A case study of the effect of temperature on aggressiveness in the Monilinia-peach pathosystem

Abstract

Temperature is one of the key factors affecting the infection and development of fungal plant pathogens. Monilinia fructicola and M. laxa are the most important species causing brown rot of peach fruits worldwide. Considering that symptoms of M. laxa and M. fructicola appear in spring and summer, respectively, the virulence of these two species is expected to differ under temperature stress. To test this hypothesis, four isolates with different virulence levels from both species were selected and their in vitro aggressiveness on peach fruit was tested at different temperatures. Experiments were conducted at 4 °C, 11 °C, 23 °C and 35 °C, relating to postharvest storage temperature, spring temperature, in vitro optimum growth temperature and summer temperature, respectively. Incubation period and relative area under disease progression curve (RAUDPC) were used as aggressiveness components of the pathogens. Incubation period was shortest at 35 °C and longest at 4 °C for both species. Temperature affected aggressiveness responses of these species differently. While M. fructicola was more aggressive at higher temperatures (35 °C), M. laxa was more aggressive at lower temperatures (4 °C & 11 °C). Besides, RAUDPC values of low virulent isolates of both species showed wider distribution at all temperatures evaluated, compared to high virulents. The piecewise regression (PWR) model detected two main clusters and indicated that increased temperatures trigger disease progression rapidly and severely. The PWR model used in this study also provided an example that can be used in the management and prediction of fungal diseases. This case study presented important findings that will guide a comprehensive study plan on the effects of climate change in this pathosystem.