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Disease Note. A Culture of Puccinia helianthi Pathogenic to All Known Resistant Sunflower Genotypes. S. M. Yang, USDA-ARS, P.O. Drawer 10, Bushland, TX 79012. R. W. Berry, and C. W. Purdy, Texas Agricultural Extension Service, Lubbock 79401; and USDA-ARS, P.O. Drawer 10, Bushland, TX 79012. Plant Dis. 71:101. Accepted for publication 22 September 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0101C. Reaction of nine sunflower (Helianthus annuus L.) cultivars and
genotypes (Guayacan INTA sel. Castelar, MP555, SP894, LC274, LC
74/15-20620, Contiflor, B66-B 100, 71-538, and MP557) to the
Bushland isolate (ATCC PR10I) of Puccinia helianthi Schw. was
determined in a growth chamber. All nine were susceptible to the
Bushland isolate. The sixteen otber known sunflower genotypes and
five North Dakota germ plasm lines were previously found susceptible
to the Bushland isolate (I). From this and the results of previous studies,
we conclude that all sunflower genotypes and germ plasm lines that are
resistant to the four North American (NA) cultures of P. helianthi are
susceptible to the Bushland isolate. Four known cultures of P. helianthi
have been described in North America; the Bushland isolate is therefore
designated NA culture 5. The reasons for using the term "culture"
instead of "race" have been discussed in a previous paper (2). |