Phytophthora Rot of Broad Bean(Vicia faba) Caused by Phytophthora nicotianae in Korea

Abstract

Phytophthora rot on broad bean(Vicia faba) occurred in the experimental field at Gyeongsangnam-do Agricultural Research and Extension Services from 2004 to 2006. The fungus isolated from the diseased plants grew well on potato dextrose agar and showed an arachnoid or rosaceous colony pattern. Sporangia were conspicuously papillated, noncaducous, ovoid to globose, and <TEX>$25-64{\times}18-44{\mu}m$</TEX> in size. Oogonia and oospores were spherical and measured as 20-32 <TEX>${\mu}m$</TEX> and 16-28 <TEX>${\mu}m$</TEX> in size, respectively. Oospores were relatively small and aplerotic. Antheridia were amphigynous, spherical, and unicellula. Chlamydospores were globose and 18-40 <TEX>${\mu}m$</TEX> in size. Optimum temperature for growth was about <TEX>$28^{\circ}C$</TEX> on potato dextrose agar. The disease occurred in all parts of the plant including roots, stems, leaves and pods in the field. The symptoms similar to those of naturally infected plants were induced by artificial inoculation and the pathogen was re-isolated from the plant. On the basis of mycological and pathological characteristics, the causal pathogen of broad bean rot was identified as Phytophthora nicotianae. This is the first report of Phytophthora rot of broad bean caused by P. nicotianae in Korea.