Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

202
The weather conditions in April and in the first ten days in May were dry, but
the precipitation in the second half of May and in June did not lead to disease
development. In South Kazakhstan Oblast we observed a high correlation
between yellow rust development on winter wheat and weather conditions in
May, particularly with humidity (r=0.93±0.18) and precipitation (r=0.76±0.30).
In Kyrgyzstan and in Uzbekistan it was weaker (r=0.48-0.76). Negative
dependence was observed between rust development and air temperature in
April and May.
Wheat stripe [yellow] rust disease in Iran
M.R.J. Kamali and F. Afshari
Seed and Plant Improvement Institute, Karaj, Islamic Republic of Iran
Wheat is the most important crop in Iran, grown on more than 6.5 million
hectare. Stripe [yellow] rust on wheat caused by the fungus Puccinia striiformis
f.sp. tritici is an important disease in some wheat growing areas of Iran.
Economic appraisals of national losses have ranged from $US150 to 180 million
due to the 1994 yellow rust epidemic in Iran. The use of resistant cultivars is
the most effective, economical and environmentally safe method to control the
disease. Extensive research on stripe rust resistance in wheat has been carried
out over many years and has resulted in the release of many rust-resistant
cultivars to farmers. Adult plant resistance is considered in our breeding
programme, which can be defined as resistance that develops during the postseedling
stages. In the breeding programme for rust resistance it is necessary to
identify sources of resistance and the number of gene(s) conferring resistance
in any cultivar. When resistance is controlled by more than one or two genes, a
single mutation in the pathogen cannot break down the resistance in
commercial cultivars in a short time. In 1994, wheat yield loss due to the
appearance of a new pathotype of stripe rust was estimated at 1 million tonne
in Iran. The wide spread of susceptible cultivars in irrigated wheat areas, such
as Falat (Seri 82), sown on thousands of hectares for their wide adaptation to
abiotic stresses and different rotation systems, is perhaps the major reason for
stripe rust outbreaks in Iran in 1993 and 1994. Currently, Chamran (Attila 50Y)
is the most widely grown cultivar, grown on more than 500 000 ha in Iran. This
cultivar has become susceptible since 2003 with the appearance of a new race,
166E134A+, in Fars Province. The monitoring of yellow rust pathotypes and
their change over time to guide pyramiding of resistance genes from different
genetic backgrounds are important considerations in the wheat breeding
programme in Iran.