بررسي قارچ هاي خاكزار عوامل پوسيدگي ريشه و طوقه گندم و تعيين ميزان خسارت اقتصادي آنها

Study on Soil Borne Fungi, the Causal Agents of Root and Crown Rot of Wheat in Zanjan Province

In order to study and identify crown and root fungal pathogens of wheat and their importance at Zanjan province, 187 wheat fields were visited during 1999 to 2000. Suspected samples with symptoms such as chlorosis, withering, whiting of spikes, growth reduction, crown and root necrosis were collected. After isolating and purification, finally 98 fungal isolates belonging to five genus and seven species were identified. Rhizoctonia solani, Fusarium culmorum and Dreschlera sp. were most frequent. Pathogenicity test of these fungi and Rhizoctonia cerealis were done on wheat Flat cultivar. The results showed that, about 40 percent of wheat fields were infected by at least one of these fungi in different parts of Zanjan province. The infection percentage was 1-15 percent in studied areas. The rate of damage depended on the rate of infection and population dynamic of causal agents, which was 1 to 9 percent of yield. Results of this research also demonstrated that wheat was highly affected by soil-borne fungi in poor soil and low organic matter in comparison to fertile soils.