Population Structure and Genetic Variation of Phytophthora infestans, a Causal Agent of Late Blight of Potato in Nepal

  • S. K. Shrestha Plant Pathology Division Nepal Agricultural Research Council (NARC),Khumaltar, Lalitpur

Abstract

Phytophthora infestans (Mont.) de Bary is a heterothallic Oomycetes fungus with compatible mating types designated as A1 and A2. The population structures and genetic variability of the fungus was investigated collecting isolates from different potato growing areas of 15 districts of the country. In some areas both old population, A1 and new population, A2 mating types are prevalent whereas in other locations either A 1 or A2 are present. At hgh hills A2 mating type is predominant but at mid hlls and Terai A1 is dominant. Frequency of A2 mating type is increasing and spreading in new areas by dsplacing A 1 at hlls. Prevalence of both compatible A1 andA2 mating types in the same areas may have chance of sexual recombination producing oospores, which may survive for a longer period in the soil and become primary source of inoculum The Nepalese population  P.infestans is associated with Merent isozyme genotypes. The appearance of new generations from oospores may have genetic variations with more virulence characters.