The growth of Botrytis fabae and B. cinerea into leaves of bean (Vicia faba L.)

SUMMARY The nature of the reactions underlying the success of Botrytis fabae and the failure of B. cinerea to colonize the leaves of bean (Vicia faba L.) have been studied. Damage to or removal of cuticle before inoculation failed to enable B. cinerea to cause spreading lesions. Nutrients including those which support good growth in vitro failed to stimulate B. cinerea to spread through leaves. The germination of spores of B. cinerea in water was more rapid and complete than of B. fabae on both glass and leaf surfaces. B. cinerea grew more rapidly than B. fabae in nutrient media, but germ tubes of B. fabae grew at a higher constant rate than those of B. cinerea in water drops on glass. In water drops on leaves, germ tubes of B. fabae grew at a constant rate but those of B. cinerea slowed after 8 hr. and then grew little more. Germ tubes of B. fabae were the same length after 24 hr. both over and away from lesions, but those of B. cinerea were markedly shorter over lesions than away from them at this time. Similar observations on pathogenicity and relative growth of the two fungi were made on six bean varieties.