Grapevine yellows (GY) are diseases associated to phytoplasmas that occur in many grape growing areas worldwide and are of still increasing significance. Almost identical symptoms of the GY syndrome are caused by different phytoplasmas and appear on leaves, shoots and clusters of grapevine. Typical symptoms include discoloration and necrosis of leaf veins and leaf blades, downward curling of leaves, lack or incomplete lignification of shoots, stunting and necrosis of shoots, abortion of inflorescences and shrivelling of berries. Those symptoms are related to callose deposition at the sieve plates and subsequent degeneration of the phloem. Although no resistant cultivars of Vitis vinifera or rootstocks are known so far, the various grape varieties differ considerably as far as symptom severity is concerned. It ranges from fast decline and death in highly susceptible cultivars to tolerant rootstocks as symptomless carriers of the pathogen.
The main viticultural production areas in the Republic of Macedonia were surveyed in 2006/2007/2008 for the presence of grapevine yellows. PCR and RFLP analyses were used to detect and identify phytoplasmas infecting grapevines. Only phytoplasmas associated with “bois noir” disease (ribosomal subgroup 16SrXII-A or stolbur) were detected. Molecular analyses showed that all phytoplasmas identified belonged to tuf-type II (VKII).
^GRAPEVINE YELLOWS - CURRENT DEVELOPMENTS AND UNSOLVED QUESTIONS, M. Maixner, Federal Biological Research Centre for Agriculture and Forestry (BBA), Institute for Plant Protection in Viticulture, 54470 Bernkastel-Kues, Germany http://www.icvg.ch/data/maixner.pdf