Abstract
Studies were carried Out to assess wheat yield losses inflicted by Puccinia striiformis is f.sp. tritici. Investigations revealed that there exists a direct linkage between the disease level and the yield loss in the most common commercially adopted wheat varieties in Pakistan. The yield was significantly negatively correlated with the proportion of leaf area affected by stripe rust. The correlation coefficient (-0.67805) depicted highly significant effect of stripe rust in lowering wheat yield. There was varying resistance level among different wheat varieties. The extensively cultivated wheat variety, Inquilab-91 was found to be most resistant with minimum yield loss of 5.77% followed by Wafaq-2001 and Bakhtawar with yield loss of 6.63% and 14.90%, respectively. Whereas Morocco, proved to be the most susceptible wheat variety with maximum yield deficit to the tune of 39.79%. Evaluation of disease resistance revealed that Inquilab-91, Bakhtawar and Wafaq-2001 exhibited 2.24, 1.57 and 1.36 fold resistance in respect of wheat yield as compared to the most susceptible variety Morocco. Sowing of Inquilab-91 and Bakhtawar is recommended to escape heavy yield losses wreaked by the stripe rust.