BIOLOGY OF CONIOTHYRIUM-MINITANS AND ITS POTENTIAL FOR USE IN DISEASE BIOCONTROL

Coniothyrium minitans is a coelomycete with a worldwide distribution. In nature it occurs mainly in sclerotia of Sclerotinia sclerotiorum and S. trifoliorum but in the laboratory it is able to infect a range of other ascomycetous but not basidiomycetous sclerotia. Spore germination, mycelial extension and sclerotial infection will take place at temperatures between 5 and 25-degrees-C and mycelial extension will continue down to water potentials of -7.0 MPa (95 % r.h.). Maximum spore germination and germ tube growth require relative humidities above 95 %. Few other environmental parameters have been examined in relation to the physiology of C. minitans. It will grow well and sporulate freely on a range of solid substrates but growth and sporulation in liquid culture is relatively unexplored. In culture with cell walls of S. sclerotiorum as sole carbon source, chitinase and beta-1,3 glucanase are produced and these may be involved during mycoparasitism of mycelium and sclerotia of S. sclerotiorum, S. trifoliorum and Sclerotium cepivorum. Field control of S. sclerotiorum in sunflower and glasshouse control of S. sclerotiorum on lettuce have been achieved following soil incorporation of solid-substrate formulations before planting. C. minitans will survive and spread in soil for at least 2 yr and continue to give some control of disease but details of its ecology are still uncertain. The reasons for the lack of commercial interest in this biological control agent are discussed and possible ways forward are suggested.