PREDICTING GRAIN-YIELD IN AUSTRALIAN ENVIRONMENTS USING DATA FROM CIMMYT INTERNATIONAL WHEAT PERFORMANCE TRIALS .2. THE APPLICATION OF CLASSIFICATION TO IDENTIFY ENVIRONMENTAL RELATIONSHIPS WHICH EXPLOIT CORRELATED RESPONSE TO SELECTION

The principles of indirect selection can be used to assess the impact of genotype by environment interaction on selection strategies within breeding programs. The methodology can also be used to assess the opportunity for more efficient acquisition of new germplasm for a breeding program where common genotypes are evaluated in environments sampled by two breeding programs. However, the large number of environmental comparisons that is required complicates this process. To assist environmental comparison, the theory for indirect selection is related to classification methodology for grouping of environments in plant breeding experiments. To demonstrate the application of this methodology, classification was used to jointly group 18 international wheat evaluation environments conducted by the International Centre for Wheat and Maize Improvement (CIMMYT) as part of the 17th International Bread Wheat Screening Nursery (17th IBWSN) and six environments from a trial series conducted in Queensland, Australia using a set of 40 common genotypes. This process was used to identify a subset of international environments which improved indirect response for average grain yield performance in the Australian environments over that for selection on average grain yield performance over all 18 international environments. Similarly, classification was used to identify subsets of international environments which improved indirect response to selection in five of the six Australian environments. More efficient strategies for acquiring useful wheat germplasm for Australian wheat breeding programs from the CIMMYT program by extending this methodology are discussed.