Survey on physiologic races of Uromyces phaseoli typica in Rio Grande do Sul and Santa Catarina in 1968 and 1969

Abstract

The identification of physiologic races of bean rust (Uromyces phaseoli typica Arth.) is made each year in southern Brazil, in order to survey the prevalent races and to determine the appearence of new ones. Five hundred and thirteen urediosores were isolated from samples collected in fourteen places in Rio Grande do Sul and nine in Santa Catarina. The samples were collected from November, 1967 to May, 1968, and from November, 1968 to June 1969. The most frequent races were B₁, B₁₁, B₂, B₃, B₅ and B₁₀ with 22.4, 18.0, 11.9, 11.1, 10.1 and 6.6% occurrence respectively. The other races determined in this region constituted 19.9% of the isolates identified in this period. Races B₂, B₅, B₆, B₁₀, B₁₁, B₁₂ and B₁₀ increased is 1969; whereas, races B₁, B₃, B₄, B₇ and B₈, decreased. The variety Cuva 168-N, one of the most commonly cultivated, is susceptible only to race B₁₁. The increase of frequency of this race in recent years is due either to the susceptibility of this variety or to the fact that this races does not compete with other races.