Ultrastructural study of host–parasite interactions. II. Decay of lettuce caused by Botrytis cinerea and phyllosphere bacteria

Abstract

Botrytis cinerea causes a fast-spreading soft rot in lettuce that, under favorable conditions, completely destroys the tissues in less than 72 h. Within the first 24 h, the fungus penetrates the cuticle into the foliar parenchyma, destroying the cell wall and cellular content. Dictyosomes and mitochondria are altered and disappear first. Chloroplasts resist longer but are deeply modified with inflating and stacking of thylakoids, an increase in number of osmiophilic globules, and the disintegration of the plastidial membrane. Lomasomes and microbodies appear. Cell walls are made visible by Thiéry's technique. Bacteria invade dead tissues and seem to participate in a more complete destruction of the host and the fungus.