Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

314
resistant despite the high susceptibility of one of the parents. This high level of
resistance was maintained until F 5. Usually in traditional resistance breeding,
to get resistance, backcrossing is conducted with the resistant parent. Instead
of this approach, we made backcrosses with susceptible parents. Interesting
results were observed in this case when backcrossing with susceptible parent
Sanzar 8. Thus, backcrossing of the progenies of the crosses Ravi × Sanzar 8
and CIMMYT-UZ × Sanzar 8, with Sanzar 8, has resulted in an increased
number of resistant lines with durable resistance.
Introduction.
Stripe [yellow] rust, caused by Puccinia striiformis Westend. f.sp. tritici (Pst), is
an important disease of wheat (Triticum aestivum L.) throughout the world.
Growing resistant cultivars is the most-effective, economical and
environmentally sound approach of controlling stripe rust (Line and Chen,
1995).
The development of cultivars of wheat with resistance to destructive disease
pathogens that reduce grain yield and quality constitute major wheat breeding
objectives. To gain resistance in wheat varieties from different sources of
resistance, hybridization is the still principal plant breeding procedure of
breeding new varieties used to obtain genetic recombination and to bring
together multigenic combinations for improved performance of the whole
plant.
Hybridological analyses of plant diseases are one of the main divisions of
genetic analyses. Results of genetic analyses of plant diseases give an
opportunity to predict successes of remote and intercrossing hybridizations,
which is very important for efficiency in practical resistance breeding.
The inheritance of yellow rust, one of the most destructive diseases of bread
wheat, was studied using the artificial infectious background of the
experimental field of the Laboratory of Cereal Grains Genetics of Institute
Genetics and Plant Experimental Biology of ASUz.
Materials and methods
The experiment screened samples of bread wheat from local (released,
cultivated and prospective varieties and lines), and germplasm from nurseries
from CIMMYT (ESWYT, HTWYT, SAWYT, YR/LR) and ICARDA (CWA-
RTN), assessing yellow rust and leaf rust resistance. The infection background
was created by mixing pathogen spores with powder at a ratio of 1:300, for
1 m 2 plots at +13–15°C and 80–90% RH. Hybridization was conducted at the
end of April and beginning of May. Hybridization among screened samples
involved four types of recombination: among resistant parent samples