June 33,1923 
Biologic Forms of Puccinia gramtnis 
1017 
hybrid strains combine the desirable characters of Victory with the rust 
resistance of White Tartar, it is to be hoped that Forms III and IV of P. 
graminis avenae do not exist in the United States. If they do not, the 
problem of developing good varieties of oats resistant to stem rust seems 
to be well on the way to solution. 
The provisional Form V was collected in two localities in Saskatchewan, 
Canada, and in one in Iowa. It may be a mechanical mixture of Forms I 
and II. Inoculation experiments to determine this fact are in progress. 
It is especially interesting to note that the Swedish form of rust is 
more virulent than any of those so far found in the United States, 
because Eriksson (2) long ago called attention to the fact that P, graminis 
avenae was exceptionally virulent in Sweden. The senior author was 
also impressed with this fact during a recent visit to Sweden. Several 
grasses, which are moderately susceptible to the avenae form of rust 
in the United States, but which seldom rust heavily in the field, were 
very generally and severely infected in Sweden. The fact that there 
are tremendous numbers of barberry bushes in some oat-growing regions 
of Sweden, and the additional fact that oats are so commonly grown 
might account for the abundance of the rust. In addition, however, 
Eriksson evidently was correct in assuming that the stem rust of oats 
was especially virulent in Sweden. This emphasizes still more the 
fact that the specialization of P. graminis avenae may be different in 
different countries. The present results indicate that the forms may 
also differ even in various regions of the same country. On the other 
hand more than one biologic form may occur in the same locality or 
even on the same plant. 
While the virulent Swedish form of stem rust of oats may possibly 
exist in the United States, fortunately it does not seem to be either 
abundant or widespread in those Northern States in which White 
Tartar is commonly grown. The work of Durrell and Parker (i) 
indicates also that White Tartar is quite generally resistant to stem 
rust. 
The practical significance of the existence of several biologic forms 
of Puccinia graminis on oats in the United States will depend on the 
number and the virulence of forms which may be found in the future. 
This problem is now being thoroughly investigated. 
LITERATURE CITED 
{i) DuRRErr, L. W., and Parker, John H. 
1920. COMPARATIVE resistance OP VARIETIES OP OATS TO CROWN AND STEM 
RUSTS. Iowa Agr. Exp. Sta. Research Bui. 62, 56 p., 7 fig., 4 pi. 
Bibliography, p. 56c-56d. 
{2) Eriksson, Jakob. ' 
1902. uEBER die speziausierung des getreideschwarzrostes in schweden 
UND IN anderen landern. In Centbl. Bakt. [etc.], Abt. 2, Bd. 9, 
p. 590-607, 654-658. Bibliographical footnotes. 
{3) Garber, R. J. 
1922. INHERITANCE and YIEED WITH PARTICULAR REPERENCE TO RUST RE¬ 
SISTANCE AND PANICLE TYPE IN OATS. Minn. Agr. Exp. sta. Tech. 
Bui. 7, 62 p., 6 pi. Literature citations, p. 41-43• 
{4) HOERNER, G. R. 
1919. BIOLOGIC PORMS OP PUCCINIA CORONATA ON OATS. In Phytopathology, 
V. 9, p. 309-314, pi. ^20. Literature cited, p. 314. 
{5) Levine, M. N., and Stakman, E. C. 
1918. A THIRD BIOLOGIC FORM OF PUCCINIA GRAMINIS ON WHEAT. In Jour. Agr. 
Research, v. 13, p. 651-654. 
