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Genetic structure and distribution of Pythium aphanidermatum populations in Pennsylvania greenhouses based on analysis of AFLP and SSR markers

     ¹ Rice Research Center, Noble Foundation, Ardmore, OK, 72160, United States of America
² Oklahoma State University, Stillwater, OK
³ Plant Pathology, The Pennsylvania State University, 111 Buckhout Laboratory, University Park, PA, 16802, United States of America

Pythium aphanidermatum is one of the most aggressive species in the genus and has a wide host range, but little is known about its population genetic structure. We tested 123 P. aphanidermatum isolates with six AFLP primer combinations and four SSR markers. The genetic diversity of P. aphanidermatum was 0.34 with AFLP and 0.55 with SSR markers. The number of SSR genotypes ranged from three to eight for each locus, and a total of 14 SSR genotypes were found among all isolates. Three major genetic groups were identified with the combination of AFLP and SSR marker data. The genetic structure observed among P. aphanidermatum isolates was related to location and mefenoxam fungicide resistance rather than host. Four genotypes (PA1, PA2, PA5, and PA7) were found in the population from a commercial greenhouse, and the genetic diversity of a greenhouse population was similar to that found in the whole sample. The molecular tools for P. aphanidermatum isolates identified the possible gene flow within and between populations in Pennsylvania greenhouses.

Key words: Pythium aphanidermatum, Fungicide resistance