Hl

“HIUHIMWHIW

1

E “WNWIWHUNHINIW

214

"—1
I
.0:

WVBWGATWN; ON THE
BLACK ROOT 0F STRAWBERRFES
Thesis for the jcgree of M. 5.

Forrest C. Strong
I 9 .2 7

 

 

 

 

1." .IO'. .‘flli.nu-llllli|lu' ' ll..2llll Ill V E 7‘ 1‘ ‘1;ll

 

 

NVESTIG T101 8 ON THE BUACK ROOT
OF S"RAWBZURT“‘

Thesis presented for the Decree of
‘aster of Science.
Michigan State College.
by .

Forrest 0} Strong

1927

 

ACKNOWLEDGXENTS.

The writer is indebted to Doctors
3. A. Bessey, G. H. Coons, and C. W.
Bennett for valuable suggestions through-
out the course of the experiments, and
to Doctors 3. A. Bessey and G: H. Coons

for criticism and correction of the

manuscript.

‘lJ,/

“ii

{3353%i)

IKVESTIGATLONS ON THE BLACK ROOT OF STRAWBERRIES

INTRODUCTION

The strawberry industry in Kichigan is of considerable import-
ance. In 1924 the U. S. Department of Agriculture reported 5,500 acres
devoted to the culture of this fruit. The same year Kichigan shipped
554 carloads of berries, ranking tenth in the commercial production of
strawberries in the United States. There are four phases of the indus-
try: lst, the commercial production of berries for the nearby large
city markets; 2nd, the growing of berries for the canneries, in which
Michigan ranks first in the United states; 3rd, the commercial pro—
duction of strawberry plants by the nurseries; and 4th, the growing of
the berries in the small plantation for the home. The largest acreage
set out for commercial production of the fruit and plants is located
in southwestern Michigan in Berrien and St. Joseph counties, while
other smaller centers are located in Wayne, monroe, montcalm, Kent,
Van Buren, Allegan, Grand Traverse, and other counties. Local planta-
tions are to be found through the entire state.

The varieties most commonly grown are the Senator Dunlap,
Brandywine, Gibson or Pokemoke, and Premier, although others may be
more popular in vicinities. Also several everbearing varieties are

grown, the Progressive probably being most used.

THE STRAVBSKRY DISBJSB SITUATION
Among the cultivated crops the strawberry has long been consid-

ered One in which the disease hazard for the grower is small. Kildew,

IO

leafspot, and a few fruit rots have at one time and another attracted
the attention of growers. For the most part these diseases are of minor
importance, and no control measures are practiced.

There is, however, a situation in strawberry culture which is
a subject or concern to the growers. This is the failure of plants
newly set out to become established, the dying of plants, often those
the first year, which in severe cases may involve a considerable area
in a plantation. Such dead areas may be so numerous as to render the
plantation unprofitable after two or three years.

The following case which came under the writer's observation
is typical of the situation commonly found in strawberry fields in the
state. In the spring of 1925 a new plantation of 20 acres was set at
T more in Kontcalm County. The first stand was so poor that a second
and in some places a third setting :as necessary to produce a full
rowed stand. Figure 1 illustrates the condition of the field in the
spring of 1926, and at this time many plants were dead or diseased.
The manager of the plantation stated that the securing of a good stand
was becoming increasingly difficult. A small plantation near Bridge-
man gave a similar hisnory. This field, although set under fairly
normal conditions and in the customary manner, gave a very unsatisfac-
tory stand. Figure 2 shows a typical area in this plantation.

It has long been known that strawberry plantations can rarely
be kept at high productivity for more than two years. The standard
practice in strawberry growing is to plant in the spring or late summer.

The first crOp is harvested the following spring. Runners from the

mother plants are there allowed to strike between the original rows,
and these original rows are then plowed up. The third year it is
commonly found that the stand is so poor and choked with grass that
7the plantation is on the down grade in production. The problem pre-
sented in the running out of the patches is not one of soil fertility,
for the strawberry seemingly does well on soils low in fertility, and
many plantations on rich soil show poorer stands than those in light
soil.

It is suggested that along with drought injury and winter
killing, the disease which is the subject of this article is an impor-
tant factor in the difficulties which have been met with in securing
and maintaining a stand of strawberries. As the discussion proceeds,
it will be seen that we are concerned with a root disease which by its
weakening effect on plants, renders them low in vitality and subject
to injury by various factors such as drought and frost, and the con-
ditions to be described will be seen to play an important role in the

deterioration of strawberry plantations in this state.

THE BLACK ROOT DISEASE
The aspect of a strawberry plant affected with black root is
typical. The diseased plant shows poor vitality, is characteristically
stunted, and has tendency to dry up at the onset of dry weather con-
ditions. The plant shown in Figure 3 died two days after the photo-

graph was made. Such a plant on being dug up is found to have a root

system in which the roots are all black, corky in texture, and apparent-
1y dead. If a diseased plant as yet not in the wilting stage is examined,
there will be seen young white lateral roots pushing out from roots
with blackened cortex tissue (Figure 4). Upon examination of such a
root the diseased cortex will be found to peel off readily leaving the
vascular cylinder, from which the secondary roots arose, still more or
less white and apparently functioning. It should be borne in mind that
roots dying from age present uch the same general appearance as that
just described. The examination of a younger plant which is affected
with black root yields a more clean cut picture of the black root dis-
ease. Bven these younger plants show characteristic evidences of the
disease by the production of smaller leaves and fewer main roots, to-
gether with the reduction in number of lateral roots. Young plants
affected with blacx root lack vigor as is manifested by their slow
growth and reduced runner production. Some of the main roots of such
plants will be rotted their entire length and brown to black in color.
from few to many lesions are to be found on the main roots, and many

or all of the lateral or Secondary roots will either be rotted off or
show distinct rotted areas (Figure 5). The lesions on the main roots
vary in size from .5 to 5 cm. in length and usually encircle the root.
At first they are reddish brown and later become black. These lesions
when in the early stage exhibit a brown water-soaked appearance but
very soon become shriveled and shrunken. Very often the rotting in-
volves all of the root tissue, affecting the stele or vascular cylin-

der as well as the cortical tissue {See Figures 6 and 7). Such roots

break at the rotted portion. The lesions on the laterals resemble in
minature those on the longer roots. It is probable that the attack
upon the lateral roots is very important in producing the general
effects of black root, since the root hairs through which water and
plant food materials enter the plant largely occur on these portions
of the root system. The loss of tkese lateral roots then reduces the
efficiency of the root system. This lack of a properly functioning
root system is seen in plants affected with blach root or root rot
during dry periods of summer and especially during the picking season
if it is at all dry. On a hot day the leaves will wilt down and then
recover during the night. If the dry weather continues, the plants
will die with the berries hanging green and ripe on the stems, while

the leaves may become purplish or bronzed and the petioles turn red.

PREVIOUS WORK

The writers on strawberry culture have for a long time referred
to black root as a diseased condition whose cause was unknown. There
is little to be gained oy referring to these scattered notes, since
none of the older writers made more than casual comment on the severity
and probable cause.

What may be a typical case or black root was described by
Clinton (3) under the heading "Leaf Scorch", but he stated that no
fungus appeared to be affecting the roots. This condition may have
been due to black root. Eletcher (7) in 1917 describes "root rot or

black root" of strawberry and states that the disease was prevalent in

New York, Michigan, and lassachusetts in the years 1902--l908. "When
the berries are about half grown the plants wilt and turn yellow; the
roots are decayed. Most of this trouble is due to winter injury, but
a bacterial disease is associated with it in some cases. Poor culture,
lack of fertility, the crowding of plants in the row, insufficient
mulching, and wet land are favorable for this trouble." Heald (8) in
1920 mentioned the ”dying out” of strawberry beds in western Washington,
and ascribed the trouble to Shizoctonia. The next year Smith and Horne
(ll) in California described a rot of strawberries in which the cortex
of the root decays. Ho parasite was found and the rot was believed to
be due to water logging of the soil or sudden drying out of soil
moisture. The summer of 1925 the disease was reported from Kississippi
by Real (9) who wrote "A root rot of strawberry has been discovered

in many parts of the state the present season. The disease causes a
distinct wilting of the plants, accompanied by pronounced discoloration
of the roots and crown tissue. A species of Eusaran has been isolated
from the affected crown, but at present it is not shown if this fungus
is parasitic or reSponsible for the death of the plants. This trouble
is serious and is causing many growers of strawberries considerable
alarm."

Investigations on black root date from this time and are not
very extensive. In 1923 Berkeley and Jackson (1) reported the isol-
ation or various soil bacteria which they thought to be the causal
organisms. Later, in February 1924, Berkeley (2) further reported that

black root was present again the second season and did much damage.

The soil bacteria isolated previously failed to cause infection when
tested by inoculation into plants. A species of fusarium was suspected
and mycelium was found in sections of diseased roots. In 1924 Sher-
bakoff (10) reported black root as a disease of wide occurrence in the
southern states and also further north. He stated that it is of con—
siderable economic importance in certain sections. He isolated a fun-
gus from the diseased roots but was unable to identify it because it
remained sterile in culture. Coons (4) also in 1924 described black
root of strawberries in Michigan and stated that the conditions of
infection indicate Rhizoctonia as the causal organism. In 1926 Darrow
(5) summed up the situation as follows: "There are severe troubles
known as black root which are caused by fungi or bacteria. Ho thorough
studies of these troubles have ever been made, but their effect is to
kill the roots and so shut off the intake of water and dissolved
minerals." Again—~"Little is known of the cause or control of crown
or root diseases of strawberries. They are often very serious and

may cause serious injury which is not recognized as due to disease.
They may even be the most important of all strawberry diseases." Late
in 1926 Wardlaw (12) reported on the Lanarkshire disease of straw-
berries in Scotland. His description is identical with the black

root disease in this country. He isolated a Pythium which upon in-

oculation produced typical symptoms of disease.

t1]

OCCURRENCE OF THE DISEAS
The black root of strawberries is widely distributed not only

in the United States, but abroad. What appears to be a similar dis-

ease has been reported from Scotland and Africa.* In the United
States and Canada, as already shown in the preceding section, the
disease is known from‘hississippi, Tennessee, Alabama, New York,"
Ontario, California, and Washington. On the trip made by the 5th
Annual heating of the American Phytopathological Society in 1923
through western New York state and Ontario, Canada, the disease was
observed at various places.

Collections in Michigan have shown the disease to be widely
distributed, specimens having been obtained from Berrien, Ingham,
Wayne, Konroe, St. Joseph, Allegan, Kontcalm, and Van Buren counties.
It is evident that this disease is extremely wide spread and coin-
cident with the culture of strawberries. Since strawberry plantations
are established with nursery plants and new varieties are constantly
being introduced by nurseries, one might suspect that we are dealing
with a disease of strawberries distributed perhaps on nursery stock
and thus becoming introduced and established in the fields.

Opposing this view is the fact that wild plants have been
found either killed out entirely or showing marked evidences of the
disease by the presence of lesions and rotted roots. These wild
plants have been found in many places in the state, and many cases
have been observed in locations where strawberries have never been
grown as a crOp. It will be remembered here that wild strawberry

patches arise from seedling plants, the seeds having been carried by

 

* Verbal communication to Dr. G. H. Coons by Dr. E. J. Butler Imp.
Bur. of hycol.

** Verbal communication to Dr. G. H. Coons by Dr. H. 3. Thomas of
Cornell Univ.

birds. This situation tOgether with the wide spread distribution of
the disease strongly indicates that the disease occurs more or less
irrespective Of soil types, and the cause is to be sought among the

naturally occurring soil organisms.

THE NATURE OF BLACK.ROOT

As has been said, examinations of the roots of plants affected
with black root showed rotted roots and various sized browned and
blackened areas, as illustrated in Figures 6 and 7. These lesions
indicate a parasitic organism as the cause.

The black root of strawberry had every earmark of a parasitic
disease. It has been pointed out that the situation was confused by
drought and winter injury. In order to determine whether we were
concerned with a disease caused by some parasitic organisms and not by
some soil or climatic factors, a series 0f preliminary experiments
were performed.

bead and dying plants typical of the black root conditions
were dug up and their root systems chopped into small pieces. This
mass of debris was placed in pots so that strawberry plants could be
grown with new roots passing through this material. A series of 19
pots were filled two-thirds full of clean sand, a one inch laver of
debris added, and the pot then filled with sand. As a control in this
experiment, pots of clean sand with no black root inoculum were em-
ployed. Also pots containing a layer of debris which had been steri-
lized by treating at 15 lbs. pressure for 30 minutes in an auto-clave

were used as additional controls. Young runner plants with root tips

10
TABLE I .

EFFECT 03' BLACK ROOT MATERIAL 0N YOUNG ROOTS OF STRAWBERRY:

Runners rooted (a) in clean sand plus black root '
materia1,(b) in clean sand plus autoclaved black
root material, (0) in clean sand.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Inoculated Control
(a) (b)clean sand I(o)
Clean sand plus plus autoclav— Clean sand
black root material ed black root
PlantHNo. ofllet No.01 Plant No. of Plant No. of
‘ _19_._ NO. :1 Ho. 149.1931
1 a 2 17 a 6 1 b O l o O
2 3 18 4 2 O 2 O
3 6 19 6 3 07 3 O
4 8 20 z 4 O 4 0
5 O 21 3 6 O 5 O
5 4 22 3 6 G 6 O
'l 2 23 3 7 O ‘7 0
a e 24 1 a * ?
9 rr9 4i :2 o
10 8 26 6 10 0
11 8 27 3 11 0
12 2 28 1 12 O
13 z 29 4 13 **5
14 7 30 4
15 4 31 9
16 o 32 z

 

 

 

 

 

 

 

 

 

* Plant 8 (b) had one suspicious brown stripe
** Plant 13 (b) had 3 typical lesions.

11

just showing were set into these pots. Erequent waterings were made
to keep the sand and debris inoculum moist. Examinations and readings
of the condition of the roots were made in about 14 days. The result
of the test as shown in Table I was conclusive. In this experiment
out of 32 inoculated plants typiCnl black root appeared on 29 while

in the sand controls, 7 plants remained healthy, as evidenced by the
white roots. The 14 plants inoculated with sterilized debris showed
11 plants healthy, 3 plants were noted as suspicious since they had
roots with slight discoloration which might be confused with t'ue
infection.* The great number of lesions appearing on the roots of
inoculated plants as compared with the clean plants in the sand con-
trols as well as the plants inoculated with sterilized debris indic—
ates quite clearly that the disease is infectious and transmissable
from one plant to another and parasitic in nature rather than attri-
butable to some soil factor or to winter injury. Examination with the
microscope of sections made from diseased roots gave abundant evidence

of septate hyphae in the root tissues.

ISOLATION OF THE CAUSAL Ogd;h 8X5
Lany plantings were made of bits of blackened roots in petri
dishes containing nutrient medium. haterial for use in making such
plantings was procured partly from strawberry plants sent in to the
Botanical section of the Experiment Station for disease diagnosis, and

partly from plants collected by the writer and others of the Botanical

 

* A plausible explanation or this might be that it is natural infect-
ion due to presence in a diseased field and in an open pot.

12

Staff in various parts of the state where strawberries are grown ex-
tensively.

Prune agar was commonly used as the medium for isolation pur-
poses since its slightly acid reaction discourages bacterial arowth.
Potato dextrose anar. cornmeal agar, and strawberry root agar were
also used. The technique of making these plantings was to wash the
roots carefully to remove the dirt. The roots were dried of excess
moisture on sterile paper toweling, split lenjthwise, the splitting
being merely initiated by sterile needles or forceps. Plantings were
made from the interior tissues now exposed and which had not been
touched by anythi a, in order that no contamination might be intro-
duced. flashing the roots with disinfectants was unsatisfactory since
no growth resulted from plantings made from materials so prepared.

The range of material employed and the number of plantings
made are believed by the writer to be extensive enouyh to afford a
fair sampling of black root material as it occurs in Kichigan and to
indicate the organisms chiefly involved. The isolations from diseased
tissue were extended over a period of nearly three years and involved
the making of more than 2,300 isolations from diseased plants collected
in various parts of the state. The fungi appearinr most often in these
plantings were: a species of Coniothyrium, a species of Gloeosporium,
and a species of Eusarium (brown). The first two appeared with great
frequency, the Busarium appearing more often in earlier isolations

than in the later ones. Other organisms appearing occasionally were:

13

Acrostalagmus sp., ared Fusarium, Pythium sp., as well as various

species of chor and of Penicillium.

TESTS OF SUS?E TED ORGANISfiS FOR PATUOGEKICITY
Following the isolation of Coniothyrium ep., Gloeosporium sp.,
and the brown Fusarium in plantings from diseased tissue, these or-
ganisms were secured in pure cultures and tested by repeated transfers.
Several series of inoculation experiments were set up, using them as

inocula to test their pathogenicity.

TESTS WITH FUSARIUfi (BROWN) SP.
Inoculation of Strawberry Runner Plants Grown on Agar

The first inoculation experiments were made in the greenhouse.
Runner plants were set in 500 and 1000 cc. Evlenmeyer flasks which
contained a solution of nutrient medium solidified with agar. This
medium covered the bottoms to the depth of about 2.5 cm. Following a
10 minute treatment in a 2--43 chlorozene solution to give surface dis—
°nfection and a rinsing with sterile water, each runner plant was
introduced into a flask so that the node where the root tips were
showing just touched the surface of th medium. Roots 3 to 4 inches
long developed in about two weeks. These roots were inoculated by
introducing bits of mycelial mats into the agar close to the roots.
The runners remained attached to the mother plants throughout the

entire period of the experiment.

14

In three series of inoculation experiments using the brown
Fusarium, infection amounting to an average of 44% resulted. Plantings
were made from bits of roots browned by contact with the inoculum, but
recovering of the Fusarium organism was not always successful. Infected
areas on the roots inoculated were not very typical of the black root
disease. Alth01gh a certain pathogen icity was indicated, decision is

reserved as to the importance of this organism in the black root disease.

MES 18 WITH CONIOTHYRIUX SP.
Inoculation of Strawberry R‘nner Plants Grown on Nutrient Agar
Coniothyrium sp., whicr was characterized oy the production of
black pyaiidia, showed up with considerable frequency on the isolations
made from diseased plants. This species produced infection on 4 out
of 5 plants groan on agar in a preliminary inoculation experiment.
The rotting of roots and lesions were typical of Black Root disease as

fOund in the field.

Inoculation of Strawberry Seedlings on Sterile Sand

his same organism was used to inoculate strawberry seedlings*
grown in deep culture dishes on sterile sand. In this exper 'ment, out
of 24 seedlings inoculated, 21 were infected. See Table II. In the

controls consisting of 42 plants, 2 were dead. These 2 plants showed

 

* Akenes of strawberries ripened the previous summer were disinfected
and sowed on sterile sand in deep culture dishes 6"--8" in diameter.
Due to the fact that the stravberry akene has a hard coat, it is
possible to treat it in concentrated su phuric acid for periods of
8--lO minutes without ingury to the young embryo. De Zeeuw (6) has
shown that this is the best way to sterilize such seeds as are not
injured by concentrated sulphuric acid. The percentage of germination
is also increased. Success in the use of this method lies of course

15

no fungi externally or internally. This is thought to be the natural
death of the plant due to lack of nutrition. Some time after the
death of the plants infected, ycnidia appeared on the roots, stems,
and seed leaves. These pycnidia were submerged in the tissue of the
host. Plantings were made of diseased seedlings, and the Coniothyrium

was recovered in pure culture.

ESTS WITH GLOEOSPORIUH SP.
Inoculation of Strawberry Seedlings on Sterile Sand

A brown acervulus forming organism identified as Gloeosporium
sp. also showed up quite consistently on plate isolations. In pre-
liminary inoculation experiments with this organism on strawberry seed-
linqs grown in deep culture dishes on sterile sand, 20 infected plants
resulted from 21 inoculated. The same controls were used as for the
inoculation with Coniothyrium sp. in the preceding section.

Infection takes place in shorter time than in the field due
probably to the ideal growth conditions for the fungi. The results
of the several series of seedling inoculations are arranged in

summarized form in Table II.

 

in the rapid addition of sterile distilled water after the removal of
the sulphuric acid. If addition of water is slow or the quantity of
water is not sufficient, heating will ensue. By using sterile pipettes
and growing in sterile sand cultures, the writer has been successful
in growing sterile seedling plants for as long as six weeks without the
entrance of any contamination. The seeds germinate and start growth

at once. They will grow to a height of about 2 to 5 cm. in from 8 to
15 days. When about this height and before they have to rely much on
their own food manufacturing powers, they were inoculated.

16

TABLE II

SUKMARY OF SEEDLING INOCULATIONS.

 

 

 

 

 

Inoculated with Inoculated with Control
Gloeosporium sp. Coniothyrium sp.
No. of Tim. Plants No. of i Plants“h No.0f m, Plants
Plants 9 Infected Plants T me Infested Plants ”me Infected
l2 13 12 46 13 0
days days
11 13 11
21 days 20 24 days 21 42 days 2 *
195 21 184 21 21
days 383 days 363 111 days 16 *

 

 

 

 

 

 

 

 

 

 

 

* These plants showed no fungi externally or internally.
This is thought to be the natural death of less vigorous

plants due to lack of nutrition.

FURTHER EVIDEKCBS OF PATHOGEKICITY
of
Coniothyrium sp. and Gloeosporium sp. for Strawberry Roots.

The next series of inoculations were undertaken in the field
where runner plants were set in pots filled with clean sand, (Figures
8 and 9) the purpose being to secure the natural conditions of plant
growth and yet avoid as much as possible the contamination from the soil
in which the mother plants were growing. In this way it was sought to

demonstrate for the two organisms shown to be capable of producing

black root under laboratory and greenhouse conditions, the production

17

of disease c0mparable to the field form of black root. The runner
plants remained attached to the mother plants throughout the entire
period of the experiments. The runner plants were selected before
any roots had started, so that all root production was made in the
clean sand. The inocula consisted of pure culture material of the
Coniothyrium sp. and the Gloeosporium sp. grown on various media,
prune agar, potato dextrose agar, cornmeal mush, and sterile rotted
manure. The chief method of inoculation was to introduce pure cul-
ture material of these organisms into the sand in the pots where the
runner plant roots were growing.

Early in these series of inoculations, spore suspensions were
used. Later mycelial masses were used in small quantities, and it
was found that inoculations giving the highest per cent of infection
and in the shortest period were those in which large pieces of mycelial
mats were laid against the roots.

At intervals of about 2 and 4 weeks the plants were removed
from the pots and examined. They were then either carefully reset or
were brought to the laboratory, photographed, and reisolations made
from the lesions.

The inoculation tests of August 2, 1926, have the most decisive
results of any, for in this series lesions in the control plants were
absent. The results of this experiment which followed the general tech—
nique just described are given in Table III, and show after a 12 day

period in the case of 13 plants inoculated with G13e05porium sp. 100;

18

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

anonoH o Hades nHOHuOH neH Haves uHOHnoH em Hayes
0 o n MH
0 o N NH
0 N HH HH
0 o mH 0H 0 m 9H 0H
0 n n m o H o m
o o o m 0 HH nH m o m m m
o o o h o H NH 5 o N m h
o o o m o 5 m o c n w o
o o o n o b e m o o o m
o o o w o v m w H m m w
o o o n o N w n o H o n
o o o m o w NH m N m m m
o o o H o m nH H o n H H
muoou muoou nuOOH «noon muoon npoou
mpoou nHuE HduoudH .oz nuoon anE Hwhmde .oz muoon anE HmumumH .oz
eouuom no no unnHm eoupom no so ande douuom no no uanm
unonoq anonoq mnoHneH mnonoa mHOHmoq mnoHnQH
mHthnoo .mm EdHumnpoHnoo .mn suHuommooOHw

 

 

 

 

38.2: he «73

.32 .N 63. .3sz game as .3 323385 no n33? .3584

HHH Manda

19

infection either in the form of lesions on main roots or on laterals,
or severe effects leading to rotting of the entire root. Similar
results were obtained with Coniothyrium sp. except that no roots were
completely rotted in the period of this test.

During the course of this investigation, many such tests were
made, all of them giving conclusive evidence of the pathogenicity of
the two organisms; ‘ut in many of these cases, especially with long
periods of observation, a small amount or disease deveIOped naturally
in the controls. The data of these tests being too extensive to be
given in full are summarized in Table IV a, b, and c.

The type of experiment possible under field conditions, if one
desires to work with plants as nearly normal as possible, is one in
which a medium free from infectious organisms is used for rooting the
runners. The possibilities of chance introduction of organisms on
the runner plant and from dust is considerable, and proper conclusions
from experiments with soil organisms, such as those considered here,
must be based upon the relative amounts of infection in inoculated
plants and the similarly handled controls.

It will be noted from a study of Table IV that in general the
control plants show a small amount of infection which is to be regarded
as casual infection which practically cannot be avoided in field work
of this nature. Comparison of this infection in the control plants with
the far greater infection found in the inoculated plants as shown in
columns 7 and 8 of Table IV a and IV b the writer believes to be con-

clusive evidence of the pathogenic nature of the two organisms.

20

TABLE IV a

SMMBY 0F INOCULATIONS OF CLEAN RUNNER

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PLANTS WITH GLOI'IDSPORIUM SP. SUMMER 1926
s 2 :2
f3 2 e “n" 33' 8 3;
H :1 H o o o o 7.:
a) M d 0 -H 4-7 H H o n 8 fl 9:
m ° '3. g 2 3 3-“. 3 2 '3 3 a .2 e
Date of a» 7.. 0 H5 H4: H043 no
N M an .32 22122 2°:
'*'3 'n-g .4 o Ins::3 $101 a o a *3
Inoculation cup. 50 dH “OH .2“: one on?
+3 H (D +3 A 91 H l-o D: 0 *d O 'H *0 O
2 2 2 2 ‘3 2 2 2 2 2 2 v n 2
H <3 a. 4 e. a? .4 «4
July 19% es
27 day gEaggng 40 27 104 2.6 .55 75% 4:1
July lgng
series 14 5 22 1.6 .32 80 5 1
10 day reading ‘
July 12%
1 * 2 4. .9 .66 9 10:1
37dday reazir as 15 1 10 6 0
July 216E
13 day reading 54 5 11 .2 .05 75 4:1
July let '
July 27th
10 day reading 25 13 72 2.9 .05 98 58:1
August 2nd
10 day reading 13 12 94 6.4 0 100 -....
Aug“3t and 13 13 113 8.7 2.50 71 3.5:1
29 day reading
August ith
s seried ---
8 day reading 19 15 117 5-0 0 100
August 233 series 6 5 75 12.5 2.5 80 5:1
27 day reading
KuEEit 17th 16
August 24th
14 day reading 18 15 142 8.0 2.20 75 3.5:1
octoberlggdserie 9 125 14.0 3.40 75 4:1
26 day reading
OctOberi dsggie4
Averages 6.9 1.4 72

 

*One plant rooted
**Ster

since first readi

this series of tests.

ng
le sand, sterile pots, and ditinfected plants used in

 

TABLE IV!)

21

SUMMARY OF INOCULLTIONS 0F CLEAN RUNNER

212525 1122 conxornnaruu SP.,SUMMER 1926.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8 u .§ 8 ”.3
A 3 06 g +7 8.45
on g 300 :3 3H 8 gag.
Dateof g3 ‘35:. ’53 3.3 .32 a g-H-g'd
a: vi :3» 4-7 0-H 430
an. 33 3 03%:1250912‘329
Immhtion a Fir-l 8 83 210.3 a:
-3‘H 'g o a -H 9.5. o s 10 3
OO 0 «PM 0 ethO'UOH-HO
5‘ “a 53° 5“ <8. 3 8‘68
8! a. .4334...
July 102th series ‘ '
27 day r5361 24 13 55 2.7 .65 755 4:1
July 10th’ 1 24 1 25 1 1 32 '71 3 4 1
10 dggreagim .8 1 ' ' ' '
July 1051:,r1
27 day 2nrea31ng °' 24 20 127 5.3 .66 67 6:1
July fem ies
15 day ranging 31 5 13 e42 005 89 80431
Jul? a§é§t’flii°' 31 31 560 16.0 5.3 70 3.4:1
Julia§n3t° {168 33 32 375 11.3 5.3 53 2:1
._;UL__JL_EL__1!;
August 2nd, .
12 day reading 10 10 143 14.3 0 100 -—-
August 24th
14 day reading 16 14 145 6.0 2.2 72.5 4:1
Date 6 2nd *’
6 5 100 15.6 3.4 79 5:1
263.7%.
* °°t°fl 1 10 117 11 7 1 5 66 7 1
26 dgzreaiii 0 ' ' ’
Average 8.9 120 78.2

 

“ Sterile sand, sterile
this series of tests.

pots, and disinfected plants used in

 

TABLE- IV 0

SUMMARY OF CONTROL PLANTS

 

 

 

 

 

 

 

 

 

 

 

 

 

SUMJER 1926
n
8 ..
2 5 2 5
s. ,3 '*
Date of E 0 cl '5 cm
Fl «1 h 3 u a g H
corresponding 3 “33 o 3.5 g 2 3’ p. g
inoculations 0 g ‘3 H u 3 2 3
July l?§§'series 5 3 4 .66
27 day reading
July £3 h8 ies
12 day mains 3? 66 6 .32
July let
13 day reading 39 2 2 .05
July 213t ' . 47 38 247 5.30
35 day reading
August 2nd
10 day reading 9 0 0 0‘
August 2nd
29 day reading 9 2 22 2.50
August 17th. .
14 day reading 29 5 11 .37
August 24th
14 day reading 27 12 53: 2020
October Egg series 7 7 24 3.40
26 day reading
October 33:15: 2 0 32 1 60
26 day rea ing 3 1 0
.Average 1:40

 

 

 

 

 

‘.Iight plants rooted since first reading

“ Sterile sand,sterile pots, and disinfected plants used in this

series of tests.

 

23

The data compiled in columns 2, 5, and 4 are from actual records
made in the field. Column 5 is obtained by dividing the total number
of lesions by the total number of plants inoculated. Column 6 is ob-
tained in like manner for the control series or the experiment. The
seventh column shows the percent of infection in the inoculated plants
of a series which properly is to be attributed to the inoculation. These
percentages were obtained in each series by finding the difference
between the averafle number of lesions per p.ant in the control and the
average number of lesions per plant in the particular series 0: inocu-
lated plants considered. This difference divided by the average lesions
per plant for this particular series of inoculations giv s the percent-
age of infection that may reasonably be attributed to the inoculation.
Expression of the results in this way avoids the distortion which would
arise if the infection was based on the number of plants showing a
blackened or discolored area on the roots. A control plant shovinfi one
lesion would be riven equal weifiht with an inoculated plant which might
have 10 to 20 or more lesions.

Column 8 shows the increase in infection in the inoculated
plants to that found in the control.

The lesions and rotted roots found and recorded on the inoculated
plants were identical in appearance with the lesions and rotted roots
found on plants which were growing in cultivated strawberry fields and
on wild plants. These lesions at first are brown shriveled areas

usually encircling the root and having white healthy root tissue adjoin—

24

ing. These lesions were seen to increase in lenwth until an entire
root was involved.

Severe infection followinc inoculation with small pieces of
mycelial mats of Coniothyrium sp. is shown in fixure 10. Iiid infection
following inoculation with a spore suSpension of the same organian is
shown in El are 11. bevere infection following inoculation with Gloeo—
sporium sp. is shown in figure 12a, while early stages of infection are
shown in figure 13. Typical control plants are illustrated in Figures

12b and 14.

HISTORY OF C, 7L IRES

In making the inoculation tests upon runner plants in the
field as further proof of the pathoyenicity, part of the pure cultures
used of the two organisms Uoniothyrium sp. and Gloeosporium sp. were
recovered from infected seedlings inoculated with these two organisms
earlier in the season. In each case infection followed and typical
black rcot disease lesions were demonstrated on the roots. The respect-
ive organisms were recovered in each case. Chart I gives a graphic
representation of the history of one Coniothyrium culture.‘ Similar
histories could be shown of other cultures of this organism. chart II
shows similar representation of the histories of cultures of Gloeo-

sporium sp. orlginatin: from different parts of the state.

25

GEAR! I

CON/OTHYRVI/M 5}.

[Hanf show: :9 ‘l

 

 

typical [exam Key
[3 [nocu/af'iOn s
' on flanfs
. by-“ Tssuc F/qnf—
O"? 5 In ,7: fr;
dis/ms
27816 . Tuf nix
cuff qrcs
A F/flflf Cal/fans
0M” W/Ifljs I I I 4,00%
Inflcfioq
Fake/of)»: . . . ‘V‘lz'l‘
l A A Haze 710-26 _ 81129

//A\\\ l\ -.....
Illl\\\

Chan 8-2- 26
Winner -.'-:-.-- Inge? ion

 

 
    

774,773 ."""§\1n207::wn I . I I.;§02:q
W¢1500“..£. 8W.“ [fife
afions :.H..:g 8 lb 2‘ gran-c cu/furcsfl'

Asipum culfuresf

a: Numerafor= re; solar of
Canoofhyr/ ( 5
Denom/ pa‘for :f/anf/z. .75 I77 I /

 

 

 

 

Graphic Representation of the Proof of Pathogenicity
of Coniothyrinm sp.

26

CHART II

A? 83338on «c

hpfioanowonpwm mo «3.8 on» no 33353.33.” adage

.Q‘Q.‘ “NQ{CQ\K hi¢§efi~£0£§q
. n ‘JsLOKoOCOxW \O
tsfiéonst u LokQLfik~3>\
L.

Q0
fl «~k3\\3u “(six 0; 30 Q.»
oumo g t unfit Mn.
QNfix.“ not 0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

3 3
sweeti— _ 32 kc O
waivw
” a ‘ .fiOiN- “0* “
~.N.§ .\L.\’\ §.\ n tsO
«Nflxk {5.x o3. a. K
mtfixk ta\9 CQ
»~.MN..« «to .xQxCOtN D
Mx ‘N‘Nfi CNN?“ K
.4 want}... {wk u. \ka 32¢an 8
«firm cohg. x
. $3“. 3.9m
. tscusxtN
tfikuOXQN t0\ 0. ON . UN.) 33%.“
3&9 .quwhm— _ 4 _
tsxqutN
‘~.‘u§ 9~.\‘.° 9N.N\IK
“N .0} Q 9N.Q\.9 QN.N.M ¢~.hN.Q
«52*
35-9 3.5% $.03 3&8... 3o? é
eons“ tit“ kkentouw o\o\\fl .so\< n3V¢0

a. tsEomnEQ G

 

27

ORGAIIISMS INVOLVED
The organisms which from the writer's work seem chiefly to be
concerned in the black root disease of strawberries are two Fungi
Imperfecti, as yet unidentified with any known species and possibly
representing forms as yet undescribed. The following brief character-

izations will suffice to record their salient characteristics.

COHIOTHYRIUX P.

The pycnidia are ovoid to pyriform with a definite round ostiole,
without prominent lips: black when filled with spores, but appearing
dark brown after the spores are discharged. Valle thin almost membran-
aceous. Pycndia 160 microns to 300 microns in height and 140 microns
to 170 microns in diameter.

Spores exuding in an inky black mucilagenous mass which accum-
ulates at the apex of the pycnidium. Seen singly the spores are ful-
iginous one celled short ellipsoid to ovoid, rounded at both ends and
usually Z-guttulate. Size 3.8--4.8 microns x 2.7--3.7 microns, average
4.2 x 3.1 microns.

This species does not appear to be the same as Coniothyrium
Eragariae Oud. which is described as having somewhat larger spores, 11.6
x 9.3 microns.

GLOEOSPORIDJ SP.

Acervuli on tissues of the s rawberry plant 70--130 microns in
diameter, cup shaped to saucer shaped when young but becoming flattened
with age.

Spores produced singly on the ends of short conidiophores. As
the mass of slime embedded spores increases the later conidiophores
elongate to penetrate this mass to its surface so that eventually, when
the spores are washed away, an old acervulus shows a mass of long
slender conidiophores 40 to 50 microns long. Spores hyaline, one
celled, slightly curved oblong, rounded at one end, slightly pointed
at the other, 6.6--9.9 microns x l.8--2.6 microns, average 8.6 x 2.2
microns. In mass the spores are a very pale brown. No distinct setae
are present on the acervulus.

Note: When grown in culture the acervuli are often considerably larger
than those described above, reaching a diameter of over 300 microns,
but the spore size remains the sane. The shape of acervulus and the
fact that in cultures the basal tissues are rather thich and the pro-
duction of the elongated conidiophores of the older acervuli are not
typical of the commoner species of Gloeosporium but pending further
cultural studies and studies in the field, it seems best for the pre-
sent to designate it by this name.

28

'l‘FJiPBlATURE REE!“ 10:38 013‘ THE TWO ORGl £181.25

in order to find the optimum temperature for nycelial growth
and spore formation a te perature apparatus was set up and arranged to
run with nine compartments giving a gradual rise in temperature frOm
7 C. up to about 40 O.

A set of nine prune agar petri dishes was made having four
cultures of Coniothyrium sp. per plate. These cultures were started
from plantings of small bits of mycelium. A similar set of plates was
made using Gloeosporium sp. Spore droplets were used in this case to
inoculate the plates. The results of this experiment at the close of
the seven days are shown in Table Va and Vb.

In this one series of experiments the optimum temperature for
growth of mycelium was around 22--25 C. for the Coniothyrium with a
maximum diameter of 4.5 cm. for colony and about the same for the
Gloeosporium. Spore formation was limited to around 22 C. for the
Conictryrium wnile spore formation occurred freely over a wider range
_of temperature, 20.5--22.5 0., for Gloeosporium. These figures are

tentative only and require further experimental work for verification.

ROOT TREATIiIT BIPERIKJWTS
Attempts were made to find a root treatment which would be
effective in checking or completely controlling this disease. The
first experiment involved the use of two chemical compounds in regular
use as fungicides, viz: mercuric chloride and formaldehyde. Also two

organic mercury compounds Semesan and Uspulan were used.

29

TABLE V a.
TEMPERATURE RELATIONS 0F CONIOTHYRIUM SP.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Av. H H
Temp. Mycolial growth Spore formation_
Trial Trial iriai Erin Tria Trial hriai Trial
.1. 2 L 4 a 2 a 4
5.190 . 3 1 3 3 "' " ' '
10 4 6 ‘ ‘ . . - - - "
14.5 *¢ 44 44 44 - - - _
16 o O ” “ +44 44 - ‘ 4 -
20.5 444 444 444 44 4 - _ _
22.0 444 444 4444 444 44 4 44 44
22.5 44444 44444 444 444 4 - - g
25.5 H 4444 4444 44444 44444 4 4 4 -
39 o 5 fl - C ‘ . o C n -
TABLE V b.
TEMPERATURE RELATIONS OF GLOEOSPORIUM SP.
A74 T
Temp. chelial Growth Spore Formation
WWW—T171317 WWW-ff”? 1 '
6 . 000 § . O O a i - -
10. 6 'H‘ “ “ “ - C - -
14.5 ‘*‘ 444 444 444 4 - - -
16.0 4444 4444 4444 4444 4 4 4 4
20.5 4444 4444 4444 4444 444 44 44 44
22.0 44444 44444 44444 44444 4444 444 444 444
22.5 44444 44444 44444 444444 4444 444 444 444
25.3 4444 44444 444:4 444 4 4 g g

 

 

 

 

 

 

 

 

 

 

N0 growth or no spore formation are indicated by -, a slight
growth of mycelium or a small production of spores is
indicated by 9; greater mycelial growth or spore formation
are indicated by 44 , 444 ’ 4444 etc.

J
A
4
5.4
vvo
4-
l
,.
.5.
6»:
4-4«
‘2
IT
2‘.'
”t .4.
{
19-94

41

4

J!

4.

3.

d.

These compounds were dissolved in water in various dilutions,
and the plants plunged up to the crown in the solutions for periods of
30 minutes. These plants were then rinsed in tap water and set out
in the experimental field. As controls every third row was planted
with rows of untreated plants. Each treatment appeared six different
times in the field nine rows apart. The Senator Dunlap variety of
plants was used in four repetitions of the treatments while the Pre-
mier variety was used in two of the repetitions. Results do not
warrant further details of the experiment. A condensed form of the
results is given in Table VI. Three months after the plants were set
sample plants were taken at random from all treated and untreated rows,
and the root systems examined. Lesions and rotted roots were as abun-
dant on the treated plants as on the untreated.

A second attempt to use a chemical compound to contr:1 this
disease was undertaken. in this case copper sulphate was used. The
purpose of this experiment was to endeavor to partially sterilize the
soil to eliminate some or all fungi and yet not make the soil toxic to
root growth.

Old rows of strawberries where killing was severe were selected,
and the tops of the plants were hood of: even with the surface of the
soil. The rows were then thoroughly dug and ChOpped up to a depth of
5 inches and a width of about 15 inches. These longer rows were then
divided into seven short rows each 15 feet long. Cepper sulphate sol-
ution was sprayed evenly over Plot #1 with a compressed air sprayer so

that the plot received 10 gms. copper sulphate. Each succeeding plot

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

.. .. .. .. «3:83 33. 8m 2: Hosanna 2
.. .. .. .. .. .. 8m 02 .33 on com} 33...: m
.. .. .. .. and: :3 8.... 03 an. on 84> 33%: m
.. .. .. .. 33333 83. com 2: 233° a
.. .. .. .. e332 nice 8... 8H .5... on com} .3.an o
33. :8
.. .. .. .. 33. 35 8a o3 .32 on 8...} 3.8% u
.. .. .. .. 232.33 one». 8m 03 33:8 4
.. .. .. .. .. .. .. 8m 2: 5a 3 3m} omen »
.. .. .. .. .83 to» and: 8m 2: .53 3 82) «8 mm a
uuoou no «defined hare aaoanoouo wanna oom con Houpnoo H
Specs n .393 32 Apnea...” noun. an... manna nods-um :3»
2.433 .3303 an Inga 38340.5 tom

 

 

353 no .3

 

 

 

 

 

.Boom Moan Mom domufioo m4 wage 30m .3 mama

A; as

 

32

received an additional 10 gms. of copper sulphate up to the fifth plot
where 50 gms. of c0pper sulphate was applied. The sixth and seventh
plots were not treated. The plots were well watered after application
of the copper solutions. The next day runner plants having an average
of three 2--3 in. roots were set into these plots, 25 plants per plot.
The results of this experiment show little if any control of
the disease infection. On inspection of the root system three weeks
later, lesions were as prevalent on the plant roots from the treated
plots as on those in the untreated plots. Furthermore the harmful
effect of the copper solution was shown in the heavier treatments. In
the 40 gm. per plot treatment the formation of lateral roots was in-
hibited while in the 50 gm. per plot treatment distinct injury of the

larger roots was evident.

DISCUSSI N

Evidence is presented of the parasitic nature of the black
root disease of strawberry, and the proof is given for assigning the
disease to two organisms, Coniothyrium sp. and Gloeosporium sp. The
role that climatic factors play in aupmenting the effects inaugurated
by these organisms has been mentioned.

As has been shown, black root is to be found generally dis-
tributed in strawberry plantations in Kichigan. The two organisms
whose pathogenicity has been demonstrated have been isolated from
strawberry roots gathered from many places more or less distant. The

similarity of the lesions found on cultivated and wild strawberries

mahes it seem possible that the wild plants also are affected with a
black root disease of the same nature as that of the cultivated plants.
This suggests that these fungi may be soil organisms of wide distribu-
tion. The fact that in this study two organisms have been found, each
capable of producing typical black root conditions, together with the
fact that the literature of the disease shows other organisms assignable
as pathogens, makes it seem probable that the black root conditiOn in
strawberries may be the result of attack by any one of several pathogens
perhaps naturally occurring in the soil.

The host range of the organisms isolated in this work is not
known. it would be natural to expect them to attack plants closely re-
lated to the strawberry and probably other plants. 30 evidence of
disease has been observed on plants of the genus Potentilla.

Although some work has been done on the control phase, the
treatment of roots has not been successful as yet in checking the dis-
ease. If the organisms causing this disease are shown to be wide
spread, root treatment will be useless. Whether these organisms and
others which may cause the disease were originally spread by diseased
plants which deve10ped in nurseries cannot be said. This is possibly
not the case, but it behooves the growers of plants for sale to fur-
nish as strong, vigorous, and healthy plants as possible. The grower
who sets plantations for the fruit crop must select only this kind of
plants for setting. The practice of setting a plantation in the spring,
harvesting the one crop the followinr year, and plowing up the plant-

ation is one to be recommended. Another control measure to be recom-

34

mended is that of rotations. This is the setting of plantations on
land where strawberries have not been grown for some years, or if
possible where strawberries have never grown. The leading nurserymen
practice this method to obtain as vigorous and as healthy plants as
possible. The ultimate control is as with so many plant diseases, to

be sought in the selection or breeding of disease resistant plants.

SUMMARY

1. Black root of strawberry was found from reports in the
literature and collections, to be a widespread disease 0f cultivated
and wild strawberries whose etiology had not been shown.

2. By inoculation with strawberry debris, the parasitic nature
of the disease was determined and microscopic examination showed con-
stant association of fungus hyphae in the lesions.

3. Coniothyrium sp. and Gloeosporium sp. have been isolated
many times from typically diseased roots and their pathogenicity to
plants grown under controlled conditions has been proved.

4. In several series of field inoculation tests using runner
plants, the typical disease has been produced by each organism leaving
no doubt of the etiolOgical relations of these two forms.

5. Technical descriptions of these two species of organisms
are given.

6. Treatment of strawberry plants with standard disinfectants
before setting did not control black root.

7. General control measures such as would make for strong vig—

orous plant growth are recommended. Ultimate control of this disease

will doubtless depend on selection of resistant strains.

”5
b)

1. Berkeley, G. H., and Jackson, A. B.
Strawberry Black Root Abst.
Phytopathology 14:348 1924

2. Berkeley, G. H.
Rept. of Dominion Field Plant Pathologist, St. Catherines
Ont.
dept. of Dominion Botanist
1924

3. Clinton, G. P.
Notes on fungus diseases, etc. for 1905.
Report of Connecticut Agr. Expt. Sta.
Report of the Station Botanist 1905:263-277 P1. 13-19.l906

4. Coons, G. H.
Black Loot of Strawberry Mich. Agr. Expt. Sta. Quarterly
Bul. 1:1:25-26. 1924

5. Darrow, G. n.
Essentials in Strawberry Culture. American Fruit Growing
Magazine 46 (4):9,42 (5) 7, 23 (6) 7, 18, 19 (7)
7, 26 (8) 8, 26, several figares 1926.

6. deZeeuw, Richard
The Comparative Viability of Seeds, fungi, and Bacteria
when subjected to Various Chemical Agents.
Centraiblatt fur Bakterologie 51:4—23, 1 fig. 1911-1912

7. FletCheI‘, So 2"].
Strawberry Growing xvii plus 525 pp. 24 P15. 22 Figs.
Mackillan Co. 1922

8. Heald, F. D.
Report of Division of Plant Pathology
29th Annual Rept. Wash. Agr. Expt. Sta. 1919
Vash. EXpt. Sta. Bull. 155:54-58. 1920

9. Neal, D. C.
New rlant Diseases in mississippi.
36 Annual Rept. of Miss. Expt. Sta. 1922-23. 1925:34-35. 1923

10. Sherbakoff, C. D.
Three Little Known Diseases of Strawberries.
(Abs.) PhytOpathology 14:60 1924

36

ll. Smith, E. H., and Horne, J. T.

Olericulture. Rept. of Calif. Agr. Expt. Sta. 1921:87-89
1922

C o I“! o

The Strawberry Disease in Lanarkshire

The Annals of Applied Biology 14:197—201 1927

12. Wardlaw,

37

' :TIPLAILlTIC‘E-I or PLATES
Plate I

'dgmel.
A 20 acre plantation near Edmore, Iichigan, showing effects
of black root.
Figure 2.
Plantation near Bridgeman, Rich. showing effects of black root.

Plate II

Figure 0.
Typical disease plant succumbing to biac: root.

Plate III
Figure 4.
Badly diseased plant from Edmore plantatiOn showing
root production from blackened roots.

F“
{J
C+
(D
”‘3
Sv
.._3

Plate IV
Figure 5.
Early stage of black root showing rotted roots and lesions

~--‘ 3 ‘r s! n
from Lahore, mich.

Plate V
Figures 6 and 7.
Typical lesions and rotted roots.

Plate VI
Figures 8 and 9.
Runner plants potted in clean said, inoculated and controls.

Plate VII
Figure 10.
Severe infection following inoculation with Coniothyrium sp.

Plate VIII
Figure 11.
Infection following inoculation with snore suspension of
Coniothgrium sp.

Plate IX
Figure 12a.
Severe infection following inoculation with Gloeosporium sp.
Figure 12b.
Control plant

Plate K
Figure 15.
lnfect'on following inoculation with spore suspension of
GlOeosporium Sp.
Plate XI
Figure 14.
Control plant.

PLAT! I

I-Vf'g'f -. v.
' "Q

s»

 

PLATE II

, \/-;, ‘ ‘
.‘, 1‘s,

, |
I"!
'\

\

 

Figure 3.

PM!!! III

 

 

Figure 4.

PLATE IV

‘

 

 

Figure 5.

 

PLATE V

 

 

 

PLAEE VI

 

PLATE VII

 

 

Figure 10.

PLATE VIII

 

 

Figure 11.

PLATE I!

 

 

Figure 18.

PLATE X

\ “‘m‘x
"S
‘5 1 ‘
/ I f
w,
9' _r' ,
H‘
z. r
l
V
1
r/
L
l”"
;‘ 43“
L . "

 

Figure 13.

PLATE XI

j
i.» '

 

Figure 14.

 

VOA-.1} u
3.4.}. D

.\.

.. .lll.