Races, disease symptoms and genetic variability in Pyrenophora tritici-repentis isolates from Oklahoma that cause tan spot of winter wheat

Abstract In recent years, tan spot of wheat caused by the fungus Pyrenophora tritici-repentis has become more prevalent in Oklahoma. Experiments were conducted to investigate race structure, disease symptoms and genetic variability P. isolates collected from winter over three decades. Race determination was for 16 based on expression necrosis and/or chlorosis produced differentials. Variability expressed 12 determined 13 hard red cultivars grown addition, among 17 using amplified fragment length polymorphism-polymerase chain reaction (AFLP-PCR). All except one (El Reno) classified as 1. Isolates varied widely producing cultivars, but with a chlorotic halo predominant (56.4%). AFLP-PCR analysis primer pairs total 494 alleles which 285 polymorphic. The overall diversity 25.2%. Genetic relationships cluster principal component showed only minor differences between isolates, did not form tight clusters or groups. predominantly 1; however, they range cultivars. lack distinct grouping AFLP marker study indicates that used this likely originated single lineage.