VIEW ARTICLE

Ecology and Epidemiology

Volume, Nuclear Number, and Aggressiveness of Conidia of Monilinia fructicola Produced on Media of Varied Glucose Concentrations at 15 and 25 C. Douglas J. Phillips, Plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, Postharvest Quality and Genetics Research Unit, Horticultural Crops Research Laboratory, Fresno, CA 93727; Dennis A. Margosan(2), and Bruce E. Mackey(3). (2)Biology technician, Agricultural Research Service, U.S. Department of Agriculture, Postharvest Quality and Genetics Research Unit, Horticultural Crops Research Laboratory, Fresno, CA 93727; (3)Consulting statistician, Western Regional Research Center, Albany, CA. Phytopathology 79:401-403. Accepted for publication 27 September 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-401.

Conidia of two isolates of Monilinia fructicola were produced at 15 and 25 C on potato-dextrose agar made with 20, 150, or 300 g of glucose per liter. At 15 C on agar containing glucose at 20 g/L, both isolates produced conidia that had greater volume, nuclear number, germination after 5 hr, and aggressiveness (measured as lesion development) than conidia produced at 25 C. Increasing glucose concentrations significantly influenced the aggressiveness of one isolate and the spore volume, nuclear number, and germination after 5 hr of both isolates. When the isolates were grown on agar containing glucose at 300 g/L, no significant differences resulting from temperature occurred in the germination after 5 hr and aggressiveness of both isolates and in the spore volume and nuclear number of one of the isolates. The aggressiveness of both isolates was more positively correlated with spore volume and nuclear number than with germination after 5 or 24 hr. Of the factors studied, the volume of the spore was the most useful estimate of the potential aggressiveness of conidia of M. fructicola.