Sixteen Cycles of Recurrent Full-Sib Family Selection for Grain Weight in Two Maize Populations
Full-sib family selection for greater grain weight per plant is expected to increase the frequency of favorable alleles for this trait in random-mating populations of maize (Zea mays L.). This study was undertaken to assess responses to selection and changes in genetic variances accumulated during 16 cycles in (i) the open-pollinated population Jarvis Golden Prolific, and (ii) the population descended from the F2 generation of the single cross NC7 ✕ CI21. Selection responses were measured in replicated experiments that included Cycle 0 and several advanced selection cycles, and by estimates of accumulated gains through all 16 cycles of the selection experiments per se. In addition to increases in mean grain weight, changes in responsiveness to environmental effects were evaluated by regression analysis. The selection experiments were designed to provide estimates of genetic variances from progeny test data of each selection cycle. Gains due to selection were linear for 16 cycles at a rate of 2.4% cycle−1 for the Jarvis population and 4.5% cycle−1 for the NC7 ✕ CI21 population. Advanced selection cycles were more responsive to environments than the original populations. Additive genetic variance showed no trend associated with selection in the Jarvis population, but declined with selection in the NC7 ✕ CI21 population. Accumulated gains were greater in the NC7 ✕ CI21 population, even though the genetic variance in that population was smaller initially and has decreased in later selection cycles.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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