DETECTION OF Phaeoacremonium tuscanum AND BOTRYOSPHAERIACEAE SPECIES ASSOCIATED WITH GRAPEVINE DECLINE IN IRAN AND THE POTENTIAL ROLE OF PRUNING DEBRIS ON THE SURVIVAL OF THE PATHOGENS

During spring and summer of 2010 and 2012, several surveys were conducted in different vineyards in Kohgiluyeh & Boyer-ahmad (southwestern Iran) and Kerman (southeastern Iran) provinces, with the aim of isolating and identifying fungi associated with grapevine decline diseases. The samples collected comprised diseased grapevines showing yellowing, defoliation, reduced growth, wilting, interveinal chlorosis, internal black spots and wood discoloration in cross section, as well as woody vine debris taken from the vineyards floor. Isolations were made from symptomatic wood tissues and pycnidia on the bark of pruning debris on malt extract agar supplemented with 1 mg ml-1 streptomycin sulphate (MEAS) and potato dextrose agar (PDA) media. Based on morphological and molecular characteristics four species: Phaeoacremonium tuscanum, Diplodia seriata, Botryosphaeria dothidea and Neofusicoccum parvum were isolated and identified from samples collected. In this regards, D. seriata and B. dothidea were recovered from diseased grapevines and pruning debris while N. parvum was obtained only from pycnidia formed on the bark of grapevine pruning debris. Pm. tuscanum was isolated from grapevines showing yellowing, defoliation, small chlorotic leaves, internal black spots and brown to black streaking in cross section. Pathogenicity tests were conducted on green shoot cuttings of 'Askari' cultivar under greenhouse conditions. Based on the results of pathogenicity tests, all tested species were pathogenic and caused significant wood discoloration on inoculated cuttings 25 days after inoculation. The fungi were re-isolated from the margin of the lesions, completing Koch’s postulates. Based on our knowledge, this is the first report of Pm. tuscanum from grapevine in Iran. This is also the first report of D. seriata, N. parvum and B. dothidea from pruning debris on the vineyard floors in this country.