Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

esistance to the yellow rust populations in Ethiopia, which requires further
confirmation through greenhouse studies. To sustain wheat production in the
region, particularly in Ethiopia, monitoring of races and inventorying of
resistance genes are of prime importance.
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Introduction
Yellow rust caused by Puccinia striiformis f.sp tritici is an important disease of
wheat in the highlands of East Africa (Ethiopia, Kenya, Uganda and Tanzania)
and in Yemen. The different planting dates in different agro-ecological zones
and the presence of volunteers in wheat fields provide continuous sources of
inoculum within or between countries in the area (Bonthuis, 1985). Due to
similarities in the distribution of cereal rust races among the East African
countries, a common epidemiological zone has been proposed (Saari and
Prescott, 1985; Stubbs, 1988). Rust spores are carried by wind among East
African countries, and it could even extend to West Asia (Dubin and Rajaram,
1996). Similarity of races had often been reported from East Africa (Danial,
1994) and the West Asian countries (Hakim and Mamluk, 1996). For instance,
the yellow rust virulence for the CIMMYT-originated bread wheat cv. Attila 'S'
was detected in Uganda some time before it appeared in Ethiopia in 1998.
Yield losses due to yellow rust could be 58 to 96% depending on the
susceptibility of the cultivars and environmental conditions (Eshetu, 1985).
A number of cultivars have been released in Ethiopia for use by farmers.
However, the cultivars become susceptible soon after release. There are also
cases where advanced lines became susceptible before their release. Therefore,
knowledge of effective resistance genes in the country and region would
enable breeders to target those useful genes in their breeding programmes,
with the hope of avoiding rust epidemics and subsequent crop losses in the
future. Hence, the resistance of commercial cultivars and advanced lines of
bread wheat must be monitored regularly to determine their effectiveness
against the existing yellow rust pathotypes. The objective of this study was to
monitor the resistance of commercial cultivars and promising genotypes of
bread wheat against the prevailing yellow rust population.
Materials and methods
An Ethiopian Wheat Rust Trap Nursery that consisted of commercial cultivars
and advanced lines of bread wheat (Tables 1 and 2) was tested at 12 locations
in Ethiopia during the main season of 1995–2005. However, only six locations
at which yellow rust occurred each year are considered in this study. The
locations considered hot-spots for yellow rust were Kulumsa, Asasa, Bekoji,
Meraro, Arsi Robe and Sinana. The locations range in altitude from 2200 to