Characterization of Sclerotinia and mycoparasite Coniothyrium minitans interaction by microscale co-culture

Aims: To characterize the interaction of Sclerotinia sclerotiorum and S. minor with strains of the mycoparasite and commercial biocontrol agent Coniothyrium minitans using novel perfusion chamber gasket co-culture. Methods and Results: Sclerotinia were cultured in perfusion chamber gaskets and then flooded with Coniothyrium conidia. After germination, Coniothyrium failed to show any form of directed growth, making contact with Sclerotinia hyphae in a random manner. In turn, some Coniothyrium hyphae coiled round Sclerotinia counterparts and although no intracellular growth was observed, Coniothyrium proliferated, while the hyphae of Sclerotinia became vacuolated and lost the cytoplasm. When co-cultures of Sclerotinia with Coniothyrium were flooded with FITC-lectins, small difference in fluorescence between the fungi was found with FITC-Con A suggesting that cell walls of both the species exposed mannose. In contrast, Coniothyrium fluoresced poorly in comparison with Sclerotinia when FITC-wheat germ agglutinin was used, indicating a marked paucity of N-acetylglucosamine exposure by cell walls of Coniothyrium, hence reduced exposure to chitinolytic enzyme action. Conclusions, Significance and Impact of the Study: The approach employed supported direct sequential microscopic observation of Coniothyrium and Sclerotinia as well as the utilization of representative fluorescent moieties to characterize relative carbohydrate cell wall exposure.