The isolation and characterization of melanin-deficient mutants of Monilinia fructicola

Monilinia fructicola (Wint.) Honey, the causal agent of brown rot of stone fruit, has melanin associated with the cell walls of the conidia and in the outer rind of its stroma (fruit mummy). The importance of melanin for the survival of the conidia and the integrity of the stroma was assessed by isolating and characterizing melanin-deficient mutants. These mutants produced conidia which were more readily killed by high temperature, desiccation, freezing, u.v. irradiation and digestion with hydrolytic enzymes. Mutant stroma were shown to have reduced tensile strength. In M. fructicola, melanin functions to provide the conidia with resistance to a variety of environmental stresses.