Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

262
Wheat yellow rust epidemics in
Uzbekistan in 2009
R.C. Sharma, 1 A. Amanov, 2 Z. Khalikulov, 1 C. Martius, 1 Z. Ziyaev 3 and S. Alikulov 3
1. ICARDA, Central Asia and the Caucasus Regional Programme, Tashkent,
Uzbekistan
2. Principal Consultant to the President's Office, Uzbekistan
3. Uzbek Research Institute of Plant Industry, Tashkent, Uzbekistan
Abstract
Severe wheat yellow rust epidemics occurred in many parts of Uzbekistan in
April and May 2009. This yellow rust outbreak was experienced from the midsouthern
region bordering Afghanistan and Turkmenistan to the north-east
region of Fergana valley adjoining Kyrgyzstan and Tajikistan. The southern
region of Uzbekistan experienced early, more severe epidemics than the
northern part. The epidemics spread from irrigated to some of the traditionally
rainfed wheat areas that had not experienced yellow rust problems for a long
time. All released and candidate wheat cultivars planted in the epidemic zones
showed susceptibility to yellow rust; a few showed severe infection for the first
time. Late winter and spring weather conditions were unusually wet, creating
favourable environments for development of yellow rust epidemics.
Fungicides were sprayed to control the disease; however, frequent rains
reduced the effectiveness of the chemicals. Estimates of grain yield reductions
would depend upon cultivar, level of epidemics and effectiveness of
fungicides. The older wheat cultivars showed up to 100S, whereas more recent
cultivars showed up to 80S reaction to yellow rust. The most widely cultivated
wheat cultivar in Uzbekistan, Kroska, showed high levels of susceptibility to
yellow rust. There could be substantial economic losses, considering that
Uzbekistan annually produces over 6 million tonne of wheat. The
susceptibility on a few cultivars for the first time raises suspicion of new
yellow rust virulence in Uzbekistan, which needs to be confirmed. Despite
these severe epidemics, several advanced lines from the International Winter
Wheat Improvement Programme (IWWIP) and other sources have shown
resistance to yellow rust, underscoring the value of germplasm exchange.
Identification of advanced breeding lines of winter wheat resistant to yellow
rust in the severe epidemics in 2009 could be useful not only for Uzbekistan
but also for other wheat improvement programmes in Central Asia, as well for
the IWWIP to target for developing yellow rust-resistant wheat.