Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

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Introduction
Bread wheat in Kyrgyzstan is an important strategic crop as it is a major food
for the population. It occupies more than half the total arable area of
agricultural crops cultivated in the country. At present, virtually all farms have
no possibility of growing high yielding varieties with a high level of
productivity and high grain quality because of rust diseases, the main factors
limiting wheat yield.
Annual crop losses due to rust diseases (P. striiformis, P. triticina) in
Kyrgyzstan are 10–30%. In 2001, an epiphytotic of yellow rust was recorded in
Kyrgyzstan with crop losses estimated at between 40 and 60% (Dzhunusova,
Yahyaoui and Morgounov, 2002).
Although wheat research in Kyrgyzstan started in 1936, breeding wheat for
biotic stresses such as rust diseases was initiated only in recent years. In 2002, a
wheat breeding programme started in Kyrgyzstan for resistance to yellow rust,
in close collaboration with CIMMYT and ICARDA. A few hundred resistance
lines were selected and went to the breeding programme for adaptation to
ecological conditions, and yield trials were conducted for selection of the best
cultivars (Azibrosh, Zubkov, Zagadka, Almira, Djamin, Hans, Petr).
Material and methods
A total of 930 samples of wheat were included in field tests, including 450 from
the Central and West Asian Rust Trap Nursery (CWA-RTN), RWKLDN and
1st Ug99IRSTN2007; 370 entries from FAWWON-SA, FAWWON-IRR, WON-
SA and WON-IRR nurseries; 76 entries from Central Asian countries; and 34
released cultivars from Kyrgyzstan.
The nurseries and varieties were evaluated at two experimental sites in Chu
region and Issyk-Kul region. The accessions were evaluated for resistance to
disease by observation under natural infection. Each sample was hand-sown in
1 m rows with 35 cm between rows. Cvs Morocco, Dostuk and DKyzyl were
used as susceptible check varieties and as spreaders in the field.
Disease severity and reaction types of each entry were scored using the
modified Cobb’s scale (R-MR-MS-S) of Peterson, Campbell and Hannah (1948).
The entries were then classified according to their CI values: resistant (0–10);
moderately resistant (10–30); moderately susceptible (30–50); and susceptible
(50–100). The samples in the resistant and moderately resistant groups were
selected as candidate resistance lines. They were screened again in the
following 1 or 2 years and for the final breeding phase they were also
evaluated for their agronomic qualities in the field (Breeding nursery, AYT,
YET). In the final selection they were also evaluated for their reaction to rust