Genetic gain in early stages of a soybean breeding program

Multistage testing of genotypes is an essential feature in plant breeding p rograms. Little research is available to help breeders test efficiently. Ou r objective was to determine the genetic gain obtained in selected stages o f a soybean [Glycine max (L,) Merr.] breeding program and to determine ways to increase the overall gain, if possible. The mean selection differential and genetic gain and their regression coefficient were determined fur test s at the F-3, F-4, and F-6 generations of the Ohio State University-Ohio Ag ricultural Research and Development Center breeding program during 1985 to 1997, Genetic gain for yield averaged -1.4% in the F-3 stage, 3.7% in the F -4, and 9.1% in the F-6 stage, where percentages are based on the mean of t he common check genotypes. Overall changes in maturity were small at each s tage. improvements in lodging resistance occurred in the F-4 and F-6. Negat ive yield gains in the F-3 were attributed to use of unreplicated plots and to the necessary selection pressure for early maturity. Examination of the selection differentials for individual lines indicated that selection coul d be intensified in the F-4 and F-6 generations with little risk of discard ing potentially superior cultivars. The conclusion that near equality of th e selection intensity across stages would be beneficial for this breeding p rogram confirms the theoretical recommendations reported in earlier researc h.