Selection indexes in the simultaneous increment of yield components in topcross hybrids of green maize

Abstract: The objective of this work was to define the most suitable selective strategy for the simultaneous increment of yield components of green maize, by comparing three selection indexes weighted by economic weights and by the REML/BLUP method, in the assessment of predicted genetic gains for traits of interest. An experiment with 75 topcross hybrids from partially inbred S1 lines of green maize was carried out in Jataí, in the state of Goiás, Brazil, using a randomized complete block design, with four replicates. The following yield traits were evaluated: straw ears and commercial ears, grain mass, ear length, ear diameter, and number of ear rows. The selection indexes of Smith and Hazel, Williams, and Mulamba & Mock were applied and weighted for four economic weights (1, CVg, CVg/CVe, and h2). Among the tested selection indexes, those of Williams and Mulamba & Mock are the best-fit ones for the selection of topcross hybrids of green maize, as they provide positive and more balanced selection gains for all evaluated traits. The REML/BLUP method shows better predicted genetic gains than those achieved by the three selection indexes, besides being efficient for the selection of topcross hybrids of green maize.

摘要：本研究旨在确立最适配的选择策略，以同步提升青饲玉米（green maize）的产量构成性状，通过比较三类基于经济权重加权的选择指数，并结合限制极大似然估计/最佳线性无偏预测（REML/BLUP）法，对目标性状的预测遗传增益开展评估。试验以巴西戈亚斯州雅塔伊市的75份青饲玉米半自交S1系衍生的顶交杂种（topcross hybrids）为供试材料，采用随机完全区组设计，设置4次重复。本试验测定的产量相关性状包括：秸秆穗产量与商品穗产量、籽粒质量、穗长、穗粗以及穗行数。本研究应用了史密斯-黑泽尔（Smith and Hazel）、威廉姆斯（Williams）以及穆兰巴与莫克（Mulamba & Mock）三种选择指数，并设置4种经济权重（1、遗传变异系数CVg、CVg与环境变异系数CVe之比、狭义遗传力h²）进行加权分析。在所测试的三类选择指数中，威廉姆斯指数与穆兰巴与莫克指数为青饲玉米顶交杂种选育的最优适配指数，可对所有测定性状带来正向且更为均衡的选择增益。相较于三类选择指数所得结果，REML/BLUP法可获得更优的预测遗传增益，且在青饲玉米顶交杂种的选育中同样具备高效性。