COMPARISON OF TECHNIQUES FOR THE PRODUCTION OF SCLEROTINIA-TRIFOLIORUM ASCOSPORES IN THE LABORATORY FOR FORAGE LEGUMES RESISTANCE TESTS

This study aimed to improve the production, under controlled conditions, of Sclerotinia trifoliorum ascospores to be used for selection tests on forage legumes. Sclerotia of this fungus, produced in the laboratory, were buried 1-2 cm deep in permanently soaked vermiculite, at T = 15 degrees C, 12/24 h of fluorescent light, air moisture > 80% in order to differentiate apothecia. The ascospores were harvested by aspiration and collected on a membrane filter. Various types of apparatus containing sclerotia have been tested for their ability to maintain live apothecia and for the facility of spore catching. The aspiration method has been found to be much more efficient than the previous method of cutting off apothecia. Moreover, it was observed that using this harvesting technique the best apparatus presented small and independent compartments (truncated plastic bottles). The ascospores can be stored, on the membrane filter at 5 degrees C and in dry conditions in order to preserve their germinating ability for a period of 3 months at least. This spore harvesting method permits availability of large quantities of a cheap inoculum for S. trifoliorum resistance test on forage legumes all year round.