Botrytis fabiopsis, a new species causing chocolate spot of broad bean in central China

Abstract

The current study was conducted to identify Botrytis spp. isolated from symptomatic broad bean plants grown in Hubei Province, China. Among 184 Botrytis strains, three distinct species, B. cinerea, B. fabae and a previously undescribed Botrytis sp., were identified based on morphology of colonies, sclerotia and conidia. The novel Botrytis sp. is described herein as a new species, Botrytis fabiopsis sp. nov. At 20 C B. fabiopsis grew on potato dextrose agar (PDA) at 12-13 mm d(-1), similar to B. fabae (13 mm d(-1)), but slower than B. cinerea (17-19 mm d(-1)). It formed pale gray colonies with short aerial mycelia and produced gray to black sclerotia in concentric rings on PDA. B. fabiopsis produced greater numbers of sclerotia than B. cinerea but fewer than B. fabae. Conidia produced by B. fabiopsis on broad bean leaves are hyaline to pale brown, elliptical to ovoid, wrinkled on the surface and are larger than conidia of B. fabae and B. cinerea. Phylogenetic analysis based on combined DNA sequence data of three nuclear genes (G3PDH, HSP60 and RPB2) showed that B. fabiopsis is closely related to B. galanthina, the causal agent of gray mold disease of Galanthus sp., but distantly related to B. fabae and B. cinerea. Sequence analysis of genes encoding necrosis and ethylene-inducing proteins (NEPs) indicated that B. fabiopsis is distinct from B. galanthina. Inoculation of broad bean leaves with conidia of B. fabiopsis caused typical chocolate spot symptoms with a similar disease severity to that caused by B. fabae but significantly greater than that caused by B. cinerea. This study suggests that B. fabiopsis is a new causal agent for chocolate spot of broad bean.