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Avirulence in the Wheat Septoria tritici Leaf Blotch Fungus Mycosphaerella graminicola Is Controlled by a Single Locus

December 2000 , Volume 13 , Number  12
Pages  1,375 - 1,379

Gert H. J. Kema , Els C. P. Verstappen , and Cees Waalwijk

Plant Research International, P. O. Box 16, Wageningen 6700 AA, The Netherlands

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Accepted 4 September 2000.

Segregation of avirulence in Mycosphaerella graminicola, a heterothallic ascomycete that causes wheat septoria tritici leaf blotch, was studied in F1, BC1, and F2 populations by inoculation assays on five wheat cultivars in the seedling stage and by amplified fragment length polymorphism and random amplified polymorphic DNA analyses. F1 was generated by crossing isolates IPO323 (avirulent) and IPO94269 (virulent). All F1, BC1, and F2 progeny isolates were virulent on the susceptible check cultivar Taichung 29 and were avirulent on the resistant check cultivar Kavkav-K4500. Avirulence segregation was observed in F1 and in several BC1 and F2 generations on the differential cultivars Shafir, Kavkaz, and Veranopolis at a 1:1 ratio. Avirulence for the three differential cultivars always cosegregated. We conclude that avirulence in isolate IPO323 is controlled by a single, seemingly complex locus.

Additional keywords: gene-for-gene, specificity.

© 2000 The American Phytopathological Society