Field-based assessment of slow rusting resistance against yellow rust in some commercial dryland wheat cultivars

Yellow rust caused by Puccinia striiformis f. sp. tritici is an important disease that threatens wheat production in cool environments. Slow rusting parameters including final rust severity (FRS), apparent infection rate (r), relative area under disease progress curve (rAUDPC), and coefficient of infection (CI) were evaluated in a set of twenty-one dryland wheat genotypes along with susceptible control in 2017 and 2018 growing seasons. This study was conducted in field plots at Ardabil and Agricultural Research Stations under natural and artificial infection conditions. Artificial inoculation was carried out by yellow rust inoculum having virulent genes against importance resistance genes. Seedling reaction was also evaluated under field conditions. Results of evaluations for resistance parameters showed that cultivars Sardari, Ohadi, Homa along with susceptible check had the highest values of FRS, CI, r and rAUDPC, therefore were mined as susceptible cultivars. Six cultivars were resistant or moderately resistant at both seedling and adult plant stages, two cultivars showed resistant or moderately resistant reactions at seedling, but moderate or moderately susceptible reactions at adult plant stage. Nine cultivars (entries; 6, 9, 10, 12, 14, 15, 19, 20 and 21) were susceptible at the seedling and had moderate (MR, M or MS) reactions at adult plant stages. Accordingly, these cultivars with low level of different parameters supposed to be having gene/s for varying degrees (good or moderate level) of slow rusting resistance or high temperature adult plant (HTAP) resistance. The remaining cultivars/lines had low level slow rusting resistance.