Effects of Arbuscular Mycorrhizal Fungus and Different Phosphorus Doses Against Cotton Wilt Caused Verticillium dahliae Kleb.

The objective of this work was to study the influence of Arbuscular Mycorrhizal Fungus (AMF) and different phosphorus dosages on the development of Verticillium dahliae Kleb. induced wilt in cotton. Sayar-314 cotton variety which is sensitive to Verticillium wilt, AMF G. intraradices and phosphorus dosages of 0, 40 and 80 kg ha-1 were used in the experiments implemented under naturally V. dahliae-contaminated field conditions during the years of 2007 and 2008. According to the obtained results, it was found that there occurred a reduction in the disease chart. Also, it was observed that the application reduced the severity of the disease by 22-29.22% in green portions of cotton plants and their stem sections in field divisions particularly to which G. intraradices and phosphorus of 40 kg ha-1 had been applied together in both years. On the other hand, phosphorus dosage of 80 kg ha-1 had a negative effect in suppressing the infection. Phosphorus (P) content of cotton plants leaves increased in mycorrhizal fungus treated divisions compared with those untreated. Besides, due to the infection, cotton yield decreased by 14-21% in the divisions without AMF application. It was also concluded that if AM fungus was applied along with lower dosages of phosphorus, it would mitigate the severity of V. dahliae-induced infection in cotton, increase the yield despite the infection and induce phosphorus uptake in the plant.