بررسی و شناسایی گونه های قارچی عامل بیماری پوسیدگی ریشه و طوقه گندم در استان اصفهان

Wheat, Triticum aestivum L. is a strategic plant in the world which, due to climatic changes, has been attacked by a number of diseases including root and foot rot disease, with a high severity. To identify the causes of the foot and rot disease of the wheat field in Isfahan Province, Iran, 100 wheat fields were kept into considerations, where the infected wheat samples were obtained, in the years 2014-2015.After transferring the specimens to the laboratory and keeping them in the refrigerator, the crown and root parts, which had signs of the disease, were separated and washed for a period of one hour under a gentle stream of tap water. Then, from a gap between healthy and contaminated tissue, fragments of 0.5 to 1 cm were prepared and for surface sterilization of the samples, 1% sodium hypochlorite solution was used for 30-60 seconds. After three times washing with sterilized distilled water and drying them between two layers of sterile filter paper, the was cultured on culture medium of Dextrose Agar (PDA) containing Streptomycin Sulfate under a sterile conditions. In each mattress, place 3 pieces and keep them at 25 ° C. After the growth of the colonies, the casing was prepared from the margin, and the fungi were isolated. Purification of isolates was done by single-spore and or tip method, depending on the type of fungus on 2% agar water culture medium and then the specific cultures media such as TWA. Identification of isolates was based on apparent characteristics such as colony growth and color, spore form and type of phialides, and measurement of spore length and width using valid keys. The result showed that, there are infections by several fungal diseases, out of which 314 isolates were obtained. The related isolates were identified to be Bipolaris sorokiniana, Gaeumnomyce graminis var. tritic, Phytophthora nicotianae, Fusarium. culmorum, Fusarium semitectum and Fusarium solani. These species were got into pathogenicity tests on three wheat varieties, Back cross roshan, Parsi and Pishtaz inoculated at glass house conditions by the well grown inoculum of every isolates on sterile wheat seeds in compression to control. The results indicated that, B. sorokiniana, G. g.var. tritici, and F. culmorum were of higher severity rates on the foot and root of the plant in compression to other species with 75, 65, 65, 64 present, which had a direct relation with the plant growth respectively. The B. sorokiniana had the greatest roll in terms of infection and distribution than the other ones. Considering the disease appearance days after inoculations, revealed that, B. sorokiniana with the lowest days of 28 was the lowest, whereas F. solani the highest with 77 days.