Maturity Effects on Genotype × Environment Interactions in Grain Sorghum

Genotype × environment (GE) interaction is an important consideration in plant breeding because of its effects on progress from selection. This study examines the effects of genotype maturity on GE interaction for grain yield and yield components. Fifty-four grain sorghum [Sorghum bicolor (L.) Moench] genotypes included in three maturity groups, early, medium, and late, were evaluated in 48 environments across Nebraska and Kansas in 1978 and 1979. The soil ranged from sandy types (mixed, mesic Typic Ustipsamment) to intermediate types as represented by Typic Haplustoll, course-silty, mesic and fine-silty, mixed, mesic, Aridic Argiustoll, to clay loam at the opposite extreme (deep with high water holding capacity) as represented by fine, montmorillonitic mesic, Typic Argiuboll. In the analysis of variance combined over years and environments within year, genotype, genotype × year, and genotype × environment within year sums of squares were partitioned into components representing within and among maturity groups. More than half of the interaction effects sums of squares was attributed to differences among maturity groups. The GE interaction increased with an increase in duration of plant growth (maturity). Genotypes showed larger interaction with environments within year than with years, irrespective of maturity. The results suggest that a reliable evaluation of relative genotype performance can be made if the genotypes under test do not include a wide range of maturity. Minimizing differences in maturity among genotypes reduces GE interaction. Testing at more locations or environments at given locations should be done rather than testing in more years. For a desired level of precision, the amount of testing required for a set of genotypes with a wide range of maturity and long-growth duration is greater than that required for genotypes with a narrow range of maturity and short-growth duration. Increasing number of replications per test more than two, environments in a year more than eight, and years of testing more than two, was not effective in increasing efficiency in genotype evaluation, especially in early and medium maturing genotypes.