Investigation causative factors of grapevine dieback and decline in Bardaskan, Kashmar and Khalil abad areas

During growing seasons 2010-2012 samples of grapevine with various viruses and phytoplasma symptoms were collected from different vineyards in Khalilabad, Kashamr and Bardaskan .At the present study, Five important viruses including GFLV ΅GVA ΅GLRaV1 ζ GLRaV3 ζ GFKV were examined by DAS-ELISA testing of 124 samples,from vineyards in Khalil abad, Kashmar and Bardaskan.Among 124 suspected field samples, 45 were confirmed to be infected by GFLV. The rate of incidence varied from 0 to 36 %. The most infectious plants were observed in khalilabad.Grapevine fanleaf virus (GFLV) is the major causal agent of the grapevine degeneration /decline disease. GFLV causes a variety of symptoms in grapevines that differ in type and severity. Symptoms include chlorotic mottling, yellow mosaic with partially or completely chrome-yellow leaves, and vein-banding with light-green to chrome-yellow chlorotic bands along the veins and also shoots of affected vines may have shortened internodes and abnormal branching (Korcheshmeh).Meanwhile some affected plants show first symptoms on leaves represented by a sudden drying and scalding of margin area. Scalded areas continue to expand towards the central area of leaf where in some cases reddening of the lamina observed.Detection of phytoplasma is also was done by PCR_RFLP. The results indicate that grapevine stolbur phytoplasmas infecting vineyard in Khorassan province are distinguishable on 16S ribosomal gene from those reported in the major grape growing areas worldwide and tentatively classified as belonging to the ribosomal subgroup 16SrXII-A. The analyses carried out on samples collected from several plants showing these symptoms showed no indications of bacterial pathogen or associated fungi of Esca presence. Since the symptoms are physiologically similar to other that disrupt the plant water movement, it was thought that drought, nutritional deficiencies and other possible pathogens could have combined action in the syndrome therefore more analyses were performed.