Induction of cutinolytic esterase activity during saprophytic growth of cucurbit pathogens, Fusarium solani f.sp. cucurbitae races one and two (Nectria haematococca MPI and MPV, respectively)

Cutins from fruit of Cucurbita maxima and Cucurbita moschata cultivars, apple and a C16 alcohol (hexadecanol) were used to induce cutinolytic esterase activity during saprophytic growth of strains of the two cucurbit pathogens, Fusarium solani f. sp. cucurbitae, race 1 (Nectria heamatococca mating population (MPI) and F. solani f. sp. cucurbitae, race 2 (MPV). Four strains of MPV and 11 strains of MPI were included in the study. Although we were primarily interested in the two cucurbit pathogens (MPI and MPV), six strains of the pea pathogen F. solani f. sp pisi (MPVI) were included to provide a comparison since most of the knowledge on cutinase activity in N. haematococca has come from a study of that group. Cutinolytic esterase was induced in all strains from both MPV and MPVI but was not detected in any of the 11 strains from MPI regardless of the induction conditions. The amount of cutinolytic esterase activity induced in the MPV strains differed according to the strain and both the source and the amount of cutin used in the induction medium. Information on the influence of cutin source and pH on the induction of cutinolytic esterase activity during saprophytic growth of strains from MPV demonstrates that the gene is regulated differently from that in MPVI.