Host ranges and favorable temperatures for disease development of three Pythium species isolated from damped-off bentgrass

Abstract

Pythium aphanidermatum, P. arrhenomanes and P. volutum are causal agents of damping-off in creeping bentgrass (Agrostis stolonifera L.) in Japan. The optimum temperatures for hyphal growth of the three species were 35ºC, 30ºC, and 25ºC, respectively. We inoculated seedlings of grasses, cereals, and vegetables with the Pythium species at 23ºC and 32ºC in post-emergence tests. P. arrhenomanes showed the highest pathogenicity against seedlings of grasses, cereals, and allium, with stonger effects at 32ºC than 23ºC. P. volutum caused more severe symptoms in grasses at 23ºC than 32ºC. Only P. aphanidermatum caused damping-off at 32ºC in alfalfa, a Fabaceae species. In summary, the three Pythium species showed different temperature optima for growth and disease development, having different host ranges.