Abstracts The present study was carried out in order to investigate the rate of negative effect of wheat yellow rust pathogens on characteristics related to the cluster and yield of wheat cultivars in climatic conditions of north of Khuzestan. The study was carried out using a split plot design in randomized complete blocks with three replications. In this design, the conditions of presence and absence of wheat yellow rust were considered as the main factors, and the most important cultivars planted in the region including Dez and Chamran were considered as the secondary factors. The results of variance analysis indicated that both group of factors had a significant effect on all characteristics except for the cluster length on which yellow rust had no significant effect due to its reliance on genotype. It was also concluded that the mutual effect was only significant on the grain yield at a level of 5%. Chamran and Dez cultivars with average of 503.33 and 4808.33 kg/hectare had the highest and the lowest yield, respectively. Yellow rust disease had a severely negative effect on all characteristics except for the cluster length, which finally led to a decrease of 53.92% in the yield compared to appropriate conditions. Given the moisture rate of the weather as the most important factor for the disease spread, it is hoped that the losses caused by yellow rust can be prevented by utilizing suitable managerial methods and most importantly irrigation schedule program and applying appropriate pesticides, which the results indicated that can be justified in regard to economy. Keywords: yellow rust; wheat; cluster

Keywords: yellow rust, Wheat, cluster