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Investigation of the causes of poor germination ofBotrytisspp. on broad bean leaves (Vicia fabaL.)

Physiological Plant Pathology
Publication Date
DOI: 10.1016/s0048-4059(80)80009-9


Germination and germ tube growth by Botrytis cinrea and B. elliptica were strongly inhibited at sites on broad bean leaves which failed to develop lesions during the first day after inoculation. Studies on the antifungal activity of inoculum droplets (diffusates) showed that the epiphytic microflora (particularly bacteria) were the major cause of inhibition of Botrytis. In addition diffusates from broad bean leaves retained some antifungal activity after sterilization by filtration. Filtered diffusates from Vicia faba were more active than those from leaves of French bean or tomato. Inhibitory activity within filtered diffusates arose from the interaction between conidia and the broad bean leaf but was not caused by the accumulation of known phytoalexins from V. faba. Germination of B. cinerea was inhibited on redeposited broad bean leaf surface wax. Antifungal activity was associated with the primary alcohol fraction of the wax; other components stimulated fungal growth. Properties of the inhibitor detected in filtered diffusates from broad bean leaves were similar to those of an inhibitor released from redeposited wax into inoculum droplets containing conidia of B. cinerea. The inhibition of B. cinerea in vivo and in vitro by the antifungal factors potentially active on the leaf surface was overcome by the addition of glucose to inoculum droplets. Epiphytic microflora and the inhibitor released from wax respectively required the highest and lowest concentrations of glucose to overcome their antifungal activity. Botrytis fabae was inhibited by both unfiltered and filtered diffusates from bean leaves inoculated with B. cinerea or B. elliptica, but germinated much more rapidly than the non-pathogens on the leaf surface. The mechanisms by which B. fabae may overcome the potentially inhibitory factors within inoculum droplets is discussed.

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