Highly clonal Pythium aphanidermatum population infecting greenhouse plants in Japan

Abstract

A highly controlled environment inside the greenhouse could provide suitable temperatures, nutrients, and light intensity for the crops. However, Pythium root rot continually threatens the productivity of numerous kinds of crops in hydroponic systems, including tomato, poinsettia, spinach, lettuce, and rose. It is caused by Pythium aphanidermatum, which grows well in the warmer temperatures inside the green house and is able to survive in low temperatures as well. In this research, we studied 165 isolates of P. aphanidermatum collected from three prefectures in Japan. We developed 10 reliable microsatellite markers to evaluate the genetic diversity of P. aphanidermatum. In total, 34 multilocus genotypes (MLGs) were observed. The index of association suggested that the population was highly clonal. This result was supported by the low result of Fst (0.075) and the short genetic distance per locus visualized in the minimum spanning network. The clonal population suggested that asexual reproduction was dominant.