Submitted to: Vitis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 9, 1998
Publication Date: N/A
Interpretive Summary: Grapevine yellows disease in Virginia causes abortion of fruiting clusters, and eventual death of infected vines. This disease and grapevine yellows diseases elsewhere are attributed to pathogenic phytoplasmas - minute, cell wall-less bacteria that cannot be isolated in pure culture in the laboratory. The disease in Virginia closely resembles flavescence doree and other serious diseases of grapevines in Europe and Australia, but we found that the phytoplasmas infecting Virginia grapevines are different from other grapevine yellows pathogens. One of the phytoplasma species in Virginia grapevines is also associated with an aster yellows disease in the U. S.; we found this phytoplasma also in wild grapevine (Vitis riparia). The other phytoplasma had not been previously known. Our work found no evidence of flavescence doree, bois noir, or Australian grapevine yellows phytoplasmas in Virginia. Our identification and molecular characterization of the phytoplasmas in diseased grapevines in Virginia should aid scientists, crop consultants, diagnostics companies, and others to devise effective measures to control spread of the disease.
Technical Abstract: Grapevine yellows disease in Virginia closely resembles flavescence doree and other grapevine yellows diseases, but the phytoplasmas infecting grapevines in Virginia are distinct from other grapevine yellows pathogens. RFLP analysis of PCR-amplified 16S rDNA indicated that a Virginia grapevine yellows phytoplasma, designated VGYIII, was distinct from all other phytoplasmas studied, but was most closely related to spirea stunt (SP1), walnut witches' broom (WWB), and poinsettia branch-inducing (PoiB1) phytoplasmas in subgroups E, G, and H, respectively, of 16S rRNA group 16SrIII. RFLP analysis also indicated the existence of sequence heterogeneity between the two rRNA operons in the genomes of SP1 and WWB. Based on the results from RFLP and sequence comparisons with other group 16SrIII phytoplasmas, the VGYIII phytoplasma was classified in a new subgroup, designated 16SrIII-I. A second phytopasma (VGYI) was detected in cultivated grapevines (Vitis vinifera L.) and in wild grapevines (V. Riparia Michx.) and identified as a member of subgroup 16SrI-A. There was no evidence of flavescence doree, bois noir, or Australian grapevine yellows phytoplasmas in Virginia.