Virulence Factors of Puccinia graminis f. sp. tritici Pers and Associated Yield Traits on Bread Wheat Landraces in Ethiopia

Bread wheat is severely affected by stem rust disease caused by Puccinia graminis f. sp. tritici Pers (Pgt) in Ethiopia. This study was conducted with the aims of identifying virulence pattern of Pgt, bread wheat landraces possessing effective resistance genes and variability in bread wheat quantitative traits. A total of 49 landraces were tested at seedling stage against eight Pgt races in greenhouse. Field study was concurrently conducted on the same landraces inoculated with five virulent races. Differential lines possessing Sr21, Sr9e, Sr6, Sr9g, Sr9a and Sr9d genes were highly susceptible to Pgt. The majority of landraces had Sr24 gene which was resistant to the most virulence races of Pgt including TRTTF, TKPTF, TTRTF and TKKTF. The Gompertz model provided the best overall fit to comparing disease progress and statistics. While most landraces studied on field trails were categorized as low partial slow rusting resistance, the remaining landraces were divided into two groups according to the severity level: high and moderate partial resistance. With the exception of days to maturity, days to heading and plant height, other traits were negatively affected by Pgt. Genotypic and phenotypic variability was significant in all landraces with values of the latter exceeding the former. High heritability coupled with high genetic advance was recorded for number of quantitative traits showing resistance to stem rust. This study provides a detail account of the resistance mechanisms of bread wheat landraces and their variability. The information can be used in stem rust resistance breeding program in Ethiopia and elsewhere.