abstract
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Stripe (yellow) rust has been a devastating disease of winter wheat in Central Asia in the past 20 years. Frequent stripe rust epidemics occurred in Uzbekistan between 2001 and 2013. In 1 out of 4 years stripe rust epidemics have occurred at early growth stage of winter wheat prior to onset of winter. Under mild winter, severe stripe rust infection can occur in February and continue through May depending upon temperature and precipitation. Under prolonged epidemics, fungicides are sprayed up to four times to control the disease. Extraordinary stripe rust epidemics occurred in Uzbekistan in 2009 and 2010 when all commercial varieties showed susceptibility. This necessitated an urgency to identify resistant varieties. The collaborative efforts among Uzbek wheat research programs and International Winter Wheat Program (IWWIP), a cooperative project involving the Ministry of Food, Agriculture and Livestock of Turkey, the International Maize and Wheat Improvement Center (CIMMYT) and the International Center for Agricultural Research in the Dry Areas (ICARDA) identified three stripe rust resistant varieties in 2010. Since then 11 wheat varieties resistant to stripe rust have been identified through international collaboration in Uzbekistan. The varieties with high level of stripe rust resistance are ‘Gozgon’, ‘Buniyodkor’, ‘Huma’, ‘Iftihor’, ‘Shams, ‘Ravon’, ‘Gallakor’, ‘Shukrona’ and ‘Taraqqiyot’. The varieties with intermediate level of resistance are ‘Yaksart’ and ‘Hazrati Bashir’. Gozgon and Yaksart are being cultivated on large acreage while other varieties occupy small areas depending upon specific traits and geographical area recommendation. Stripe rust resistant varieties occupied more than 50% area under wheat cultivation in Uzbekistan in 2018 compared almost none in 2010. Stripe rust continues to appear on susceptible varieties almost every year in Uzbekistan, but no large scale epidemics have been recorded in the past 5 years. Cultivation of resistant varieties in stripe rust hot spots slows down spread of disease geographically. Wheat farmers continue to control stripe rust on susceptible cultivars using fungicides. However, fungicides are not sprayed on resistant varieties, thus reducing the cost of wheat production. The regional and international collaborations on stripe rust research in the past 10 years are showing positive results towards providing options to the winter wheat farmers to replace the susceptible cultivars with the resistant ones. This information on stripe rust resistant varieties in Uzbekistan could be useful for the national and international winter wheat improvement programs in either further evaluation for varietal identification or using them as parents in the crossing.