Biology and Ultrastructural Characterization of Grapevine Badnavirus 1 and Grapevine Virus G.

Abstract: The biological characteristics of grapevine viruses, such as their transmission and hostrange, are important for the adoption of successful prophylaxis strategies. The aim of this studywas to investigate the traits of two newly described grapevine viruses widely distributed in Croatia,grapevine badnavirus 1 (GBV-1) and grapevine virus G (GVG). The vine mealybug (Planoccocusficus) proved to be a vector of GBV-1 and GVG capable of vine-to-vine transmission with overallexperimental transmission rates of 61% and 14.6%, respectively. Transmission was also demonstratedby grafting, with an overall transmission rate of 53.8% for GBV-1 and 100% for GVG, as well as bygreen grafting using the T-budding technique. Symptoms of GBV-1 and GVG were not observedon the woody cylinders of the indicators LN 33, Kober 5BB, 110 Richter and cvs. Chardonnayand Cabernet Sauvignon. Seed transmission and mechanical transmission were not confirmed.Electron microscopy revealed accumulation of GBV-1 particles and viroplasms in the cytoplasm,but no alternations of the cell structure. Infection with GVG revealed the proliferation of tonoplastassociated vesicles inside phloem cells and cell wall thickening.