Abstract:
Wheat stem rust caused by Puccinia graminis f. sp. tritici is one of the most destructive diseases of wheat which causes considerable yield losses in wheat growing areas worldwide. Disease resistant cultivars provide one of the best means of controlling wheat stem rust. The current study aimed at assessing the distribution of wheat stem rust in Arsi and Bale zones in 2017 cropping season and evaluating wheat genotypes resistance at seedling and adult plant growth stage against the four predominant wheat stem rust races; TTKSK, TKTTF, TRTTF and JRCQC. Wheat stem rust distribution was conducted in the main wheat belt areas of the country namely in Arsi and Bale zones. Both seedling and adult plant stage evaluation conducted on 202 wheat genotypes under greenhouse and field conditions, respectively. The seedling resistance was evaluated by inoculating the wheat genotypes with four races separately using completely randomized design with two replications at Ambo Agricultural Research Center. The same wheat genotypes were evaluated for adult-plant stage resistance at Kulumsa Agricultural Research Center using augmented design with five repeated checks per blocks. Field survey result revealed that the distribution of stem rust varied depending on agro-ecologies and varieties grown. Overall the average prevalence of stem rust was 63.0% with individual zone prevalence of 52.2% in Arsi and 73.9% in Bale. From surveyed wheat stem rust samples, five races (TKTTF, TTTTF, TTRTF, TTKSK and TRTTF) were identified from Arsi and Bale zones. The most predominant races were TKTTF (53.0%), TTTTF (31.0%) and TTRTF (10.0%). These races are virulent for 17-18 Sr genes. Seedling evaluation results showed high level of variability in responses of genotypes for the four stem rust races. Phenotypic variation was observed for infection types and level of stem rust severity for wheat genotypes for field evaluation. There was highly significant difference among reference variety and new genotypes for different disease parameters for each single race nursery. From this study, five genotypes (ETBW 9045, ETBW 9464, ETBW 9569, K6295-4A and Alidoro) showed seedling susceptible and field resistant reaction for the three major bread wheat stem rust races (TKTTF, TRTTF and TTKSK). Therefore, this genotypes will be potential source of resistance for further wheat breeding and pathological activities.
