Influence of the soybean cyst nematode (Heterodera glycines) on the incidence of brown stem rot in soybean and adzuki bean

Experiments were carried out in pots to study the influence of the soybean cyst nematode (Heterodera glycines) on the incidence of brown stem rot (BSR) in soybeans (Glycine max) and adzuki beans (Vigna angularis) caused by the soilborne fungi, Phialophora gregata f.sp. sojae and P. g. f.sp. adzukicola. The presence of H. glycines increased the incidence of BSR in susceptible soybean (cv. Nakate-Hikarikuro) and adzuki bean (cv. Erimoshozu) for both pathogens. The disease-enhancing effects of H. glycines were not shown in the soybean cultivar Peking, which is resistant to the nematode. In a soybean cultivar resistant to BSR (cv. BSR302), the incidence of BSR was low, even under the presence of H. glycines. In split-root experiments using the two BSR susceptible cultivars, the disease-enhancing effects of H. glycines were not observed in either soybeans or adzuki beans, whose roots were inoculated separately with P. gregata and H. glycines.