Abstract: Brown rot disease caused by Monilinia fructicola is one of the major postharvest diseases of flat peach, which causes serious postharvest loss. Meanwhile, the pathogenicities of M. fructicola for different fruit hosts are different. In this investigation, we studied the biological characteristics of M. fructicola under different culture conditions including temperature, pH, and light, and we also examined the impacts of culture temperature, pH and time on the activities of cell wall degrading enzymes. The results showed that the optimum pH for spore germination and germ tube extension of M. fructicola was 5.0 and it grew well in a weak acidic environment, while the spore germination rate was significantly lower in an excessively acidic environment. The optimum temperature for colony growth was in the range of 20?28 ℃, and the pathogen could not grow normally at a temperature above 36 ℃. Temperature affected colony morphology, and at different temperatures, the colony morphology characteristics were different. Light had little effect on the hyphal growth. The activities of the cell wall degrading enzymes endoglucanase (EG), β-glucosidase (BG), polymethylgalacturonase (PMG), and polygalacturonase (PG) were the highest at 28 ℃. The activities of EG and BG reached the highest values at pH 6.0, while the activities of PMG and PG reached the highest values at pH 7.0. The activities of these four enzymes were the highest after cultivation for 5 days. Regardless of changes in pH, temperature and incubation time, BG activity was higher than EG activity and PG activity was higher than PMG activity.

Key words: Monilinia fructicola, biological characteristics, cell wall degrading enzymes, culture conditions