SELFING STUDIES WITH PHYSIOLOGIC RACES OF WHEAT STEM RUST, PUCCINIA GRAMINIS VAR TRITICI

Abstract

Forty-two cultures of wheat stem rust (Puccinia graminis var. tritici Erikss. and Henn.), comprising 34 physiologic races, were subjected to selfing studies each of which involved the inoculation of barberry plants with the sporidia of a race, and the determination of the races in the uredial cultures derived from the aeciospores. In all of the cultures studied, the pathogenic properties expressed on the differential hosts appeared to be inherited according to the same principles. On the varieties Marquis and Kota (Triticum vulgare), pathogenicity of the races in the progeny tended to resemble that of the parent race. On Reliance (T. vulgare), avirulence was a dominant character, virulence a recessive one. On the durum wheats Arnautka, Mindum, and Spelmar, virulence was a dominant and avirulence a recessive character. On Einkorn (T. monococcum) and on Vernal (T. dicoccum), avirulence was dominant to virulence. In the progenies of some races, pathogenic variation occurred though it did not transgress the circumscribed limits of the parent race; the population therefore consisted chiefly of substrains (biotypes) of the same race.