Nine wheat varieties were studied in two stages of growth, the seedling stage and the heading stage, for their reaction to a number of physiologic races of leaf rust of wheat, Puccinia triticina Erikss. Several varieties susceptible to certain physiologic races in the seedling stage were found to acquire, as they grew to maturity, a resistance to these races. In the adult plant, the resistance was greatest in the uppermost leaves but diminished progressively on lower leaves. The varieties tested fell into three groups on the basis of their rust reaction. (1) Renown and Regent, which developed adult plant resistance to all of the 19 races to which they were tested. In these two varieties, and possibly in other derivatives of H-44 and Hope, adult plant resistance to physiologic races of leaf rust may be a generalized phenomenon comparable to the resistance such varieties show towards stem rust. (2) Thatcher, Apex, Marquis, Reward, and Kenya R.L. 1373, which showed adult plant resistance only to certain physiologic races, a condition not hitherto encountered in other cereal rusts. (3) McMurachy and Warden × Hybrid, each of which reacted somewhat similarly in the seedling and heading stages, the former being susceptible and the latter resistant in both stages.
Genetic relationship between the adult plant resistance gene Lr12 and the complementary gene Lr31 for seedling resistance to leaf rust in common wheat
