Effect of temperature and water activity on in vitro germination of Monilinia spp.

Aims:  This study evaluated the effect of temperature (0–38°C) and water activity ( a w : 0·87–0·99) on the lag phase prior to germination and the percentage of germination over time for Monilinia laxa , Monilinia fructicola and Monilinia fructigena . Methods and Results:  More than 80% of viable conidia germinated at 25°C and 0·99 a w within 2 h for M. fructicola and M. fructigena and 4 h for M. laxa . There was no germination at 38°C, and all three Monilinia spp. germinated at 0°C. At the lowest a w (0·87), none of the Monilinia spp. was able to germinate at any of the incubation temperatures studied. Whereas at 0·90 a w , conidia were only able to germinate at 15, 25 and 30°C for the three species studied, except for M. fructicola at 15°C. In contrast, at 0·95, 0·97 and 0·99 a w , germination occurred at all studied temperatures less 38°C. Generally, the lag phase was longer at low levels of a w (0·90–095), and differences were more evident as temperatures were far from the optimum (0–5°C). Conclusions:  Germination and lag phase period were markedly influenced by temperature and a w , and in general when conditions of temperature and a w were suboptimal, the lag phase was longer and the percentage of germination was lower. Significance and Impact of the Study:  Knowledge of the germination requirements of this fungus is important in order to understand their behaviour in natural situations and to provide baseline data required for the construction of new prediction models. Our study might be used to develop a predictive model to understand and control the disease caused by Monilinia spp.