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Historic, archived document

Do not.assume content reflects current
scientific knowledge, policies, or practices.

, BULLETIN No. 629 §

Contribution from the Bureau of Plant Industry
WM. A. TAYLOR, Chief

Washington, D. C. PROFESSIONAL PAPER February 11, 1918

GREENHOUSE EXPERIMENTS ON THE RUST
RESISTANCE OF OAT VARIETIES.'

By JouHNn H. Parker, formerly Scientific Assistant, Office of Cereal Investigations.

CONTENTS.
' Page Page
GO GiuiC HONG eee weet ee od wis 1 | Evidences of rust resistance in cereals.-....-.-. 5
The culture of cereal rusts in the green- Wxperimentalvdatays sesamiae ey eeieevenas 8
LENO TRIO Lo a TE Se AI OE a ae iG MID ISCUSSIONOLRES ULE Sear ewes septa eu ale 3
BD xperimental methods. - 459.2... 4-2-2. 222: 25|Summary,and conclusions:. 2 -2.-2-2----2- 14
SourcesioLmateriali; sso2 ee seo) 22k oe ee ia ele iGerabunercitedeesee ue ae Nae ee une ee 16
INTRODUCTION.

The rusts have long been recognized as one of the most serious
limiting factors in the production of wheat and oats, both in the
United States and in other countries. Considerable work has been
done on the problem of controlling rust in wheat through resistant
varieties and some results have been published, but very little specific
information has been made available on the rust resistance of oat
varieties in the United States.

The importance of the oat crop among the small grains in the
United States is second only to that of wheat, and the problem of
rust control is perhaps even more acute, for oats are more widely
grown in localities favorable to rusts. For this reason a proper
choice of varieties, based on accurate experimental tests, is a neces-
sary factor in successful oat culture. The present paper presents the
results obtained in greenhouse culture work with the crown rust of
oats, Puccinia lola avenae McAlpine (PI. I, fig. 2, and Pl. IT), and

1The work here described was a part of the graduate studies of the writer during the
college year 1915-16 at Cornell University and was a continuation of investigations
conducted for several years while in the United States Department of Agriculture. The
departments of plant breeding and plant pathology in the university provided every
facility for the work, which was carried out under the supervision of Dr. H. H. Love,
to whom thanks are due for many helpful suggestions.

16710°—18—Bull. 629 —

z BULLETIN 629, U. S. DEPARTMENT OF AGRICULTURE.

the stem rust of oats, Puccinia graminis avenae Erikss. and Henn.
(Pl. I, fig. 1, and Pl. III). These rusts are both rather common in
the United States. The stem rust probably causes the greater loss
in the Northern States and the crown rust in the Southern States.

THE CULTURE OF CEREAL RUSTS IN THE GREENHOUSE.

Obligate parasitism is a well-known characteristic of the rust
fungi, and all attempts to grow them in artificial media have failed.
They are easily cultured on the living host, however, and, as pointed
out by Carleton (2), it is possible to make many interesting studies
by this method. Carleton described the method of inoculation used
by him and gave suggestions concerning work with rusts.

Evans (4) has tested the rust resistance of oat varieties in the
greenhouse and concludes that the Indian varieties are far more sus-
ceptible to the crown rust than to the stem rust.

Melhus (8) has described and illustrated the apparatus used and ~
has given his methods in culturing parasitic fungi on the living host,
including notes on culture work with the crown rust of oats.

Fromme (5) has published a comprehensive paper dealing with
the culture of cereal rusts in the greenhouse, in which he briefly
reviews the work of previous writers and describes in some detail
his own methods, particularly the results obtained with the crown
rust of oats.

Stakman (12) briefly describes culture methods used in his green-
house studies of biologic forms of the cereal rusts and calls attention
to the effects of temperature, humidity, and light on the incubation
period. In a second paper (13) he has briefly described similar
methods used in the additional study of cereal rusts on plants grown
in the greenhouse.

Melchers (7) has suggested the use of lao tubs with
window-glass covers as moist chambers. He also advocates wetting
the leaves to be inoculated by the “ finger-rubbing ” method instead
of with an atomizer and keeping the pots bearing the rusted leaves
in shallow pans of water, to avoid the necessity of overhead watering.

EXPERIMENTAL METHODS.

In the greenhouse experiments of the writer, methods similar to
those ye e cited were employed. For the infection studies on seed-
ling oat plants 4-inch pots were used, and 5-inch pots for the plants
inoculated at heading time. Greenhouse potting soil of approx-
imately the same make-up was used throughout the work. For the
studies of plants at heading time four se¢ds of a variety were sown
in each pot. When the plants were 6 to 8 inches high they were
thinned to two in a pot, the number usually reserved for subsequent
inoculation.

1 The serial numbers in parentheses refer to “ Literature cited,” p. 16.

Bul. 629, U. S. Dept. of Agriculture. ; PLATE I.

Fig. 2.—CROWN RUST OF OATS: UREDINIA ON LEAVES, TELIA ON STEM.

Bul. 629, U. S. Dept. of Agriculture. PLATE Il.

FIG. 1.—SEEDLING OAT PLANTS INOCULATED WITH CROWN RUST.

Fic. 2.—SEEDLING OAT PLANTS INOCULATED WITH STEM RUST.

‘SMOA14 ANVIA
ing s31nisnd TIWWS M3S4 V AINO ONIMOHS SLSNY NMOYO HLIM GSLOAZAN] SLVO LYNG JO SNIVYULG OM] JO SSAV]E ONITGRSS

PLATE III.

Bul. 629, U. S. Dept. of Agriculture.

RUST RESISTANCE OF OAT VARIETIES. 3

About 15 seeds per pot were sown for the seedling work, and the
_ plants were thinned later, so that on an average about 8 plants
per pot were inoculated. Plantings were made every few days
from November, 1915, to April, 1916. Thus, there was always a
series of plants coming on; as soon as one series had been inoculated
~ another was about ready.

’ The cultures were kept in a cool greenhouse (night temperature,
— 50° to 55° F.; day temperature, 60° to 65° F.) and watered not less
often than every alternate day. The inoculations on the seedling

| Fig. 1.—Glass-topped galvanized-iron moist chamber used for seedling plants,

plants were always made when the first (seedling) leaf was still
_ vigorous and of a normal green color; that is, when the plants were
only 3 to 5 inches high. This first leaf was always the only one
inoculated. All others, with the “shoot,” were kept trimmed off.

Spore material of both the oat rusts was obtained from the Min-
nesota Agricultural Experiment Station and increased for use as
needed on stock cultures of the White Tartarian oat, the variety
used as a check.

About ten varieties usually constituted the series treated on any
one day, one set being inoculated with stem rust and the other with
*” crown rust. No plants were left uninoculated, but one pot of White
| Tartarian serving as a check on the other varieties was always sown
_ and inoculated with each series.

The inoculations were made by removing urediniospores with a
| flattened needle from a leaf bearing a heavy infection and placing

4 BULLETIN 629, U. S. DEPARTMENT OF AGRICULTURE.

them on the previously moistened leaf to be inoculated. When all
leaves in a pot were inoculated they were sprayed at once with an
atomizer and placed in the moist chamber shown in figure 1, where
they were allowed to remain 48 hours. These moist chambers, which
will hold about forty 4-inch pots, cost less than $10 for four. No
trouble was experienced from the leaves burning or turning yellow,
and almost 100 per cent of the inoculations were successful.
Inoculations of older plants were made in the order of heading
of the varieties, beginning on April 10 and continuing to May 9,
1916. There were 12 to 18 plants in each series. The stem-rust
spores were always placed
on the sheath inclosing the
emerging panicle, while
theinoculations with
crown rust were made on
the uppermost leaf blade.

inoculated plants were
sprayed with an atomizer
to insure the presence of a
film of water and then
kept in the moist chamber
for two days. A special
large glass-topped galvan-
ized-iron moist chamber
was made, holding eight-
een 5-inch pots and allow-
ing the tallest plants to re-
main upright (fig. 2).
The incubation period
for the two rusts was ap-
proximately the same.

Fic. 2.—Glass-topped galvanized-iron moist cham- Generally, though not al-
ber used for mature plants,

stem rust appeared first. Cool temperatures seemed to lengthen the
incubation period, for during November the house was cooler than
during the succeeding months and the uredinia during this time were
noticeably slower in appearing. Other factors, such as light, also
may have affected the results.

Notes on the appearance of flecks usually were made in 7 to 9 days,
and those on the formation of uredinia after a period of not longer
than 12 days. Further notes usually were taken on the quantity and
character of infection. No counts of uredinia were made; nor should
too much emphasis be placed on whether or not all the leaves inocu-
lated were equally infected, for it is obviously impossible to be cer-

4

As with the seedlings, the ~

ways, the uredinia of the —
Fy, >]

’

RUST RESISTANCE OF OAT VARIETIES. 5

| tain that the same number of spores was applied in each case. The
| time of appearance, size of uredinia, and character of infection are
_ deemed of greater importance.

The seedling plants were discarded as soon as final notes were ob-
_ tained. Those in the series inoculated at the time of heading were
_ allowed to mature in order to obtain herbarium specimens and seed
® for further work.

SOURCES OF MATERIAL.

The seed of all the varieties tested except Early Ripe? was ob-
tained from the 1915 crop grown in rod rows in the rust nursery at
Ames, Iowa. Most of these varieties were secured from Mr. C. W.
Warburton, of the Office of Cereal Investigations, Bureau of Plant
Industry; others were obtained from the Minnesota Agricultural
Experiment Station. The forms listed under the Latin (specific)
names (greenhouse Nos. 265 to 303) were obtained from Director
Bubak, of the botanic garden at Tabor, Bohemia, through Prof. G.
M. Reed, of the University of Missouri.

None of these varieties may properly be called a pure line, although
some of these rows are traceable (several seasons back) to single
plants. Others represent bulk material from rod rows, field plats,
or commercial seed stocks. Some of the foreign material is in great
need of more careful classification. Mixtures in the previous han-
dling of both the domestic and foreign material sometimes have
occurred, but it may be said safely that a majority of the varieties
were true to name and for the most part pure, so that where eight
or more seedlings were studied most of them really represented the
true type of the variety under the name of which they were grown.
In the trials on older plants, however, where only two individuals
were studied, slight mixtures of the seed sample were more serious.’

EVIDENCES OF RUST RESISTANCE IN CEREALS.

Before proceeding to a detailed description and consideration of
the observations made and conclusions drawn it will be well to refer
to the observations of earlier wurkers on rust resistance in cereals.

Cobb (8) described certain wheat varieties which were resistant
and mentioned the occurrence of dead areas of host tissue. Marryat
(6) also observed these dead areas in immune varieties, and Biffen
(1) mentions unopened pustules which shed no spores. Stakman
(12) observed similar indications of real resistance on (a) seedling
leaves of certain wheat varieties and on (0) leaves of a wheat sus-
ceptible to the stem rust of wheat but inoculated with the stem rust
of oats. He states that the more resistant a form proved, the more
pronounced was the tendency of the rust to kill small areas of the

1 Seed of this variety was obtained from Dr. H. H. Love. It is very similar to Burt
and perhaps identical with that variety. Evidence tends to show that the origin of the

two varieties was the same.
2 All such instances are indicated in Table I.

6 BULLETIN 629, U. S. DEPARTMENT OF AGRICULTURE.

leaf and that the pustules developed in these areas were always very ©
small. A further indication of immunity is said to be the fact that —
in the immune forms the incubation period is longer than in sus- |
ceptible ones. a
In a second paper (13) Stakman reports additional studies of the
relation between Puccinia graminis and plants highly resistant to its
attack. The occurrence of the same characteristic flecks or areas of @
killed tissue is again reported, but a new term, “ hypersensitiveness,”
is used to describe the phenomenon. 3 |
Although no histologic studies have yet been made of the oat
material, the external macroscopic evidence is in such close agree-
ment with the observed conditions in wheat that there can be little
doubt that a struggle between host and parasite of a very similar
nature takes place within the tissues of the resistant oat varieties.
Concerning the indications or signs of resistance which were ob-
served in the present study, it may be well to repeat that they are
very similar to those in wheat. They are—

. The prolonged incubation period.

. The formation of flecks (yellow areas of dead host tissue).

3. The formation of larger blotches of dead tissue and, in extreme cases,

the premature death of the whole seedling leaf.

4. Small uredinia, sometimes not completely or promptly rupturing the
epidermis, and in Puccinia graminis avenae the formation of purple ~ |
blotches adjacent to the uredinia.

. The small number of uredinia (relatively unimportant).

6. The production of normai telia of the crown rust on seedling leaves of

varieties which these other criteria indicate are resistant.

N ee

Ot

So far as known to the writer, the occurrence of telia on young
seedling leaves of cereals grown in the greenhouse has not been re-
corded in literature. Melhus (8) states that in his cultures, which
appear to have been on older plants, “ teleutospores developed in two
to three weeks.”

Tt is certain that: in the hundreds of seedlings described as very
susceptible in the present experiments telia were not produced on a
single one following a normal and abundant production of uredinia.
The fungus on these leaves seems to have finished its life cycle under
these conditions by producing the uredinia. After having remained
a normal green color for some time after the formation of uredinia,
the leaf finally dries up. That part of the life cycle so common
to the rust fungus when on ripening grain plants in the field is
not completed. On the other hand, quite early in the work it was
observed that in a comparatively short time telia were present on the
leaves of seedlings which gave other evidences of being resistant and
on which no normal uredinia had been produced. The spores from
these sori appear in every way normal, so far as determined by micro-
scopic observation. |

‘RUST RESISTANCE OF OAT VARIETIES. ener

On the upper leaf blades of the plants inoculated at the time of
heading, where one would normally expect the ultimate production
of telia, the resistant plants seemed to produce them at a remarkably
early stage. These early telia were produced, in all cases observed,
only. on leaves infected with the crown rust. It is the belief of the
writer that such a hastening in the completion of the life cycle of
the fungus is entirely comparable to the well-known instances in
the seed plants of the influence of unfavorable conditions, such as
drought, poor soil, and injury, in hastening the period of blooming
and the maturing of seed.

The teliospores are to be considered necessarily as the final stage
in the year’s life cycle of the rust. These spores do not serve to
spread the infection during the current season, but provide a means
for the reproduction of the disease another season or when conditions
are again favorable. :

It may be argued that the ability which the fungus in these par-
ticular varieties possesses to produce this final spore form is the best
possible indication of extreme susceptibility. Nevertheless, it is
certainly true that if a variety is able to prevent the formation of
the summer-spore stage of the rust, the spread of the disease will be
checked in localities where only such varieties are grown.

This unusual occurrence of telia on seedling leaves is thought to be
an additional evidence of resistance. It has been used sometimes in
making the distinction between resistant and susceptible individual
plants. Whether this interpretation is accepted or not, the presence
of telia on seedling plants of some and their absence on other strains
grown under identical conditions is very good evidence of real dif-
ferences in the protoplasmic reaction of the two hosts, for the prog-
ress of the rust fungus following infection is quite different in the
two instances. The same stimuli, whether they are chemical, enzymic,
or osmotic, which cause the formation of flecks in some varieties
and not in others may exercise a rather direct influence on the ability
of the parasite to produce a particular spore form at any given time.

Norton (10) reports the abundant occurrence of aecia of the
asparagus rust on plants which were resistant to the uredinial stage
of the rust.

Smith (11), in studies of the water relations of asparagus rust, has
found that “a very direct relation exists between atmospheric mois-
ture and the prevalence of the several spore forms of the rust,” and
that “ the teleuto stage may occur in asparagus beds little affected by
the rust, and apparently not preceded by any trace of the other
spore stages.” He concludes that “the teleuto stage is then to be
regarded as a provision for surviving any condition unfavorable to
the fungus, whether of food supply, moisture, temperature, or resist-
ance by the host, without regard to season.”

8 BULLETIN 629, U. S. DEPARTMENT OF AGRICULTURE.

Morgenthaler (9) conducted experiments to determine the effect
of various influencing factors on the production of teliospores and
found that “the time of appearance of the teleutospore stage is not
dependent alone on the season of the year, but may be hastened or
retarded by many other influences.” He also states—

Ann nett [Lowel _<thuialimnstiid dial ° cued gn aba

It is also true that the chemical constitution of the host may provide condi-
tions either favorable or unfavorable for the nourishment of a particular para-
site. There are cases known in which the same rust will produce uredospores
copiously on one host and only sparingly on another. There may be in certain
host plants substances toxic to the fungus, as tannin, which further influence
the nourishment of the parasite, and with it its spore production.

This ability of various conditions to influence teleutospore production may
also be regarded as a method of protection which the rusts have against
influences which are unfavorable for the normal development of the fungus.

EXPERIMENTAL DATA.

Table I presents the results of all the varietal tests, including inocu-
lations of both rusts made on seedling plants and on the plants at
time of heading. The inoculations made were as follows:

“eee ett. 3 feos oe

Stem rust:
Seedlings: 28 l ee Y P Es a ee ee 12:256
PRO AMSA. pa oe a eT 260
Crown rust: .
Seedlings ee cl Se NNT eel ee ee Pe en ne ee 1, 480
Héaded™plantse 2 26. 02h ee a se ee ee ee 260 :
{6} i: Ea ce SN Lee en A AN ee eet a TRA Ais 2 3, 256

The varieties are arranged alphabetically by name in Table I,
except that those bearing the Latin names under which they were
received are placed in a separate list, as are also the varieties of red
oats which are derivatives of Avena sterilis.

The greenhouse number (column 2), the classification list number
(column 3), the Cereal Investigations number (column 4), the Seed
and Plant Introduction number (column 5), and the Minnesota Ag-
ricultural Experiment Station number (column 6) are included in
Table I in order that identification may be more certain. It is thus
quite possible to compare the record of any variety in this list with
statements made in literature regarding it or with field records.

In columns 7 to 10 of Table I the letter S indicates the undoubted
and complete susceptibility of that variety under the conditions of
the experiment. A question mark (7), S?, or R? indicates some
doubt and the need of further tests, while R-+ S indicates that both
resistant and susceptible plants were observed. The letter R has been
used only where normal irfection did not occur. In these instances
the evidence seemed convincing that plants of the variety when tested
in the manner here described prevented the formation of normal
uredinia and may therefore be regarded as resistant. In a great

Jatt SS a ae

ee t

id

RUST RESISTANCE OF OAT VARIETIES. 9

majority of cases all leaves or culms inoculated showed infection

{normal uredinia) except in certain varieties where there were very

evident signs of resistance and to which attention is directed in the

footnotes to Table I.

TABLE I.—Swummary of notes on the rust resistance of oat varieties tested in the
greenhouse at Cornell University, Ithaca, N. Y., 1915-16.

[R.= resistant; S.= susceptible.]

Identification numbers. Crown rust. Stem rust.
rs o : 2 :
,|2 1/3 =. = 3
= |) Sas ists : a eis a of ‘
Siaa |H.o 6 oe EO Ss 59 SS
euleame arse le |) as Bo | 2 | Be
[2 (2%! a E 3s gs 3 | 4
GAO. lo Boe D a BD a
1 2 3 4 5 6 7 8 9 10
Common (sativa) varieties:

Md aM Ceuta Anes sere ap 272 S. Ss. Ss. S.
PAD erlaeieces ee poy on) LAS Atala lt A Sarat eae Ss. S. S. 1$.?
American Banner......- Oia te: aa Ee See 275 S. S. Ss. S.
"Archangel: -- = 25.22.22 ..: 1 eae ee eat ixterseast 280 S. S. S. S.
Archangel x Early Goth-

TEN aVGl SS Sores Se oat ee, DB treo) bape | teenie 305 s. Ss. S. Ss.
NB AIATI CT a ens os fe BO a ea eH to Eas 348 Ss. s. Ss. Ss.
iBreknelig@-are cee Es ea ae PLD G Reames Se S. S. S. 2 Ren.
IB PROUT see te eee A Drees Wecenie te ees 354 Ss. Ss. S. Ss.
Black Anthony.....-.-- NOVA as oe alloeeeolleacece Ss. Ss. Ss. Ss.
Blacks Beauibyeee. 2-4) 2: Ose bomllae eel G ee 342 S. S. S. S.
Black Diamond......... 108} 1814)....- lee a ata tee Shea eae tense lisarhSi a tenets Bee
Black Tartarian.-....-- PGA) aie Seale egerati pepacitoi be lea Ss. Ss. S. Ss.
Bumper Crop......-.--- QIN. WON eae (py ae Ss. Ss. Ss. S.
Challenges 232 awe ss Sine ne ee ee ban ean 273 Ss. S. Ss. Ss.
Clydesdale.............- SO era 2O Se eccera| eesvale U = S. Ss. Ss. 38.?
Colorado No. 9.........- SO Oe | Saree leer 336 Ss. 8. Ss. S.
Conqueror = QE RSLA OS ecard ste Ss. Ss. Ss. Ss.
Culberson selection .. - - - Opener! Gola tee S. S. S. Ss.
Danish Giant.=<.......- 69S: (CSA baer Sea i ea Ss. Ss. Ss. Ss.
Early Champion........ Aas ae Hen Be eum e. Cots Ss. 4R.? S. |5R.+S.| Mixed seed.
Early Gothland......... DH ee pe are Tee Bes OX SH 68.? S. ave?
English Wonder. ......- 104) 1807|..-_- RSE sear: S. S. S. S.
Garton No: 5.22.22..--2- oe Bales CON el ene [eens S. s. S.
Garton No. 396......--- AG ieee es se 405 S. S. S. S.
Goldmine ers 2 eS LOS USOSa ere ee Lee S. Ss. S. S.
Green Mountain. - .-. Olea y= se Lees S. She ii sh 8.
Green Russian.........- ZA ee Re OIA Sk | el FSO Shy Chea aS vale pelaesa etsy Do.
JOHNSONESt Beet LOG SISOS ao =O erie oe era S. S. S. S.
USS eee as ee 98] 1800)..-.. ees Ieee Ss. Ss. Ss. s.
Line On GAPS s abkecocanee Blab issee ge cea hae ea | 341 Ss. Ss. Ss. S.
HST O WO ae ee es a eet es earns hans abd | 6 S. Ss. S. S.
incon eee eee oe es eaetel roe | 340 Se S. Ss. Ss.
IRicket tame ee ose: SRS UMZS Eee se see ne Ss. Ss. S. Ss.
Roosevelt ....-.-.-----.- 43)_...-. Wesiejevel ets 391 es Ss. S. Ss.

9 OR. \ u 129.2 Ke R.

Ruakura Rustproof9....| 79|....-- HOW ae eee (48) PER+ ps2 Hits fb Do.

1 Normal infection on one plant; on the other, only a few uredinia surrounded by purple blotches.

2 Only a few abnormally small uredinia in 14 days after inoculation.

3 No uredinia in 10 days after inoculation, and finally only one on each culm, accompanied by purple
color of host tissue.

4 Only a few tiny uredinia on each leaf.

5 Normal] uredinia on one culm; only a few on the other.

6 Infection only fairly vigorous.

7 Unusually small uredinia first appeared 14 days after inoculation.

8 Normal infection on one culm; no uredinia on the other.

9 The results with this variety probably were more interesting and valuable than those from any other
included in the test, for there were signs of resistance to both rusts at both stages of growth. This variety
is of undoubted value as a source of the character of rust resistance, the more so because of its resemblance
to yellow and white oat varieties of the Avena sativa group.

10 Six leaves severely rusted; on four only extremely small uredinia. In two pots of seedlings later
inoculated no normal infection resulted.

11 Flecks only; no uredinia. Within two weeks the small dark telia, characteristic of resistant varieties,
were formed.

2 Uredinia moderately abundant, somewhat small and surrounded by yellow flecks.

13 On one plant uredinia were abundant and of normal size. On the other plant they were small and
tardy in breaking through the epidermis.

10 BULLETIN 629, U. S. DEPARTMENT OF AGRICULTURE.
TABLE I.—Summary of notes on the rust resistance of oat varieties tested in the
greenhouse at Cornell University, Ithaca, N. Y., 1915—16—Continued.

[R.= resistant; S.= susceptible.]

Identification numbers. Crown rust. Stem rust.
Ae : g g
Variety. Sais SP ca 2s a6
W Bis. B Z } bs 5 z 3 a é Remarks,
ap |= <j op Gey op od
R=} =O }e | a =i n q n
Sie lee | Oa le mal eae te laa
ipey WN Aes a a a BY
1 2 3 4 5 6 7 8 9 10
Common (sativa) varieties—
Continued.
ScopiishaChict)--=ss5sss CP! TUB oes ellesoSelle =a! Ss. Ss. Ss. S.
SensatlOnenne yeaa 10 7)| SP STi oe a eee ake Ss. S. S. Ss.
Shadeland Challenge...-| 71).....- Ooo ceclleseue- S. Ss. Ss. Ss.
Shadeland Climax __--..! 72).-...- 681 R2 eee Ss: Ss. Ss. Ss.
ITC i AR es nr ee ence 1D [is Sk ea Sen th bare ee 285 Ss. s. Ss. Ss.
SIDS ANG Mee see Sree Net 1A oe alleys eoleesiots 286 Ss. S. Ss. S.
Sixty-Day (Minn.)...... Bee beset a 261 S. Ss. Ss. Ss.
Sixty-Day (parent). ..-- a a |e ere 4 eee nose Ss. Ss. S. Ss.
Slonmekings=s sees OG |e eT S02 ee ae ae eee es |e eee ees S. Ss. Ss | me Sue
Stuberetermas- iri ais SUES Shs SIZ telZ 26) Ee 5es | eee eee Ss. Ss. S. Ss.
Swedish Select.........- Gime SAE ees, ee eee 271 S. Ss. Ss. S.
White Bonanza--.--2.._- GA te atone a es 403) Ss. S. S. Ss.
White Russian.........- TUS} Soe A Bees SS SHEMET Sl oh 301 S. S. Ss. Ss.
WihiteRartaniam (Ghecks)s ato |pess-e | sae enee pee Ss. Ss. 158.? R.
White Tartarian.....-- ON SUS OS te esees | haces | eke ees [pee sere Sew e ae 16$.?
White Wonder.........- iy Ameer ene ie beret 299 Ss. Ss. Ss. Ss.
Wininenee lige necoeussesoe G4) eee (00 Fa) eran gue enn Lee wet ATS das Alla re Ss.
Osa ek eee aA ae 1H sea es 609|25259].....- Ss. 18 §.? S Ss.
Avena sativa (botanical
races):
Avvena, Sativas-.--.-.-.- QO |Berac lee ee. PGs sscce Ss. Ss. S. S.
ACESS MON ban aes eee DO a eas eel eee Eeees Ieee eae S. Ss. S. S.
INS GELS D ISI a a eae a 266 | Sees es es esa S. S. S. Ss.
SAWS HAUIMO Dieters ws ws eee QOT asso eres Peal eos (eee S. S. S. Ss.
aN Seta Of ari Ves es a ae ee i DTA ese IN| eS ke Aaa is 19 $.? Ss. Ss. Ss.
TAUISUSCLOSAs ae ee i ss DALAT ihe al eae SI aa elle Oe 20S.? Ss. Ss. Ss.
A’ Ss. .aristata 99... 023.5.) 276 |e eee | eee ape de (Renee = 8. Ss. Ss. 8.
FAR SIMUL CQU= sa aee eee DA Ales Peeve Wench [ee aily 9S ie ss Ae Si Ss. Ss. Ss.
DY oy Speier ae? 7c ie eee ieee tal eco ioe [ee uces | S. S. S. S.
LD) Oe ae Face DIMAS es ae fe eee | See Ss. S. Ss. Ss.
AB Yo)aeiies S hrsee 08 tet ee oer DSO ees eee aa eee ee Ss. S. S. S.
TD Xo Ea Bike i i ee Seed ee DASSIN Sr ae alle cagiel hile, Ss Logs Seri eens S. S. Ss.
ID Yoyo Mea he conee hn ee As) We eae target al fe Le Se Se S. S. S. S.
ID) Oo eee a OBS [See weal ane eal hte ae [igre af! Se S. S. Ss.
Bo meee Ser ae tye ihe Bae es DBA | Bs OE ls See Sorell mae Te ean ear She S. Ss. Ss.
DO a: ea eee ee OAS Nae Mi Wek | ln Sts So S. 21 R.? S. Ss.
1D Lo fet ise rUa as eta es 286 |e [era eile tie ae S. S. Ss. Ss.
ID Oe SUTRA Rae. Qeill = Bose Reset? lecseeee EO Ss. S. S. Ss.
I) Qs ea he et ORS emt eee tonal Ngee ee NA 2 Ss. Ss. S. Ss.
DOSY GAR aleve tones fay4e33 egies a ieee il eee Pompous S. S. Ss. Ss.
DD) OES a as ee OXON) eee tal a el Vi a daca Ged 2 S. S. Ss. S.
PAWS PAG ERAVAS = ese PASH aisle 6 ete [eve eee Cee S. S. S. S.
ORG SU eae DAO PANT Nill eae a a ae aa 2R.? S. S. |23R?+8S.
Ti) QA Set ae ee DOS ie: Celle raiee: lise) AAO Ss. S. S. Ss.

14 Normal uredinia in the usual time on one plant; on the other culm subepidermal uredinia, at first
small and surrounded by spots of purple color, but later rupturing the epidermis and attaining normal
size. :

1s Uredinia usually numerous, but small. Epidermis not always ruptured early; on some plants only
flecks with tiny uredinia were formed.

16 Few uredinia, normal in size but accompanied by blotches of purple color, probably an anthocyanin,
similar in appearance to those commonly present on sorghum and maize plants. These blotches were
oiten observed adjacent to stem-rugt uredinia and may indicate an unusual disturbance in the physiologic
activities of the host cells, whethe¥ or not they are directly related to the question of resistance.

7 Light infection; uredinia few and of small size.

18 Light infection; uredinia tardy in appearing and never reaching normal size.

19 Normalinfection on five leaves; light infection on two leaves.

2 Normalinfection on six leaves, medium on two, and only a light infection on two.

21 Only a very few tiny uredinia, formed 14 days after inoculation.

“2 No uredinia on leaves of first seedlings inoculated; the leaves appeared dry and dead within a few
days afterinoculation. In thesecond seriesinoculated, only one leaf was severely infected. Eight showed
medium infection, and on one no uredinia appeared.

23 Normal infection on one plant; no indication of infection on the other.

RUST RESISTANCE OF OAT VARIETIES. : 1a

TABLE I1.—Summary of notes on the rust resistance of oat varieties tested in the
greenhouse at Cornell University, Ithaca, N. Y., 1915—16—Continued.

[R.= resistant; S.= susceptible.]

Identification numbers. Crown rust. Stem rust.
s |3 2 % z
Variety. CA ice Sar ca) ( ae t as Remarks.
3 S-ladt é n aes n fe S|
Oia We } <q Bp rel op S38
sa Weald (ec) rs alee bel a) es
Se eet eo ae a) S| aid
Srike Oo aa D a Dn cv
1 2 3 4 5 6 7 8 9 10
Avena sativa (botanical
races)—Continued. . ; 5 |
A.S. trisperma.......... DOAN A yal cera a haan 24 R.? 2% R.? Ss. iS)
PAC Sas RIMM Aise oe ae AON MES SHI a Sa Rene au an S. S. Ss. S
PAVMS eon CAs eee se ee DS Rei | secre eat Ge aes ipa Ss. S. Ss. S
A. Ss. praegravis.-........ 290 ae ae ea NBC ese aa S. Ss. 8. S Mixed seed.
TA Se TIMUELCAe ee ose SOM ee ae ees [pee a S. S. S. S
BID) OI Ae es ett SO Diarra ietias PSs tel Be a S. Ss. Ss. Ss
HTS) Owe he ont cele wie SSO RST ee SN SOO en HE Ss. 26R.? S. S
Miscellaneous species of
Avena:
Avena barbata..........- HILO bern a rege Dagan” 278.? |28R.?+8S.] °S. Ss.
LSNUAIS TS Seem eal tins ti GPRD | eer a eGR at PDS aL S Ss. Ss. Ss.
ONE AGI SP Se Cot Sy Ais CaN TBR ANC eae 29 §.? 30 R.? Ss. Ss.
WAWNT AUT a eet We ea eat tee, LCOS) seg ae eR ee al ep eR a PSI Siiyetin pena wae S. Do.
BAe Te OLA ONAL A wees Wie iy. TMM sense yaaa ge Nei a Ss. S. Ss. S.
A. ludoviciana........--. TNT Ob de as yl pie leaps S. Ss. Ss. Ss.
FNS NaN Lele aces eae ee a ee METS aes Oe lee Zoo lene oes Ss. Ss. S. Ss.
RID) Cepia ee he IG eo eae 16894 aes Ss. Ss. Sei esieRa? Do.
A. orientalis pugnax....| 268)......|..-.-|..---|------ S. S. Ss. S.
EASFOMUBISUISE ety ae ae COA OKO cease lee MAE ote Ni aa S: Ss. Ss. S.
A. 0. tartarica..........- iG) ee es as CONTAC vai S. S. Ss. Ss.
PAUOMSITMLIC As ee DUR etaetacs a RIN it Acc Ss. Ss. S. | 32 R.?
EAU OM PUA A ease Sires DITO NA sib rel SiO all ea ene 2 aR Ss. Ss. Ss. Ss.
PAM OM ODUUSA LAE aes pi DO FAR A Se si ias S| Ae oral et S. 33 R.? Ss. Ss.
ANs OWI OURS SE 2a eos A OST Ses SS erates PISS ae Ss. Ss. S. | %4R.? Do.
Avena sterilis and varieties:
Avena sterilis..........- 116 My se Dilupo i eee Ss. 35 §.? Ss. S.
HD Ope eee ee 29 Ree eee CU et anv see ao? S. 8. S. S.
Algerian Red. - /1.). 25.2 Alm Daetseteat eke ON ioe Bete uit S. S. S. S.
INGOV ONG Bs Sis) TA ares eee mae Ge eee GO Fyre sy pe) pea es 36 R.? R. Ss. S.
JER ODE ie) 5 Nea a inellin e cieay NCAR ei eae Ra as Se Hem te 37 §.? 38 R, S. Ss.

24 In the first series inoculated, small uredinia on two out of nine leaves, flecks only on seven. Allleaves
S008 dry and dead. In the second series inoculated, heavy infection occurred on five and light infection
on five.

25 Flecks only 10 days after inoculation; later a few tiny uredinia, accompanied and surrounded by
many flecks.

a No uredinia 10 days after inoculation; later a few tiny ones on each leaf, surrounded by flecked areas
of host tissue.

27 In the first series fairly heavy infections were obtained on all leaves inoculated, but uredinia were
small. In the second series normal infection on two leaves, medium on eight, and light on two.

28 Heavy infection on only one leaf; only a few tiny uredinia on the other two.

29 In the first series of inoculations fairly vigorous infections were obtained on some of the leaves. On
other leaves only a few small uredinia appeared, the leaf soon drying and turning brown. In a second
series, normal infection occurred on all leaves inoculated.

m # Flecks only 10 days after inoculation. A few small uredinia appeared later, accompanied by distinct
ecks.

31 On one plant, uredinia nearly normal in size, but accompanied by purple blotches; no uredinia were
produced on the other plant.

32 Uredinia few and small; infection not heavy.

33 No evidence of infection in 10 days after inoculation; the few uredinia finally produced were small.

34 Uredinia normal on one plant; on the other small and surrounded by purple blotches.

35 Flecks only on one of the two leaves inoculated. The leafsoon dried up. A large number of normal
urcdinia appeared on the tip of the other leaf. On most of the leaf surface, however, there were very few
uredinia but many flecks.

36 Of the first series of 11 leaves inoculated 5 were heavily infected, while on 6 only flecks were evident.
In the second series inoculated uredinia were produced on all leaves but were accompanied by many yel-
lowish flecks, and larger blotches of dead host, tissue surrounded each uredinium.

37 In the first series of leaves inoculated 6 out of 10 leaves were rather heavily rusted, 1 showed light infec-
tion, and on 3 only flecks appeared. In the second series nearly normal infections were secured on all
the 8 leaves inoculated. In the third series medium to good infection resulted on all 11 leaves inocu-
lated. Many of the uredinia were of normal size, but surrounded by light yellowish green flecks.

‘ 38 y oO uredinia. Rather indistinct light-green flecks were observed, indicative of the presence of rust
yphe.

uo BULLETIN 629, U. S. DEPARTMENT OF AGRICULTURE. |

TasLe 1.—Summary of notes on the rust resistance of oat varieties tested in the
greenhouse at Cornell University, Ithaca, N. Y., 1915-16—Continued.

[R.= resistant; S.= susceptible.]

Identification numbers. Crown rust. Stem rust.
pect ; : ;
al eh ales 2 z 3
> 2 e a
Variety. 413 22 a 4 a a a3 Remarks.
ey || Secs | LS iota) os a0 eo:
qe D = <j ¢ ~ rs ~
elg2lesei4i2¢| 4 gp }s | ge
be Ss i) Be pie ee 1 Pe See omlt ee lace
SHS 'o) o| op 4 nN &
1 21a tale Ne 7 8 9:4) to
Avena sterilis and varie-
ties—Continued.
IB Unb eeeee eee eaee 10|asee* 606leaet eee 39 R.? DUAR he Sh. Ss.
WD) OMe See rs, Hille w ence Fil) eWay pene bee 2R.? S. S.
Hankyanipesse: aoe cee - |= 652 [Persons] =a ettee ees oe PASAERS) || S. S.
COOKBE Reese eerie SEE ore Til hae Rex GOS 6% R.? 46 R, S. S.
al huni eee ae (Se oe 6O4F Wers| Ss see AS |p ES TBR S: S.
Golden Rustproof......- Gil Seen 509(s | eeeee 49S? 50 R.? S. S.
OW Be Eel 931796 | eee eel SN See S. S. S. Ss.
Italian Rustproof. -.-.--. DAs Bist ese alsaacee Ss. Ss. S. | 2S.22
| Dio eeen ae ee Bia) BOF ecg eee S. S. S. S.
Italian Rustproof selec- | 58)..___. [4094 |< era ee ee a2 R. 38R S. S.
tion.
Red Rustproof.......... OE ee (pyre 309 S. S. S. Ss.
Red Rustproof selection! 52|...._- 261TH Oe ee 54$.? Ss. S. |°R.+S.
Oneee Eee a ote 62| aes! 5IS=15 | Sa lease 56 R.? 57 R. Ss. Ss.
De ss a Paes Us| eee ROO Gos) os ae 58 S.? S. S. S.
SiberianuRedeepn 2 ss aa: i!) aaa eek: Sed eat age geen: | Ss. Ss. S. |59 R.?
Turkish Rustproof se- | 53...... OOO Oe Se ae fee Ss Ss. Ss. S.
lection. |
DD) OMe eet AS cl Mins e ke png O20 | error | © R.? | & R. S. Soa

39 Three series of inoculations were made. In each some leaves were rather heavily rusted, others lightly,
and on some no uredinia (only flecks) were formed. Telia were freely produced on leaves where no normal
uredinia had previously ruptured the epidermis.

40 Normal uredinia on one leaf; flecks only on the other.

41 Tn the three series of inoculations made no leaf was heavily rusted. Only a few had even a slight infec-
tion, while most of them very quickly showed large reddish brown blotches of dead tissue and smaller
yellowish green flecks and no uredinia (see PI. III).

42 Normal infection at the base of each leaf, the upper portion heavily flecked and soon turning brown
in color, with no normal uredinia.

43 In the seven series inoculated, there were both susceptible and resistant plants, the former with many
normal uredinia, the latter with few and small uredinia or flecks only. On many leaves, large blotches of
host tissue were killed soon after inoculation. On some ofthese, telia were later developed.

44 Of five leaves inoculated, on only one were normal uredinia produced and these only at the base. On
one leaf a few tiny uredinia were formed, and on three flecks only appeared.

45 In the first series of 6 leaves inoculated, a few light-green flecks furnished the only evidences of infec-
tion. In two later series of 6 and 10 leaves inoculated, normal infections occurred on 8 of the 16, while the
other 8 had only small uredinia or flecks.

46 No uredinia appeared in three weeks after inoculation; then only tiny ones on one leaf. Distinct
flecks were evident.

47 Of 9 leaves in the first series inoculated, 1 was heavily rusted, 6 medium, and on 2 only flecks appeared.
Of 14 leaves in a second series, fairly normal infection occurred on all, though some uredinia were rather
small. No sharp indications of resistance.

48 Two leaves inoculated; on neither were any normal uredinia produced. Uredinia small and accom-
panied by flecks.

43 In the first series of 8 leaves, normal infection occurred on 5, light on 2, flecks only on 1. In the
second series of 9 leaves, 4 were heavily rusted and 5 lightly.

50 No uredinia in 11 days after inoculation, then only 1 or 2 small ones on each leaf. There were also
blotches of dead host tissue.

5. No uredinia normal] in size or vigor; after 21 days they were still small. é

52 Of 6 inoculated leaves in the first series, normal infection was produced on 3 and very small uredinia
and flecks on 3. Nonormalinfection occurred on 9 leaves inoculated in the second series. There were
only a few tiny uredinia with many flecks.

53 No signs of infection except dead leaf tips.

54In the first series of 9 leaves inoculated, normal infection was secured on 6, while only flecks ap-
peared on 3in the time characteristic for uredinia. Telia were formed later. In the second series, the

2 leaves inoculated were rusted heavily. ;

55 Normal (very heavy) infectign on one culm; only a very few small uredinia on the other.

56 No evidences of infection on the leaves of the first series inoculated. Only a few tiny uredinia were
formed on the 9 leaves in the second series inoculated.

57 Only a few very small uredinia; many flecks. ; :

58 Of 10 leaves in the first series inoculated, 6 were heavily rusted and a light infection on 4. Of 11 leaves
in the second series, 6 were heavily rusted, on 4 only a few very small uredinia developed, and on 1 only
flecks appeared in the time usual for uredinia formation. An abundance of telia later occurred.

59 No uredinia of normal! size and vigor; only a few tiny ones on each leaf. MEI £

60 Of the first series of five leaves inoculated, one was very heavily rusted, three had only a light infec-
tion, and on one only flecks were produced. All leaves of the second series inoculated were rather
heavily rusted, but numerous flecks were observed, also indicating some degree of resistance.

61 Infection not heavy; uredinia on each leaf few and small.

RUST RESISTANCE OF OAT VARIETIES. 13
DISCUSSION OF RESULTS.

The notes in Table I on the varieties which showed resistance to
one or both rusts indicate that rust resistance is very specific and
that a particular variety may be entirely susceptible to one rust and
somewhat resistant to the attacks of another.t

Of the 122 strains tested, 80 unquestionably were susceptible to
both rusts in both stages of growth. This does not imply that these
varieties are not of great commercial value in other respects and is
not sufficient reason for discarding them from cultivation, for at
present there are no suitable varieties to substitute for the best of
them. It probably does remove them, however, from the list which
is to afford promise of rust-resistant varieties. Heavy infections
were obtained on practically all of these, and at least some normal
uredinia were formed on all. While such greenhouse tests do not
represent field conditions accurately, the optimum conditions for
infection provided should make the evidences of resistance which
appeared in some varieties all the more valuable. Some of these
varieties may show some resistance under field conditions and some
of them have properly been recommended as rust-escaping because
of their early-ripening habit, as, for instance, the Sixty-Day and
Kherson varieties.

In 80 out of the 122 cases the results at two distinct periods in the
life of the host plant have led to identical conclusions as to the sus-
ceptibility of the variety. In some of the resistant varieties, also,
both seedlings and mature plants gave the same evidences of re-
sistance, though the results are not always in agreement. These
susceptible varieties need not be discussed in further detail, but the
list includes the following commonly grown sorts: American Ban-
ner, Big Four, Ligowo, Lincoln, Siberian, Sixty-Day, Swedish
Select, and White Russian. In this list are included also most of
the botanical species represented and nearly all of the recently intro-
duced foreign varieties.

In the Avena sterilis group also, where most of the resistance to
crown rust is found, several strains are very susceptible to the crown
rust, as, for instance, Greenhouse No. 296, Red Algerian, and one
strain each of Golden Rustproof, Italian Rustproof, Red Rustproof,
and Turkish Rustproof.

Not all varieties of the Avena sterilis group show perceptible re-
sistance to either rust, and great care should be exercised in recom-
mending to farmers these or other varieties as rust resistant. Still
ereater care is necessary in choosing a strain to use as a parent

17The studies of these varieties indicate the necessity for selecting and working from

individual plants, for certainly within the same variety, and even within a line supposed
to be pure for other characters, differences of a major degree in rust resistance exist,

14 BULLETIN 629, U. S. DEPARTMENT OF AGRICULTURE.

variety with the purpose of obtaining a resistant variety through
hybridization.

None of the seedlings of the 23 varieties belonging to the Avena
sterilis group showed any resistance to the stem rust, and in only
three of the varieties did the plants inoculated at heading time give
any evidence of resistance to this rust. It is entirely safe to conclude
that all of these varieties are quite susceptible to stem rust, and the
Avena sterilis group probably will offer little in the way of resistance
to stem rust that is of value to the plant breeder.

Of these 23 varieties 16 show some degree of resistance to crown
rust, Certain strains were strikingly resistant in both the seedling
stage and at heading time, and from the clear-cut evidences of re-
sistance there can be no doubt of the presence of resistance to crown
rust in varieties of this group.

These varieties which are actually resistant to crown rust, if found
to be high in yield, should replace some of the “rustproof” types
now being grown in the Southern States. They may be of use also
in the breeding of rust-resistant varieties for culture in other sections
of the country.

Table I shows that here are many more cases of resistance to the
crown rust than to the stem rust. This is especially true of the work
on seedlings, where none of the varieties tested except White Tar-
tarian and Ruakura Rustproof showed any resistance to stem rust.

In the studies of both rusts, more apparent cases of resistance are
recorded from the inoculations made on the plants at the time of
heading. This may be due to the fact that plants are more susceptible
as seedlings than when more mature. It is more likely, however, that
some of the failures to get normal or heavy infection were due to the
fact that it was more difficult to wet thoroughly, and hence inoculate
heavily, the upper leaf blades and sheaths than the young seedling
leaves.

The use of the word “immune” is avoided, for m the forms studied
none were observed in which very distinct evidences of infection did
not appear. The words “resistant” and “ resistance” are used only
in a relative sense and refer to that condition in which normal
urediniospore production by the fungus was either prevented or
seriously interfered with. As Stakman (13) has pointed out, the
quality which is called resistance may actually be, in the extreme
sense, susceptibility or hypersensitiveness.. It amounts to “ commer-
cial resistance,” using that expression to describe a variety which will
suffer less severe damage in the field than some others.

SUMMARY AND CONCLUSIONS.

(1) Two distinct rusts of oats are common in the United States:
a) Stem rust, Puccinia graminis avenae Erikss. and Henn., and (0b
) g ?

RUST RESISTANCE OF OAT VARIETIES. 15

crown or leaf rust, Puccinia loliit avenae McAlpine. The stem rust is
more common in the North, while the crown rust, though practically
always present, seems to be most abundant and serious in the South.

(2) Greenhouse studies are of value in determining varietal: re-
sistance under optimum conditions for infection. These studies, how-
ever, should always be supplemented by rust nursery and field trials.

(3) Plants of more than 120 strains of oats were inoculated at two
different periods of growth (the seedling stage and the heading stage)
and their reaction to both rusts determined.

(4) The inoculations made on these varieties were as follows: Stem
rust.—Seedlings, 1,256; headed plants, 260. Crown rust.—Seedlings,
1,480; headed plants, 260. Total, 3,256.

(5) Of more than 120 strains tested, 80 were found to be entirely
susceptible to both rusts at both stages of growth. Unquestionable
resistance to stem rust was present in only two varieties, White Tar-
tarian and Ruakura Rustproof. Several varieties of the red-oat
group (Avena sterilis), including certain strains of Burt, Cook,
Appler, Italian Rustproof, Red Rustproof, and Turkish Rustproof,
are very resistant to the crown rust. Ruakura Rustproof and certain
recently introduced species of Avena also gave indications of resist-
ance to crown rust.

(6) Rust resistance is shown to be specific, for many of the varie-
ties which are resistant to crown rust are thoroughly susceptible to
the stem rust under identical conditions. The evidences of resistance
described for wheat are shown to apply also to resistant oat varie-
ties. In addition, the early production of telia on seedling leaves
has been observed and is believed to be an indication of resistance.

(7) Further search must be made for varieties resistant to stem
rust.

(8) Varieties of the Avena sterilis group W hich are really resistant
to the crown rust, if found to be high in yield, should replace other
“rustproof ” cae: now being grown in the Southern States.
None of the varieties of this group which have been tested will with-
stand the attacks of stem rust.

(9) A basis is now offered for making lahore and crosses to
produce improved oat varieties resistant to crown rust and suitable
for culture in the several oat-growing areas of the United States.

(9)

(10)

(11)

(12)

(13)

LITERATURE CITED.

BIFFEN, R. H.
1907. ‘Studies in the inheritance of disease resistance. In Jour. Agr.
Sci., v. 2, p. 109-128.
CARLETON, M. A.
1903. Culture methods with Uredinesx. Jn Jour. Appl. Micros. and
Lab. Methods, v. 6, no. 1, p. 2109-2114.

Coss, N. A.
1890-94. Contributions to an economic knowledge of the Australian
rusts (Uredineae). In Agr. Gaz. N. S. Wales, v. 1, p. 185-
214, illus., 1890; v. 3, p. 44-68, 181-212, illus., 1892; v. 4, p.
431-470, 5038-515, illus., 1898; v. 5, p. 239-253, illus., 1894.
Evans, I. B. P.
1908. Report of the acting botanist and plant pathologist. In Rpt.
Transvaal Dept. Agr., 1906/07, p. 155-172.

FROMME, F. D.
1913. The culture of cereal rusts in the greenhouse. Jn Bul. Torrey
Bot. Club. v. 40, no. 9, p. 501-521. Literature, p. 519-521.
MArRRyYAT, DoroTHEA C. E.
~ 1907. Notes on the infection and histology of two wheats immune to

the attacks of Puccinia glumarum, yellow rust. Jn Jour.
AST SC, V.2; Dta2, Ds 129—13s0 spl. 2

MELCHERS, L. HE.
1915. A way of obtaining an abundance of large uredinia from arti-
ficial culture. Jn Phytopathology, v. 5, no. 4, p. 236-237.
MELHUS, I. EH.
1912. Culturing of parasitic fungi on the living host. Jn Phyto-
pathology, v. 2, no. 5, p. 197-203, 2 fig., pl. 20.
MorGENTHALER, OTTO.
1910. Uber die Bedingungen der Teleutosporenbildung bei den Ure-
dineen. Jn Centbl. Bakt. (ete.), Abt. 2, Bd. 27, No. 1/3, p.
73-92, 18 fig. Literatur, p. 91-92.
Norton, J. B.
1918. Methods used in breeding asparagus for rust resistance. U. S.
Dept. Agr., Bur. Plant Indus. Bul. 263, 60 p., 4 fig., 18 pl.
SMITH, R. E.
1904. The water-relation of Puccinia asparagi. . . Jn Bot. Gaz., v. 38,
no. 1, p. 19-48, 21 fig.
STAKMAN, E. C. n
1914. A study in cereal rusts; physiological races. Minn. Agr. Exp.
Sta. Bul. 188, 56 p., 9 pl. Bibliography, p. 50-54.
1915. Relation between Puccinia graminis and plants highly re-

sistant to its attack. Jn Jour. Agr. Research, v. 4, no. 3,
p. 1938-200, pl. 28. Literature cited, p. 198-199.

16

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