Detection and distribution of Grapevine rupestris stem pitting-associated virus in grapevine

Grapevine rupestris stem pitting-associated virus (GRSPaV) is a widespread virus of grapevine. In this study, we compared the detection efficiencies of two primer sets and evaluated virus distribution among different grapevine materials. The results of RT-PCR analyses showed that primer pair RSP52/53 was 10% more sensitive than RSP9F9R, with total detection rates of 89.3% and 78.6%, respectively. Five different parts of six grapevine cultivars, which were collected in May and August, were used as materials in GRSPaV detection analyses. The results showed that the fourth petioles were a suitable material for analysis, and fourth petiole materials collected in May and August yielded the same result (50.0%). The plant parts could be ranked, from highest virus detection efficiency to lowest, as follows: phloem > berries ≈ fourth petioles > tendrils > new leaves ≈ fourth leaves. A comparison of the titers of GRSPaV among the upper, middle, and lower above-ground parts and roots of three in vitro grapevine samples by quantitative real-time PCR showed that the highest concentration of GRSPaV was in the root, followed by the upper above-ground part.