The incidence of grapevine yellow speckle disease in Australian grapevines and the influence of inoculum source on symptom expression

Abstract

Field observations and indexing indicated a high incidence of grapevine yellow speckle disease (GYS) in grapevines grown in Victoria. GYS showed symptoms in 38 % of the cultivars examined in the field and was detected in a further 24% by indexing cultivars not showing symptoms in the field. Indexing confirmed the presence of GYS in a random sample of vines showing GYS symptoms, while glasshouse tests showed that grapevine fanleaf virus and grapevine yellow vein virus were absent in such vines. Bud-graft inoculations of three indicator varieties, Cabernet franc, Mataro and Mission Seedling 1, with GYS from six different sources established that the source of inoculum had a significant effect on the intensity and pattern of symptoms produced, which suggests the existence of strains of the GYS pathogen. Evidence is presented which suggests that GYS is spreading in the field. Attempts to transmit the disease via contaminated pruning tools were unsuccessful.