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

Aims: This study evaluated the effect of temperature (0-38 degrees C) and water activity (a(w): 0 center dot 87-0 center dot 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 degrees C and 0 center dot 99 a(w) within 2 h for M. fructicola and M. fructigena and 4 h for M. laxa. There was no germination at 38 degrees C, and all three Monilinia spp. germinated at 0 degrees C. At the lowest a(w) (0 center dot 87), none of the Monilinia spp. was able to germinate at any of the incubation temperatures studied. Whereas at 0 center dot 90 a(w), conidia were only able to germinate at 15, 25 and 30 degrees C for the three species studied, except for M. fructicola at 15 degrees C. In contrast, at 0 center dot 95, 0 center dot 97 and 0 center dot 99 a(w), germination occurred at all studied temperatures less 38 degrees C. Generally, the lag phase was longer at low levels of a(w) (0 center dot 90-095), and differences were more evident as temperatures were far from the optimum (0-5 degrees 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.