P-180 - Virus Survey of Muscadine Grapes in North Carolina

Muscadine grapes are native to the southeastern United States and are grown in both commercial and home vineyards.  The muscadine industry in North Carolina (NC) is highly diverse and can be split into two large areas: commercial processing (wine production) and fresh-market sales. Despite the economic importance of muscadine grapes in NC, knowledge about viruses affecting this crop is very limited. A muscadine survey was conducted in 2024 aiming to identify viruses infecting the crop and to assess their incidence in NC. Samples were collected from 210 asymptomatic vines across 8 locations and virus tested at the NC State Micropropagation Unit. Muscadine vines were tested for grapevine leafroll associated virus complex (GLRaV-2, 3, 4, 7), grapevine red blotch virus (GRBV), grapevine virus A and B (GVA and GVB), grapevine rupestris stem pitting-associated virus (GRSPaV), tomato ringspot virus (TRSV) and grapevine Syrah virus-1 (GSyV-1). RNA was extracted from samples and then virus tested using RT-qPCR assays. Amplicons were generated by conventional RT-PCR and send to sequence. Preliminary results revealed 39% incidence of GLRaV-2 and 23% incidence of GVB. Sequenced amplicons showed 91% identity to the GVB replicase and 97% to 99% identify to the GLRaV-2 coat protein. This is the first time viruses were reported to be present on NC muscadine vineyards. Additional testing will continue in 2025 to understand the implication of muscadines viruses to the yield/quality of the crop as well as potential insect vectors.