Presence of two species-level groups in Globisporangium splendens isolates in Japan

Abstract

Globisporangium splendens, formerly classified as Pythium splendens, is one of the most common pathogenic oomycetes on ornamental plants, but this species has not been widely characterized in terms of its intraspecific variations in molecular phylogeny and virulence. In this study, G. splendens isolates from seven Prefectures in Japan were characterized for their morphology, mating compatibility, and molecular phylogeny, based on the internal transcribed spacer sequences of ribosomal RNA gene and mitochondrial cytochrome oxidase 1 and 2 gene sequences. We also examined the virulence of isolates on Pelargonium and papaya, which are known to be host plants of G. splendens. All G. splendens isolates had similar morphology and optimal growth temperatures. Mating compatibility tests revealed that all G. splendens isolates from Okinawa and Kagoshima Pref. were antheridial isolates, whereas all isolates from the other locations were oogonial isolates. The virulence on Pelargonium and papaya differed significantly among the isolates. Phylogenetic analyses based on the sequences of the three genes showed that G. splendens isolates were separated into two phylogenetic groups. Our study indicated that molecular intraspecific variation in G. splendens is considered to be species-level variation, which widely distributed in Japan, and it had no correlation with morphology or virulence on host plants.