Crude garlic extract significantly inhibits replication of grapevine viruses

Abstract

Efforts to control viral diseases of grapevine include the production of certified material and development of virus‐resistant transgenic grapevines. However, effective antiviral agents, once the viruses have infected the plants, are still lacking. This study shows that a crude garlic extract has significant antiviral activity against grapevine viruses. Replication of grapevine leafroll‐associated virus 2 (GLRaV‐2) was obviously inhibited in grapevine cv. Cabernet Sauvignon calli treated with diluted (1:100) garlic extract. The relative RNA levels of GLRaV‐2 and grapevine fleck virus (GFkV) in cv. Summer Black grapevine in in vitro‐grown plantlets 10 days after treatment with diluted (1:100) garlic extract were about 22% and 20%, respectively, of that in controls. The viral RNA accumulation of GLRaV‐2, GFkV, grapevine virus A (GVA), grapevine fanleaf virus (GFLV) and grapevine rupestris stem pitting‐associated virus (GRSPaV) in field‐grown grapevine cv. Centennial Seedless plants sprayed with diluted (1:100) garlic extract were about 31–40%, 26–38%, 18–31%, 17–42% and 15–18%, respectively, of that in controls. Moreover, the garlic extract treatment led to a significant decrease in viral RNA accumulation of GLRaV‐3, GLRaV‐2, GVA, GFkV, GFLV, GRSPaV and grapevine Pinot Gris virus in pot‐grown grapevine cv. Shine Muscat plants, and viral disease symptoms in these plants were obviously attenuated. In addition, this extract significantly induced expression of pathogenesis‐related protein genes and stimulated activity of antioxidant enzymes in grapevines. Taken together, these results indicate that the crude garlic extract acts as a significant inhibitor against a broad range of grapevine viruses.