PATHOLOGICAL STUDIES ON WHEAT POWDERY MILDEW DISEASE IN EGYPT

Abstract

Wheat still remains as the major, nutritious, convenient and economical source of food all over the world. In Egypt, the annual production of wheat crop reached to 6.5 million tons of grains which produced in 2.5 million feddans up to 1999/2000 growing season. Wheat plant is subjected to attack with several common diseases, such as rusts, loose smut and powdery mildew. Wheat powdery mildew caused by Erysiphe graminis f. sp . tritici became one of the most important fungal diseases which attack wheat in Egypt. Although, it still has a minor importance as compared with wheat rusts, as detrimental effects on yield might be occurred in some area, in some years and on some cultivated varieties. Therefore, this study was conducted to find out the effective control measures against wheat powdery mildew disease. The obtained results could be summarized as follows: I-Thirty five isolates of Erysiphe graminis f. sp. tritici were obtained from 16 different wheat varieties cultivated in the experimental and commercial fields during 96/97 and 97/98 growing seasons. 2-Reaction of these isolates led to identify five physiological races, i.e. 1431, 1631, 3435, 3631 and 3635. However, the race 3635 was the most virulent and frequently isolated as compared with the other races. While, race 1431 showed the lowest of both virulence and frequency compared to the other races. 3-With regard to geographical distribution and prevalence, all the five races of the pathogen were found in both governorates of