تعيين برخي ويژگي ها، ارزيابي بيماري زايي و تنوع در جدايه هاي Gnomonia leptostyla، عامل آنتراكنوز گردو در ايران

STUDY ON SOME CHARACTERISTICS, ASSESSMENT OF PATHOGENICITY AND DIVERSITY IN Gnomonia leptostyla ISOLATES, CASUAL AGENT OF WALNUT ANTHRACNOSE IN IRAN

Anthracnose caused by Gnomonia leptostyla (Fr.) Ces & de Not. is the most serious foliar disease of walnut. In this disease, premature leaf drop is one of the major causes of poor kernel fill. During summer and fall 2005-2007, samples of walnut tissues with symptoms of black spot were collected from East and West Azarbaijan, Ardebil, Zanjan, Qazvin, Mazandaran, Hamedan and Tehran provinces. Forty five isolates of Gnomonia leptostyla (anamorph: Marssonina juglandis) were isolated using Oat Meal Agar and Corn Meal Agar media. Acervular conidiomata were produced by all isolates at 21°C, under photoperiod (16 h light: h darkness) after 18-21 days. All isolates were heterotallic. Fertile perithecia with asci and ascospores were produced in vitro after 75-90 days at 4 °C in darkness. In pathogenicity experiments, a conidial suspension ( 105 spore/ml) was atomized onto mature, fully expanded leaflets. After 16 days, macroscopic brown spots were observed on leaves. 24 days after inoculation, acervuli were produced on surface of spots. There were significant differences among the isolates for pathogenicity. The results indicated that there was a significant positive correlation between the number of spots and the leaflet specific fresh weight (LSFW), so the upper leaflets on the leaves, and especially the terminal ones, with the highest LSFW were tae most susceptible ones to the disease.