Genotype ✕ Environment Interactions in the Regional Testing of Soybean Strains1

Estimates of genotype ✕ environment interactions were obtained from seven regional Uniform Soybean Tests grown in 1954‐56. All of the second order and nearly all of the first order interactions were significantly different from zero at the .05 level of probability. Estimates of the genotype ✕ year interactions were generally smaller than estimates of the genotype ✕ location interactions but in practice will have a greater effect on the error variance of a line mean, since testing over a long period of time is seldom done. Evidence was cited to suggest that locations may be effectively substituted for years in regional tests to permit a rapid turnover of breeding material and that data from 10 to 15 locations in a single year should be sufficient to eliminate low‐yielding strains.