Morphological studies on infection process of cucumber leaves by conidia of Botrytis cinerea stimulated with various purine-related compounds.

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 16 hr after inocu lation 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 18 hr after inoculation and alternative addition of inosine solution, especially when the glucose solution was removed after 18-24 hr 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.

Conidial concentration as an important factor determining the type of prepenetration structures formed by Botrytis cinerea on leaves of French bean (Phaseolus vulgaris)

“…development, but not to penetration; the addition of KH2PO4 or ^Â TP to the inoculum was necessary to bring about penetration. A similar effect of related phosphates on penetration observed by Akutsu et al (1981b). They used inocula of 10^ conidia/ml of 0-28 M glucose and found good germination and further development of .6. cinerea on cucumber leaves, but no formation of multicellular appressoria and no penetration.…”

“…At low conidial concentratioDS, however, penetration started mainly from HA or IC, penetration from these structures also being dependent on the nature of the stimulant added to the glucose in the inoculum. Our results indicate that the observations made by Akutsu et al (1981b) of penetiations occurring only from 'secondary' appressoria couid be explained largely from their use of inocula containing glucose and a purine-related compound and a moderate conidial concentration. The high proportion of G A in inocula with high conidial concentrations was associated with a rapid penetration (within 12-24 li after inoculation),, whereas with lower coiiidial concentrations an appreciable penetration (from HA or IC) was not achieved befoie 2-4 days after inoculation.…”

“…Preliminary observations revealed that ueder certain conditions penetration of host cells occuired from the tips of conidial germ tubes.. This contrasted with the multicellular ('secondary') appressoria formed on cucumber leaves by B. cinerea in inocuia containing a purine-related compound and glucose (Akutsu et al, 1981b). Differences that existed between the experimental conditions used in the two reports have now been used as a basis for assessing the importance of some of those conditions as a factor in determining the type of structure formed before penetration.…”

Botrytis cinerea in greenhouse vegetables: chemical, cultural, physiological and biological controls and their integration

“…The germ tube of B. cinerea conidia may penetrate directly or after forming appressoria when infecting petals (Elad 1988(Elad , 1989. However, production of appressoria and penetration via stomata have been reported (Akutsu et al 1981;Van den Heuvel and Waterreus 1983;Elad 1988). Wounded host tissue (Gartel 1970) and the presence of dead cells in the infection could assist the infection process (Sharman and Heale 1979).…”

A method for monitoring the sensitivity of Botrytis cinerea to pyribencarb

“…Spraying was performed 3 hr prior to inoculation for the preventive effect assay. For inoculation, conidial spores of B. cinerea were suspended in medium containing 0.3% yeast extract and 2% glucose, 14,15) and paper discs (6 mm in diameter, thick type; Toyo Roshi Kaisya, Ltd.) dipped in the spore suspension (1ϫ10 5 spores/ml) were placed in the center of cotyledons. The inoculated plants were incubated in a chamber with high humidity at 20°C.…”