Effects of Temperature on Spore Germination and Mycelial Growth of , , and Isolates Associated with Sweet Cherry Canker Diseases.

Although fungal canker diseases constitute a limiting factor to orchard productivity and longevity, little is known about the effects of temperature on spore germination and mycelial growth of the fungal causal agents. Accordingly, the germination of spores and colony growth of , , and were evaluated after incubation on 2% water agar and 4% potato dextrose agar, respectively, at 5, 10, 15, 20, 25, 30, 35, and 40°C. Temperature optima for spore germination and mycelial growth were derived from nonlinear models fitted to germination rates and colony diameter data. The optimal temperatures for spore germination of were 28.5°C for ascospores and 29.2°C for conidia. The optimal temperatures for conidia and ascospore germination were 25.8 and 23.1°C, respectively. The germination of ascospores and conidia of at temperatures below 15°C required an incubation time of at least 72 h. Ascospores of and conidia of germinated at 10°C after 36 h. The optimal temperature for colony growth of was 24.6°C, whereas it was 21.7°C for both and . Our study indicates that temperature requirements for basic biological functions are higher for than for and . The overall higher temperatures of California relative to other cherry-producing regions in the United States or worldwide could explain the prevalence of Calosphaeria canker in the state. Conversely, and appear better adapted to cooler temperatures.