Evaluation of 4 cycles of S1 recurrent selection in BSP1 and BSP2 popcorn populations
The improvement of germplasm and breeding populations is an important objective of maize breeding programs. S1 recurrent selection has been shown to be an effective means of intrapopulation improvement for many different crops and has been practiced extensively in maize. The objective of this study was to evaluate the direct and indirect response of 4 cycles of S1 recurrent selection in BSP1 and BSP2 popcorn breeding populations. The populations per se, interpopulation crosses, and both populations crossed to a tester from a different heterotic group were evaluated across seven environments throughout the U.S. Midwest. Regression estimates revealed that popping expansion increased 0.64 cc g−1 (or 1.63%) cycle−1 for the BSP1 population, 0.61 cc g−1 (or 1.52%) cycle−1 for the BSP2 population, 0.65 cc g−1 (or 1.64%) cycle−1 for the population cross, BSP1 x BSP2, and 0.63 cc g−1 (or 1.60%) cycle−1 for the reciprocal population cross, BSP2 x BSP1. Improvement for popping expansion in the populations crossed to the C0 and tester was about a third of what was observed in the populations per se, revealing an increase in the number of favorable alleles for popping expansion. Selection was effective in reducing root and stalk lodging. A European corn borer evaluation revealed an initial high level of resistance to leaf feeding and stalk tunneling within both populations with no significant differences across cycles or among crosses. Improvements in other agronomic traits were in also in the desired direction. These findings indicate that selection for increased popping expansion and improvement in other popcorn quality and agronomic traits can be done concurrently. The analysis of variance revealed that reciprocal effects (REC) played a role in the popping expansion trait but were not-significant for the other traits. This implies that testing reciprocal crosses for expansion could be useful if the objective of the testing is to identify the hybrid with the best popping expansion. The analysis of variance for GCA, SCA, and genetic effects revealed that additive-associated distances played a major role in traits affecting popping expansion and agronomics.