Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

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striiformis f.sp. tritici), stem rust (Puccinia graminis f.sp. tritici) and leaf rust
(Puccinia triticina) pathotypes are evolving in this region, causing breakdown
of widely utilized sources of resistance in wheat. Hence, knowledge of
effective resistance genes in the region will enable breeders to target those
useful genes in their breeding programmes and avoid eventual rust epidemics
and consequent crop losses.
Wheat cultivars grown in CWANA were resistant to the prevalent rust
populations when initially released. After a few years of cultivation, the
corresponding virulence emerges and the resistance genes became less
effective. A good example is the rapid spread of the virulent yellow rust race
that defeated the Yr9 resistance gene in the 1980s, which caused a widespread
epidemic on bread wheat from East Africa all the way across Western Asia to
Pakistan. Currently, most wheat cultivars grown in CWA are susceptible to
yellow rust. The wide cultivation of susceptible cultivars in East Africa and
CWANA region may have an important impact on rust inoculum
development, virulence change, and consequent epidemics. To develop
appropriate, practical and easy to handle methodologies for effective screening
for different types of resistance, we tested the known resistance genes for
yellow rust against various virulence types and at different rust hot-spots in
CWANA.
Materials and methods
Known yellow rust resistance genes and commercial cultivars (Table 1), that
have been used in the Cereal Rust Trap Nursery and tested at several locations
in CWANA, were selected based on their differential responses to yellow rust
isolates under artificial inoculation, as well as their reaction to natural
infections at several locations in Azerbaijan, Ethiopia, Lebanon, Iran,
Tajikistan, Turkey, Syria and Yemen.
Table 1. Yellow rust resistance genes and commercial cultivars
Resistance Genes
YrA, Yr1, Yr6, Yr5, Yr3N, Yr3V, Yr7, Yr9, Yr10, Yr15, Yr17, Yr27, YrSP
Yr6+
Source or Origin
Avocet isolines
Heines Peko
Yr7+ Reichersberg 42
Yr8 +18
YrSD
YrSU
YrCV
Commercial Cultivars
Yuna, Destluck, Tarragui, Zhetysu and Karakylchyk
Seri 82, Alamout, Attila, Shirodi, Darab, Cham 1 and Triticale
Compair
Strubes Dickopf
Suwon 92×Omar
Carstens
Cultivated in Central Asia
Cultivated in West Asia