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Resistance

Fusarium oxysporum f. sp. pisi, Race 6: Occurrence and Distribution. William A. Haglund, Plant pathologist, Washington State University, Northwestern Washington Research and Extension Unit, Mount Vernon, WA 98273; John M. Kraft, research plant pathologist, Vegetable Crops Research, USDA-SEA-FR, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350. Phytopathology 69:818-820. Accepted for publication 19 February 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-818.

A new race of Fusarium oxysporum f. sp. pisi was isolated repeatedly from commercial pea-growing areas in western Washington. This race was first observed in 1971 and by 1977 had been recovered from 175 of 640 fields examined. This pathogen was detected either in fields previously free of visible wilt symptoms or in fields with a low incidence of race 2. The symptoms and the cultural morphology of the pathogen are identical to those of races 1 and 5. Race 6 can be distinguished from races 1, 2, and 5 by the reaction of six differential cultivars including New Season, WSU 23, and WSU 28. This pathogen meets all requirements of being classified as a new race of pea wilt in that (i) it is widespread, (ii) host resistance is inherited by a single dominant gene, and (iii) pathogenicity tests using differential cultivars with single gene markers for resistance or susceptibility to races 1, 2, and 5 are identical with field reactions. Therefore it is proposed that this new strain be designated race 6.