Construction of an Infectious DNA Clone of Grapevine Geminivirus A Isolate GN and Its Biological Activity in Plants Analyzed Using an Efficient and Simple Inoculation Method.

The pathogenicity of grapevine geminivirus A (GGVA), a recently identified DNA virus, to grapevine plants remains largely unclear. Here, we report a new GGVA isolate (named GGVA QN ) obtained from grapevine 'Queen Nina' plants with severe disease symptoms. The infectious clone of GGVA QN (pXT-GGVA QN ) was constructed to investigate its pathogenicity. Nicotiana benthamiana plants inoculated with GGVA QN by agroinfiltration displayed upward leaf curling and chlorotic mottling symptoms. A simple, quick, and efficient method for delivering DNA clones of GGVA QN into grapevine plants was developed, by which Agrobacterium tumefaciens cells carrying pXT-GGVA QN were introduced into the roots of in vitro-grown 'Red Globe' grape plantlets with a syringe. By this method, all 'Red Globe' grape plants were systemically infected with GGVA QN , and the plants exhibited chlorotic mottling symptoms on their upper leaves and downward curling, interveinal yellowing, and leaf-margin necrosis symptoms on their lower leaves. Our results provide insights into the pathogenicity of GGVA and a simple and efficient inoculation method to deliver infectious viral clones to woody perennial plants.