased movement of photosynthates when Fruit
peduncles were treated with auxin, gibberellic acid, or
kinetin. Kriedemann (I968), Found with Washington Navel

oranges that kinetin enhanced the movement of photosynthates

to the fruit. Weaver et al. (I969) found significant increases

 

in weight of berries whose clusters had been dipped in
A—chlorophenoxyacetic acid, gibberellic acid or benzyladenine.
Gibberellic acid was most effective in increasing the amount
of assimilates into the grape berries. Dipping clusters of
fruit of Black Corinth grape in gibberellin caused more
assimilates to accumulate in berries on unsprayed shoots than
on shoots sprayed with gibberellin. They proposed that
gibberellin enhanced the mobilizing power of the shoots, thus
enabling them to compete more effectively with the fruits For
assimilates.

Recently Hatch and Powell (l97l) Found that IllC-sorbitol
could be mobilized in an acropetal direction in apple seedlings
under the influence of IAA+GA+Benzyladenine applied in agar
or lanolin paste, once the root competition had been removed
by stem girdling. Combinations of two growth regulators or
any one regulator alone was not as effective as the three
together. They concluded that exogenously applied growth
regulators can direct the movement of certain compounds in
apple shoots, and that growing regions and developing Fruits
or seeds, which are known to compete for many substances,
are able to do so because they contain relatively high concen—
trations of various hormones as compared with other plant

parts.

 

 

MATERIALS AND METHODS

An experiment to regulate watercore and sorbitol content
of apples was conducted in I970 in a nearby commercial orchard
of 8-year old Jonathan apple trees growing in sod on seedling
roots. Fairly uniform single trees in respect to size,
vigor and crop load were selected to provide 8 replications
for each treatment. The treatments were designed to increase
(+) or decrease (—) accmulation of sorbitol in the Fruit, as
compared with a nontreated control, as follows:

I. Control (nontreated)

2. Sorbitol injection (+), whereby O.l M sorbitol

solution was injected into several apple limbs

and branches through 2 cm deep x 0.5 cm diameter
holes. Sorbitol absorption by trees varied

From l2 to 25 liters during an injection period

that varied From I2 to 72 hours.

3. Fruit thinning (+), in which an approximate ratio of

A0-60 leaves/Fruit or I fruit per 6 linear inches

of limb was provided.

A. Ethephon spray (+), at IOO ppm by spraying to leaf

run-off at l0 days before harvest.

5. N°-benzyladenine (+) or (-), at 250 ppm by spraying

to leaf run-off at 2 weeks before harvest.

6. Partial defoliation (-), accomplished by pruning
away 2/3 of the Current season's growth.
7. Lime sulfur (calcium polysuWide) sprays (-), a
5% solution was sprayed to run-off at l0 days
before harvest (chemical defoliation).
8. SADH (N-dimethylaminosuccinamic acid) (-), a
2000 ppm solution was sprayed to leaf run-off at
A5 days before harvest.
The first harvest was made at the ideal time for long term
storage on September 25. A second harvest was made on October
9. The apples were collected in l bu. Field crates lined with
polyethylene film to minimize fruit moisture loss and stored
on the day of harvest. One bu. Fruit samples were randomly
assigned to storage conditions in air at 2°C and in 3% 02 and
5% C02 at 0°C. The controlled atmosphere was established
within one week after the final harvest by means of a Tectrol
centrolled atmosphere generator. Fruit samples were removed
For examination From air storage after 3 and 6 months of
storage, and From CA after 6 months. Final examination was made
after IO days at 20°C to Facilitate the development of
disorders.
Ground color was determined by visual comparison with
Ditton Laboratory green-yellow apple and pear color charts,

numerically rated as A = green and 8 = yellow.

 

The presence of watercore, internal breakdown, core
browning and brown heart was observed by cutting each fruit
transversely and progressively from the calyx end toward
the equator. The severity of the disorder was numerically
rated as 0 = none, I = trace, 2 = slight, 3 = moderate,

A = severe. An index was then calculated by multiplying the
number of fruit by each rating, summing the results within a
replication and dividing by the total number of Fruits
examined. The presence or absence oF lenticel spots, and
Jonathan Spot disorders was observed and noted. Flesh
firmness was measured using a U.C. Fruit Firmness Tester with
a 7/l6 inch tip and recorded in pounds. One measurement

was taken From a peeled portion of each I0 Fruits.

Sampling procedures for nutrient element determinations
of Fruits were made as described by Perring and Wilkinson
(I965). K was extracted with water and then measured with
flame spectrophotometry. Levels of P, Ca, Mg, Mn, Fe, Cu,
and Na were determined using photoelectric spectrometry
(Kenworthy, I960). Respiration was measured as C02 evolution

by infra-red analysis (Dilley et al. I969), and ethylene by

 

gas chromatography (Burg and Burg, I962).
Apple fruit sorbitol was determined by gas chromato-
graphy (Farshtche and Moss, I969). Sample preparation was

as follows: Two wedge shaped slices selected from the center

 

part of the Fruit were Further cut into smaller pieces with
a Vegomatic food preparer and frozen immediately at -lO°C.
In order to Facilitate the making of a very Fine powder,
the apple pieces were later frozen in liquid nitrogen for
2 minutes and blended immediately For 30 seconds in a Waring
blender. A 30 gm sample was Freeze-dried at -200C. The
resulting mass of apple tissue was powdered with a small
pestle and samples of 20 mg were placed in centrifuge tubes
to which 0.A ml of trimethylsilyl (TMS) reagent was added.
Composition of the TMS reagent was 3 parts hexamethyldisilazane,
l part trimethylchlorosilane and l part piridine by volume.
The TMS reagent was reacted with apple tissue for l/2 hour
and afterward the mixture was centrifuged 30 minutes at 2000 rpm.
A 2 ul aliquot of the supernatant solution was injected into
a U—shaped glass column, 6 Ft x 2 mm |.D. packed with IS%
carbowax 20 M coated on 80-l00 chromosorb U, at a temperature
of I65°C. Retention times were 2 minutes For Fructose,
3.5 minutes for sorbitol, A.2 for a D glucose and 9.2 minutes
forB D glucose.
The following orchard treatments were applied to Jonathan
apple trees in I97l in the same orchard used the previous year:
I. Control (nontreated).
2. Calcium sprays, applied A times at intervals of two
weeks beginning l2 weeks after Full bloom, using

lime sulfur at 2%, CaClz at l%, or Ca(N03)2 at 5%.

I9

3. Calcium sprays, applied once at 8 days before
harvest, as lime sulfur at 5%, CaClz at A%,
or CA(N03)2 at l0%.
A. Defoliation, whereby leaves were completely
removed from several limbs that were girdled
to impede translocation of photosyntates from
other Foliage.
5. Postharvest dips, using A% CaClz solution for
I0 minutes, or 5% lime sulfur solution For
I5 seconds.
The apples were collected in l bu. Field crates lined with
polyethylene film and stored immediately at 3°C. Fruit samples
were removed for examination after 6 and 8 months of storage.
Final evaluation was made after an additional 2 weeks at 20°C.
The role of leaves on size, watercore and porosity characteris-
tics of the Fruit from 5-year-old Jonathan apple trees grown
at the Horticulture Research Farm was examined. Treatments
consisted of individual girdled granches with 0 or A0 leaves
per fruit on A trees.

The internal atmosphere oF harvested Fruits was sampled
immediately in the orchard by the method of Johnson (I97l).
Porosity was measured by gas Flow through the apples by the
system shown in Fig. I. A barostat was employed to maintain
a constant atmospheric pressure at point A. The water outlet

(8) was connected to a two gallon bottle (C). From bottle (C)

20

Fig. l. Method used For evaluation of porosity
characteristics of Jonathan apples.

Fig. 2. Method used to measure porosity of pith
discs of Jonathan apples.

 

 

 

 

 

22

came two connections, one to a manometer and another one to

a two way stopcock (F). When water was allowed to flow

freely upon release of clamp (K) a given amount of pressure
developed in bottle (G) which was registered on the manometer.
This pressure was equal to (H) or the distance between the
outlet connecting to atmospheric pressure and the water outlet
connecting to bottle (C). The pressure to be developed

inside bottle (C) could be readily adjusted by increasing or
decreasing (H). All measurements were taken at 50 mm
pressure on the manometer. When the stopcock outlet was open,
the pressure inside bottle (C) was maintained by water Flow
from the bottle (A). The outlet of the two way stopcock was
connected to a rotometer (G) calibrated from 0 to 80 ml of
air/min over a scale distance of IO cm. The outlet of the
rotometer was connected to a 7 inch l8 gauge hypodermic
needle. The hypodermic needle with a cleaning wire inserted
was pushed into the seed cavity of the apple fruit through

the calyx end. The wire was necessary to prevent plugging

of the needle with juice and/or cortical tissue during
insertion. Care was taken to move the wire in and out to
insure Free flow of air through the needle. By turning the
stopcock, air was allowed to Flow through the apple to the
ambient atmosphere. To insure that leakage was not occurring
at the point of entrance of the needle, the apple was immersed
for a few seconds in a beaker with water. Flow of air was

clearly observed through the apple lenticels. Approximately

23

one minute was allowed for equilibration of flow before
making the Final reading on the flow meter. The data are
expressed as ml/min/inch2 of fruit surface area, calculated
according to the method by Baten and Marshall (I9A3).

For measurements of gas flow through flesh and core
tissue disks, the procedure outlined in Fig. 2 was Followed.
Cylinders of 20 mm diameter were cut with a stainless steel
cork borer. A section of two mm thickness was cut from pith
tissue and located in position A. High vacuum grease was used
on the inner wall of the cylinder (B) and the threaded cap
surface to prevent leakage. Gas diffusion measurements were

made as described above For whole apples.

RESULTS

The effects of orchard treatments applied in I970 are
summarized in Tables l-5, in which the treatments are listed
in order of increasing or decreasing effectiveness on fruit
disorders or other parameters investigated.

A significant reduction in watercore index (Table I)
occurred in Fruits From the chemically deFoliated trees which
had the lowest amount of watercore. The control, sorbitol
Injection and ethephon treated fruits had the highest watercore
index. The ethephon treatment yielded more watercore than the
partial defoliation treatment accomplished by pruning of the
terminal growth.

The sorbitol content of the Fruit was lowest From the
chemically deFoliated trees and was significantly lower than
the sorbitol injection, ethephon and SADH treatments (Table 2).

Fruits From chemically deFoliated trees were significantly
lower in breakdown incidence than Fruits From trees receiving
sorbitol injection, the control, or ethephon treatment when
examined after 3 months of air storage (Table 3). After 6
months of storage in air or CA, the chemical defoliation
treatment yielded the lowest amount of internal breakdown.

It was significantly lower than control, sorbitol injection,
ethephon, or Fruit thinning treatments after 6 months of air

storage and significantly lower than all other treatments

2A

 

25

Table 1. Effect of orchard treatments on watercore of Jonathan
apples at harvest, 1970.

 

 

 

Treatment w?:::::§e
Chemical defoliation 0.91 a
Partial defoliation 1.08 a b
SADH spray 1.18 a b c
Fruit thinning 1.20 a b c
N643enzy1adenine spray 1.21 a b c
Control (nontreated) 1.22 b c
Sorbitol injection 1.27 b c
Ethephon spray 1.49 c

 

Means followed by the same letter are not significantly different.

(P < 0.05, Tukey's test).

26

Table 2. Effect of orchard treatments on sorbitol of Jonathan
apples at harvest, 1970.

 

 

Treatment Sorbitol

Z dry Wt.

Chemical defoliation 3.20 a
N6'benzyladenine spray 3.95 a b
Partial defoliation 4.06 a b
Fruit thinning 4.15 a b
Control (nontreated) 4.35 a b
SADH Spray 4.57 b
Sorbitol injection 4.57 b
Ethephon spray 4.79 b

 

Means followed by the same letter are not significantly

different (P <0.05, Tukey's test).

27

Table 3. Effect of orchard treatments on internal breakdown of
Jonathan fruit after 3 months of storage at 2°C in air,

 

 

 

1970.
Treatment Internal Breakdown
(index)
Chemical defoliation 0.174 a
SADH spray 0.682 a b
N°-benzyladenine spray 0.774 a b
Partial defoliation 0.786 a b
Fruit thinning 0.996 a b
Sorbitol injection 1.356 b
Control (nontreated) 1.437 b
Ethephon 1.555 b

 

Means followed by the same letter are not significantly different.

(P < 0.05, Tukey's test).

28

after 6 months of CA storage (Tables A and 5). With the
exception of SADH on sorbitol content, treatments designed to
decrease watercore, sorbitol content, and internal breakdown
accomplished the objective. Likewise, all treatments applied
to increase watercore, sorbitol and internal breakdown
(Tables I, 2, 3, A, 5) were effective In the desired manner.

A delay in Fruit harvest resulted in a highly significant
increase in watercore index, sorbitol content and Internal
breakdown after 6 months air storage and after 6 months of
CA storage plus 2 weeks at 20°C (Table 6). Weight, ground
color, K content and the K/Ca and Mg+K/Ca ratios also increased
significantly with a delay in fruit harvest (Table 6).

As shown in Fig. 3, watercore index and sorbitol content
were positively correlated (r = 0.688 ****) at the late harvest.
The square enclosure in the lower left portion in this graph
(and the rectangular enclosures in subsequent graphs) outline
the results from treatments that yielded relatively low
amounts of sorbitol and low incidences of watercore or breakdown.
Sorbitol content at harvest and breakdown index aFter 3 and 6
months oF air storage, and after 6 months of CA storage, were
positvely correlated (r = 0.633 ****, r = 0.696 **** and r =
0.692 ****, respectively) see Figs. A, 5 and 6. Watercore
Index and Internal breakdown after 3 and 6 months of air storage
and after 6 months of Ca storage were positively correlated

(r = 0.767 ****, r = 0.727 **** and r = 0.780 ****, respectively)

29

Table 4. Effect of orchard treatments on internal breakdown
of Jonathan apples after 6 months of storage in air
at 20C, 1970.

 

Internal Breakdown

 

Treatment

(index)
Chemical defoliation 0.293 a
N6-benzyladenine spray 0.894 a b
Partial defoliation 1.113 a b c
SADH spray 1.171 a b c
Control (nontreated) 1.480 b c
Sorbitol injection 1.516 b c
Ethephon spray . 2.072 c
Fruit thinning 2.226 c

 

Means followed by the same letter are not significantly different.

(P < 0.05, Tukey's test).

30

Table 5. Effect of orchard treatment on internal breakdown
of Jonathan fruit after 6 months of storage in CA
at 00C plus two weeks at room temperature, 1970.

 

 

Internal Breakdown

 

Treatment

(index)
Chemical defoliation 0.44 a
SADH spray 1.33 b
Partial defoliation 1.63 b
N6-benzyladenine 1.85 b
Fruit thinning 1.92 b
Sorbitol injection 2.00 b
Control (nontreated) 2.01 b
Ethephon spray 2.71 b

 

 

Means followed by the same letter are not significantly

different (P < 0.05, Tukey's test).

3l

Table 6. Effect of time of harvest on watercore index, sorbitol
content, internal breakdown, lenticel spot, fruit weight,
ground color, firmness, K, Ca, Mg, K/Ca, Mg/Ca, Mg+K/Ca,
as measured at harvest, 1970.

 

 

Fruit Characteristic Harvest date

 

 

 

Sept. 25 October 9
Watercore (index) 0.99 1,40 ****
Sorbitol content (Z dry wt.) 2.91 5.49 ****
Internal breakdown after 6 mo.
air storage at 30C 0.78 1.65 ****
Internal breakdown after 6 mo.
CA storage at 00C plus two weeks
at 20°C 1,14 2,33 ****
Lenticel spot after 6 mo. air
storage at 3°C. 1.42 5.68 ****
WEight (gm) 132.8 148.5 ****
Ground color (rating) 5.34 6.34 ****
Firmness (lbs) 16.18 15.53 Md:
K 0.84 0.76 ****
Ca 0.056 0.056
Mg 0.030 0.029
K/Ca 15.09 13.52 **
Mg/Ca 0.53 0.52
(Mg + K)/Ca 15.63 14.04 **

 

**** = P < 0.0005
*** = P < 0.001
** = P < 0.01

 

 

 

32

Fig. 3. The correlation of sorbitol content and watercore
Index at harvest.

**** P < 0.0005
y = l.ll2 + 3.l6(x)

Fig. A. The correlation of sorbitol content at harvest
and internal breakdown index after 3 months of
air storage at 20C plus 2 weeks at 200C.

**** P < O 0005
y = n.229 + l.037(xl

33

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3A

The correlation of sorbitol content at harvest
and internal breakdown index after 6 months of
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The correlation of sorbitol content at harvest
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y = 3.050 + I.066(x)

35

 

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36

see Figs. 7, 8 and 9. Calcium content was negatively corre-
lated with breakdown Index (r =-0.505 **), as shown in
Fig. l0.

Measurements of C02 and CZHQ evolution revealed that the
fruit was picked preclimacteric at the first harvest and post-
climacteric at the second and third harvests (Fig. II and IZI
SADH-treated fruits of the First and second harvests had the
lowest respiration and ethylene evolution rates, whereas
fruits From the ethephon, sorbitol injection, and control
treatments had the highest. The trend toward a lower rate of
C02 evolution observed For lime sulfur-treated Fruits at the
second harvest, was verified at the third harvest when It
yielded the lowest rate of respiration of all treatments. Lime
sulfur treated fruits had the second lowest rate of CZHQ
evolution, with SADH—treated fruits being the lowest. Respirae
tion measurements after 3 months of storage revealed similar
differences to those measured shortly after harvest (Fig. l3).

Examination of the effect of orchard treatment on
mineral composition of the Fruit revealed that Fruits from
ethephon, control and Fruit thinning treatments had a signi—
Ficantly lower amount of calcium than SADH-treated Fruits. K
was significantly higher as a result of the ethephon treatments
than that of fruit thinning. The ratios of K/Ca and (K+Mg)/Ca
were significantly higher for ethephon than for partial
defoliation, N6 benzylademine and SADH. No significant

differences were Found between treatments For Mg content or

Fig. 8.

37

The correlation of watercore index at harvest and
internal breakdown Index after 3 months of air
storage at 20C plus two weeks at 20°C.

**** P < 0.0005

y = l.72l + 2.I5A(x)

The correlation of watercore Index at harvest and
internal breakdown index after 6 months of air
storage at 2°C.

**** P < 0.0005

y = l.A08 + 2.2l3(x)

INDEX

BREAKDOWN

INDEX

BREAKDOWN

38

    
  

 

 

 

 

    

 

I'- o.707¢7 .00:
A0
‘ .
3.5
3,0
2.5
I
2.0 ’
A . (only-I
1.5 ‘ A sum-I
. in"...
:3 . (sum) ethephon
I. u comm“...
. an..."
.5 o inn 5."...
a same
.5 1.5 2.0
WAIERCOIE INDEX
r 0 127.7 . . . .
4.0
3.5
3.0
2.5
2.0
1.5 . (qul
. Scan-I
rm..."
{3 - (Inn!) ethephon
n u‘ nun-mo..."
4, i
. . n..."
5 g o I... 5."...
it- nun

 

 

 

WAIEICORE INDEX

39

Fig. 9. The correlation of watercore index at harvest and
internal breakdown index after 6 months of CA
storage at 00C plus two weeks at 20°C.

**** P.; 0.0005

y : 'O.908 + 2.332(X)

Fig. IO. The correlation of calcium content and Internal
breakdown index after 6 months of air storage at
20C.

** P < 0.01

y = 0.0623 — 0.0003l8(x)

INDEX

BREAKDOWN

DRY WV.

6 I.

CALCIUM CONTENT

r-OJIOOSono.

A0

 

 

 

  

 

 

A0
3.5
3.0
25
2.0
1.5 ("val
A Sorbitol
13 O . (Elhnl) ethephon
0 g :‘ nun-4......
{5, I mnlnu
'5 O o 1;... sun...
n sumo
,5 1.0 1.5 2.0
WAIERCORE INDEX
.012
.010
r- 0 5mm - . .
.0.1 A (onlrol
Sotbllol
Hum."
.0” oo. . (1mm) ethephon
a N° Inn-ylod-nm-
- m»...
A”. T ' 0 I"... 5.“...
0 sum
.000
.031
.09:
.091
.099
.oan
.045

 

 

BREAKDOWN

INDEX

 

 

AI

Fig. II. Effect of the different treatments on the
respiration rate of Jonathan apples.

 

 

\lIIII I
u oo~ pmu>¢<1 auwu< m><o
h o n v n n — o n v n a p h v n N
x O < m l Ill l.
.82..» of: lfilfi.
IQ la
DES-st allelic IQIxLIQ Ifil
Olmlt‘iultloz IIIOII
IOJOUAZ
.lmll.‘. owlnb .............
3...... .Otasom llll
.o-.IOU Ii
2
I4.

:25: 2 :o

 

.nuhuflx O .00

.ocpsox nu dam

Op

5—

0—

o—

 

‘H /‘x/‘oa Iw

A3

Fig. l2. Effect of the different treatments on the
ethylene evolution of Jonathan apples.

 

 

 

 

IILI

 
   

bmw>¢(1 mwwg( m><0
Q h 0 n v a N p O 0 h o n v M N — O
x a < w I am, If
.a—.am oisnlw .... /,
Iguas‘ol; o........ //
oc.co‘o.>ucoaoz OlIo .... /8. ll l\1¢\u
cocsu‘. u ..... x. / .D
03.33;. ..a£....... .. .... a./ \fi \
.007. .ozasom I I 4x AVIAN
.Os.c0IU ./ d/m. .. \.
, . .,,,.........--¢ 3...... .....
l/ul.l...l. is“ ......

   

 

oo
huu>a<x 0 AUG,

2
hwu>u<1 ma Axum

 

45

Fig. l3. Effect of the different treatments on the
respiration rate of Jonathan apples after
3 months of air storage at 2°C.

A6

 

0.2 m><o

Z.

mi.»

 

pmw>¢<1 o .nUO

 

az<m II
53.1.“ 0...: “la
03.52; OI.

Cinciozncoaol oio
coatoa.u .....

.C—IC.‘. o..b& .......
.30.... .33som .ll

.0. ECU l

hmw>x<1 mm .ummm

 

Op

0—

 

:u/ 6)I/‘ODI-u

 

47

the ratio Mg/Ca (Table 7). Ca content of the fruit was
negatively correlated with internal breakdown, sorbitol
content and core browning. The ratios of K/Ca and (K+Mg)/Ca
were positively correlated with internal breakdown, sorbitol
content, and core browning in fruits harvested on October 9
and stored in Ca for 6 months (Table 8). Watercore and
internal breakdown were negatively correlated with Ca content
of fruits harvested October 9 and stored 3 or 6 months in
air (Tables 9 and lO). Firmness was positively correlated
with Ca content of fruits stored 3 months in air (Table 9).
Orchard treatments also affected other Jonathan apple
disorders. N6—benzyladenine had the lowest incidence of
lenticel spot, but it was only significantly lower than
ethephon (Table ll). Chemically defoliated trees produced
fruits with a significantly lower amount of core browning and
brown heart than fruits from trees receiving the sorbitol
injection or no treatment. Ethephon fruits had a significantly
higher amount of core browning than fruits from all the other
treatments (Table l2). Core browning was positively correlated
with watercore and internal breakdown on fruits from both
harvest dates and with sorbitol content of fruits from the
October 9 harvest. No significant correlation was found for
lenticel spot or brown heart with watercore, sorbitol

content or internal breakdown (Table l3).

 

 

Lia

. ummu m >waH . . v m .udemMMHw %Huamoflwflnmwm uOd mum
A . mo o

 

Hmuuma MEMm onu hp woBOHHow magma

 

 

qu.o n Hw.ma oq.ma nmo.o n m mw.o n moo.o mmumm mm<m
mam.o n m qa.ma mm.qa qmo.o a m qw.o n m wmo.o cowumfiaowww Hmowfiwao
Nmo.o a Ho.qH oq.mH Nmo.o n m 05.0 a m wmo.o zmuam mcflcmwmamwcmnioz
qu.o n mm.ma mH.NH mNo.o m mn.o n m mmo.o coaumflaowww Hmfluumm
oqq.o a m wo.qa qu.qa qNo.o a m wn.o n m mmo.o coauomnafl acuflnuom
omo.o a m oq.qH uk.ma mmo.o n sk.o m smo.o massages passe
mmo.o n m oo.oH om.ma mmo.o a m Nw.o m mmo.o Awmummuuaocv Houucoo
qu.o m n¢.oa wq.oa mNo.o m om.o m Nmo.o amuaw scammSum
a N N

mu\wz mo\mz+z mu\M wz M mo uawfiumwuw

 

 

Onofi .moammm amaumcow mo uamucoo Hapmafle do mucmaummpu whmzouo we uumwmm .m

magma

 

49

 

 

 

 

Table 8. Significant correlation coefficients for fruit mineral content
with internal breakdown, core browning, and brown heart of
Jonathan apples after 6 months of CA storage at 0°C + 2 weeks
at room temperature, 1970.
Early harvest Middle harvest
Sept. 25 October 9
El Internal Sorbitol Internal Core Sorbitol
ement .
Breakdown Content Breakdown Brownlng Content
K 0.379 * 0.342 * n.s.
P
Na
Ca -0.36l * -0.515 ** —0.345 * -0.355 *
Mg
Mn
K/Ca 0.527 *** 0.454 ** 0.345 *
Mg/Ca
(Mg + K)/Ca 0.526 *** 0.456 ** 0.346 *
(Mg + P)/Ca
P/Ca 0.374 * 0.358 *

 

*** P < 0.001

** P < 0.01

* P < 0.05

50

Table 9. Significant correlation coefficients of fruit mineral content
with watercore, firmness and internal breakdown of Jonathan

apples after 3 months of storage at 2°C.

 

 

Early harvest

Middle harvest

 

 

Sept. 25 October 9
Element Firmness Internal Firmness Internal Watercore
Breakdown Breakdown
K
P
Na
Ca 0.351 * —0.44l ** 0.557 *** -0.397 * -0.464 **
Mg
Mn
K/Ca 0.374 * 0.436 ** 0.496 **
(Mg + K)/Ca 0.377 * 0.427 ** 0.482 **
(Mg + P)/Ca
P/Ca 0.374 *

 

*** P < 0.001

** P < 0.01

* P < 0.05

5i

 

 

 

 

 

Table 10. Correlation coefficients of fruit mineral content with watercore
and internal breakdown of Jonathan apples after 6 months of
storage at 2 C.
Early harvest Middle harvest
Sept. 25 October 9
Element Internal Watercore Internal Watercore
Breakdown Breakdown
K n.s. n.s. 0°378 * n.s
P
Na
Ca n.s. n.s. —0.505 ** —O.464 **
Mg
Mn
K/Ca n.s. n.s. 0.559 *** 0.496 **
(Mg + K)/Ca n.s. n.s. 0.554 *** 0.482 **
P/Ca n.s. n.s. 0.408 * n.s.
*** P < 0.001
** P < 0.01
* P < 0.05

 

52

Table 11. Effect of orchard treatments on lenticel spot of Jonathan
apples after 6 months of air storage at 2°C and 6 months
of CA storage at 0°C.

 

 

Lenticel Spot

 

 

Treatment Air
(Z) (Z )

N6'benzyladenine spray 1.662 a 2.17 a
Fruit thinning 4.32 a 3.37 a
SADH spray 3.01 a 3.47 a
Sorbitol injection 4.27 a 3.63 a
Chemical defoliation 4.15 a 3.82 a
Control 3.18 a 4.57 a
Partial defoliation 3.60 a 4.61 a
Ethephon spray 4.23 a 6.65

 

Means followed by the same letter are not significantly different.
(P< 0.05, Tukey's test).

 

 

 

 

 

 

53

Table 12. Effect of orchard treatments on core browning and brown heart
of Jonathanoapples after 6 months CA storage at 0°C plus 2
weeks at 20 C.

 

 

 

Core Brown
. Browning Heart
Treatment
(index) (index)
Chemical defoliation 0.62 a 0.09 a
SADH spray 4.13 a b 0.77 a b c
Fruit thinning 4.43 a b 0.72 a b
N6-benzy1adenine spray 5.38 a b 1.38 a b c
Partial defoliation 5.86 a b 1.19 a b c
Sorbitol injection 6.25 b 2.25 b c
Control 6.85 b 2.86 c
Ethephon spray 13.43 c 1.46 a b c

 

Means followed by the same letter are not significantly different.

(P < 0.05, Tukey's test).

 

54

Table 13. Correlation coefficients for ground color, watercore and
sorbitol at harvest and internal breakdown with firmness,
lenticel spot, core browning and brown heart of Jonathan
apples as measured after 6 months of CA storage at 00C.

 

 

 

Factor Harvest Firmness Lenticel Core Brown
date spot browning heart
Ground color Sept.25 n.s. n.s. n.s. n.s.
Ground color Oct. 9 -0.403 * 0.372 * 0.340 * 0.422 *
Watercore Sept.25 n.s n.s. 0.378 * n.s.
Watercore Oct. 9 n.s n.s 0.678 **** n.s.
Sorbitol Sept.25 n.s n.s n.s. n.s.
Sorbitol Oct. 9 n.s. n.s. 0.425 ** n.s.
I. Breakdown Sept.25 n.s. n.s. 0.706 **** n.s.
I; Breakdown Oct. 9 —0.408 * n.s 0.595 **** n.s

 

**** P < 0.001

** P < 0.01

* P < 0.05

 

 

 

55

SADH consistently produced the firmest fruits at harvest
and after 3 and 6 months of storage (Table l4). The ground
color was more yellow for control and ethephon-sprayed fruits
and was greener for the N6-benzyladenine, partial defoliation,
and sorbitol injection treatments. No significant difference
was found for treatment effect on fruit size (Table is), yet
fruit size was significantly related to the appearance of
watercore, internal breakdown and core browning (Table l6).

The Ca and defoliation treatments applied in l97l signi-
ficantly reduced watercore in fruits of the late harvest
(Table l7). Ca(N03)2 sprays had an intermediate effect between
control and the CaClZ treatments or the single application of
lime sulfur. Similar trends for watercore occurred at the
early harvest when it was of relatively low severity; however,
the single massive application of CaClz and hand defoliation
gave significant reductions. There was no fruit remaining on
the hand defoliated trees at the second harvest (October 28).
Significant reductions in sorbitol were achieved by lime
sulfur applied once and by CaClZ sprays, with lime sulfur
being best at the second harvest. Similar differences occurred
at the first harvest where hand defoliation was likewise
effective (Table l7). Internal breakdown was significantly
reduced, when evaluated after 6 months air storage, by the
single massive application of lime sulfur, both CaClz orchard
sprays, and by the lime sulfur and CaClz dip treatments.
Internal breakdown was significantly reduced by all treatments
when fruits were evaluated after 8 months of air storage at

20C. (Table l8).

 

56

Table 14. Effect of treatments on flesh firmness of Jonathan apples at
harvest, and after 3 and 6 months of storage.

 

 

Flesh firmness Flesh firmness Flesh firmness
Treatment at harvest after 3 months after 6 months
of air storage of CA storage
at 200. at 0°C.
Sorbitol injection 15.48 a 10.57 a 11.95 a
Fruit thinning 15.63 a b 10.80 a 11.98 a
N6-benzyladenine spray 15.81 a b 10.86 a 12.20 a
Partial defoliation 15.81 a b 11.13 a 12.35 a b
Ethephon Spray 15.86 a b 10.93 a 11.73 a
Chemical defoliation 15.87 a b 11.07 a 12.18 a
Control 16.51 a b 10.80 a 11.45 a
SADH Spray 16.73 b 12.21 b 13.57 b

 

Means followed by the same letter are not significantly different (P < 0.05,

Tukey's test).

 

 

57

Table 15. Effect of orchard treatments on ground color and fruit size
of Jonathan apples.

 

 

 

 

 

Treatment Ground Color Fruit Size
Control 6.25 a 145.2 a
Ethephon spray 6.12 a b 151.0 a
Chemical defoliation 6.00 a b 138.0 a
Fruit thinning 5.87 a b 135.2 a
SADH spray 5.75 a b 139.0 a 1
N6—benzy1adenine spray 5.63 a b 142.7 a
Partial defoliation 5.63 a b 138.2 a
Sorbitol injection 5.50 b 135.9 a

 

Means followed by the same letter are not significantly different.

(P<0.05 Tukey's test).

58

Table 16. Linear correlation coefficients between fruit size and
incidence of watercore, internal breakdown and core

browning of Jonathan apples.

 

 

 

 

Disorder Fruit Size
Early harvest Middle harvest
Sept. 25 October 9
Watercore n.s. 0.434 **
Internal breakdown
After 3 mo. in air at 20C n.s. 0.522 **
After 6 mo. in air at 200 n.s. 0.416 *
After 6 mo in CA at 00C n.s. 0.393 *
Core browning n.s. 0.481 **

 

** P < 0.01

* P < 0.05

59

 

Table 17. Effect of orchard treatments on watercore and sorbitol content of
Jonathan apples at harvest, 1971 - 1972.

 

 

Harvest Date

 

 

 

October 10 October 28
Treatment Watercore Sorbitol Watercore Sorbitol
(index) Z dry wt. (index) Z dry wt.
Control 1.10 a 5.74 a 2.25 a 7.19 a
Orchard sprays
L.Su1fur mult.app1ic. 0.78 ab 4.98 ab 1.15 be 5.21 bc
L.Su1fur sing.app1ic. 0.84 ab 3.94 bc 1.00 b 4.25 b
CaClZ mult.app1ic. 1.00 ab 3.23 c 1.07 b 4.98 bc
CaCl2 sing.app1ic. 0.65 b 4.20 bc 1.02 b 5.20 bc
Ca(NO3)2 mult.applic. 0.85 ab 5.02 ab 1.50 c 6.38 a c
Ca(NO3)2 sing.app1ic. 0.84 ab 4.85 ab 1.50 c 6.75 a
Hand defoliation 0.65 b 4.07 bc — -
Post harvest dip
CaCl2 0.95 ab 4.83 ab - -
Lime Sulfur 1.00 ab 4.61 ab - -

 

Means followed by the same letter are not significantly different.
(P < 0.05, Tukey's test).

60

Table 18. Effect of orchard treatments and post harvest dips on the
incidence of internal breakdown of Jonathan apples after
6 months (A) and after 8 months (B) of air storage at 2°C
plus 2 weeks at 200C.

 

 

(A) (B)
Treatment Internal Internal
Breakdown Z Breakdown Z
Control (nontreated) 29.2 a 44.00 a
Orchard sprays
L.Su1fur mult. applic. 3.5 a b 2.05 b
L.Su1fur sing. applic. 1.5 b 1.37 b
CaClZ mult. applic. 0.0 b 0.00 b
CaC12 sing. applic. 0.1 b 0.16 b
Ca(NO3)2 mult. applic. 3.4 a b 7.47 b
Ca(NO3)2 sing. applic. 8.6 a b 5.75 b
Hand defoliation 2.8 b ~
Post harvest dip
CaCl2 1.0 b 0.00 b
Lime Sulfur 0.4 b 3.71 b

 

Means followed by the same letter are not significantly different.

(P < 0.05, Tukey's test).

6l

Internal breakdown was correlated in a positive manner
with sorbitol (r = 0.5l3 7"7"7") and with watercore content at
the midharvest date (r = 0.362 *). Sorbitol and watercore
were positively correlated (r = 0.413 **). Fruit size
(weight) was positively correlated with watercore and sorbitol
content for both harvests (Table l9).

Analysis of the C02 evolution of apples harvested
October 28 revealed that fruit from all Ca sprayed trees had
a lower respiration rate than nontreated control fruit.

Fruits sprayed with CaClz several times during the growing
season had the lowest rate of respiration (Fig. 14).

The effect of CaClZ and lime sulfur sprays on the internal
concentration of Csz in apple fruits was periodically analyzed
beginning August l5. The results presented in Fig. 15 show
that CzHu was below l ppm up to September 20. At this time
the nontreated fruits increased in C2H4 to 9 ppm and continued
to increase thereafter. Fruits sprayed several times with
CaClz or with lime sulfur were delayed in their increase of
Cqu concentration until 5-8 days later. Once Csz production
was accelerated, it was considerably lower in Ca-sprayed
fruits than in nontreated fruits.

Postharvest dips with CaClz and lime sulfur significantly
increased the incidence of lenticel spot on fruits examined
after 6 months of air storage. The control fruit had the
highest percentage of lenticel spot on fruits evaluated after

8 months of air storage at 2°C, but variability among all

62

m0.0 v m k.
H0.0 v m v.31
Hoo.o v m a««

 

 

 

 

 

 

«ii sfik.o 4* 4N4.o «« bms.o 4 bam.o Aemv .03 bangs 6m606><
Illl. x Nom.o iall «s8 mam.o n3owxmwwm HmnuoucH
*«a wom.o «« maq.o ucoucoo Hobanuom
umm>umm umm>umm umo>pmm umm>umm
mm 03860 . OH 03860 mm bbboubo OH 4666060
myooumumz unwuaoo Heuflnuom Heuumm

 

.ooom um mxooz N msaa com um omeOum “Hm msunoE o Mouwm csopxmwun Hmcumucfl can uswflms
unspm mmmum>m cu dump umm>um£ an maoououms mam ucwucoo Houfipnom unsum mo mucofloflmmmoo oowumamupoo .mH oHLmH

 

63

Fig. l4. Effect of the different treatments on the
respiration rate of Jonathan appies.

 

 

 

UoOm pmm>¢<z mwpu( m>(o
a o n v m N F
o
o
O Clio lilo
0/ O O o—
w...
lll|«.nuqd.w.fid.llll.|llllll. up
..« a i 6 /
If...“ ............ .. ...........<.....u.. .,/q
.. I I
In». C Gillll 0‘
{O o.
o/ i\o
(o\
. .III .:
'llcll |\.||/
llllll /
/
/
w—
ON
: : Puou olo
: : 0°10U1i¢¢< : : MOZBU 1l|.< NR
: : Dvou 'II .130 2:3... m a 0- In.
4“. O-Otau W .- ........ —°~.RIU l-|

 

 

au/bx/Coa 1w

 

65

Fig. 15. Internal content of ethylene of Jonathan
apples as related to treatment and time
of harvest.

ETNYLENE

PPM

22

20

 

 

o—o control
var—r: 1.5 muHip. applic.
t—t Ca C12 muHip. applic. /
o—o CoC|7 single applic.
/O
o
/\./
0
if *4}
/ 4......
«’1 TH
7/|0 77'30 8170 910 9,30 10 20 n 10 II 30
HARVEST DATE

67

samples diminished the statistical significance (Table 20).
Jonathan spot was significantly reduced by CaClZ and lime
sulfur applied either as sprays or dips, and by one massive
orchard spray of Ca(N03)2. Soft scald was significantly
increased by the lime sulfur dip treatments (Table 21).

No significant effect of treatments on flesh firmness
was noted at harvest (Table 22). After 6 months of air storage
the fruits sprayed several times with CaClZ and Ca(N03)2, or

dipped in CaClz solutions were significantly firmer than the

 

control. Control fruits were also consistently larger than
fruits from other treatments at all harvest dates (Table 23).
A summary of the most important correlations found in
the orchard experiments during the years 1970-71 is presented
in Table 24. Sorbitol and watercore were positively corre—
lated both years for fruit of the middle and late harvest
dates. Sorbitol and watercore were positively correlated with
internal breakdown in both years at the middle harvest. Fruit
from the late harvest was not stored. Fruit size, as measured
by weight, was positively correlated with sorbitol and water—
core for the middle and late harvests and with internal
breakdown for fruits of the middle harvest in both years.
Fruit porosity measurements by analysis of the internal
atmosphere of McIntosh apples at harvest time revealed there
was a relatively constant percentage of 002 and 02 until

October 10 being approximately 1 and 19%, respectively.

 

68

Table 20. Effect of orchard treatments and postharvest dips on the
incidence of lenticel spot of Jonathan apples after 6
months (A) and aftgr 8 months (B) of air storage at 2°C
plus 2 weeks at 20 C.

 

 

(A) (B)
Treatments Lenticel Spot Lenticel Spot
Control (nontreated) 0.0 a 56.60 a
Orchard sprays
L.Su1fur mult. applic. 0.0 a 12.33 a
L.Su1fur sing. applic. 0.5 a 11.50 a
CaCl2 mult. applic. 0,0 a 16.90 a
CaC12 sing. applic. 0,4 a 13.12 a
Ca(NO3)2 mult. applic. 0.0 a 10.16 a
Ca(NO3)2 sing. applic. 0.2 a 41.60 a
Postharvest dips
CaClz 3.1 b 18.60 a
Line Sulfur 17.7 c 12.36 a

 

Means followed by the same letter are not significantly different.

(P < 0.05, Tukey's test).

 

Table 21. Effect of orchard treatments and postharvest treatments
on Jonathan spot and soft scald of Jonathan apples after
6 months of cold storage at 2°C plus 2 weeks at room

 

 

temperature.
Jonathan Spot Soft Scald
Treatment
Z Z
Control 49.1 a 3.9 a
Orchard sprays
L.Su1fur mult. applic. 4.3 b 0.7 a
L.Su1fur sing. applic. 18.7 bcd 1.2 a
CaCl2 mult. applic. 7.5 be 0.0 a
CaClz sing. applic. 9.7 bcd 0.1 a
Ca(NO3)2 mult. applic. 29.4 a cd 2.1 a
Ca(N03)2 sing. applic. 13.0 b d 0.5 a
Hand defoliation 33.8 a d 1.1 a
Post harvest dips
CaCl2 17.5 bcd 1.0 a
Lime Sulfur 18.4 bcd 27.3 b

 

Means followed by the same letter are not significantly different

(P < 0.05, Tukey's test).

70

.Aummu m.%ox:H .mo.o v mv unouwmmflw xfiucmoHMHdwflm uoc mum pmuuoa 05mm 6L0 >3 woBOHHOM mcmwz

 

 

b m Nw.NH i i m No.6H unmabm bang
b km.ma . I 6 mH.bH Naomo
mawv umm>pmnuwom
n m Nm.NH I i m no.0a COHumHHomow wcmm
b m am.ma m ma.ba b ow.mH 6 mm.ma .UAHaam .mcnm NAmozvmo
b km.ma m Nb.mH m Nw.mH m oo.bH .oaaaam .babe Namozvmo
b m km.NH m mm.sa 6 oa.mH m os.bH .oaabam .manm Naomo
b mm.mH m mk.mH m NN.mH m mk.oa .oaaaam .bH:s Naomo
b m km.ma m km.ma m mH.mH m ms.bH .buaaaa .wcam bswfiam.a
b m mo.ma m ow.ma m mk.ma m kk.bH .onaaam .babe “spasm.d
mmmuam ppmfiuno
6 NM.NH m m~.sH m Nq.mH m aa.m4 Houbcou
wwmuoum uwm mo uwo>umm umw>pmm umw>uwm
msucoe o uwum< wm Honouoo ON Monouuo OH Monouuo

 

uwo>um£ um mmaadm cmzumcom mo wwofiEufiw

.oom um meMOum Ham mo mSucoE o umuwm can wEflu
cmmaw co mucoEummuu uwo>~m£umom mam pumsuuo mo mowwwm .NN wanme

71

 

 

Table 23. Effect of orchard treatments on weight of Jonathan apples at
harvest.
October 10 October 20 October 28
Treatment Weight in gm Weight in gm Weight in gm
Control 128.7 a 144.0 a 142.5 a
Orchard sprays
L.Su1fur mult. applic. 106.0 ab 120.5 ab 111.7 b
L.Su1fur Sing. applic. 109.5 ab 117.2 ab 117.5 abc ’
CaCl2 mult. aDPlic. 96.0 b 109.7 ab 100.2 b d
CaClz sing. applic. 107.2 ab 101.2 b 93.7 b
Ca(N03)2 mult. applic. 119.0 ab 127.5 ab 131.0 a
Ca(N03)2 sing. applic. 119.2 ab 121.0 ab 125.0 a cd
Hand defoliation 98.2 ab - '

 

Means followed by the same letter are not significantly different.

(P < 0.05, Tukey's test).

72

Table 24. Summary of correlations from orchard experiments with Jonathan
apples according to relative time of harvest, 1970 and 1971.

 

Harvest date

 

Early Middle Late
Factors compared

 

g/25/70 10/9/70 10/10/71 10/28/71

 

Sorbitol vs watercore n.s. 0.688 **** 0.413 ** 0.568 ***

 

Sorbitol vs internal breakdown

After 3 mo. in air at 2°C n.s. 0:623 **** _ _
After 6 mo. in air at 20C n.s. 0.695 **** 0.513 *** -
After 6 mo. in CA at 0°C n.s. 0.692 **** — -

After 8 mo. in air at 2°C - - ‘ '

Watercore vs internal breakdown

 

After 3 mo. in air at 2°C n.s. 0.767 **** - -
After 6 mo. in air at 2°C 0.593**** 0.727 **** 0.362 * -
After 6 mo. in CA at 0°C n.s. 0.780 **** — —
Weight vs watercore n.s. 0.434 ** 0.424 ** 0.714 ****
Sorbitol vs weight n.s. n.s. 0.316 * 0.701 ****
Weight vs internal breakdown n,s. 0.416 * 0.501 *** -
**** P < 0.0005
*** P < 0.001
** P < 0.01
* P < 0.05

73

Beginning October 12 the 002 concentration increased reaching
4.60% on October 20 with the 02 decreasing to 16.25%; this
coincided with a progressive increase of watercore to the
severe category on October 10 (Table 25).

A similar study showed no significant changes in C02
and 02 for Jonathan fruits sampled on the tree, yet late
harvested apples accumulated 002 and decreased in 02 content
when stored at 20°C for 8 days. The increase in watercore
coincided with the 002 increase and 02 decrease (Table 26).

Porosity measurements of severely watercored apples
showed a much lower rate of outward gas flow from the pith
than non-watercored fruits (Fig. 16). Porosity measurements
of pith discs from watercored and non-watercored apples also
showed a constant low gas flow rate for watercored tissue and
a higher gas flow rate from apple discs without watercore
(Fig. 17). An experiment designed to measure the effect of
removing the skin and cutting away increasing amounts of flesh
tissue on the porosity of Jonathan applesindicated an increase
in porosity with time for non-watercored apples and a fairly
constant low rate of gas flow through watercored fruits
(Fig. 18). Similarly, late harvested fruits showing external
symptoms of breakdown after two weeks at room temperature
following harvest, were of low porosity as compared with fruits
without internal breakdown (Table 27). A survey of the change

in porosity of fruits from 12 Michigan orchards as the fruit

 

74

Table 25. Mean internal atmosphere and watercore development of
10 McIntosh apples by harvest date.

 

 

 

Harvest. CO2 02 Watercore
date 2 Z (index)
8/30 1.19 19.76 0.0
9/10 1.25 19.51 0.0
9/20 0.98 19.90 0.4
9/25 1.05 19.32 0.8
9/30 1.12 18.97 0.8

10/5 1.25 19.23 1.6

10/10 1.03 19.97 1.0

10/12 1.90 18.34 1.5

10/15 3.90 17.00 1.6

10/17 4.25 16.48 2.4

10/20 4.60 16.25 3.2

 

75

Table 26. Mean internal atmosphere of 15 Jonathan apples from 3 trees
as related to harvest date, watercore, and subsequent break—
down development after 8 days at 20°C.

 

 

 

 

Upon Harvest Plus 8 days at 68°F

Harvest CO2 02 CZH4 C02 02 Watercore Breakdown
date Z Z po Z Z (index) (index)
9/20 0.95 19.5 1.24 1.24 18.7 0.0 0.0
10/1 0.92 19.7 3.28 1.18 18.9 0.5 0.0
10/5 1.02 19.4 5.65 1.07 19.4 0.5 0.0
10/10 0.86 20.5 14.30 0.76 10.9 1.0 0.0
10/15 1.01 19.5 18.71 0.96 19.3 1.2 0.0
10/20 1.11 19.6 17.63 1.23 19.1 1.2 0.0
10/25 1.14 19.3 20.14 1.09 18.9 1.7 1.0 '
10/30 1.03 19.4 24.25 1.18 18.7 2.0 0.5
11/3 1.18 19.2 38.26 3.85 16.9 3.4 1.75
11/5 1.28 19.0 63.35 4.10 16.2 3.2 2.3

 

 

76

Fig. 16. Gas flow characteristics from the pith outward
of watercored and non-watercored Jonathan apples.

 

 

77

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78

Flg- 17. Gas flow through characteristics of pith
discs from watercored and non-watercored
Jonathan apples.

 

 

 

 

 

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79

 

mwpDz.I 2. mi:

0

one. or... 2.83 \\ an \x on o. 2 o v
\N \\ 9 m

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.‘I‘.

 

vegetatu} .

 

1:095:03 go: o o

zqaug/ugw/gn

 

Fig.

18.

80

 

 

 

 

Effect of skin peeling and flesh removal

on gas flow characteristics from the pith
outward of watercored and non-watercored

Jonathan apples.

 

 

 

 

 

 

 

 

 

 

 

ul man /in¢|\2

2000

1900

1800

1700

1600

1500

1400

1300

1200

1100

1000

81

 

 

 

 

— non woiercored O
'-- woiercored
O
I’O”
0 12 27 44 61 72

'I. WEIGHT REMOVED

 

82

Table 27. Porosity of late harvested (October 28) Jonathan fruits
showing distint external breakdown symptoms after being
two weeks at 20°C, as compared with fruits not showing
breakdown symptoms.

 

 

Porosity Breakdown
ul/min/inch2 (index)
Fruits with external 31 a 3.4 a
breakdown symptoms
Fruits w/o external
breakdown symptoms 573 b 1.0 b

 

Means followed by the same letter are not significantly different
(P < 0.05, Tukey's test).

83

approached maturity indicated a steady increase in porosity

up to the harvest of October 11. Porosity increased
positively with fruit size until October 4 (Tables 28 and 29).
After October 11, and as the fruits developed watercore
symptoms, there was a decrease in the rate of gas flow through
the pith area. This resulted in a decrease of the positive
correlation value of porosity to weight or size. A negative
correlation between watercore and porosity developed by
October 28 (Table 29).

The role of leaves on the growth, watercore development
and porosity characteristics of Jonathan fruits is summarized
in Table 30. Fruits from ringed and defoliated branches were
significantly smaller, less porous and lower in watercore than
control fruits or fruits from ringed branches with leaves.
Fruits from the latter branches also were larger by weight
and had significantly more watercore and less porosity than
control fruits.

Late harvested fruit which received Ca orchard sprays
had significantly less watercore and higher rates of gas flow

through the pith than control fruit (Table 31).

84

 

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85

 

 

 

Table 29. Correlation coefficients of porosity to weight (fruit
size) and watercore by harvest date. Jonathan apples.
Harvest date Porosity vs. Porosity vs.
“Eight watercore

9/20 .413 *** _

9/27 .522 *** _

10/4 .613 *** —

10/11 .414 *** n.s.

10/18 .370 *** n.s.

10/28 .070 n.s. —.379 ***

 

*** = P < 0.001

I

86

Table 30. Effect of leaves on the weight, porosity and watercore
development of Jonathan apples.

 

 

 

Fruit Wt. Porosity Watercore

Treatment gm. ul/min/inchz (index)
Fruit from ringed
branches with leaves
removed 62.6 a 10 a 0.0 a
Fruits from ringed
branches with leaves
remaining 148.5 b 338 b 2.6 b
Control fruits 130.9 b 612 c 1.0

 

Means followed by the same letter are not significantly different.
(P < 0.05, Tukey's test)

Branches ringed August 15/71

All fruits harvested October 15/71

87

Table 31. Effect of orchard treatment on porosity and watercore development of
late harvested (Oct. 28) Jonathan apples.

 

 

 

, Watercore Porosity Weight in
Treatments Index ul/min/Inch2 gms.
Control 1.95 a 140 a 130.15 a
Orchard sprays
L.Sulfur mult. applic. 1.12 b 667 b 115.35 a b
L.Su1fur sing. applic. 1.00 b 614 b 109.87 a b
CaC12 mult. applic. 1.00 b 607 b 103.47 a b
CaClZ sing. applic. 1.00 b 459 b 96.47 b
Ca(N03)2 mult. applic. 1.15 b 548 b 130.35 a
Ca(NO )2 sin . a lic. 1.00 b 594 b 115.20 a b
3 g PP

 

Each value represents the mean of 40 observation

Means followed by the same letter are not significantly different. (P<0.05,
Tukey's test).

DISCUSSION

The highly significant correlations of sorbitol to water-
core, sorbitol to internal breakdown and watercore to internal
breakdown (Table 24) suggest that fruit sorbitol metabolism
at harvest time is of primary importance on the development
of internal breakdown (1B) during storage. The positive
correlation of watercore to sorbitol agrees with the findings
of Williams (1966) and Kollas (1968), and substantiates the
hypothesis that watercore develops as the cells lose the
capacity to metabolize sorbitol and/or incorporate it into
storage compartments.

Evidence is presented in Tables 1-5 and Figs. 3-9 supporting
the hypothesis that watercore and internal breakdown can be
regulated by manipulation of sorbitol content in Jonathan
apples. Reduction of both was attempted by removal of the
source of sorbitol. 0f the three treatments used, partial
defoliation, complete hand defoliation and chemical defoliation,
the latter was more effective than partial defoliation in
reducing 1B, sorbitol, and watercore (Tables 1-5). This was
probably because chemical defoliation resulted in more leaf
damage or leaf removal than partial defoliation. Chemical
defoliation by lime sulfur (Tables 17-18) was as effective
as complete hand defoliation in reducing watercore, sorbitol
content and IB. Although a somewhat higher content of fruit

Ca (60 ppm) was found after chemical defoliation than in

88

 

89

fruit from ethephon-sprayed or non-treated trees (Table 7),
it is doubtful that Ca was the key factor in the reduction
of 18. All fruits, regardless of treatment, had
adequate Ca according to the results of other investigators
(Sharples, 1967; Perring, 1968; Stebbins, 1970). It is
indicated that the effect of defoliation in reducing 18 was
due to the reduction of sorbitol in the cells or its accumula-
tion in the intercellular spaces. The fact that fruits from
defoliated trees had lower respiration and ethylene evolution
rates than fruit from nondefoliated trees (Figs. 11 and 12),
as well aslower sorbitol and watercore than control fruits,
indicates that the defoliation treatments prevented the ab-
normal metabolic stresses reported to be induced in fruit cells
by watercore (Smagula, 1968; Williams, 1966; Bangerth, 1972).
The available data does not suggest the mode of action
for N6-benzyladenine in reducing fruit sorbitol and subsequent
IB development during storage. A possible explanation is
offered by Shindy and Weaver (1970). They found that grape
leaves dipped in benzyladenine or gibberellic acid became
strong ”sinks” so as to withhold the export of photosynthates
to other parts of the plant. Later Quinland and Weaver (1970)
compared carbohydrate transported to grape clusters dipped in
gibberellic acid from shoots with and without benzyladenine
and GA sprays, and found that less photosynthates moved from
the sprayed shoots. They concluded that the growth regulators
caused the leaves to better compete for metabolites with the

grape clusters.

 

9O

N6-benzyladenine-treated fruits had lower rates of
respiration and Cth evolution than fruits from the control,
ethephon, sorbitol injection, or fruit thinning treatments
(Figs. 11 and 12). This is in accordance with the response
to kinetin found for green leafy vegetables (Dedolph §£_§l.

1961); broccoli (Dedolph et al. 1962), and strawberries

 

(Dayawon and Shutak, 1967); but different from the results
of Smock et a1. (1962) where a stimulation of the respiration

1:

rate in preclimacteric apples was observed. Therefore,
is likely that N6-benzyladenine reduced sorbitol and 18 by
reducing the flow of metabolites from the leaves to the fruits.
Another method for reducing sorbitol within fruits was
by extension of the physiological age in which fruits could
metabolize the sorbitol as supplied from the leaves. SADH
used for this purpose reduced watercore, sorbitol and 1B.
This confirms earlier reports by Edjerton and Hoffman (1965);
Batjer and Williams, (1966) and Lord §£_§l. (1967). Fruits
receiving SADH also had lower respiration and ethylene
evolution rates at the early and midseason harvest dates than
fruits from all other treatments. This is in agreement with

the findings of Rhodes et al. (1969) and Miller and Lougheed

 

(1971). Unfortunately, two of the four trees utilized had
been trunk ringed at ground level by rodents and this apparently
had an effect on the treatment. There were indications that

flow of metabolites to the roots was impeded since the ringed

91

trees died the following year. Accumulation of metabolites
in the above ground parts of the tree during the treatment
year could have accounted for the erratic results obtained
for this treatment.

Trees that were fruit thinned or injected with sorbitol
solutions had fruit with higher respiration and ethylene
evolution rates than fruits from the defoliation, kinetin,
or SADH treatments (Fig. 11, 12 and 13). This suggests that
fruits from the sorbitol injection and thinning treatments
were under the abnormal stress exerted by watercore conditions
reported by Smagula et a1. (1968).

Treatments that hastened fruit maturation, and thereby
the period in which fruits could metabolize sorbitol, caused
an increase in fruit sorbitol at harvest. Ethephon-sprayed
fruits had the highest amount of watercore, sorbitol, and 18
of all treatments (Tables 1-5) and the highest rates of C02
and CZHQ evolution (Figs. 11, 12 and 13). Since all treat—
ments were harvested at the same time, it is likely that
ethephon caused the highest sorbitol and watercore contents
because of its effect in advancing maturity. The stimulation
of the respiration rate is in accordance with the results of

Russo et al. (1967) with bananas. Even though the onset of

 

the climacteric rise was not accelerated appreciably by

ethephon, this effect was probably due to the short time

 

92

of fruit harvest. Testey and Shanmuganathan (1971) found
similar results for Northern Spy apples sprayed with different
concentrations of ethephon.

The reduction in watercore, sorbitol, and 1B obtained in
1970 with lime sulfur suggested that other sources of Ca should
be investigated. The reductions of watercore content at
harvest attained by Ca(NO3)2 and CaClZ orchard spray applica—
tions in 1971 (Table 17) were similar to those reported by
Boon e£_§l. (1968) and Bangerth, (1972).

The effective reduction of sorbitol content by multiple
orchard applications of CaClZ (Table 17) and of respiration
rates by all Ca sprays (Fig. 14) suggest a dual benefit from
Ca. First, calcium may facilitate metabolism of sorbitol
and its incorporation into storage compartments as suggested
by Bangerth g£_§l. (1972); this concept is further supported
by the highly significant negative correlation of calcium
content to watercore and to sorbitol (Tables 8 and 9).
Secondly, if the accumulation of toxic compounds is needed
for the development of breakdown (Clijters, 1965; Wills, 1970),
the lower respiration due to Ca treatment would retard or
prevent a level favoring breakdown development.

The delayed and lower production of ethylene of fruits
sprayed several times with CaClZ or lime sulfur (Fig. 15)
offers further evidence that the metabolism was affected by

Ca (Fig. 14). The role of Ca in slowing metabolism and

 

93

delaying the production of CZHg by the apple fruits is not
clear. A possible explanation is the known effect of Ca in
maintaining the integrity of cell membranes and thereby a
better compartmentalization of cell substrates (Jones and
Lunt, 1967).

The presence of watercore (Figs. 16 and 17 and Tables
25, 26, 28, 29, 30 and 31) limits the free flow of gases within
the apple fruit. Internal measurements of gaseous content
showed McIntosh and Jonathan apples accumulated 002 and
became lower in 02 content in the internal atmosphere as the
severity of watercore increased (Tables 25 and 26). In
severely watercored apples, the core was almost impervious
(Fig. 18). Cutting away the peel and flesh did not increase
porosity and a puncture was required to measureably increase
gas flow. Many heavily watercored fruits which developed
breakdown symptoms shortly after harvest were of low porosity
in comparison to apples without breakdown (Table 27).

The increase in porosity with fruit enlargement (Tables
28, 29 and 30) is likely due to the increase in volume of the
intercellular spaces (Hoff and Dostal, 1968; Kerawala, 1968).
As fruits mature they reach a condition, perhaps when sorbitol
accumulates in the intercellular spaces, that results in a
gradual decrease of the positive correlation of weight to
porosity (Table 29). This is indicative of the gradual
obstruction to gas flow that fruits develop as watercore

forms and is in accordance with the findings of Trout et al.

94

(1942). They found increased resistance of the fruit to gaseous
diffusion with increasing age. After removal from storage
increased accumulation of C02 and reduction of 02 in the
internal atmosphere of the fruit was found. Ben-Yehoshua
g£_§l. (1963) also found a marked increase in the resistance

of the fruit to gas diffusion associated with avocado fruit
ripening and softening. He estimated a decrease in the air
volume of ripe avocados, and suggested that resistance to

gas flow was due to a clogging up of the air spaces. Extensive
waterlogging in senescent cells of bean endocarp was also
reported by Sacher (1959).

That calcium treatments prevented the accumulation of
sorbitol and formation of watercore condition is evident from
the gas flow characteristics of fruits sprayed with calcium
(Table 31). These late harvested fruits had a significantly
higher porosity and lower watercore content than nontreated
fruits.

The effect of the different treatments on other storage
disorders are presented in Tables 11, 12, 20 and 21. N9-
benzyladenine was the most effective treatment in reducing
lenticel spot (Table 11), and chemical defoliation was the
most effective in reducing brown heart and core browning
(Table 12). These beneficial effects of chemical defoliation

were probably due to the decreased watercore, since advanced

 

 

 

95

maturity and watercore conditions have been associated before
with the development of brown heart and core browning

(Chace, 1959; Kerawala, 1968; Dewey and Dilley, I968).

SUMMARY AND CONCLUSIONS

The purpose of this study was to investigate the
possibilities of regulating the development of internal break-
down of Jonathan apples by manipulation of the sorbitol content
of the fruit prior to harvest. Information gained would
perhaps be of value in developing cultural or handling
practices to reduce the incidence of internal breakdown of
apples in commercial storage.

Defoliation of the trees approximately one week before
fruit harvest was effective in reducing sorbitol and watercore
at harvest, and subsequent development of internal breakdown.
Complete defoliation, either chemically or by hand, was more
effective than partial defoliation by pruning terminal growth.
Since there was a significant positive correlation between
sorbitol and watercore and between sorbitol and internal
breakdown it is concluded that defoliation modified internal
breakdown as a result of its effect on the sorbitol content of
the fruit.

Fruit thinning, injection of sorbitol into the tree, and
orchard sprays with ethephon increased sorbitol and watercore
content at harvest and subsequent development of internal
breakdown. Fruits from these treatments also had higher
rates of respiration and ethylene evolution than apples fron

chemically defoliated or kinetin-sprayed trees. It is probable

96

 

97

that the significant increase in sorbitol and watercore, and
therefore internal breakdown, of ethephon-sprayed trees was
due to acceleration of fruit ripening.

Several applications of CaClz and single applications of
lime sulfur as orchard sprays significantly reduced the
sorbitol and watercore content of the fruit at harvest, and
internal breakdown during storage. The significant negative
correlations of sorbitol to Ca and internal breakdown to Ca,
when considered with the findings of other investigators

(Bangerth et al. 1972), indicate that Ca facilitates the

 

metabolism of sorbitol and its storage as fructose in the cells.
Fruits sprayed with Ca or lime sulfur had lower respira-
tion rates and less C2H4 production than nontreated fruit of
the same chronological age. This lower metabolism would
decrease the possibilities for accummulation of toxic compounds
that may develop as a result of watercore. These apples would
be less likely to be affected by such accummulation of volatile
metabolites since the fruit tissues possess better gas
exchange properties. Tissue porosity, as measured by gas
flow from the pith outward was negatively correlated with
watercore content.
Apparently there is an important interrelationship of
sorbitol metabolism and calcium content that affects the

development of watercore and internal breakdown.

 

LITERATURE CITED

 

 

 

LITERATURE CITED

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phytohormones on maturation and post-harvest behavior
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Abdel-Kader, A. S., L. L. Morris and E. C. Maxie. 1966.
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Anderson, J. 0., P. Andrews, and L. Hough. 1961. lThe bio-
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Askew, H. 0., E. T. Chihenden, R. J. Monk, and J. Watson.
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Batjer, L. P., and M. W. Williams. 1966. Effects of
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101

Chong, C. and C. D. Taper. 1971. Daily variation of
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