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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).

References: (1) S. M. Yang. Ann. Phytopathol. OC. Jpn. 52:248. 1986. (2) S. M. Yang et al. Plant Dis. 70:883. 1986.