Identification of resistance to Puccinia striiformis f. sp. tritici in some elite wheat lines

Race-specific resistance of wheat to yellow rust caused by Puccinia striiformis f. sp. tritici has been reported as short-lived. Partial resistance, a kind of quantitative resistance, has been reported to be more stable. Partial resistance in terms of slow rusting parameters including final rust severity (FRS), apparent infection rate (r), relative area under disease progress curve (rAUDPC), and coefficient of infection (CI) was evaluated in a set of twenty six wheat genotypes along with susceptible control during 2010-2011 cropping year. This study was conducted in field plots at Ardabil Agricultural Research Station (Iran) under natural infection conditions with twice artificial inoculation. Artificial inoculation was carried out by yellow rust inoculum having virulence against Yr2, Yr6, Yr7, Yr9, Yr22, Yr23, Yr24, Yr25, Yr26, Yr27, YrA, and YrSU. Seedling reaction was also evaluated in greenhouse by using race 66E0A+, Yr27+. Results of mean comparison for resistance parameters showed that, lines C-89-4, C-89-17 and C-89-16 along with susceptible had the highest values of FRS, CI, and rAUDPC, therefore were selected as moderately susceptible or susceptible lines. The lines C-89-7, C-89-8, C-89-9, C-89-10, C-89-13, C-89-14 and C-89-20 had susceptible reactions at seedling stage and low level infection at adult plant stage. Accordingly these lines with low level of different parameters are supposed to have gene/s for varying degrees of partial resistance or high temperature adult plant resistance (HTAP) that can be used for future manipulation in wheat improvement programs after confirmatory studies. The remaining lines were immune or had low level of infection. Thus, these were selected as resistant lines. In this study correlation coefficient between different parameters of slow rusting was highly significant. Based on the results, FRS, CI and rAUDPC are suitable parameters for selection under field conditions.