Development of stem rust on susceptible and resistant wheat

Abstract

A quantitative study was made of the development of wheat stem rust ( Puccinia graminis f.sp. tritici Eriks. & E. Henn.) race 21-ANZ-2,3,7 (Race 21) and race 126-ANZ-6,7 (Race 126). The wheat W 2691 is susceptible to both races; Reliance is susceptible to Race 126 and highly resistant to Race 21. There were no significant differences between the resistant and susceptible varieties in uredospore germination and development of Race 21 during the first 2 days. Four days after inoculation of primary leaves of W 2691 the rust was well established, flecking was apparent on the fifth day, and the fungus had sporulated by the eighth day. On primary leaves of Reliance plants germ-tubes of Race 21 penetrated the tissues and a few small hyphae had developed within 4 days of inoculation. Necrosis of the host cells was recorded in 95 % of the infection sites and mycelial growth was almost completely inhibited until the leaves became yellow at senescence. Inoculation of primary leaves of Reliance plants with heavy suspensions of uredospores of the avirulent Race 21 produced marked stunting of the plant but no such reaction was observed when the susceptible variety W 2691 was inoculated.