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Genetic recombination in Venturia effusa, causal agent of pecan scab

Carolyn Young: Noble Research Institute, LLC

<div><em>Venturia effusa</em> causes pecan scab, the most prevalent disease of pecan in the southeastern USA. Mating type idiomorphs were recently characterized and the sexual stage was subsequently produced <em>in vitro.</em> To investigate sexual reproduction and recombination of traits in <em>V. effusa</em>, select isolates were crossed in pairwise combinations on oatmeal agar. After a 4 mo cold treatment, the pairings were incubated at 24C with a 12h photoperiod for 14 d to allow maturation of the ascospores. Ascospore progeny from crosses between isolates NFVe23 (cv. Pawnee) × NFVe24 (native), Albino (cv. Desirable) × NFVe47 (cv. Choctaw) and Albino (cv. Desirable) × NFVe78 (cv. Pawnee) were generated. A total of 32, 13 and 30 single ascospore progeny were isolated from each cross, respectively. The parental isolates and ascospore progeny were screened with eight SSR markers and primers for the mating type idiomorphs. Genotyping using SSR and mating type loci, and phenotyping the crosses with the albino parent, revealed recombination in the ascospore progeny. Based on these markers, the proportion of recombinant progeny were 0.97 for NFVe23 × NFVe24, 1.00 for Albino × NFVe47 and 0.90 for Albino × NFVe78. Identification of the sexual stage and characterization of recombination in <em>V. effusa </em>will provide a better understanding of the impact of the sexual cycle in the epidemiology of pecan scab in the field as well as provide insight into approaches to manage this disease.</div>