Virulence, Aggressiveness, Evolution, and Distribution of Races of 'Puccinia striiformis' (the Cause of Stripe Rust of Wheat) in North America, 1968-87.

摘要

Thirty-nine races of Puccinia striiformis, the fungus that causes stripe rust of wheat, have been identified in North America, beginning with four races present when monitoring began in 1968. Additional races were detected as follows: one each in 1968, 1972, 1975, 1978, 1980, and 1982; two each in 1974, 1984, and 1985; three each in 1981 and 1987; five in 1977; and six each in 1976 and 1983. Eleven of the races were first detected on newly released wheat cultivars that were resistant to previously known races. Those 11 races caused severe epidemics within 3 years after release of the cultivars. Within a few years after detection of the new virulences, new combinations of virulences appeared. Reassortment of all existing virulences occurred in the absence of a sexual cycle. North America can be divided into seven wheat-growing regions of stripe rust occurence, based on geographic barriers, prevailing winds and other weather, cropping methods, and virulence of the races. They are region 1: eastern Washington and Oregon, northern Idaho, and eastern British Columbia; region 2: western Montana and southern Alberta; region 3: southern Idaho and northern Utah; region 4: western Oregon and northern California; region 5: northwestern Washington and western British Columbia; region 6: central California; and region 7: the area east of the Rocky Mountains.