EARLY MATURITY SOYBEAN PRODUCTION SYSTEM - GENOTYPE-X ENVIRONMENT INTERACTION BETWEEN REGIONS OF ADAPTATION

An early soybean [Glycine max CL) Merr.] production system involves gr owing soybean cultivars of a maturity group earlier than those that ut ilize the full growing season, It is proposed as a hedge against droug ht stress that has contributed to a large reduction in the soybean pro duction area in the southern USA during the last decade. The objective of this study was to compare the magnitude of genotype x environment interactions within and between regions of full season and less than f ull season adaptation, Thirty-two Maturity Group I genotypes were eval uated in four environments in both Kentucky (KY) and Minnesota (MN). F or yield, within state genotype x environment interactions were signif icant in both states whereas the genotype x state interaction was not significant. Within and between state interactions were all significan t for seed protein and oil concentrations. In all eases, the percentag e of possible genotype x environment crossover interactions that were significant was <10%, The yield response in KY to correlated selection in MN was predicted to be 0.94 as efficient as direct selection in KY , and the response to simulated selection at 25% selection intensity w as equal for MN and KY selection. In light of this similar genotype pe rformance between states, we recommend not initiating new breeding pro grams for genotypes specifically adapted to an early soybean productio n system,