AN INVESTIGATION OF THE GRAIN-YIELD ADAPTATION OF ADVANCED CIMMYT WHEAT LINES TO WATER-STRESS ENVIRONMENTS IN QUEENSLAND .2. CLASSIFICATIONANALYSIS

The objective of this study was to use classification methodology to c haracterize the genotypic variation and line by environment (L x E) in teraction for grain yield of a sample of advanced CIMMYT wheat lines a nd three local check cultivars tested over six Queensland environments . The environments were managed to differ in the magnitude of water st ress they imposed on the lines at the critical developmental stage of anthesis. The grouping of lines was based on grain yield. The yield di fferences among the groups were investigated in terms of yield compone nts and dry matter production and partitioning attributes. Groups of C IMMYT lines which outyielded the two groups which contained the three Queensland cultivars were identified. The yield advantage of the group s of CIMMYT lines decreased with increasing severity of water stress a t anthesis and in the environment where the most severe stress was cha racterized there were no yield differences among the groups of lines. The yield advantage of the groups of CIMMYT lines was generally associ ated with a higher number of grains per unit area and in some cases a higher grain size. While phenology variation could account for some of the yield differences among the line groups there was considerable yi eld variation among line groups with similar phenology patterns across the environments. Additional measurements taken on the lines to chara cterize differences in dry matter production and the partitioning of t he dry matter to yield components were not effective in explaining the yield variation among the groups of lines after the effects of phenol ogy were taken into account. While the incidence of the large L x (wat er-stress) interactions encountered in this study would complicate sel ection for yield, the identification of groups of advanced CIMMYT line s which outyielded the Queensland cultivars in five of the six environ ments suggests that the L x (water stress) interactions do not preclud e scope for further improvement of grain yield of wheat in Queensland.