DIVERSITY OF
. ILLINOIS
;
NQN CIRCULATING
CHECK FOR UNBOUND
CIRCULATING COPY
UNIVERSITY OF ILLINOIS
Agricultural Experiment Station
BULLETIN No. 264
WHEAT ROSETTE AND
ITS CONTROL
IN COOPERATION WITH OFFICE OF CEREAL INVESTIGATIONS
BUREAU OF PLANT INDUSTRY, U. S. DEPARTMENT OF AGRICULTURE
BY H. H. McKiNNEY, R. W. WEBB,
AND G. H. DUNCAN
URBANA, ILLINOIS, APRIL, 1925
SUMMARY
Rosette is a disease of unknown cause occurring on a few varieties of winter
wheat. Altho in many ways it behaves as a definite disease restricted to these varieties,
there are indications that it may constitute only a very severe phase of what appears
to be a mosaic disease occurring on a rather large number of winter wheats.
Rosette was first observed in 1919 near Granite City, Madison county, Illinois.
Later it was found in Sangamon, Mason, and Logan counties, Illinois, and in
LaPorte, Porter, and Tippecanoe counties, Indiana. When the disease was first observed
it was thought to be the take-all disease, but later studies show that it is distinct from
take-all.
Altho rosette has caused great loss in infested fields, it has never been of general
economic importance because it is controlled by the use of resistant varieties. The
disease appears in the early spring, producing spots in the infested fields where it
causes the plants to become dwarfed. Many of the older leaves of infected plants turn
a. blue-green color, whereas the younger growing leaves develop a typical mosaic mottling
at some time in their development.
No fungus is consistently associated with the vital tissues of diseased plants in
the early spring. Helminthosporium sativum and other fungi occur superficially on a
few of the plants and later in the spring a secondary rot sets in.
Microscopic examinations show the presence of necrotic areas, or lesions, in the
interior of the tissues of the crown region of diseased plants and a characteristic
inclusion body is also present in many of the cells. These cell inclusions are also
associated with plants of varieties which are affected with a mosaic mottling of the
leaves, but which never develop the rosette symptoms. Cell inclusions have never been
found in the plants of any variety growing in soil known to be free from the leaf
mottling causal agent.
These cell inclusions are similar to certain of those associated with the known
virus disease of other plants, and they also are similar to some which are found in asso-
ciation with certain of the virus diseases of man and the lower animals. Their exact
nature is not known.
The cause of rosette has been attributed by some workers to Helminthosporium
sativum; however, the experimental evidence presented in this paper does not favor this
conclusion. At the present time there are indications that it may be caused by some
unusual type of virus. The rosette and leaf mottling conditions are soil-borne. Rosette
and mosaic leaf mottling developed in great abundance in air-dried infested field soil
which had been stored under greenhouse conditions for three years.
The disease is controlled experimentally by treating infested soil with an .8-percent
solution of formaldehyde and by disinfecting the soil with steam. It is completely con-
trolled in the field by the use of resistant or immune varieties; those best adapted to
the infested areas include: Blackhull, Fulcaster, Fultz, Gipsy, Gladden, Kanred. Mam-
moth Red, Michikoff, Red May, Red Rock, Red Russian, Red Wave, and Turkey.
The list of most susceptible varieties includes: "Brunswick," Fultz (Kentucky selec-
tion), Harvest Queen (white chaffed Red Cross), Illini Chief, Missouri Bluestem,
Nigger, and Penquite. Many of the varieties which are resistant to rosette are highly
susceptible to the mosaic leaf mottling. In but few cases, however, does this condition
seem to be of economic importance.
WHEAT ROSETTE AND
ITS CONTROL
BY H. H. MCKINNEY, R. W. WEBB, AND G. H. DUNCAN'
The rosette disease of wheat was reported from Madison county,
Illinois, in April, 1919. Later, it was found in other counties in the
state and in several counties in Indiana. At that time the disease was
thought to be the take-all disease which occurs in Australia and in
Europe. However, investigations which have been reported6 show that
the rosette disease differs from take-all in plant symptoms and also in
its varietal and host ranges. Furthermore, Ophiobolus graminis, the
fungus which causes take-all, has never been found associated with the
rosette disease.
Altho in many ways rosette behaves as a definite disease restricted
to a limited number of varieties of winter wheat, this interpretation
should not be definitely accepted at this time. It was pointed out in a
previous publication10 that there is a considerable amount of evidence
which indicates that the rosette disease may constitute a severe expres-
sion of a mosaic disease.
Soon after the discovery of the rosette disease, cooperative investi-
gations of the malady were started by the Office of Cereal Investiga-
tions, United States Department of Agriculture, and the Illinois,
Indiana, and Wisconsin Agricultural Experiment Stations. It is the
purpose of the present bulletin to summarize the principal results of
these investigations.
OCCURRENCE OF ROSETTE
The rosette disease has been found in four counties in Illinois and
in three counties in Indiana, as shown in Table 1. It is very likely
that the infested area is greater than that shown in the table, but as
most wheat varieties commonly grown are not susceptible to rosette,
additional areas cannot readily be detected.
•H. H. McKinney and R. W. Webb, Associate Pathologists, Office of Cereal
Investigations, U. S. Department of Agriculture; G. H. Dungan, Associate in Crop
Production, Illinois Agricultural Experiment Station.
The writers wish to express their appreciation to Dr. W. L. Burlison and Dr.
A. G. Johnson for helpful criticisms during the preparation of the manuscript; to
Dr. C. E. Leighty, who supplied most of the seed used and furnished information in
regard to characteristics and adaptation of wheat varieties; to Mr. J. B. Kendrick for
cooperation in the control experiments; to the Board of Education of Granite City,
Illinois, for providing laboratory facilities; and to Mr. Louis Soechtig, on whose land
the experiments were conducted.
275
276 BULLETIN No. 264 [April,
TABLE 1. — DISTRIBUTION OF THE ROSETTE DISEASE IN THE UNITED STATES
State
County
Number of
infested fields
found
Approximate
acreage of infested
fields
Illinois . ...
Madison
27
670
Mason
48
1310
Sangamon
2
380
Logan
1
20
Indiana
LaPorte
7
213
Porter
6
120
Tippecanoe
1
5
The distribution of the mosaic mottling independent of rosette has
not been determined. Rosette is not known to occur in other countries
and consequently nothing is known of the origin of the malady. When
FIG. 1. — SPOT IN A FIELD OF HARVEST QUEEN (SALZER'S PRIZETAKER, RED
CROSS) CAUSED BY THE ROSETTE DISEASE
The diseased plants within the spot are considerably dwarfed in contrast
with surrounding healthy ones.
more information has been obtained on the cause of the disease and its
relation to the mosaic leaf mottling, more light may be thrown on its
distribution and origin.
LOSSES CAUSED BY ROSETTE
Altho the rosette disease appears to be confined to relatively small
areas, its importance should not be underestimated. When conditions
are favorable the disease has caused as high as 40 percent actual loss
1925~\ WHEAT ROSETTE AND ITS CONTROL 277
of grain in a 50-acre field. It is not uncommon to find many spots or
large areas in a field where practically all the wheat plants have been
killed or are severely diseased. Sometimes, however, the diseased plants
in such spots recover to a considerable extent and produce some grain,
altho the heads are much smaller than those produced by rosette-free
plants (Fig. 2). In this case, however, ripening is delayed and the
plants are green when the normal crop is harvested. The grain from
such green plants shrivels badly and much of it is lost in threshing.
When much of a field is affected by the disease and there has been
considerable recovery, the greatest quantity of grain is saved by delaying
harvest until the diseased areas are ripe. In some cases, it is best to
harvest the healthy and diseased areas separately, thus reducing losses
to the minimum.
CROPS AFFECTED
Investigations carried on thus far have not shown any other crop
than winter wheat to be affected by the rosette disease. Various crops
have been tested for susceptibility to the disease6 and only a limited
number of winter wheat varieties have been found susceptible.
DESCRIPTION OF WHEAT ROSETTE
During the first year's investigations, it was not possible to make a
complete study of the symptomatology of the disease owing to the fact
that the studies were not started until the trouble had reached a rather
advanced stage. At that time, field spotting was conspicuous, and
diseased plants showed a characteristic stunted development and the
production of an excessively large number of secondary tillers, which
gave the plants a rosette appearance. These were the field and plant
symptoms which attracted attention to the disease and which made it
conspicuously different from other wheat diseases heretofore known in
this country. A rotting of the -underground portions of tillers was evi-
dent at that time, but this condition was considered a secondary effect
rather than a primary cause.
In 1920 and each year since that time, the field studies have been
started just at the time when winter wheat plants were beginning to
show signs of spring development and before the underground portions
of the plants commenced to rot.
FIELD SYMPTOMS
Shortly after the wheat plants start their spring growth, infested
fields will develop very striking areas or spots where the diseased plants
do not develop normally (Fig. 1). These spots vary in size and shape.
In some cases, one diseased plant may be found among plants showing
no signs of disease. It is not uncommon to find spots 20 feet in diameter
and even larger. In some cases, more than 95 percent of the area of a field
278
BULLETIN No. 264
[April,
may show infestation. The spotting caused by the disease occurs inde-
pendently of topographical variations, and frequently single patches are
found which involve a poorly drained dead furrow and adjacent well
drained portions of land. Usually, the diseased plants partially recover
by sending up secondary tillers which do not ripen until after the
healthy plants are mature, thus causing a green spotting in the infested
fields during the ripening period.
Field spotting is caused by several wheat diseases and therefore it
is not specific for the rosette disease. Most of the foot rot diseases pro-
Fic. 2. — THREE POORLY DEVELOPED HEADS FROM PLANTS OF HARVEST
QUEEN PARTIALLY RECOVERED FROM THE ROSETTE DISEASE AND
THREE TYPICAL HEALTHY HEADS AT RIGHT
duce this condition, but in most cases these can be distinguished from
rosette by means of the plant symptoms. The field spotting produced
by the take-all disease caused by Ophiobolus graminis Sacc. does not
develop as early in the spring as the spotting caused by the rosette
disease.
PLANT SYMPTOMS
The first external indication of the rosette disease consists in a
retarding of the early spring development of the fall tillers. At this
time, no external lesions are consistently associated with the living tissues
of the diseased plants (Plate 1, B). Lesions produced by Helmintho-
sporium satiz-um P. K. & B. are sometimes present on the subcrown
1925}
WHEAT ROSETTE AND ITS CONTROL
279
internodea. Old lesions also occur in the spring on the sheaths of the
old, dead, outer leaves. However, as pointed out later, these lesions are
slight and they do not occur on a high percentage of the rosette-diseased
plants at this time.
FIG. 3. — DIFFERENT DEGREES OF MOSAIC MOTTLING AS IT OCCURS
ON THE CURRELL VARIETY OF WlNTER WHEAT;
HEALTHY LEAF ON THE LEFT
This mottling occurs on all varieties of wheat known to be
susceptible to rosette and on a large number of winter varieties
which do not develop rosette symptoms.
*The term "subcrown internode" is used to denote the structure in the wheat
seedling between the crown and the base of the coleoptile. Under certain conditions this'
structure becomes elongated.
280 BULLETIN No. 264- \_Apr\l,
In a week or ten days after the first appearance of the rosette
disease, the leaf blades of affected plants tend to develop a dark, rather
bluish-green color. Close examination shows that this bluish-green
coloration is confined largely to the leaves which were produced in the
fall. As new leaves begin to develop, it will be noted that they show a
very decided mottling (Fig. 3) which is typical of the mosaic diseases
occurring on the grasses.1 At the same time the diseased plants produce
numerous secondary tiller buds and new tillers develop.
When these spring tillers have emerged, the basal tissues of the
fall tillers begin to manifest a dull white to straw color, and in the
course of another week or ten days this tissue may start to turn brown
and the whole base of the plant may become rotted (Plate 1, C).
The amount of this basal rotting seems to vary considerably in
different localities and under different seasonal conditions. In the vicin-
ity of Granite City, Illinois, this rotting is more prevalent than it is
near Valparaiso, Indiana. At Madison, Wisconsin, the rotting is delayed
in the experimental plots when the spring is cool.
Microscopic examinations of the bases of the stunted tillers of
plants manifesting the early symptoms of rosette have never shown
consistently the presence of a fungus or any other known parasite.
However, it has been found that these tissues contain yellowish-brown,
necrotic areas located within the parenchymatous region. These necrotic
areas seem to resemble those found in the stems of corn plants and
sugar cane plants affected by mosaic. A rather large percentage of the
host cells in the tissues of resetted plants always show characteristic cell
inclusions (Fig. 4) which were described in a previous paper.10 These
inclusions are also found in winter wheat varieties which develop the
mosaic mottling, but which do not develop rosette. They have never
been found in wheat plants growing in soil known to be free from the
disease infestation. This subject is discussed later.
The root systems of plants in the early stages of the rosette disease
do not consistently show any external signs of infection or any other
injury. In a few cases, lesions have been found on the roots, but fully
as many have been found on the roots of plants not showing the rosette
symptoms. As the disease progresses, the root systems of affected plants
show a retarded development and they become infected to some extent
by various organisms. In dry situations diseased plants do not tend to
send up secondary spring tillers. Such plants usually die early, forming
a drooping tuft of brown, dead leaves and tillers. When heavy spring
rains occur, diseased plants may be washed entirely out of the soil,
leaving the ground bare between healthy plants. In situations of favor-
able moisture and high fertility, diseased plants often recover. Altho
the fall tillers of such plants gradually die, the spring tillers may develop
into short culms and produce heads. Such heads are usually small
and imperfectly filled.
19251
WHEAT ROSETTE AND ITS CONTROL
281
B
FIG. 4. — PHOTOMICROGRAPHS SHOWING DIFFERENT TYPES OF CELL
INCLUSIONS IN ROSETTE-DISEASED HARVEST QUEEN WHEAT;
THE CELL INCLUSIONS ARE MARKED X
A — An irregular-shaped body showing pseudopodia-like projections.
It is very common to find the vacuoles surrounded by a dense ring
as is here shown.
B — An elongated type of cell inclusion.
C — A very common type of inclusion found in wheat tissue from
plants affected by rosette or mosiac leaf mottling. This body resembles
certain of the Negri and Guarnieri bodies associated respectively with
rabies and smallpox.
282 BULLETIN No. 264 Upril,
The most constant external symptoms of the rosette disease con-
sist of (1) the arrested spring development; (2) the excessive tillering,
producing a rosette appearance; (3) the dark blue-green colo'ation of
the fall leaves during the spring growing period; and (4) thi- mosaic
mottling which occurs on the leaves. On the basis of our present
knowledge, the presence of Helminthosporium lesions or a rocting of
the basal parts of wheat plants cannot by themselves be considered
diagnostic characteristics of the rosette disease.
As pointed out above, the field spotting produced by wheat rosette
occurs earlier in the spring than that produced by the take-all disease,
and furthermore, the plant symptoms of these maladies are now known
to be distinctly different. Plants affected by the take-all disease turn
yellow and die very soon after discoloration begins. These plants show
a brown to black coloration on the tiller bases and roots. This blacken-
ing or brown coloration may be due to a staining of the tissue by the
fungus or to a definite crust of mycelium known as a "mycelial plate."
Plants affected by the take-all disease seldom send up secondary tillers
or endeavor to recover after infection. The take-all disease frequently
causes nearly mature wheat plants to bleach, producing a condition
commonly known as "white-heads." This condition is never produced
by the rosette disease.
Hessian fly injury sometimes resembles certain stages of the rosette
disease (Plate 1, D and E). In both cases, the infested plants are
stunted and some of the leaves show a dark, blue-green coloration.
However, the excessive tillering and the leaf mottling associated with
the rosette disease are not associated with plants infested with "fly."
The only time when Hessian fly infestation is apt to be confused with
rosette is late spring, and then little difficulty is likely to arise, since
plants infested with fly only will show the fly pupae or larvae and no
leaf mottling. Those plants which show both infestations usually will
show some signs of mottling.
In certain particulars the early stages of the rosette disease
resemble the early stages of the nematode disease of wheat as described
by Leukel.4 In each disease there may be retarded development of
the plants in the spring and the leaves may develop a dark green colora-
tion and become very broad and thick; but in nematode-infested plants
there is, in addition, usually a marked crinkling of the leaves and stems,
a condition not associated with the rosette disease. Also, the leaf and
stem tissues of nematode infested plants are very succulent in nature,
and show a characteristic sparkling surface. None of these characters
is associated with the rosette disease.
In reviewing the literature dealing with certain of the more obscure
tropical diseases of the cultivated grass crops, it was found that several
of these possess certain characteristics strikingly similar to the rosette
disease of wheat. Excessive tillering and dwarfing are associated with
Rosette Disease of Wheat
Illinois Ayr. KXJI. Stntinii
PLATE I
PLANTS OF WINTER WHEAT SHOWING THE EFFECTS OF ATTACKS OF THE ROSETTE
AND THE HESSIAN FLY, RESPECTIVELY, COMPARED WITH HEALTHY PLANTS.
1, Healthy plant in the spring; H and C, plants of the .tame uge as A, showing early ami
advanced stages, respectively, of the rosette; i>, healthy plant as it appears in the late
autumn ; /•', plant of the same age as /', infested by the Hessian tly. Note the similarities
in color but the differences in the extent of tillering in plants allVrted liy the two maladies
compared with the corresponding healthy plants. (From Bui. 1137, U.S. Dept. Agriculture.)
THE LIBRARY
OF THE
Ur.4- '•.••»*
1925] WHEAT ROSETTE AND ITS CONTROL 283
the Fiji, Sereh, and mosaic diseases of sugar cane.5 The leaf mottling
symptom associated with rosette is strikingly similar to the mottling
associated with the mosaic disease of corn, cane, and other grasses.1
CAUSE OF THE DISEASE
Altho a number of theories have been advanced concerning the
cause of 'the rosette disease, the exact cause is still undetermined. The
fact that the disease does not readily develop in wheat grown under
artificial conditions makes it difficult to conduct many of the experi-
ments necessary to demonstrate the causal nature of the malady.
PREVIOUS STUDIES
When the disease was first discovered, many farmers thought that
it was caused directly by abnormal winter conditions. The disease was
also thought to be due to unfavorable soil type or unbalanced nutrition.
However, subsequent observations have shown that the disease occurs
with equal severity year after year on the same soil regardless of the
severity of the winter. As shown previously,6 rosette occurs on many
different types of soils and under many different topographical condi-
tions. It has also been found6 that the disease is not essentially reduced
or increased in severity when various fertilizers and soil correctives are
applied to the infested soil. On the other hand, the disease6 is prevented
when the infested soil is disinfected with steam or with an .8-percent
solution of formaldehyde.
These observations and results show that the causal agent is soil
borne and indicate that the disease is of an infectious nature. When
these studies were started, several investigators thought that the disease
was caused by a severe infestation of Hessian fly. Careful observations
did show some of the plants to be infested with the pupae of this insect,
but by far the largest percentage of them were free from such infesta-
tion. Detailed studies on this phase of the problem conducted co-
operatively by the Bureaus of Plant Industry and Entomology, U. S. De-
partment of Agriculture,9 show that Hessian fly is not the cause of the
rosette disease. In fact these studies indicate that the disease is not
caused directly by any insect.
STUDIES ON Helminthosporium sativum
Several fungi have been found associated with the rosette disease,
but none of them has been found to occur on all resetted plants in the
early spring when the first symptoms of the disease appear. Helmin-
thosporium sativum has been found more prevalent than other fungi on
the diseased plants.
In order to determine the possible relationship between H. sativum
and the rosette disease, many observations and experiments have been
conducted. It was pointed out in a previous paper" that certain inter-
284 BULLETIN No. 264 [April,
esting correlations had been observed between the occurrence of H.
sativum and the amount of rosette disease in experimental plots at
Granite City, Illinois. However, a continuation of these and other ob-
servations at Granite City and elsewhere has not revealed a constant
correlation between this parasite and the disease in question. Data have
already been published7 which show that H. sativum causes a mild in-
fection on winter wheat plants in the autumn, but the percentage of
infected plants is much less than the percentage of rosette-diseased
plants which develop in the same plots the following spring. This re-
lationship is rather significant when it is considered that the fall Helmin-
thosporium infection is seldom severe enough to penetrate deeper than
the first two or three leaf sheaths, and it seldom causes any vital injury
to the leaves. Furthermore, it has been shown by one of the present
writers7 that the Helminthosporium disease does not develop to any
extent at very low temperatures and it has been found that the rosette
disease occurs in the spring before the Helminthosporium fungus
renews its activity.
In order to obtain further evidence on this relationship, inoculation
experiments have been carried out to determine if pure cultures of
Helminthosporium sativum will cause the rosette disease. Numerous
experiments have been conducted in the greenhouse and it has been
found, as others have also found, that H. sativum is parasitic on wheat.
However, the rosette disease has never been produced in these experi-
ments. It wras found rather early in these investigations that the rosette
disease occurs only in wheat plants which have passed thru a complete
or shortened winter period; hence it was useless to carry on infection
experiments out of season or under ordinary greenhouse conditions.
Early in the summer of 1921, small plots of rosette infested soil
near Granite City, Illinois, were sterilized with formaldehyde. Later
in the summer, some of these plots were inoculated with pure cultures
of Helminthosporium sativum isolated from wheat plants affected by the
rosette disease, and the remaining plots were left uninoculated. In the
autumn these inoculated and uninoculated sterilized plots were seeded
with Harvest Queen wheat. The following spring, examinations showed
•that for some reason the disinfection had not been quite complete and
therefore it was not possible to obtain trustworthy data. However, it
was very evident that the introduction of H. sativum into the soil had
not increased the amount of rosette.
During the summer of 1922, the Helminthosporium inoculation
work was started at Madison, Wisconsin, in order to eliminate the possi-
bility of accidental rosette contamination which often occurs in the
rosette-infested district near Granite City. An elaborate set of experi-
ments was carried out, but owing to the severe winter of 1923 heavy
winterkilling occurred in all of the plots. However, a few wheat plants
escaped winterkilling in all of the plots and no rosette developed among
7925] WHEAT ROSETTE AND ITS CONTROL 285
plants in the soil which had been inoculated with H. sativum. Rosette
did occur among the few surviving plants which were in the rosette
infested soil which had been shipped from Illinois.
In the summer of 1923, the inoculation experiments were repeated
at Madison, Wisconsin, and precautions were taken to prevent winter
injury by means of a hay mulch. As a result, very little winter injury
occurred in any of the plots and dependable data were obtained on the
relationship between Helminthosporium sativum and the rosette disease.
These experiments are described and the results given as follows:
Methods Employed in Studies
These studies were conducted out-of-doors in plots 30 inches wide
and 36 inches long. Each plot was surrounded by a frame constructed
of pine boards 8 inches wide. This frame was set 3 inches into the soil;
thus 5 inches of the frame served as a protective wall surrounding the
plots. Openings were cut at the bottom of each frame to provide for
surface drainage. The soil used in these plots consisted of sandy loam
field soil obtained from the Experiment Station farm at Madison, Wis-
consin. This soil was not infested with the rosette causal agent, but in
order to safeguard against accidental contamination the soil was steril-
ized with steam.
Two strains of Helminthosporium sativum were used in these
studies. One, designated No. 408, was obtained thru the kindness of Dr.
F. L. Stevens. This strain was isolated by Dr. Stevens from a rosette-
diseased plant grown in a rosette-infested field near Granite City,
Illinois, and is the one which he12 designates Helminthosporium No. 1.
The other strain, designated No. 407, was isolated by one of the writers
(Webb) from a rosette-diseased plant showing the late stages of rotting.
The plots were inoculated by applying water suspensions of the
conidia to the upper four inches of the soil some time before sowing
the seed and again at the time of sowing as indicated in Table 2. One
plot was devoted to each strain of the organism. One plot of sterilized
soil was left uninoculated to serve as a control and one plot was devoted
to rosette-infested soil from Granite City to serve also as a control.
In order to obtain results from soil in which Helminthosporium
sativum had become thoroly established, one of the plots inoculated the
previous year (1922) with strain No. 407 and another plot consisting of
infested Minnesota soil were also included in the experiment. The Min-
nesota soil was very kindly supplied by Mr. J. J. Christensen of the
Minnesota Agricultural Experiment Station. This soil was inoculated a
number of years previous to 1923 with a pure culture of //. sativum
isolated from diseased spring wheat grown in Minnesota. Mr. Christen-
sen2 previously reported that he had obtained a rosette-like manifesta-
tion in spring wheat grown in this artificially inoculated soil; conse-
quently it was important that this soil should be included in the series.
286
BULLETIN No. 264
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1925~\ WHEAT ROSETTE AND ITS CONTROL 287
Harvest Queen wheat seed was sown in each of the inoculated plots
and the controls. The same lot of seed was used for all of the plots
except those containing the Minnesota soil and the accompanying con-
trol. This last lot of seed was somewhat lower in susceptibility to rosette
than the first lot; however, its susceptibility was sufficiently high to
serve as an accurate test for the infectiousness of the experimental soil.
In addition to Harvest Queen seed, one row of the Currell variety of
winter wheat was sown in the control plot containing the rosette-infested
soil. This variety does not develop the rosette condition, but it does
develop a severe type of leaf mottling when grown in rosette-infested
soil.
Results
The results of the infection studies with Helminthosporium sativum
are given in Table 2. In all cases where early spring (April 15) obser-
vations were made, it was found that Helminthosporium infection was
much more prevalent on plants growing in the' plots which had been
inoculated with pure cultures of H. sativum than it was on plants
growing in the rosette-infested soil. It is especially significant that such
a high percentage of infection took place in plants growing in Plot
5, which was inoculated with culture No. 408. This Plot and Plot
4 were purposely inoculated very heavily in order that H. sativum
might be given the maximum opportunity to produce the rosette disease.
However, this fungus failed to produce rosette or the mosaic leaf
mottling.
A high percentage of rosette and mosaic leaf mottling (98 percent)
developed in the early sown rosette-infested control (Plot 2) and 46
percent rosette and leaf mottling occurred in the late sown rosette-
infested control (Plot 7) which accompanied the Minnesota soil.
All of the plants grown in the Helminthosporium-infested soil, obtained
from Minnesota, were exceedingly robust and there was no sign of
rosette or leaf mottling on any of the plants. The reduced amount of
rosette in the above rosette-infested control is assigned to the lower
susceptibility of the seed used and to the fact that the seed was not
sown until very late in the fall. It has been shown previously6 that
late sowing tends to reduce the amount of rosette.
The photographic evidence obtained from these experiments is
shown in Figs. 5, 6, 7, and 8. It is of interest to note that the rosette-
infested soil used in Plot 2 had been stored in a warm greenhouse at
Madison, Wisconsin, for three years previous to using it in this experi-
ment. During this three-year period the soil was under air-dry condi-
tions and in spite of this the percentage of rosette and leaf mottling was
not reduced.
Altho the results of the inoculation experiments are of a negative
nature, it seems rather evident that they warrant consideration at this
288
BULLETIN No. 264
FIG. 5. — CONTROL PLOTS 1 AND 2 USED IN THE INOCULATION EXPERIMENTS
WITH Helminthosporium sat'wum TO DETERMINE WHETHER THIS FUNGUS
CAUSES THE ROSETTE DISEASE IN HARVEST QUEEN WHEAT
Plot 1, control consisting of steam-sterilized soil obtained from the
farm of the Wisconsin Agricultural Experiment Station at Madison, Wis-
consin. No rosette developed in this plot.
Plot 2, control consisting of rosette-infested soil obtained in 1920 from
a field near Granite City, Illinois. Typical rosette and mosaic leaf mottling
occurred in 98 percent of the Harvest Queen plants in the five rows on
the left. From 95 to 98 percent of the Currell plants in the row on the
extreme right developed typical leaf mottling, but no rosette occurred in
this variety. These results are in accord with all previous experiments.
During the three-year interval between the collecting of this soil and
the starting of this experiment, the soil remained in an air-dry condition
in a warm greenhouse at Madison, Wisconsin. No loss of virulence of the
causal agent under study occurred.
7925]
WHEAT ROSETTE AND ITS CONTROL
289
-INOCULATED PLOTS 4 AND 5 WHICH ACCOMPANIED THE CONTROLS
SHOWN IN FIG. 5
These plots contained the same sort of soil as Plot 1, sterilized in the
same manner. They were adjacent to the controls and subjected to the
same conditions. Plot 3 (not photographed) contained the same strain
of the fungus as Plot 4 and presented the same appearance.
Plot 4 was heavily inoculated with Helminthosporium sativum (cul-
ture No. 407) isolated from a resetted wheat plant in the late stages of
the disease. No rosette or mosaic leaf mottling occurred, and in spite of
the Helminthosporium infection present, no marked injury is noted.
Plot 5 was heavily inoculated with Helmintkosporium sativum (cul-
ture No. 408), supplied by Dr. F. L. Stevens and isolated from a wheat
plant in the late stages of the rosette disease. No rosette or mosaic leaf
mottling occurred, and the plants showed no ill effects from the Helmin-
thosporium infection.
The plants in Plots 4 and 5 developed in exactly the same manner
as in control Plot 1. A good crop of grain was produced in all three plots.
290
BULLETIN No. 264
[April,
time. Certainly if Helminthosporium sativum were the direct cause of
the rosette disease it could have been demonstrated in some of the
experiments cited. Stevens11' 12 considers that this parasite causes
rosette (called foot rot by him); however, as pointed out previously"
it is not clear that Dr. Stevens obtained the characteristic symptoms of
the rosette disease in his inoculation experiments. He did obtain the
typical infection produced by H. sativum on seedlings, but this type of
FIG. 7. — REPRESENTATIVE PLANTS OF HARVEST QUEEN TAKEN FROM
THE PLOTS ILLUSTRATED IN FIGS. 5 AND 6
A — Plant from Plot 5 inoculated with culture No. 408.
B — Plant from Plot 4 inoculated with culture No. 407.
C — Plant from Plot 1 containing sterilized soil control.
D — Resetted plant from Plot 2 containing rosette-infested soil. .
injury should not be confused with the rosette disease which attracted
the attention of plant pathologists in 1919.
It has been reported2 that Helminthosporium sativum produces
dwarfing, proliferations, and dark green foliage on certain varieties of
spring wheat and barley; however, all data available at present indicate
that these conditions occur very irregularly in spring wheat and barley
and that they are not identical from the standpoint of cause with the
similar conditions associated with the rosette disease.
In view of the above evidence, we feel there is justification for
considering that the rosette disease of winter wheat is due to some other
cause than Helminthosporium sativum. All of the evidence which has
been obtained indicates that wheat rosette is an infectious disease, and
at the present time there is considerable indication that the disease may
1925}
WHEAT ROSETTE AND ITS CONTROL
291
be caused by a virus. All of the external symptoms of rosette are com-
monly associated with the mosaics of corn and sugar cane, and the
microscopic symptoms are also similar to those associated with certain
of the mosaic diseases. The mosaic mottling occurs on a large number
of varieties of winter wheat and it would not be surprising to find a few
B
FIG. 8. — TYPICAL HARVEST QUEEN WHEAT PLANTS FROM
STERILIZED AND FROM INFESTED SOIL
A — From a plot containing steam sterilized soil.
B — From a plot containing soil obtained from the Minnesota
Agricultural Experiment Station, which contained Helmin-
thosporium sativum. No rosette or mosaic mottling developed
in this plot and the progress of the plants was the same as that
of plants grown in the sterilized control plot.
C — Rosette-diseased plant from rosette-infested soil. Forty-
six percent of the plants in this plot developed rosette. This
percentage would have been higher if the seed had been sown
earlier in the fall. Also, the particular strain of Harvest Queen
used in this plot and in the accompanying plots is slightly less
susceptible to rosette than that used in Plots 1 to 5.
292 BULLETIN No. 264 [April,
varieties which become stunted and proliferate freely as is the case with
certain varieties of sugar cane and corn when infected with the mosaic
virus. Owing to the unusual conditions necessary for the development
of rosette and the mosaic mottling, it has not been possible to demon-
strate the virus nature of these troubles by the usual methods employed
in the study of the mosaic diseases. It is hoped that studies now under
way may throw some additional light on this phase of the problem.
CELL INCLUSIONS
Cell inclusions have been described in a previous publication10 and
they are illustrated here in Fig. 4. Similar inclusion bodies are also
associated with several of the mosaic diseases. As pointed out by one
of the present writers in a report,8 there has been considerable contro-
versy regarding the exact nature of many of the cell inclusions asso-
ciated with virus diseases. Many investigators have held that they are
definite parasitic organisms, while others hold that they are reaction
products and have nothing to do with the cause of the disease. Altho
the exact nature of the cell inclusions occurring in wheat is not known,
it has been found that these inclusions have considerable diagnostic
value.
SPREAD OF THE DISEASE
As stated previously in this paper and in an early publication,6 the
rosette-disease causal agent is in the soil and is spread by the move-
ment of the soil. Experiments have been conducted to determine
whether the malady is carried in the seed or in the stubble, but negative
results were always obtained.
CONTROL MEASURES
The rosette disease of wheat has been controlled, in the areas where
it has been found, by the use of varieties that are either immune from,
or highly resistant to, the disease.
More than two hundred varieties and selections of winter wheat
from all parts of the United States have been grown on rosette-infested
soil in Illinois and Indiana during the past five years and the data
obtained from the experiments appear in the literature.6- 14 Certain of
these published results, however, are sufficiently important to be in-
cluded here. The susceptible varieties, arranged according to classes,
are presented in Table 3, which is reproduced from a previous14 publi-
cation. The Cereal Investigations (C. I.) accession number, or other
source of seed and head descriptions are given for each variety. The
percentage of plants infected in each variety was determined on the
basis of macroscopic symptoms of the disease.
Harvest Queen (known as white chaffed Red Cross and Salzer's
Prizetaker) is the only widely grown variety that has proved highly
1925] WHEAT ROSETTE AND ITS CONTROL 293
susceptible. The varieties "Brunswick," Nigger, Penquite (Velvet
Chaff), Missouri Bluestem, Selection from Indiana Swamp, Fultz
(selection by Kentucky Agricultural Experiment Station), Miller's
Pride, and Illini Chief are very susceptible. These highly susceptible
varieties represent about 4 percent of the total number of varieties tested
and this relatively small percentage is striking.
Twelve varieties, aggregating 6 percent of the series, proved slightly
susceptible and an equal number of varieties showed slight traces of the
disease.
Inconsistent results have been obtained with a few of the varieties
at different places and during different years, but, for the most part,
results have been very uniform. The varieties and selections resistant to
the rosette disease have been listed in previous publications.3- 14
The more important, hard, red, winter-wheat varieties for central
and northern Illinois conditions in this list are Beloglina, Black Hull,
Kanred, Malakof, Michikoff, P 1066, P 1068, and Turkey Red. Among
the more prominent soft, red winter wheats that are resistant to rosette
are Early Harvest, Eversole, Fulcaster, Gladden, Mammoth Red,
Mediterranean, Michigan Amber, Red Rock, and Red Wave.
Red Wave, which appears among the resistant or immune varieties,
has largely been substituted for the Harvest Queen variety, while Fultz,
many strains of which are either immune or highly resistant, has been
used to some extent. A number of hard, red, winter wheats of the Turkey
type, such as Illinois 10-110 and Kanred, are immune and some of these
have been sown. The large number of varieties which are not suscep-
tible to rosette makes the practical control of this disease relatively
simple, but the presence of flag smut in southern Illinois in the same
area with rosette presents complications. Several varieties are either
immune or resistant to flag smut, as shown by Tisdale, Dungan, and
Leighty.13 The varieties resistant to flag smut are fewer in number than
those resistant to rosette and the varieties which are resistant to both
diseases are still fewer in number.
Of the many varieties that have been grown in both the flag smut
and rosette experimental plots, tho.se that are immune from rosette, and
either immune from, or highly resistant to, flag smut are Early Harvest,
Eversole, Grandprize, Illinois 10-110, Kanred, Mammoth Red, P 1066,
P 1068, Red Rock, and Shepherd.
The Red Wave and Fultz varieties, while resistant to rosette, are
somewhat susceptible to flag smut, and Illinois 10-110 and Kanred,
while practically resistant to both diseases, are not well adapted to the
southern Illinois areas. Shepherd, however, is a variety that seems to
offer excellent possibilities. It is resistant to both the rosette and flag
smut diseases and has yielded well in variety tests on Experimental
plots in southern Illinois. A resistant selection of Harvest Queen (the
so-called Salzer's Prizetaker) has been developed, and while this selec-
294
BULLETIN No. 264
TABLE 3. — VARIETAL RESISTANCE IN WHEAT TO ROSETTE DISEASE
Varieties of winter wheat found susceptible to the rosette disease, in experiments
conducted in the crop year 1921-22, at Granite City, Illinois, and at Wanatah, Indiana,
grouped according to classes, with head characters for each and percentage of infection.
Variety
C. I. No. or source
Head
characters*
Percentage of plants
infected1"
Granite
City, 111.
Wanatah,
Ind.
Hard Red Winter
Pesterboden
Budapest
5789
BWG
BWG
AWG
BRG
trace
0
0
0
0
0
0
0
0
80-90
1-2
95-100
95-100
95-100
5-10
0
0
0
75
95-100
95-100
95-100
0
0
0
95-100
1
1-2
0
0
trace
trace
trace
2
98
1
trace
trace
2
1
trace
45
0
55
50
5
25
1 +
3
1 +
trace
trace
trace
20
75
90
75
1
trace
1-2
40
trace
2
trace
trace
Turkey
Malakof
4898
Soft Red Winter
Alabama (Wis. No. 81)
Brown Bearded
5785
3118
"Brunswick"0
Ind. Sta
China
Pennsylvania
Bluestem.. . .
Currell
5342
ARC
ARG
BWG
AWG
AWG
AWG
AWG
BWG
AWG
AWG
AWG
AWG
ARG
ARG
AWV
AWV
AWG
BRG
BRG
BRG
BRG
BWG
BRV
ARG
ARG
ARG
BRG
BRG
AWG
(Club)
BRG
ARG
3326
Fulcaster
Stoner (Marvelous)
Fultz
3605
5308
Fultz
3598
Fultz. ...
1923
Fultz (Kentucky Selec-
tion)
6896
Gipsy
Niagara
5307
Harvest Queen
(Control)
Granite City, 111. . .
4882
Harvest Queen
Harvest Queen
Kans. Sta
Harvest Queen
Kessinger .
Ind. Sta.d
Illini Chief
5956
Illini Chief
Ind. Sta
Jones Fife
Jones Fife
Leap
Ind. Sta. (R. 25) . .
Ind. Sta. (R. 13)...
5618
Mediterranean
3332
Mediterranean
3467
Mediterranean
Miller's Pride ....
Missouri Bluestem
Nigger
4865 . .
1912
5366e
Penquite (Velvet Chaff)
Poo'.e
3068
5653
Red May
Enterprise
3399..
Red Cross
5318
Sel. from Ind. Swamp. .
Sel. from Ind. Swamp. .
Selection No. 13631 ...
Selection No. 131156..
Common White
Honor
4834
3334
4081
4808
6161
See bottom of next page for explanatory notes.
1925] WHEAT ROSETTE AND ITS CONTROL 295
tion is susceptible to flag smut, efforts are being made to develop a strain
from it which will prove resistant to both diseases.
Altho only about 10 percent of the winter-wheat varieties and selec-
tions grown on rosette-infested soil have shown definite symptoms of
the disease, that is, distinct stunting and excessive proliferation, fully
85 percent of the varieties, which have heretofore been considered
resistant to the rosette disease, have shown a mosaic leaf mottling in
various degrees of severity. All varieties which are susceptible to rosette
are also susceptible to the leaf mottling. In general, the mottling does
not seem to interfere with the development of the plants; however, in a
few cases (Malakof, Crimean, and Currell) the mottling is severe and
it appears to affect the normal development of the plants. It is of inter-
est to note that certain varieties show a variation in the distribution and
severity of the rosette symptoms for different years and it is of further
interest to note that certain varieties frequently show gradations be-
tween typically resetted and healthy plants.
Other possible control measures have been investigated, and, while
they have proved effective, they are not practical from the field stand-
point. Sterilization of infested soil with either steam or formaldehyde
adequately controls the disease. Moreover, the fall date of planting in
infested soil bears a definite relation to the disease. Within limits, the
distribution and severity of the disease decreases directly with delayed
planting. No symptoms have been noted with Harvest Queen (the most
susceptible variety) when it was planted so late in the fall that it did
not emerge until spring, or on any of the spring varieties.
CONCLUSIONS
The cause of wheat rosette is still unknown. There are indications
that it may be a phase of a mosaic disease.
The causal agent is soil borne and the disease recurs every year
when susceptible varieties of winter wheat are sown on infested soil.
The disease has not been noted in spring wheat.
Since the disease occurs in relatively few varieties it can be success-
fully controlled by sowing those which are resistant. The mosaic leaf
mottling which occurs on resetted plants and also independently of
rosette occurs on a large number of varieties when sown in infested soil.
However, this leaf mottling does not seem to cause a reduction in crop
yield in most varieties.
Notes to Table 3 :
»A = awnless; B = bearded; W = white chaffed; R = red chaffed; G = glabrous, or smooth
chaffed; V = velvet chaffed.
bTrace = less than .5 percent; 0 = no disease: — := not tested at that place.
'Received by the Indiana Agricultural Experiment Station from Brunswick, Germany.
"•Either a somewhat resistant strain or mixed somewhat with some similar resistant variety.
•A strain descended from a single plant selection. Other varieties of the Fulcaster group to which
this strain is similar are generally immune.
296 BULLETIN No. 264
LITERATURE CITED
1. BRANDES, E. W.
1919. The mosaic disease of sugar cane and other grasses. U. S. Dept. Agr. Bui.
829, 1-25.
2. CHRISTENSEN, J. J.
1922. Studies on the parasitism of Hflminthosporium sativum. Minn. Agr. Exp.
Sta. Tech. Bui. 11, 1-42.
3. JOHNSON, A. G. McKiNNEY, H. H., WF.BB, R. W., and LEIGHTY, C. E.
1924. The rosette disease and its control. U. S. Dept. Agr. Farmers Bui. 1414.
4. LEUKEL, R. W.
1924. Investigations on the nematode disease of wheat caused by Tylenchus tritici.
Jour. Agr. Res. 27, 925-955.
5. LYON, H. L.
1921. Three major cane diseases: mosaic, Sereh and Fiji disease. Hawaiian Sugar
Planters' Assoc. Exp. Sta. Bui. Bot. ser. 3, pt. 1, 1-43.
6. MCKINNEY, H. H.
1923. Investigations on the rosette disease of wheat and its control. Jour. Agr.
Res. 23, 771-800.
7.
1923. Influence of soil temperature and moisture on infection of wheat seedlings by
Helminthosporium sativum. Jour. Agr. Res. 26, 195-218.
1925. Certain aspects of the virus diseases. Phytopath. 15 (in press).
9. , and LARRIMER, W. H.
1923. Symptoms of wheat rosette compared with those produced by certain insects.
U. S. Dept. Agr. Bui. 1137, 1-8.
10. , WEBB, R. W., and ECKERSON, S. H.
1923. Intracellular bodies associated with the rosette disease and mosaiclike leaf
mottling of wheat. Jour. Agr. Res. 26, 605-608.
11. STEVENS, F. L.
1920. Foot-rot of wheat. Science, n. s. 51, 517-518.
12.
1922. The Helminthosporium foot-rot of wheat, with observations on the morphol-
ogy of Helminthosporium and on the occurrence of saltation in the genus.
111. Dept. Regis, and Educ., Div. of Nat. Hist. Survey Bui. 14, 77-185.
13. TISDALE, W. H., DUNCAN, G. H., and LEIGHTY, C. E.
1923. Flag smut of wheat, with special reference to varietal resistance. 111. Agr.
Exp. Sta. Bui. 242.
14. WEBB, R. W., LEIGHTY, C. E., DUNCAN, G. H., and KENDRICK, J. B.
1923. Varietal resistance in winter wheat to the rosette disease. Jour. Agr. Res. 26,
261-270.
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