Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

New approaches in traditional
resistance breeding
313
Kh.S. Turakulov and S.K. Baboev
Institute of Genetics and Plant Experimental Biology AS Ruz, Uzbek Academy of
Sciences, Kibray, Tashkent, Uzbekistan
Abstract
The development of cultivars of wheat with resistance to destructive
pathogens that reduce grain yield and quality constitute major wheat breeding
objectives. To incorporate resistance in wheat varieties from different sources,
crossing is still the principal procedure for breeding new varieties, utilizing
genetic recombination and bringing together multigenic combinations. In this
respect, an experiment was conducted to study the inheritance of yellow rust
on bread wheat. We screened released and prospective varieties and selected
lines of bread wheat from local, CIMMYT and ICARDA germplasm sources for
yellow rust and leaf rust resistance. Among screened material, crosses were
made between four groups. In the first group, the crosses were made among
resistant lines and cultivars (resistant × resistant). In the second group, crosses
were made between susceptible cultivars and lines (susceptible × susceptible).
In the third group, crosses were conducted among resistant and susceptible
material in a reciprocal manner (resistant × susceptible; susceptible × resistant).
Finally, in the fourth group, we crossed moderately resistant and moderately
susceptible cultivars and lines. Except in group one, the crosses were
conducted among parents with different distinct morphological traits and
disease reactions in order to identify eventual morphological markers for
resistance. Plant colour analysis of progeny showed that resistance was more
frequent in progenies which tend to have a greyer green colour rather than
greener. There was no difference in disease reaction in plants having spikes
with awns or without. Early heading was associated more with resistance than
susceptibility. In late heading progenies, both resistance and susceptibility
occurred equally. Progenies with tall plants were more resistant but lodged
more easily. Almost in all groups, we obtained progenies with R, MR, MS and
S types of reaction. In progenies of crosses involving moderately resistant and
moderately susceptible parents, we obtained a range of reactions, including
resistant, moderately resistant, moderately susceptible and susceptible plants.
In some crosses, such as Superwheat 1659 × Djagir and F19 × Sanzar, we
observed slow rusting in the progenies. These progenies expressed an
increased latent period, decreased infection frequency and a reduced length of
infection lesions (stripes). In the crosses between susceptible and resistant
entries (e.g. Morocco × Ravi), it was found that some progenies were highly