Biological characteristics of Monilinia fructicola isolates from stone fruits in eastern West Virginia.

Monilinia fructicola, the causal agent of brown rot, was recovered from decayed stone fruits (peach, plum and nectarine) in 11 West Virginia orchards. There was significant variation among these isolates with respect to colony morphology, growth rate, sporulation level, sensitivity to fenbuconazole, vegetative compatibility and virulence. Species identification was confirmed using ITS sequences from the nuclear ribosomal RNA gene. The cultural phenotypes on potato dextrose agar (PDA) ranged from white to dark, melanized colonies. The growth rate of the isolates on PDA ranged from 0.3 to 3.2 mm day−1at 4 °C, from 2.9 to 7.6 mm day−1at 10 °C, and from 4.8 to 19 mm day−1at 24 °C. There was a statistically significant relationship between the growth of the isolates on PDA and their aggressiveness on nectarines at 24 °C, especially at higher inoculum concentrations. Sporulation of 3-day-old cultures on peach agar at 24 °C varied from profuse to no sporulation, with some isolates sporulating only sparsely after 10 days. The EC50for fenbuconazole ranged from 0.003 to 0.129 μg μL−1and for two reference isolates was 0.020 and 0.016 μg μL−1. Only a few vegetative compatibility groups were identified among isolates within orchards, reflecting the lack of sexual recombination in this region. [ABSTRACT FROM AUTHOR]