Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

407
Selection of wheat cultivars for resistance to yellow rust in
Uzbekistan
V.E. Khokhlacheva, B.A. Khasanov, R.M. Bajanova, S.K. Baboev and A.U. Mavjudova
Institute of Genetics and Plant Experimental Biology of AS Ruz, Uzbek Academy of
Sciences, Kibray, Tashkent, Uzbekistan
Airstream circulation influences the spread of wheat yellow rust caused by
Puccinia striiformis f.sp. tritici in Central Asia. In Uzbekistan, yellow rust
epidemics occur every 3 to 5 years. The race composition of the yellow rust
population has also been changing. The prevalent races are 0Е0, 2Е0, 5Е0 and
160Е16. The most rational method of control of yellow rust is the use of
resistant cultivars. Thus, in our work, we evaluated the reactions to yellow rust
of nine wheat cultivars and up to 100 lines in the laboratory and in the field. In
the field, the nurseries were planted in different climatic areas of Uzbekistan.
The results showed that 77 lines and varieties were resistant in the seedling
stage and 51 lines and varieties were resistant in the adult stage. In the past,
cvs Kroshka, Kupava, Knyagna, Polovchanka, Bozsuv 1, Emnbosh, Bayaut,
Umanka and Ulugbek 600 were moderately resistant to yellow rust (5MR–
10MR). In 2009, all commercial cultivars grown in Uzbekistan were severely
damaged by yellow rust. This may indicate that the races of yellow rust have
changed in Uzbekistan. Only one new variety of bread wheat, cv. Ravi,
cultivated in a farmer's 3-ha field, was not damaged. This variety came from
CIMMYT germplasm in 2001. The monitoring of yellow rust throughout
Uzbekistan during the 2009 season showed that almost all commercial
cultivars of bread wheat were damaged by yellow rust, with severity ranging
from 50 to 100%. In some situations, fungicides were applied in the beginning
of flowering stage, sometimes twice, but the disease re-appeared in many place
This year, yellow rust has damaged soft wheat not only in irrigated fields but
also in rainfed areas. In the screening conducted in 2009, we found that 24 new
wheat cultivars were severely infected (40S–90S), 8 were moderately
susceptible (5–10MS) and 18 were moderately resistant (5–15MR) to yellow
rust. The screening of 3rd IYRTN-09 has shown that cultivars with
(Yr31+APR), (W; Yr1) or (S; Yr6+1) genes and Avocet single-gene lines with
YrA, Yr1, Yr6, Yr9, Yr18, Yr28, Yr31 and YrCV were ineffective against yellow
rust. Avocet single-gene lines with Yr5, Yr8, Yr10, Yr15, Yr17, Yr27 and YrSP
were effective against the disease. These lines were scored from 5 to 30MR.