Epidemics of Pucciniastriiformis F. Sp. Tritici in Arsi and West Arsi Zones of Ethiopia in 2010 and Identification of Effective Resistance Genes

Abstract

Stripe rust of wheat is one of the most important wheat production constraints in Ethiopia. The 2010 main season has witnessed the importance of the disease as widespread epidemic occurred throughout the major wheat producing areas that resulted in complete crop failure and as a result two popular varieties Kubsa and Galama were withdrawn from production. In order to monitor stripe rust of wheat, wheat diseases survey are conducted annually and rust trap nurseries are planted in selected wheat producing areas. In the current study, survey was conducted to evaluate the performance of the released cultivars to the major epidemic on farmers’ wheat fields. Rust trap nurseries were also planted in major representative areas of the Arsi zone to evaluate the performance of the commercial cultivars and also the stripe rust differentials. A total of 120 wheat fields were covered during the survey. Stripe rust of wheat was the most prevalent disease across the three routes. It was found in 84% of the fields inspected. The incidence and the severity of stripe rust of wheat varied according to locations, varieties, planting dates and the crop growth stage. The highest stripe rust incidence and severity was recorded on Kubsa which is the dominant bread wheat cultivar in all the three routes. Stripe rust was quite high at altitudes ranging from 2144 to 2497m above sea level. Bread wheat cultivars such as Digalu, MadaWallabu and K62954A and Tusie were found to be resistant under farmers’ field condition and can serve as important sources of resistance to the stripe rust races prevailing in Ethiopia. Of the three test locations, Meraro has the widest virulence spectrum for stripe rust of wheat and as a result most of the stripe rust differentials were not effective to the stripe rust populations prevailing at Meraro. Kulumssa and Arsi Robe have comparable virulence spectrum and almost equal number of effective and ineffective genes were identified during the season in both locations. In general, compared to the other cropping seasons, the virulence spectrum of stripe rust has increased in 2010 in all locations and the number of effective genes identified is very low in all locations. The virulence spectrum of stripe rust at Meraro has always been wide because of the favorable environmental condition. Genes Yr5, Yr15 and YrSP were effective across all the test locations. These genes can be recommended to be utilized in the development of stripe rust resistant varieties that are effective to the Ethiopian stripe rust populations in the major wheat producing areas in Ethiopia. Keywords: effective genes, incidence, severity, stripe rust, trap nursery, virulence