Association of Grapevine fanleaf virus, Tomato ringspot virus and Grapevine rupestris stem pitting-associated virus with a grapevine vein-clearing complex on var. Chardonnay

A disease complex was observed on grapevine var. Chardonnay (Vitis vinifera) in a commercial vineyard in Missouri that destroyed the affected vineyard. Conspicuous vein-clearing symptoms on the leaves of originally diseased Chardonnay vines and bud-grafted Chardonnay, V. vinifera 'Cabernet Franc', V. vinifera 'Baco Blanc', and hybrid 'LN-33' vines are characteristics of the disease complex, which is referred to as the grapevine vein-clearing complex (GVCC). By applying reverse-transcription polymerase chain reaction (RT-PCR) using virus-specific primers, we detected combinations of Grapevine fanleaf virus (GFLV), Tomato ringspot virus (ToRSV) and Grapevine rupestris stem pitting-associated virus (GRSPaV), in symptomatic Chardonnay vines. Sequencing of RT-PCR amplified DNA fragments confirmed the identity of each virus, indicating the occurrence of ToRSV yellow vein strain, and two distinct strains of GRSPaV in the GVCC-affected Chardonnay vines. This is the first report of the co-infection of two nepoviruses and GRSPaV in var. Chardonnay. This study demonstrated that mixed infections of grapevine viruses belonging to different taxonomic groups pose a great threat to vineyards under certain climatic and soil conditions.