Genotype by environment interaction and indirect selection for yield in sunflower: I. Two-mode pattern analysis of oil and biomass yield across environments in Argentina

A reference set of 10 sunflower hybrids was evaluated in 21 subtropical (northern), temperate (central), and managed environments of Argentina, to identify patterns of genotype-by-environment interaction and opportunities for indirect selection. Pattern analyses showed that the average genotypic discrimination effects of the central and northern regions for oil yield are strongly orthogonal. Photoperiod and minimum temperature would be partially underlying the observed interactions. These patterns are repeatable over seasons, which suggests that central and northern regions are different mega-environments and that selection for specific adaptation to each region would result in a faster genetic progress than selecting for wide adaptation to both regions. Cluster analysis revealed three genotypic groups: northern, central and broadly adapted. All central environments discriminated among genotypes in a similar fashion; discrimination in northern environments was more divergent across years and locations. Late planting dates in a central location associated positively with the northern environments. This represents an opportunity for indirect selection for the northern region from the breeding program headquarters in central Argentina. When photoperiod was extended to 15.5 h in these trials, genotypes exhibited responses similar to those of normal planting dates in central environments, indicating that photoperiod could be a central factor underlying this association. Analysis of specific genotype responses to photoperiod in terms of oil yield showed that these involved traits or processes distinct from time to flowering. Pattern analyses of physiological determinants and components of yield revealed the existence of different specific genotype responses to specific environmental challenges within the same genotype group.