Is the Co-Occurrence of Neophysopella meliosmae-myrianthae and N. montana (Pucciniales) Common on Grapevines in Japan?

Abstract

Grapevine leaf rust (GLR) in temperate Asia is caused by Neophysopella meliosmae-myrianthae and N. montana; the former is commonly found on commercial grape cultivars (Vitis spp.) and the latter on a wild grape species, Vitis coignetiae. The two GLR fungi were found to co-occur in V. coignetiae at two survey sites in Japan. Under experimental conditions, both fungi parasitize and develop into uredinial and telial stages on commercial grape cultivars and wild species. Despite the assumed involvement of N. montana in GLR symptoms in commercial vineyards, there has been no confirmed report of its incidence, and it is not clear whether N. meliosmae-myrianthae commonly occurs on V. coignetiae under natural conditions. In this study, we aimed to disclose the occurrence and, in particular, the co-occurrence of the two species in a wide array of commercial grape cultivars and V. coignetiae in Japan based on the detection of targeted DNA markers with specific PCR primer pairs. This study confirmed the occurrence of only N. meliosmae-myrianthae infection in symptomatic samples of grape cultivars, while the co-occurrence was observed only in V. coignetiae. Neophysopella montana was widely detected in V. coignetiae specimens.