Spore Germination and Penetration of Botrytis allii into Allium Cepa Host

Abstract

Optimal infection of onion leaves by B. allii spores occurs in the presence of light and high humidity (93-100% relative humidity [RH]). The apical region of the onion leaf was the most susceptible site for infection. Germ tubes penetrate through stomata or directly through the epidermis. The infection peg grows from the germ tube and penetrates through the cuticle into the epidermal cells. During the first 19 h of spore germination on media, several constitutive enzymes were secreted from the germ tube: cutin methylesterase, polygalacturonase and polyphenol oxidase. Inducible cellulase was secreted when carboxymethylcellulose was added to the germination medium.