Response to Recurrent Selection for Yield in Soybeans 1

Abstract

The objectives of our research were to evaluate response to recurrent selection for seed yield in a soybean [Glycine max (L.) Merrill] population and to assess the effect of selection on other agronomic characters. Forty high-yielding lines and cultivars of Maturity Groups 0 to IV were intermated three generations without selection to form the population AP6. The parents of the cycle 1 population were identified by testing 300 F3-derived lines of the cycle 0 population, subdividing the 300 lines into three sets of 100 by maturity, and selecting the 10 early, midseason, and late lines with the highest yields. The 30 parents were recombined in a diallel without reciprocals, and 300 F4-derived lines of the cycle 1 population were tested for yield. The 300 lines were subdivided into three sets of 100 by maturity, and the 10 lines with the highest yields from the three maturity classes were chosen as the parents of cycle 2. The 10 parents of each maturity were mated in separate diallels, 100 F4-derived lines for each maturity were tested for yield, and the 10 lines with the highest yields of each maturity were chosen as parents of cycle 3. Each cycle of selection required 2 years. Response to selection was evaluated by testing the individual parents of cycles 0 to 3 and a composite of the parents of cycles 1 to 3 as three maturity sets in six Iowa environments during 1979 and 1980. The response to selection for yield was similar when evaluated as the mean performance of individual parents or as a composite of the parents. There was a significant linear increase in yield of 120 ± 10 kg/ha per cycle for the mean of early parents and 24 ±9 kg/ha per cycle for the late, but no significant change in yield for the mean of midseason (- 14± kg/ha) parents. Yield of the best parent in cycle 3 was not significantly better than the yield of the best parent of cycle 0 for any maturity set. There was no consistent change in maturity, lodging, height, seed weight and protein and oil percentage caused by the selection for yield.