Abstract
Conidia of Botrytis cinerea caused typical lesions on cucumber leaves in the presence of purine-related compound (ATP, ADP, cyclic AMP, AMP, IMP, adenosine, inosine, adenine and uric acid) or allantoic acid solution containing glucose. In order to investigate the process of infection by B. cinerea stimulated with the purine-related compound or allantoic acid solution containing glucose, we examined each infection process by the fungal conidia in the presence of the solution on cucumber leaf disks under light microscope. In glucose solution, the conidia germinated, formed primary appressoria and elongated superficial hyphae, but invasion into cucumber leaves was not observed. In purine-related compound solution containing glucose, the conidia formed secondary appressoria after elongation of superficial hyphae, and invasion by them was observed. The secondary appressoria seem to belong to the multicellular type of compound appressoria group, according to Emmett's classfication of appressoria. Among purine-related compound solutions, inosine solution showed the most remarkable effects on lesion formation and induction of the secondary appressoria. Next, we examined the role of glucose and inosine in infection process by B. cinerea on cucumber leaves. When glucose solution was removed within 16hr after inoculation and inosine solution was added instead, formation of the secondary appressoria and lesions was not observed. Formation of the secondary appressoria and lesions was observed with the removal of glucose solution beyond 18hr after inoculation and alternative addition of inosine solution, especially when the glucose solution was removed after 18-24hr of inoculation, the secondary appressoria and lesion formation was the most remarkable. The above results suggest that glucose plays important role in the conidial germination, formation of the primary appressoria and following elongation of the superficial hyphae, and that inosine plays important role in the secondary appressoria formation and their invasion into cucumber leaves.
