Infection of bean plants ( Vicia faba L.) with Botrytis cinerea and B. fabae

SUMMARY The infection of bean plants ( Vicia faba L.) by Botrytis fabae has been studied by inoculating detached leaves with standard volumes of spore suspensions of known concentrations, or with single spores. Increasing the number of spores in the inoculation drops increased the number of lesions, and lesions were more readily produced on older than on younger leaves. The addition of glucose, a number of other carbohydrates, and also sodium polypectate and pectin, increased the number and rate of the spread of lesions. Xylose caused a decrease, and a number of nitrogen compounds had little effect. The number and rate of spread of lesions was increased if the surface of leaves were gently rubbed with a mild abrasive before inoculation. Calcium‐deficient plants were more susceptible than plants which had received normal nutrition. Deficiencies of other major elements had much less effect. A larger proportion of the spores in inoculation drops germinated when these drops were on older leaves, when the drops contained glucose, and on leaf surfaces that had been gently abraded. Addition of xylose reduced the amount of germination and the fungus grew very poorly in liquid culture when this was the only carbon source. The addition of small quantities of glucose allowed the fungus to use xylose as efficiently as glucose. When single spores were used to inoculate leaves, very different results were obtained with leaves taken from different plants, but under some conditions single spores often induced lesion formation. B. fabae caused lesions more readily than did B. cinerea , in spite of the fact that a greater proportion of B. cinerea spores in inoculation drops germinated.