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THESIS

 

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Studies on the Sunflower Rust, Puccinis helisnthi schw.

 

Thesis Presented for the Degree of
Master of Science,

Michigan Agriculturel College.
ACKNOWLEDGMENTS «

The writer is grateful to Dr. E. A.
Bessey and to Dr. G. H. Coons for advice
and helpful suggestions given throughout
this study and for the criticism and

correction of the manuscript.

LOZO99
Table of Contents.

Introduction.
History of the Sunflower (Helianthus annuus Schw.)
Economic Importance of the Sunflower.
Uses of the Sunflower.
Importance in America.
Importance in Hurope.
Economic Importance of the Sunflower Rust.
History and Distribution of the Sunflower Rust.
Signs of the Disease.
Spring.
Summer.
Fall.
Life History of the Causal Organism.
Previous Work.
Methods of Study.
Identity of Species.
Life History.
Morphology.
Myce lium.
Pycnia.
AC@C1O&.
Uredinia.

Telia.

Promycelia and Sporidia,
Table of Contents (continued).

Name of the Causal Organism.

Germination Studies.

VJintering and Dissemination of the Parasite.
Trash.
Wild Sunflowers.

Varietal Resistance.

Control.

Conclusions.
Introduce ti one

The swmflower, long playing an important part in
the agriculture of Northern Europe, has become recently
a crop of great promise for the Northern part of the
United States and Southern Canada. Widespread interest
is being shown in the crop and the acreage is increasing
rapidly. Its usefulness, however, may be somewhat impaired
by a disease which sometimes reaches the proportions of
@ serious epidemic. The purpose of this paper is to bring
out some little known or doubtful points and some new

facts concerning this disease, the sunflower rust.
History of the Sunflower (Helianthus annus Schw.)

Helianthus annuus is recognized as a native of North
America with a natural range of distribution extending
southward to Peruse Palmer, in his article on the food
products of the South American Indians, says the seeds of
sunflower were often gathered and “being very sweet and
oily they are eaten raw or pounded up with othe substances
made into flat cakes and dried in the sun, in which form
they appear to be very palatable to the Indians". Cham-
plain in 1615 found Indians of Georgian Bay cultivating
the sunflower and using the oil obtained on their hair.
-2-

The earliest record of the sunflower appears to be in
a history of flowers by Rembert Dodoens (15) which was
published in 1568 at Anvers, France. Dodoens described and
figured Helianthus annuus here for the first time under the
name of Peruvian Chrysanthemum as one of the new and curious
plants to be found in the Royal Gardens. He received the rare
plant from a friend in Spain and he states that the plant
is reported to have been found in Peru and in several other
provinces of America. About this same time the plant was
introduced into Italy where it grew to enormous stature,
if the reports of Jacob Antoine Cortusus, a noted physician,
are to be believed, attaining a height of forty feet.
Cortusus (15) reported, after a successful trial, that "the
leaves are very tasty when scraped to remove the hair, cooked
on a grid iron, and prepared with salt and oil, also the
flower receptacles similarly prepared are more delicate than
the bracts of the artichoke." Monardes (15), a doctor of
Seville a little after Dodoens described the sunflower and
recommended it to embellish gardens and showed that the plant
was getting fairly common among the collectors of plants
in the gardens of France. Charles de 1*Escluse in his work (14)
on the Exotics (1605) described the sunflower and stated that
for several years it had been commonly known by all Europe.
He distinguishes two species, the one unbranched and single
flowered, whide the other was much branched and many flowered.
Fragosus de Toledo, a Spanish botanist, gave a very complete

description of the sunflower in his Rapsodies (17). In the
~Za

Universal History of Plants by Jean Bauhin (7) is found

@ resune of the observations on the sunflower by the
various writers at the end of the sixteenth and the
beginning of the seventeenth century. Jean Bauhin called
it Herba maxima, the largest herb, and adds that Lobel
gave it the name of Gigante in Portugal. He accepts with
Cesalpin the name Flos Solis. Gaspard Bauhin, in his
Phytopinax, remarked on the variability of the plant in
size of flowers, its leaves, the height of its stalk, and‘
the number of its flowers (6). He observed that the flower
is sometimes white.

Jean Bauhin in a later article added that he grew both
the small and the large variety, and mentions also another
very small variety which had a multitude of flowers.

We find the sunflower entered by Guy de la Brosse in
1636 in his "Catalogue of Cultivated Plants in the Garden
of the King" under the name of Peruvian Chrysanthemum or

Flos Solis, and also a Chrysanthemum Peruviarum proliferum

 

which appears to be Helianthus multiflorus L.

In their Amateurs’ Manual of the Garden (12), Decaisne
and Naudin state the Great Sunflower or Tournesol is somewhat
naturalized in Europe and from it have arisen several
varieties which reproduce their seed, among others is men-
tioned the giant variety, the double varieties, etc. |

From France the sunflower spread northward as it

became acclimatized (for the first sunflowers brought into
-4-

France would not mature their seed there) until it was
first grown in Russia in the Province of Woronesh 1830-1840,
authorities differing on the exact date. They were first
grown on a large scale, according to Woronin (33) in a
peasant's garden in that provinee in 1841, the peasant
pressing their seeds for oil. This was the start of the
great sunflower oil industry which began to make the farmers
of the region wealthy as the demand for the oil grew and
the price increased.

Economic Importance of the Sunflower

(Helianthus annuus Schw.)

Uses of the Sunflower-

Sunflowers have been cultivated for many purposes since
the Indians were found cultivating them for their seed and
oil early in the seventeenth century. They have been widely
used as an ornamental, while the seeds are a valuable food
for birds and poultry and are used by horsemen as a remedy
for heaves. In Europe the table oil was made by cold
pressing the seeds and is in demand, and the seeds themselves
are eaten raw or roasted like the peanut in this country.
The oil, states the Scientific American (1) that is not
suitable for edible purposes is used for burning, for soap-
making, and for an inferior varnish oil. Immense quantities
of oil cake are produced in Russia and shipped to Denmark
where it is popilar as cattle food. The stems may be used

as a source of potash for the ash of the stems contains
-5-
39% K.0 and the seed husk 56%. An acre of stems will
give from 40 to 50 pounds of potash, according to the
Scientific American. The pith of the swmflower stalk has
long been used by French surgeons as a moxa and it is now
used extensively as a substitute for other materials
formerly employed in making these moxas for cauterizing
purposes. In 1915 a new utilization of the sunflower pith
became generally known through another Scientific American
article (4) on "The Lightest Known Vegetable Substance".
The pith of the sunflower stalk is this lightest known
vegetable substance with a specific gravity of 0.028, while
the pith of the elder is 0.09 and cork 0.24. This discovery
has essentially increased the commercial value of the plant.
The pith is now carefully removed from the stalk and applied
to many important uses. One of its chief uses is in the
making of life saving appliances. Cork with a buoyancy of
one to five, and reindeer's hair with one of one to ten
have been used; the pith of the sunflower has a buoyancy
of one to thirty-five. This new material is being used in
the construction of boats and life preservers. A sufficient

amount can be worn on the person without any inconvenience.

Importance in America-

There are three important seed producing areas in the
United States. These are southeastern Missouri, southern

Illinois, and the San Joaquin Valley of California. The
=-6-
United States Department of Agriculture Market Reporter (2)
estimated the 1920 crop in these three areas to be 9,850,000
pounds.

The greatest importance of the sunflower in America,
however, lies in its use for silage. United States Experi-
ment Stations commenced to report experiments with sunflowers
for silage in 1883 at New York, in 1893 at Vermont, and in
1895-1896 at Maine, while the first Canadian report was in
1893. Most of the investigators have obtained a larger
yield of sunflowers (total crop) than they did of corn, but
the early investigators did not ensilo the whole plant,
having the idea that there was little food value in the stalks.
Canadian authorities reported that butter made from the sun-
flower silage had a richer flavour and higher color than
that from corn silage. Since these early tests, but little
investigation has been made until recently through small
trials were reported by New Hampshire, Nebraska, Colorado,
and a few other states. In 1915 the Montana Station grew
a small acreage under irrigation with such success that
the planting was enlarged in 1916 and the preliminary tests
described in Bulletin 118 of the Montana Station demonstrated
the high feeding value of sumflower silage and resulted in
a widespread interest in the crop. Numerous other states
as well as the United States Department of Agriculture
have since been experimenting extensively with it as a silage

crope Their value in any region depends on the success to

be had in that region in growing other crops. Vinall, of
Pe
the United States Department of Agriculture, made an
extensive study into the problem and says: "Sunflowers
Will not supplant corn in the corm belt nor sorghums in
the central and southern Great Plains because these silage
crops.do so well in supplying the need for a silage crop
under their own climatic conditions." "In the same way
the sorghums and millets supply the southeastern states.
However in the extreme northern part of the United States
or at high altitudes in the ‘lest where the temperature
during the growing season is low, corn, sorghum and the
millets do not produce heavily and in these regions sun-
flowers are being recognized as an extremely valuable silage
crop and the acreage is increasing rapidly." It is probable,
gays Vinall in his U. S. Bulletin on "Sunflower as a Silage
Crop" (32), that sunflowers for silage will become widely
grown in the New England states, northern New York, Michigan,
Wisconsin, and Minnesota, in North Dakota, Montana,
Washington, and Oregon, and also in some of the high valleys
of the Rocky Mountain region such as the San Luis Valley of
Colorado. Sunflowers are frost resistant so that they are
green two or three weeks after corn has been killed by the
frost. The crop has been successfully grown on sandy soil
in northern Michigan and on poor clay soil in West Virginia
while the best yields are made on rich clay loams with
abundant humus. It is the coming forage crop north of the

frost line where good yields of corn are not obtained.
-8-<

One of the problems of this area north of the corn
belt is to find a suitable cultivated crop to place in
the rotation; another is to raise a sufficient tonnage
of succulent feed to make the raising of cattle possible.
The sunflower answers these problems and is rapidly inoreasing
in acreage. It practically pushes the frost line 50 miles
north and extends the cattle feeding and dairy industry

above our northern boundary into southern Canada.

Importance in Europe-

In northern Europe the sunflower plays a very important
part, especially in Russia, as one of the important crops
of the region and rated by Karsin as equal in importance
to the sugar beet. Oil production from the sunflower is
on an enormous scale there. Data from the city of Saratov
given by Karsin (19) shows that the first factory was founded
in the forties. By 1888 there were 33 l# rge factories,
equipped with British and American presses, which produced
over 28,800,000 pounds of oil. By 1893 the production
reached 54,000,000 pounds of oil from 238,000,000 pounds
of seed. The value of the 1894 crop was 7,382,050 roubles
or over $3,800,000 at the pre-war rate of exchange, the
farmers receiving about 17f per pound for their seed
( 1 rouble 17 kopecks per pood). In addition to the oil
production, the oil chke production reached 66,000,000
pounds in that year from the city of Saratov. Practically
—Qe
all of this oil cake was exported, giving employment to
@ considerable number of ships. Saratov leads in oil
production so that these figures represent about 80% of
the total Russian production. The production was consider-
ably curtailed during this period, as willbe show under
the heading "Economic Importance of the Sunflower Rust"

by the epidemics of rust.
Economic Importance of the Sunflower Rust.

The one factor which may partially offset the advan-
tages and limit greatly the value of this new crop is the
sunflower rust. The exceedingly strong parasitism of this
fungus kills the lower leaves and in severe attacks all
of the leaves. This causes a great loss of sucoulence and
of the tonnage of silage. In the feeding experiment
conducted at the Michigan Experiment Station in 1919 by
Brown (3), the sunflowers were very severely rusted and
the crop harvested so late that there were very few leaves
still green upon the plants. Accordingly, in his experi-
ments, the feeding value of sunflower silage made from
these bare stalks was not as high as other investigators
have found them to be.

In addition to the loss of succulence, there is a
drain upon the plants from severe attacks of the rust
which results in a poor filling of the heads and a conse-
quent lowering of the fat content in the silage.
-10-

The most severe and most economically important
attack of the rust fungus on the field sunflower occurred
in Southern Russia in 1866-1868, in the province of
Woronesh. At the time the epidemic struck the province
the farmers were becoming wealthy from the great develop-
ment of this comparatively new industry. large fields
of from eight to sixteen hundred acres were planted to
sunflowers for oil-seed production. Then the farmers
began to have crop failures due to the rust parasite and,
says Woronin (33), "In 1867-1868 the disease took on such
frightening proportions that it was necessary to throw
away the harvest of entire fields and to substitute other
crop s----so0 that where sunflowers grew in areas of
hundreds of acres in stretches of several miles, now
in 1872 one meets with but an occasional small field in
a twenty-five mile drive.“ The province never entirely
recovered from this blow to the sunflower industry, for
although Woronin made a careful study of the parasite and
aivocated some control measures, these were not put before
the people in popular form and no control measures were
adopted.

Thirty years later Karsin (19) writes that the sun-
flower had spread into the province of Saratov where it
began to be cultivated on an enormous scale. For a few
years the sunflower yielded well in Saratov, then the

rust reached a serious state of epidemy in this province

just as it had previously done in Woronesh. Karsin says
-ll-

in 1896 (19) that "during the previous ten years there
were five poor crops, two medium crops and only three

good crops",
History and Distribution of the Sunflower Rust.

A rust on sunflower was first observed and described
by Schweinitz in 1822 in his Synopsis Fungorum of North
Carolina. He described there the aecial stage as an
Aecidium (27), the telial stage on Heliopsidis and Vernoniae
as one species (28), and the telial stage on various species
of Helianthus as another species (29). Sunflowers, due to
their varied uses, are widespread in their distribution.
"They are grown throughout North America from Canada to the
Canal zone and in most of South America, but more especially
along the west coast from Columbia to Chile. Sunflowers
are also grown to a limited extent in Australia, New Zealand,
South Africa, Egypt, the Mediterannean region of Europe,
India and China", according to Vinal (32). Russia is the
leading country in the world in the production of sunflowers
being grown on a large scale for the seeds and oil. Next
to Russia, Hungary is the larges* roducer of sunflowers.
This widespread distribution of the sunflower makes the
distribution of the rust very widespread also, for wherever

the sunflower has gone the rust has appeared. Since Russia

was the largest producer of sunflowers it was here the
effect of the rust on the crop first began to come to the

notice of the people. In 1866 the first complaints from
~12=

the Russian farmers were heard regarding a rust epidemic
and during the following two years the sunflower industry
was dealt a very severe blow from which it never recovered.
In the period 1890-1900 the rust epidemic reached the

great sunflower plantings in the province oi saratov.

Signs of the Disease.

Spring-

The disease first becomes visible in the spring in
the form of minute yellow pycnia on the cotyledons of the
seedlings about two weeks after planting. These are usually
followed in about five days by the development of clusters
of aecial cups forming bright yellow spots which may appear
on either surface of the cotyledon. It is not unusual to
find several groups of pycnia or several clusters of the
aecial cups on the cotyledons but relatively few plants are
founds with their cotyledons so infected. Where volunteer
seedlings come uv in dense groups from a buried portion of
a head, the infected seedlings may reach ten percent of
the total in the clump. Very rarely in the field the yellow
spots of the aecial cups are found on the true leaves
of the yomg seedling. The comparatively small number ot

infections and their lack of conspicuousness makes it

very easy to overlook this stage, though it is very important.
Summer-

The first stage, which is seen and recognized by the
casual observer, is the summer stage or uredinial stage.
In 10 to 12 days after the appearance of the aecial cups
the first reddish brown pustules of urediniospores appear.
The lower leaves seem first attacked, gradually spreading
upward and the lower surfaces of these basal leaves become
nearly covered by the rusty brown pustules of the rust
while occasional pustules appear on the upper surfaces of
the leaves. fhe pustules appear as powdery, red brown masses
from which a fine brow dust arises on touching the leaf.
These increase rapidly in size and numbers, and in a few
weeks the lower leaves are almost entirely covered with
the brown pustules. These worst infested leaves wither
and die and we find the leaves entirely dead up to a height
of two or three feet by the latter part of August. Not
only the leaf blades are marked by the brown spots, but
pustules appear thickly crowded on the petioles, the main
stem itself has scattered groups, and even the involucre
and floral bracts become well spotted by the uredinial
pustules, while occasionally the flowers themselves,
especially the ray flowers, show rust spots. The develop-

ment of the rust is especially rapid during the late summer

through the month of August in this climate.
~14-
Fall-

At the end of August and beginning of September
the powdery reddish brown rust pustules of the summer begin
to darken in color and become more compact in form due to
the formation of the fall spores or teliospores. As the
proportion of teliospores becomes greater, the spots all
become dark brow or brownish-black in color giving the
characteristic fall appearance of the disease. Thus we
have three characteristic signs of the disease as the
season progresses,- the Spring stage, important but
inconspicuous, usually manifests itself by yellow spots
of pycnia and aecia on the cotyledons or on the first
true leaves of the seedlings. The Summer stage is character-
ized by the rapid spread of the parasite showing itself by
the reddish brown rust pustules which kill the lower leaves
and seriously injure the others. The Fall stage is char-
acterized by dark brown rust pustules showing very conspic-

uously on leaves, stems and involucre of the sunflower

plant.

Life History of the Causal Organism.

Previous Work-

There has been more or less doubt and uncertainty
as to the exact lite history and identity of the Puccinia

(Dicaeoma) which causes the rust of the common field
-15-

sunflower Helianthus annuus.
Woronin (33) found the fungus causing the rust
epidemics on sunflowers in Russia to be the Puccinia

helianthi Schw., described by Schweinitz (28) in 1822.

 

. He found this autoecious rust had all of the five spore
forms of a rust, namely - teliospores, sporidia, pycnio-
spores, aeciospores and urediniosporese

The Sydows, however, in their Monographia Uredinearum
(31) comment on Woronin's work as follows: "Woronin states
that he has obtained saecidia through the sowing of
teleutospores on Helianthus annuus. Neither before him
nor since this time have aecidia been found on this Helian-
thus although the species occurs commonly in many European
regions so that the statements of Woronin concerning the
possession of an secidium by the Puccinia are still
doubtful. The commonly occurring secidium of different
species in North America has never been observed in connec-
tion with the widespread Puccinia occurring there, whence
the aecidium may be an isolated form or belong to a hetero-
ecious species. In our opinion, this species (Puccinia
helianthi) possesses no aecidium."

Arthur (5), however, describes the secial stage in

his work on the Uredinales in North American Flora.
~16<
Methods of Study-

In studying the sunflower rust in its various stages
the plants were inoculated and when the organism reached
the proper stage of development small squares about 5 mm.
Square were cut out of the leaves and killed in Gilson’s
fluid. This fixer proved to be best adapted for the purpose
Since it has a stronger tendency to fasten the spores so
that they are not washed off in the subsequent transfers
in the process of dehydration and infiltration. The
paraffin method of imbedding was used and the sections
were cut from 2 to 10 microns in thickness. Due to the
spongy nature of the yowmg leaf tissue with its large inter-
cellular spaces, 7 microns proved best in most cases. In
studying the morphology of the pycnia and the aecial
cups, sections were cut but 13 microns in thickness. The
Durand method of staining (16) with Delafield's haema-
toxylon and alcoholic eosin for intercellular mycelium
gave brilliant results for the mycelium itself. To bring
out the cytological details of the fruiting bodies and
the spores, Haidenhaim’ iron alum haematoxylon (11) stain
was found preferable since the spores take the eosin of
the Durand stain too deeply.

But one investigator, Jj, Ray (24) has reported the

successful growth of a rust in a culture medium. His

method was followed and in ten trials gave negative

results with this organism. ‘Since it was apparently im=
-17=

possible to grow this fungus in pure culture in a syn-
thetic medium, the growth of the parasite in pure

culture was accomplished upon the living host. Seeds
were sterilized by the method found best by Young (35)
presoaking in water for 18 hours then dipped in 3%
formaldehyde for 30 minutes. The fruits were then
carefully opened and the kernel removed by sterile forceps
end placed on nutrient agar poured in a thin layer in
deep culture dishes. fFour kernels were placed in each
dish and in about 75% of the dishes all the seed remained
sterile as shown by examination of the surrounding agar.
Large test tubes 2 1/2 inches in diameter and 12 inches
Long were used for growing the plants. Shive 8 synthetic
solution #52 was used as the most favorable liquia

medium known for plant growth. Expressed as normal
Solutions this medium contains 18 cc. KH,P0,, 52 co. CaNOzg,
and 15 cc. of MgSO, made up to one liter with distilled
water. Quartz sand saturated with this solution proved
to be too compact for good growth of the seedlings. Best
results were obtained by forming small supports of glass
which held a small pad of absorbent cotton with the lower
edge of the cotton in the solution. Sufficient aeration
was provided for the roots in this way and the large
tubes plugged with the glass supports and cotton in place
were easily sterilized in the autoclave. Sterile seed-

lings from the deep culture dishes were then transferred
~18-

to the large test tubes by flamed forceps. When twenty
tubes contained sterile plants of from 6 to 8 inches
high, inoculations were made. The top of a pustule of
urediniospores from a plant in the greenhouse was cut

off with a sterile scalpel and a few of the spores from
the interior of the pustule transferred to a leaf of
several of the sterile plants. Typical mredinia appeared
in ten days and a second transfer was made by a sterile
needle to other sterile plants. The uredinia which
developed on these were assumed to be sterile, but more
transfers were made from time to time thus continuing

the growth of the rust in pure culture for five months.
Pycniospores, aeciospores, urediniospores and teliospores
were thus produced in pure culture and sections of

leaves were fixed, imbedded and sectioned from time to
time. From these sections, augmented by material not
grown under sterile conditions, the life history and the
morphology of the fungus was studied.

Identity of Species-

The modal curves on Plate III show the measurements
of the spores from the Puccinia helianthi of Europe
compared with the measurements of two American specimens
of the Dicaeoma helianthi-mollis of Arthur. The almost

exact Similarity of these curves would seem to prove
-19~
Woronin's and Arthur's statements and descriptions
are of the same organism, the Puccinia helianthi of
Schweinitz. It is evident that Sydow was mistaken
when we stated the Puccinia helianthi of North America
had no aecial stage. The plates numbering IV, V, and
VI show the aecia on Helianthus annuus obtained by
inoculating with teliospores of Puccinia helianthi
from Helianthus annuus of the previous year. The
entire life history as determined by numerous inocu-
lations using both the teliospores of the Helianthus
annuus and those from other wild forms of Helianthus
guch as Helianthus tuberosus, Helianthus giganteus, and

Helianthus multiflorus follows.

Life History-

The teliospores which have wintered over as pustules
on old leaves and stems germinate very easily in the
spring, forming promycelia. This promycelium soon divides
into four cells, each of which extrudes a prolongation
which rounds up at the end and swells up to form a
spherical or oval sporidium into which the contents of
the cell pass. The sporidia are then cut off and projected
some little distance by the promycelia. ‘when these
sporidia alight on the cotyledons or tender young leaves
of the sunflower seedling they germinate by means of germ

tubes if enough moisture is present. These germ tubes
=20-

enter the stomata and soon develop into a considerable
mass of one-nucleate mycelium. Ten days after the
germination of the sporidia the mycelium develops

pycnia on the upper surface of the leaf. TI ive days
later aecial cups are usually formed, either on the same
or the opposite side of the leaf. Occasionally there

is found to be an elision of the aecial stage. This
appears to be caused by dry conditions after the
mycelium has commenced to grow in the leaf tissue. When
this elision of the aecial stage occurs instead of
finding aecial cups developing following the pycnia,
uredinia may be observed developing with no external
evidence of the aecial stage. Under the normal damp
conditions of early spring the aecial stage develops

and the aeciospores are carried by the wind to other
leaves of the sunflower. There they germinate in a drop
of moisture usually by two germ tubes, one of which will
enter a stoma and start the development of the two-nucleate
mycelium. trom this two-nucleate mycelium we have the
urediniospores developing in about ten days. The
uredinial stage repeats itself every ten days during the
summer. In the fall the brown uredinial pustules darken
in color due to the formation from the mycelium of the
dark brown teliospores among the urediniospores and

as the season progresses the pustules consist entirely

of teliospores. These teliospores winter over and germinate
commencing the life cycle again.

Morphology.

Mycelium-

Puccinia helianthi has a much branched, septate
mycelium varying from 11/2 to && in the diameter of
the hyphae. At first wholly intercellular with
haustoria extending into the air spaces of the mesophyll,
later intracellular in the areas near the fruiting
bodies. Stains brilliantly with the Durand stain (16)
for intercellular mycelium. The hyphae appear more

or less granular and contain many fine vacuoles.

Pycnia-

The pycnia are amphigenous on the cotyledons but
are usually epiphytous on the true leaves in close
groups 1-2 mm. in diameter. Their color is a light
yellow with a waxy luster, becoming a dirty yellow with
age. ‘the pycnia are globoid about 100-160, in diameter.
The ostiolar filaments are agzlutinated into a column
70 to 120, long. The pycniospores are spherical or

oval l 1/2 - 2x 2 in diameter.
-22=
Aecia-

The aecia are amphigenous on the cotyledons but
are usually hypogenous on the true leaves. They are
collected in small groups 1-4 mm. in diameter on the
true leaves but usually smaller, 1-2 mm, on the coty-
ledons. Microscopical examination reveals a white
peridium with an erect margin. The outer wall is 3-84
thick and the inner wall 5-8 thick. The peridial cells
are rhomboidal in shape, measuring 20-28 x 25-40n. The
aeciospores are spherical or rounded polyhedral, occasion-
ally elliptical, measuring 15-27 x 20-32 uw. They have
a closely vérucose, colorless wall, measur ing l-2u in
thickness. Fine diagonal striations may be seen in

this wall. Tne contents of the cell are bright orange

yellow with many large vacuoles.

Uredinia-

The uredinia are mostly hypophyllous and are borne
in scattered round pustules 0.1 to 1.0 mm. in diameter,
naked early in their development with the ruptured epi-
dermis plainly evident. ‘they are dark reddish brown
in color and appear dusty to the naked eye. The uredinio-
spores are flattened to globoid, measuring 20-27 x 25-30u.
The wall is 1-2u thick, of a dark, cinnamon brown color

and more or less echintlate. It contains 2 equatorial

porese
Telia-

The telia are chiefly hypophyllous. they may
be scattered but are usually crowded into irreguler
groups 2-10 mm. across and occasionally from solid
sheets over 2.5 square centimeters of leaf surface.
On the petioles and stems they are crowded into long,
narrow groups 0.5 - 1.0 x 3.0 - 12.0 mm. When scattered
on the leaf surface the telia are 0.4 - 1.5 mm. in
diameter. In contrast to the powdery uredinia we find
the telia very compact. the pustule appears chocolate
brown to nearly black, with an inconspicuous ruptured
epidermis. The compound teliospore is made up of two
cells which are ellipsoid or oblong. ‘the teliospores
measured 20-36 x 36-56 w in 600 measurements, agreeing almost
exactly with Arthur (5). I found the modes of width and
length to be 26 x 44u. ‘hey are borne on a colorless
pedicel from 70 to 150 i in length, which remains attached
to the spore. The compound spore is slightly constricted
where the two cells meet. ‘She upper cell is more obtuse
or rounded, while the lower cell is somewhat narrowed.
Woronin.(33) found that each single cell has a thick
outer wall or exosporium of a cinnamon brown color which
consists of two layers. The inner layer, he said, usually
appears darker and is of uniform thickness while the

outer layer stands out plainly at the forward end and has
~24—

thickenings especially in the extra thickened forms
at the apex of the upper cell and at the side immediately
below the septum.

Though these cells are very closely united and never
separate from each other in nature, Woronin separated the
cells from each other by the use of concentrated sulfuric
acid. Under this treatment the outer exosporium is
decolorized, swells up, and may be seen as an unbroken
membrane surrounding the whole teliospore.

A germ pore is evident in the exosporium at the
strongest thickened part of each cell of the teliospore.
Beside the dark colored exosporium, each cell possesses
also a thin and entirely colorless membrane noted by
Woronin, the endosporium. Woronin also noted the strongly
refractive spot which is fowmd in the fine grain plasmotic
contents of each cell but he was not sure wh ether it was

an oil drop or a nucleus. S8By the use of intravital

stains I have found this to be the nucleus.
Promycelia and Sporidia-

Normal promycelia are about 10-12 x 70-80uU in size
divided into 4 cells, each of which are 9-12 x 10-l16nu.

Each of these cells develops an arm or prolongation 5-10u

long at the tips of which develop the ellipsoid to

spherical sporidia. ‘hese thin-walled spores are densely

filled with cytoplasm and measure 6-10 x 9-15yp. Further
-25-
details on this subject will be found under Germination

Studies.
Name of the Causal Organism.

The sunflower rust, Puccinia helianthi Schw. was
first described by Schweinitz in 1622. In his Synopsis
Fungorum Carolinae Superioris of that year we find three
descriptions of the disease. The first mentioned (27)
is the aecial stage described under the name of Aecidium

helianthi mollis (Schwein.) as "aecium oblong, thick,

 

whitish, with peridia crowded, pale, spores oblong.

Frequent on the dorsal side of the leaves of Helianthus
mollis, spores under the microscope luteo fuscous, vesiculose,
when old, transparent, white." The second and third (28) (29)
descriptions are of the telial stage under the genus name

of "Puccinia or Dicaemonia." Both are apparently descrip-
tions of the one species as we have it today. He describes
"Puccinia heliopsodis" (Schwein.) as follows (28): “Puccinia
moderately large, irregular, clustered, bordered by epi-
dermis, chestnut brovwm, spores oval elongate, longly
pedicelate, two-celled. Frequent on the dried leaves of
Heliopsidis also Vernoniae. Cells of teliospore equal,

Septum exactly in the middle of the snore." His third
description (29) is under the name of "Puctinia helianthi"
which he describes as "Puccinia small orbicular, crowded

black, spores globose-oval, two-celled, longly pedicellate.

On several common Helianthi, spores fusco luteus, white
~26-

transparent pedicel." Ten years later (1632) Schweinitz

applies the names Caeoma (Aecidium) helianthatum (Schw.)
and Caeoma (Aecidium) tracheliifoliatum (Schw.) Peck (22)
in 1885 applied the name Puccinia vViguirae while in 1898
Kuntze used the names Dicaeoma helianthi, Dicaeoma
heliopsodis, and Dicaeoma viguirae. The name Puccinia

helianthi-mollis was given by Jackson in 1918, while Arthur

 

named the fungus Dicaeoma helianthi-mollis (Schw.) Arth.

in his work on the Uredinales being published in the

North American Flora commenced in 1907 and not yet completed
in 1922. Part 6 containing the sunflower rust was published

in February 1922.

The synonomy of the fungus is as follows:

Aecidium helianthi-mollis (Schw.)

Synopsis Fungorum Carolinae Superioris 1:68, 1622.
Puccinia heliopsidis (Schw.)

Synopsis Fungorum Carolinae “uperioris 1:72, 1622.
Puccinia helianthi (Schw.)

Synopsis “ungorum Carolinae Superioris 1:72, 1822.
Caceoma (Aecidium) Helianthatum (Schw.)

Transactions American Philogenetic Society 2:292, 1832.
Cacoma (Aecidium) tracheliifoliatum (Schw.)

Transactions American Philogenetic Society 2:309, l&52.
Pucoinia viguiree (Peck)

Bulletin Torrey Bot. Club 12:35, 1885.
a

Dicaeoma helianthi (Kuntze)

Revue General 3°:469, 1898.
Dicaeoma heliopsodis (Kuntze)

Revue General 3° 3469, 1898.
Dicaeoma viguicae (Kuntze)

Revue General 3° 3471, 1898.
Puccinia helianthi mollis (Jackson)

Brooklyn Botanical Garden Memoirs 1:250, 1918.
Puccinia helianthorum (Rav.)

fe. Cr. Exs. 90.
Dicaeoma helianthi-mollis (Schw.) (Arth.)

North American Flora 7:427-428, 1921.

Puccinia helianthi (Schw.) is the name which is in
most gencral use, was used in one of the three original
descriptions of the fungus by Schweinitz and it seems
advisable for convenience and clarity to retain this

name in this thesis.

Germination Studies.

The teliospores formed in the fall have not been
found to germinate at once but apparently require a rest
period of two to three months. The first teliospores
which I succeeded in germinating without artificial
stimulus formed their germ tubes on November 18, 1921.
Previous to this I had succeeded in causing them to

germinate by treating leaves covered with pustules with
~28-

Chicroform vapor for one minute and then soaking them
for five minutes in one tenth of one percent acetic
acid (Hj,CO,). These germinated but formed germ tubes
only. After November 18th the teliospores germinated
readily the remainder of the winter and throughout
the spring as long as the tests were made up to the
LOth of July. The teliospores will germinate at a
temperature otf 6°C. and trash exposed to the elements
was found to be germinating as soon as’ the snow was
melted away from it. Woronin (34) states that ‘he
first succeeded in germinating teliospores in the first
days of tebruary and that germination continued rasidly
until the middle of May but that the teliospores which
hed been preserved for a longer tire (from fall to the
middle of July) began to lose their viability so that
those sown July 19th required three days to germinate
While earlier in the season they germinated in ten to
fifteen hours. Teliospores which had been kept more
than a year he found incapable of germination.

Teliospores which I preserved in the laboratory
on the leaves of Helianthus annuus germinated over 95%
in early May but decreased rapidly in germinating power.
Teliospores placed on water in a beaker on July 6 and
kept cool in running tap water showed no germination

for the first four days and only two were found which

had formed promycelia on July 12th out of over 400 spores
-29—

which were examined.

Most of my studies on promycelia and sporidia
were made in late April and through the month of May.
Germination commenced in about 18 hours under room
temperature. In the first experiments the telibspores
were scraped from the leaf pustule into a watch glass
and thoroughly mixed with distilled water to separate
the spores in the compact pustule fram each other.
These were then transferred to the surface of hanging
drops which were suspended on VanTieghem rings which
were then sealed with petrolatum. These teliogspores on
germinating gave only long germ tubes without regard to
their position whether on the surface or immersed in
the hanging drops, attaining in some cases five or six
times the l@igth of the entire teliospore and apparently
only ceasing growth when all the food material stored in
the cell was utilized. Germination seemed more often
to commence in the upper cell. The experiments were
repeated but the dry teliospores were carefully dusted from
the pustules onto the surface of hanging drops without
being first wet over in the watch glass. The growth
continued to be confined to germ tubes even though the
dry teliospores were carefully sown on the surface of
the hanging drops, as long as the sealed rings were used.
Several thicknesses of filter paper were then placed in

the bottom of a petri dish with holes cut through them
-30=

about the size of the rings. The filter paper was

then soaked with distilled water and, after sowing the
dry teliospore on the hanging drops, the cover glasses
were placed over the holes in the filter paper. A few
cases were observed here like (d) Plate I, where
sporidia were formed. Excessive moisture and lack of
air seemed to be the factors encouraging formation of
germ tubes rather then promycelia and sporidiae Another
factor might have been the large numbers of yeasts which
developed in the hanging drops in mite of using sterile
glassware and sterile distilled water. Some sterile
agar containing no nutrients was next used as the medium
on Which to germinate the teliospores. The agar was
liquefied in a water bath and clean slides were dipped
into the agar with a pair of forceps. The agar hardened
at once in a thin uniform layer over the slide and while
still warm the excess was removed from the edges and
from one side of the slide, leaving the one surface
untoucheé. Slides prepared in this way were placed on
several layers of moist filter paper in deep culture
dishes. ‘he dry teliospores were then dusted over the
moist agar to which they adhered. In about 24 hours
promycelia and sporidia like those in (h) and (j)
developed. Though conditions of moisture and air were

nearly ideal the promycelia were still not the form
~Zl@

we think of as characteristic of the rusts. The
experiment was again repeated with part of the deep
culture dishes at room temperature while the others
were placed in a runing water bath at a temperature
of12-15°Centigrade. The warmer culture developed more
rapid ly than those in the water bath and were the
same form as before while quantities of characteristic
promycelia were formed in those at the cooler temper-
ature of the water bath. One of these normal promycelia
is pictured as (i) in the accompanying Plate I. In
some cases germ tubes had commenced apparently the
formation of sporidia on a normal promycelium, but
when left under the microscope still under the same
moisture and air conditions but with room temperature
these normal promycelia reverted to germ tubes. Two
camera lucida drawings of the same teliospore at 11:30
A.M. (k) and 3:00 P.M. (1) of Plate I illustrate this
point.

Attempts were made to study the nuclear behavior
during the development of germ tubes or pramycelia
by the use of methylene blue. s#igures (a) and (e)
Plate I, illustrate how the nucleus, stained blue by
the intravital stain, passes out of the cell in all
cases observed before the reduction division takes
place which results in four cells, each of which pro-

duces a sporidium. Further studies of the nuclear
-32-

divisions following the method of Blackman (8) (9)

have bean unsuccessful up to the present in showing
the details of the nuclear behavior but it seems
certain that the nucleus passes out into the pro-
mycelium before undergoing either the heterotypic or
the homotypvic division. The sporidia which were
observed in the process of germination developed only
germ tubes and not secondary sporidia as is often
observed in this group. Woronin describes the promyce lia
as a colorless or with a faint reddish colored proto-
plasm (34). The writer has never been able to distin-
guish with certainty this reddish color in the many

promycelia observed.

Wintering and Dissemination of the Parasite.

Trash-

It has been noted by European investigators that
one of the greatest sources of infection of Puccinia

(Dicaeoma) helianthi (Schw.) is the trash from the

previous year’s crop. In my examination of fields rust
has always been found to be more abundant in fields
replanted to sunflowers and in fields adjacent to those
which bore a crop of sunflowers the previous yeare In
the summer of 1919 a large plot of the Kaerpher variety
of sunflower was grow in the east half of field #9

at the Michigan Agricultural College. The following
~ FBn

year (1920) head rows of selected heads being tested
by the remmant system were planted just west of the
previous year's plat in the same field. The portion
of the field used in 1919 had been planted to wheat
in the fall of 1919. Over twenty sunflower seedlings
bearing the aecial stage on their cotyledons were found
in this wheat field. In one case a portion of a sm-
f lower head had evidently been buried, for a derse
cluster of seedlings came up with numerous aecial
infections on their cotyledons, The first wredinia.
were found at the end of the 1920 head rows which were
nearest the plot of the previous year, and three weeks
before other plots of sunflower were marked by more
than occasional pustules the head row series were

thickly corered with the summer rust pustules.

Wild Sunflowers-

& second method of spread of the rust fungus is
by the many wild varieties of sunflower which are found
in this country. Alexander divides the wild forms into
500 species, many of which are doubtless hybrid types.
Cross inoculation experiments have resulted in infection

of all these wild forms with the exception of Helianthus

tuberosus by the spores from the cultivated Helianthus

 

annuus. Inoculation with the rust spores from Helianthus

tuberosus a8 well as all the other wild forms available

 
~34—

have resulted in infection upon the Helianthus annuus

of cultivation. Woronin ran a number of oross-inoculation
experiments (34) with other genera of the Compositae

Which are infected by forms closely resembling Puccinia
helianthi. He tested all these forms in inoculation

tests on H. annuus and found Puccinia discoidearum (Schlecht)

 

which Megnus (20) had previously show to be nearest

Puccinia helianthi in structure was capable of forming the

 

typical rust infection upon Helianthus annuus. He collected
the teliospores of Puccinia digcoidearum (Schlecht) on
Tanacetum vulgare and these sown on healthy Helianthus
annuus plants infected the latter, forming pycnia and

aecia indistinguishable from those of Puccinia helianthi.
These aeciospores he showed to be capable of infecting

Helianthus annuus, developing a mycelium which dore the

typical uredinia of Puccinia helianthi. Woronin thus
proved the surmise of P. Magnus (20) that the rust of
Helianthus annuus may be caused by Puccinia discoidearum
but he notes the growth is not as strong as is obtained
by sowing the teliospores of Puccinia helianthi Schw.
Woronin (34) therefore names the species of Tanacetum

artemisia and Chrysanthemum on which Puccinia discoide-

 

arum usually develops as possible agents in disseminating

the sunflower rust.

The rust pustules of Puccinia helianthi are not only
found on the involucre and involucral bracts of the sun-

flower head, but are also in same cases found on the
~35=

flowers themselves, though this infection rarely
extends far from the ray flowers of the head. Here

we have another possible source of dissemination for

it seems not unlikely that the seed might carry upon
their testa some of the teliospores while in practic-
ally all samples of commercial seed may be found a
considerable amount of small particles of the floral
parts and the involuoral bracts. The presence of
pustules on some of this accompanying material was
evident with a hand lens. The attempt was then made to
centrifuge the seeds themselves after a thorough
steeping in water. This proved unsuccessful but upon
Shaking the seeds first in alcohol and centrifuging the
washings there were a few teliospores found. This was
evidently due to the gummy material on the testa to
which the teliospores adhered until alcohol was used

to dissolve the gum. The presence of teliospores was
also demonstrated by scraping the seed with a scalpel
and mounting the scraoed material in water under the
microscopee Although this demonstration of the presence
of the teliospores on the seed made seed dissemination
very probable, it remained to prove the fact that these
seed.- carried teliospores were capable of causing the
spring infection of the sunflower seedlings. For this

experiment a coldframe not previously used for swmflowers
-36—

was carefully cleaned out and new soil from a field
where no sunflowers had grown was brought in and a
layer 18 inches deep placed in the coldframe. Certi-
fied seed of the Mammoth Russian variety of Helianthus
annuus grown in Missouri was purchased from the Michigan
State Farm Bureau and used in this experiment. The
soil was moistened with a sprinkler and the seed sown
thickly over the surface of a bed 4 x 4 feet and raked
in. The frame was kept covered with glass, except at
the time of the daily watering with sprinklins can and
the examination. About twenty days after the seeding
a thorough examination revealed the presence of seven
plants which bore aecial cups on their cotyledons.
Several of these cotyledons were placed in Gilsm'’s
fluid, washed, dehydrated, infiltrated, imbedded and
sectioned to prove beyond a doubt that they were the
secial cupg-.of Puccinia helianthi. We thus have posi-
tive evidence that in addition to trash other species

of Helianthus and a few related genera of the composites

we have dissemination by seede

Varietal Resi stance.

Up to the very present time very little work has
been done on the breeding of a rust resistant variety of

sunflower, although there appears to be considerable
-3 76

variance in the resistance of different varieties and
strains. <A variety test for rust resistance was
commenced by Professor Spragg of this institution in
1918 (30). The four varieties used were the Mautica
developed by Luther Burbank, the Kaerpher from South
America, the Mammoth Russian from the Vaughn Seed Store,
Chicago, Illinois, and a double mixed H. chrysanthemum
from W. W. Barnard Company, Chicago, Illinois. He
reported the double mixed and the Burbank were nearly
killed by the rust in 1918, the double American variety
being outstanding in its rust resisting power, and the
Mammoth Russian only fair. In 1919 one plant selection
of Burbank, and two each of the Nouth American and
Russian varieties were planted in duplicate series with
the South American as check. The selections from
Burbank and Russian were practically killed by rust,
the South: American being the only variety that stood
up under the attack of rust. Plate II shows the
Mammoth Russian and South American at late harvest time
in 1919. The South American still holds its: green
leaves while the Manmoth Russian is dead.

This South American variety is not resistant in
the true sense of the word, but may be described as

tolerant to the rust fungus. Many large pustules are
~28 =

formed upon the leaves of this variety, but due to

its tolerance the leaves remain green, in spite of the
heavy attack, for a much longer time than the common
Mammoth Russian swmflower. Work by Satsiferow on the
inheritance of the sunflower shows that the ordinary

field sunflower of Russia is very much mixed genetically,
and it should be possible from this heterozygous mixture

to select more resistant strains of sunflower. Satsifer-
ov (26) states that in his studies in 1912 and 1913 all
samples of sunflower were attacked gy rust with the
exception of the silver-leaved swmflower (Helianthus
argyrophyllus Alef.) in samples of which in 1912 not a
pustule of the ured iniospores or teliospores could be
found. The German summary states that this species was
found to be entirely resistant but in inoculation experi-
ments I found it possible to infect Helianthus argvrophyllus
with teliospores from both the domestic and from wild sun-
flowers. I found, on having the original Russian article
translated (26) that though resistant in 1912, in the

wet summer of 1913 rust was very prevalent and that on
nearly all samples of silver-leaved sunflower collected

in the fall, there were rust pustules. Satsiferov

says "The resistance is evidently due to the hairy covering
which prevents the spores fram entering through the stomata.
This gives hopes of developing a more resistant form

having the hairy coat of the silver leaf together with
 

-29—=

the desirable characters of the field sunflower."

Satsiferov attempted such crosses in 1913 but found
the late blossoming maternal plant (the silver-leaf)
required the use of a late blossoming field swnflower.
His crosses failed to mature seed on this account and so
were unsuccessful. He mentions the Jerusalem Artichoke
{Helianthus tuberosus) as being perfectly resistant to
rust in Russia, but this tuber forming swumflower does
not bloom in Xussia, making that cross impossible. In
this country we have the swmflower rust or a strain of
it infecting tuberosus heavily.

During the summer of 1919 I had a test plot cmtain-
ing 19 strains of sumflower, one of them being head
selections of the Kaerpher South American veriety from
Professor Spragge's plat of the previous year selected
for superior disease resistance. The other species,
Helianthus cucumerifolius, Helianthus globosus, Helianthus
fistulosus, Helianthus nanus, the double mixed tested
by Spragg were all previously tested in the greenhouse
by inoculation and found to be all more or less susceptible
to the urediniospores from both the Helianthus annuus
and Helianthus tuberosus. As the accompanying table

shows, none of these varieties exhibited rust resi stance

though the wild forms were more resistant than the culti-

vated Helianthus annuus. The most heavily rusted variety
 
Diagram of Experimental Plote

 

 

 

 

 

¥ T a v
¥ % 8 2 3 1 T
t ¥ t '
q I q t
. 6 5 5 ’ 4 t
’ t : r
t v z v t
™10"* 9 !? 8 ' 7 '
fT 8 Y v %
’ 7 1 , , , :
*™16"°15'°' 14' 13 127 ll!
! t 3 ’ 3 3 '
? — t t t
' 19 ™18'* 17 !
: t 8 '

 

Table I -- Tests of Sunflower Varieties.

 

Oct. 10
No. Species. Variety or Strain. 'Germ.t{Infec- jHt. }Stand.! Matu-
: t tion. { 1 © 1} rity.
1. H. annuus Kaerpher (selected 80 Light 3° 80 Fair
heads.)
Le " " " 50 Mod. 3° 50 "
Se " " " 85 Traces 2" 85 "
4. " " " 70 Mod. 4° 70 "
heavy.
5. " " " 60 Mod. 5 60 Good
be " " " 60 Mod. 5° 60 "
heavy.
7. " " " 60 " 7* 60 Fair
8. " " " 70 " 7" 70 "
9. " " " 85 Light 5 %' 70 "
10. " " " 2 Traces 2' 2
ll. " Burbank’'s Prolific : 90 Mod. 2° 60 1lst-Imm.
White (Mantica) : heavy.
: 90 Heavy. 5 1/2" 70 end-Fair
12. H. cucumerifolius Grandiflorus Stella 20 Light. L' 20 1 Imm.
(Dreer)
13. " " 30 8 Trace 1 30 3 Good
14. H. globosus fistulosus " 75 Light 4' 75 fair
15. H. nanus #1. Pl. " 85 Mod. 1Ye2' 70 "
16 Helianthus sp. Trade name (Japanese) 20 -- -- -- Good.
17. %H. chrysanthemum Dbl. Mixed 0 _. _ __ _.
Spragg Acc. 4 ~
18. Helianthus sp. Trade name (Texas-
Winged Taubenhaus) O -- -- O --
19, H. annuus, Mammoth Russian (F.Bureau)90 # Mod. 5° 80 Row good
heavy.
90 " 9' 90 Patch "

#12 and 14 many heads.
#19 25% of plants many heads,
 

ee ee me

— a b oo

Se ee
~40-

was the Burbank, both in the field and in the green-
house, and on account of its creat susceptibility

to the rust, at least in this locality, the Burbank
variety was used in the greenhouse for all inoculations

in studying the morphology of the rust fungus.
Control.

Since one of the greatest agencies in the
dissemination of Puccinia helianthi is the trash of
leaves and stems from the previous year’s crop, sani-
tation at once presents itself as one of the most important
means of control. ‘here sunflowers are used for silage
the entire plant is ensiloed, this ridding the field of

practically all the trash. Where grown for seed the

trash should be removed and burned, and in no case should
the same field be used for sunflowers two years in
succession. Woronin (34) found the teliospores are not
viable for over one year and my results confirm this
statement, so that a rotation which permits one year or

more to elapse between successive plantings of sunflower
should control this source of infection. Sporidia are
known to carry long distances so that it is advisable
not to grow swmflowers in a field adjacent to a field
which bore a crop of sunflowers the previous year. (See

my results under dissemination.)
41

To deal with the dissemination by other related
species of plants, the wild forms of sunflower and
also species of Tanacetum, Artemisia and Chrysanthemum
should be destroyed.

Woronin (33) suggested the burning of the previous
year’s rubbish and the avoiding of successive seedings,
in 1872. He also advocated a careful plucking out of
the sunflower plants showing the orange rust or spring
stage and the planting of sunflowers in rows instead
of broadcast to slow up the spread of the rust. This
latter is not practical since the labor and expense
would be enormous.

Karsin in a popular type of bulletin in the Xussian
language, in 1896, repeated these suggestions and, among
other ideas, brought forward the idea that soaking the
seed in lime water or blue vitriol might kill the spores
of the rust and aid in the control of the disease.

the writer conducted germination experiments and
found 1/20 of 1% copper sulphate would prevent the
germination of the teliospores. The effect of copper
Sulphate solution on the viability of the seed was then
tested in numerous experiments. Sdutions of copper sul-
phate varying in strength from 1/2 of l% to 10% were
used and the time of soaking of the seed varied from
~42~

1/2 to 3 hours. ‘he germination was only impaired

in cases of excessively long soaking when the seed
commenced to germinate in the copper sulphate solution.
When this occurred, the radicle blackened and the
seedling died, but in all cases of under six hours

soaking there was no effect upon the viability of the

seed. In fact, the germination was faster and reached
1LOO%, while the untreated check seed was about 95%, due
to the beneficial action from the presoaking.

For all purposes, a 1% solution seems advisable
with a 30-minute period of soaking, but no injury is
done if the seeds are left in the solution for several
hours. ‘the most convenient method for treating the
seed is as follows:

veigh out the copper sulphate and place ina
small cloth sack. Heat a small quantity of water and
Stir with the sack of copper sulphate, or suspend near
the surface of the hot water. In a tew minutes the
copper sulphete will be dissolved. A ten gallon stone
crock is an excellent receptacle. Pour the water into
the crock and add the copper sulphate Solution. fPour
the seed into the solution and press them under the
surface of the solution with a cover cut to fit the
crock. «w#Jeight the cover to keep the seed imnersed and

leave for 50 minutes. ‘then remove the seed and spread
~43-

in the shade to dry. A bushel may be treated at a
time in this way.

Treated seed was planted in a plot adjoining
untreated seed at Chatham Experiment Station in the
Upper Peninsula of t#ichigan. The treated plot at
Marquette, :lichigan did not develop rust until 20
days after the untreated plot, but by fall the uredinio-
spores nad spread to such an extent from the untreated
plot that there was little difference between them.

One of the County acents, Mr. C. #. Atwater of Gladwin
County, also reported that the rust developed much
later and to a less degree on the plot of treated seed
Which were sent to him from this station. He considered
the seed treatment a great success and wished to treat
all his seed tnis year.

Some treated seed was planted with corn in Lenawee
County by a farmer for silage, and at time of harvest
the sunflower plants were remarkably free trom rust,
with even the lcwer leaves large and green, with but
an occasional pustule of rust.

Sunflower seed treated with a dust treatment
instead of soaking was planted in the silare corn at
the wichienn Agricultural College farm and the plants
on July 10th showed no rust whatever, while the untreated
plants in Professor Spragg's breeding experiments were

quite heavily rusted although they were of the Kaerpher
~44—

variety. The experiment is being repeated this summer
with copper sulphate dipped seed, seed dusted with

Mackie dust, and seed dusted with Corona dust by a

number of County Agents and also by a group of farmers

in Lenawee County. Mackie dust consists of 50% dehydrated
Cus0, and 50% hydrated lime, while Corona dust contains
about 16% CuCOs and a la rge percentage of CuSO,.

It seems likely that we may find a control in the form
of a rust resistant variety by systematic plant breeding.
Professor Spragg's rust-resistant sunflower is in
reality a rust tolerant race of sunflowers from which
it may be possible to senarate a superior variety.

At tie present time the best control seems to be a
proper rotetion of crops together with seed treatiient, and
while this will not entirely control the rust, it reduces
the severity of the attack to a small amount and will
pay in the increased tonnage and succulence of the silage
and in the larger production of seed which give sunflower

Silare its high fecding value.
Conclusions.

Puccinia helianthi is an autoecious rust with
five spore forms, but which occasionally elides the
aecial stage. The rust infects all species of Helianthus
and is economically important on the cultivated varieties
of Helianthus annuus. The organism is carried over from
year to year by teliospores on thetrash of the previous
year's crop and upon the seed. The attacks of the fungus
can be, for the most part, controlled by rotation and
by seed treatment. The best treatment, so far as experi-
ments have gone, consists in soaking the seed for thirty
minutes in 1% copper sulphate solution. No true

resistant varieties of the cultivated Helianthus annuus

have been developed up to the present time.
L.

Be

Se

14.

LS.

Bibliography.

Anonymous. Cultivation and Utility of Sunflower,
Niger, and Safflower Seed. Scientific
American Supplement 82:282. 1916.

Anonymous. Sunflower Seed Production in United States.
U. S. Department of Agriculture Market
Reporter, February 5, 1921.

Anonymous. Sunflower Silage. Michigan Agr. Exp. Sta.
Quarterly Bulletin 2:163-164. 1920.

Anonymous. The Lightest Known Vegetable Substance.
scientific American 113:450. 1915.

Arthur, Joseph Charles. Dicaeoma helianthi-mollis
The Uredinales. North American Flora
7:427-429. 1921.

Bauhin, Gaspard. Phytopinax sev Enumeratio plantarun.
Basle 1596.

Bauhin, Jean. Historia plantarum universalis I,
440 p. Ebroduni (Yverdun) 1650.

Blackman, Vernon H. On the Conditions of Teleutospore
Germination and of Sporidia Formation
in the Uredineae. The New Phytologist
2:10-14, Fies. 4-6, Pl. I. 1903.

ae ee ee ee eee On the Fertilization, Alternation
of Generations, and General Cytology of
the Uredinesae. Annals of Sotany 18:323-
474, Pls. 21-24. 1904,

 

Briosa & Cavara. Funghi Parassiti Delle Plante
Cultivate ed Utili, p. 157, 2 Figs. 1691.

Chamberlain, C. J. Methods in Plmt Histology,
4rd Kevised zdition, pp. 41-45, 1920.

Decaisne and Naudin. Manuel de l* Amateur des Jardins.

De la Brosse, Guy. Description du jardin royal des
plantes medecinales. Contensant le cata-
logue des plantes, 107 pp.

De 1'Hscluse, Charles. Exoticorum libri decen.
Antwerpiae Plantinus 1605.

Dodoens, Rembert. Florum coronarium odoratarumque
nonnularum herbarum historia, 307 p.
anver 1568.
Bibliography (continued).

16. Durand, Blias J. The Differential Staining of
Intercellular Mycelium. Phytopathology
1:129-130, 1911.

17. Kragosus de Toledo, Juan. Vis cursos del los
cosas Aromaticas. Madrid 1572.

18. Jolyclerc, Nicolas. Phytologie universelle Paris 1799.

19. Karzin, I. Cultures of the Sunflower in the Volge
Regions and the Rust (Puccinia helianthi).
Repaged reprint from Nos. 7 and 8 of
Chozyain 1-17, #igs. 34-38. 1896.

20. Magnus, +. Botan. Centralodlatt 77:2-10, 1899.

ele Palmer, “dward. food products of the North American
Pls. 19-28. 1870.

22. Peck, Puccinia vigierae (Peck). Bul. Torrey Club
12:35. 1665.

23. Putnam, GW. Sunflower “xperiments. Mich. Agr.
IXp. %ta. «wuarterly Bulletin 3:49-52,

2 figs. 1920.

24. Ray, Julien. Cultures et formes attenues des
maladies cryptogamicues. Compt. end.
Paris 2:307. 1901.

25. Roze, M. Quelques Details Historiques Sur Le Grand
Soleil on Tournesh (Helianthus annuus L.)
Soc. Nat. d'Hort. France Journ. Ser. 3,
21:505-512. 1899.

26. Satsiferov, F. A. Field Hxveriments and Observations
With Sunflowers (in Russian). Sulletin
of «applied Botany. Bul. 4rgew. botanick
7:543-592. 1914. (German Summary 7:593-600.

27. Schweinitz, Ludovici Davidis de. Synopsis fungorum
Carolinae Superioris (Schriften der
Naturforschenden Gesellschaft zu Leipsig. )
68. L&22..

C60 mom rr reer nnn synopsis fungorum
Carolinae Superioris (Schriften der
Naturfo:schenden vesellscraft zu Lcipsig.)
72. 1822.

299 qn nen -- oe - - synopsis fungorum
Carolinae Superioris (Schrifetn der
5Q.

Jl.

Die

556

54.

35 6

Bibliograwhy (continued).

Naturforscnenden Vesells chaft vu Leipsig.)
73. l&2e.

Spragg, . A. and Dow, E. & rust Resisting
Sunflowers. Mich. agr. Exp. Sta.
Quarterly Bulletin 2:128-129, 1 fig.1920.

sydow, ’. snd “ydow H. Monogra mia Uredinearum
1:92-93, 859-860. 1904.

Vinall, H. N. The Sunflower as a Silage Crop.
U. S. Dept. of Agr. Bul. 1045:1-352,

& figs. 1922.

Woronin, M. Untersuchungen tiber die Entwickelung
des Kost pilzes (Puccinia helianthi),
welcher die Krankheit der Sonnenblume
verursacht. Botanische Zeitung 30:
676-653, 1872.

Voronin, M. Ueber Puccinia helianthi. Botanische
Botanische zeitung 33:340-341. 1875.

Young, H. C. Seed Visinfection for lure Culture
work. Ann. Mio. Bot. Garden 6:147-155. 1919.
 

 

 

 

 

 

 

 

 

 

 

tlate I. Gamera lucida drawings of germinating teliospores.

A-Germ tube showins nucleuse B & C-Harl; stece of
development of germ tubes. D-Prom,celium besring two

sporidia. K-Germ tube showin nucleus. K-Teliospore
Snoving germ tube vhich did not form sporidia. G-Germ

tube growins ont of drop cf water, snoridia formed at
erde H=Promycelia develoned at room temrersture on

moist arsr. I-Normal promycelium develonei at 14°C. on
moist a .7°Yre J-Promycelium developed at room temnersture

on moist acer. n-brom;celium develored at 12-15°C. on
moist ae.r. Uravn at llid- AM. L-Same promycelium st
3:€O veuwe after 31/2 hrs. at room temvernture. li-Germ
tube vith end orotrudins from a drone of water forminz
terminal sporidiae
 

Plate II. Plat showing Mammoth Russian end South

American sunflowers in trial plat of Professor

RF. A. Sprasg. The South American, at the right,

retains its leaves, while the Mammoth Russian, at
the left, is practically killed by the rust.
 

 

 

 

Plate

III. Pycnia on leaf of

Helianthus

annuusSe
 

 

 

 

Plate IV. Aecial cups on leaf of Helianthus annuus.
 

 

{

a

 

 

Plate V. Aecial cups on leaf of Helianthus annuus.
 

 

 

Plate VI. Aecial curs on leaf of Helianthus annuus.
 

 

Plate VII. Aecial cwps on leaf of Helianthus annuus.
 

 

 

 

Plate VIII. Leaf of Helianthus annuus severely in-
fected with the telial stage of the rust.
 

 

 

Plate IX. Head of Helianthus annuus showing the
pustules of teliospores on the involucre and
involucral brscts.
Plate xX. #requeney curves of width and length of
teliospores of Puccinia helianthi.

Plate XI. Frequency curve showing size of teliospore
of Puccinia helisnthi ard Pueccinia discoidearum (iin:.)

 

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