Bacillus amyloliquefaciens GB1 can effectively control apple valsa canker

Apple valsa canker (AVC), caused by Valsa mali , is one of the most serious diseases of apple trees in eastern Asia, and the most important factor limiting apple production in China. This disease is difficult to control by chemical and agricultural measures, thus biocontrol may constitute a desirable alternative strategy. A Bacillus amyloliquefaciens strain denoted GB1 isolated from ageing cucumber stems, exhibited a strong antagonistic activity against V . mali , inhibiting significantly the germination of conidia and the growth of hyphae. GB1 conidial suspensions (above 10 6 CFU/ml) applied prior to wound inoculation of apple twigs with V. mali resulted in total inhibition of infection. Strain GB1 colonized xylem and phloem tissues surrounding the wounds made on apple twigs and formed biofilms over them. Results indicate that B. amyloliquefaciens GB1 may be a promising agent for the biocontrol of AVC, and provide new insights into the ability of B . amyloliquefaciens to colonize apple trees.