Competition between aggressive and non-aggressive strains of Botrytis cinerea (Botryotinia fuckeliana) on French bean leaves

Abstract

Competition was assessed between aggressive and non-aggressive strains of Botrytis cinerea on French bean (Phaseolus vulgaris) leaves by inoculating strains simultaneously and sequentially (6, 12 or 24 h later). The lesions produced when an aggressive strain (forming large lesions) and a non-aggressive strain (forming small, restricted lesions) were inoculated simultaneously were intermediate in size between those produced by the strains when inoculated individually. suggesting that the two strains were co-existing in the lesion. However, in sequential inoculation when the second inoculation was delayed 6 h or more, lesion sizes typical of the first inoculated strain were found indicating that the first strain to be inoculated dominated the infection site. Competition between two aggressive strains, individually identifiable by genetic markers, was found to follow a similar pattern, suggesting that the dominating effect of the first strain is a general phenomenon. Domination of the lesion site by the nonaggressive strain prevented an aggressive strain from forming spreading lesions suggesting a possible use for these strains as a biocontrol agent in some disease situations.