UQ eSpace

Abstract

Semidwarf wheat germplasm from The International Centre for Maize and Wheat Improvement (CIMMYT) program has contributed significantly to the genetic improvement of wheat cultivars in Australia. This has resulted from both direct introduction of CIMMYT lines with subsequent release as cultivars and more commonly through introgression of desirable characteristics from the CIMMYT germplasm into the background of current Australian cultivars. Consequently wheat breeders in Australia are interested in the potential for further genetic improvement of grain yield from this source of material. In response to this, a largely empirical introduction and evaluation system has resulted, with considerable duplication of effort between the wheat breeding programs throughout Australia. The inefficiency of this process is increased by strict quarantine requirements in Australia which result in a two to three year lag between the availability of the germplasm and yield performance data from CIMMYT and initial evaluation of the germplasm by Australian wheat breeders. Therefore, there is a need for a more coordinated and directed introduction and evaluation of the CIMMYT germplasm. This study considered the opportunity for improving the efficiency of evaluation and introduction of CIMMYT germplasm to Australia by assessing whether the principles of indirect selection could be applied to the results of CIMMYT international performance trials to identify genotypes expressing grain yield adaptation to Australian environments. I f there was a positive indirect response to selection for grain yield in Australian environments from selection for grain yield in CIMMYT international environments, Australian wheat breeders could conduct a preliminary screen of the CIMMYT germplasm prior to its introduction to Australia. Forty lines sampled from the 17th International Bread Wheat Screening Nursery (17th IBWSN) were evaluated in a trial series in Australia which comprised of 6 environments conducted in the State of Queensland. The results of the Australian trial series and the 17th IBWSN were used for a simulated selection study where the potential to achieve indirect genetic advance for grain yield in the Australian trials was quantified. Average genotype grain yield over the international environments had a strong positive genetic correlation with that over the 6 Australian environments (rG = 0.813±0.049). Consequently the indirect response for average grain yield over the Australian environments from selection on average yield over the international environments was equivalent to direct response for selection on average grain yield over the Australian environments. However, when specific grain yield adaptation to the individual Australian environments was considered, indirect selection on average grain yield over the international environments was less effective than direct selection for grain yield within the Australian environments. Individual international environments, which improved the indirect response to selection within each of the individual Australian environments, were identified. The opportunity for achieving high indirect response to selection was greater in the higher yielding Australian environments.