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 (no rthern), temperate (central), and managed environments of Argentina, to ide ntify patterns of genotype-by-environment interaction and opportunities for indirect selection. Pattern analyses showed that the average genotypic dis crimination effects of the central and northern regions for oil yield are s trongly orthogonal. Photoperiod and minimum temperature would be partially underlying the observed interactions. These patterns are repeatable over se asons, which suggests that central and northern regions are different mega- environments and that,,election for specific adaptation to each region woul d 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 g enotypes 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 repres ents an opportunity for indirect selection for the northern region from the breeding program headquarters in central Argentina. When photoperiod was e xtended to 15.5 h in these trials, genotypes exhibited responses similar to those of normal planting dates in central environments, indicating that ph otoperiod could be a central factor underlying this association. Analysis o f specific genotype responses to photoperiod in terms of oil yield showed t hat these involved traits or processes distinct from time to flowering. Pat tern analyses of physiological determinants and components of yield reveale d the existence of different specific genotype responses to specific enviro nmental challenges within the same genotype group. (C) 2001 Elsevier Scienc e BN. All rights reserved.