Ecopathological Analysis of Apple stem grooving virus-K Harboring Talaromyces flavus

Pear black necrotic leaf spot (PBNLS) on pear trees (Pyrus pyrifolia) is caused by a Korean isolate of Apple stem grooving virus (ASGV-K). Yellow spots were detected in Phaseolus vulgaris (kidney bean) and Chenopodium quinoa which were grown near the diseased pears in year 2000 through 2003. The ASGV-K, the causative agent of PBNLS, was detected from the symptoms of the diseased kidney bean plant and C. quinoa. ASGV-harboring fungi were also isolated from symptomatic plants and from soils surrounding the infected plants. The ASGV-harboring fungus was identified and characterized as Talaromyces flavus. Ecopathological studies showed that the number of ASGV-harboring fungi on the pear leaves was not correlated with differences in temperature or severity of symptoms. Additionally, there was no difference in fungus frequency among the orchard locations or different host plants. Although the frequency of fungi isolated from the soil was not affected by changes in temperature or location, the fungi occurred at higher densities in the rhizosphere than in the plants themselves.