One hundred and fifty varieties/lines were screened against wheat leaf rust. The natural environmental conditions of Ayub Agricultural Research Institute, Faisalabad were favorable for the development of leaf rust disease of wheat. Out of 150 lines/cultivars that were screened against brown/leaf rust, 29 lines/cultivars were immune, resistance was showed by 57 varieties and the remaining were susceptible. Values of area under disease progress curve (AUDPC) of all varieties were calculated. Also

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... from the virulence and avirulence formula studied, it was shown that 57 varieties of leaf rust were avirulent and 49 varieties were virulent by leaf rust fungi, respectively. Environmental factors had great effect on the progress of leaf rusts diseases of wheat. Correlation between disease severity and environmental factors was also determined. Maximum varieties/lines showed comprehensible response to environmental factors. Four environmental factors (Temperature, Relative Humidity, Wind Speed and Rainfall) showed significant influence of disease severity. Five varieties/lines V-15, V-45, V-77, V-102, and V-118 showed considerable response to all environmental factors against brown rust. Utilization of this data for wheat improvement coupled with national varietal and gene deployment is discussed. The compiled field results show that although the virulence frequency for some of the leaf rust resistance genes remained low, yet the presence of virulence against them is alarming under the circumstances when genetic base of resistance is stumpy in the presently cultivated varieties. On the basis of data, these environmental factors were tested for correlation with leaf rust severities. It was concluded that screening and identifying the virulence pattern of leaf rust on wheat germplasm and utilizing these virulence genes on advanced lines may be helpful to produced rust resistance in wheat in order to obtain maximum production.