Distribution, prevalence and a new physiologic race of wheat stem rust in Brazil, in 1969 and 1970

Abstract

Races 11, 15/65, 15/71, 17, 17/61, 17/63 of the stem rust (Puccinia graminis Pers, f. sp. tritici Eriks. & Henn) were determined on 535 samples collected in 1969 and 1970 in the Brazilian wheat regions. Race 15/71 was determined for the first time on samples collected in 1970. Race 17/63 accounted for more than 50% of the isolates, confirming the prevalence of this race observed in the last few years. The next most prevalent race was 15/65, identified in more than 20% of the isolates. Race 15/71 stands out due to the large region in which this race was identified and considering that it was first determined in 1970. The combination of the genes Sr 7 and Sr 11 confers resistance to all occurrent races.