In maize breeding programs, temperate germplasm can be used to introgress genes from temperate inbred lines into elite tropical maize inbred lines to improve grain yield and its components across environments. This study's objective was to determine the genetic gains for grain yield and its components achieved by the introgression of temperate maize germplasm in tropical elite maize inbred lines for adaptability to South African environments. One hundred and twenty-two Introgressed inbred lines developed using the pedigree breeding method were crossed to four tropical elite inbred line testers using a line x tester mating design to obtain 488 experimental single cross hybrids. Subject to availability of adequate seed for evaluation, a panel of 444 experimental single-cross hybrids were evaluated using an augmented design in two experiments defined as populations A and B at three sites in South African environments. Grain yield and ear prolificacy had positive realized genetic gains of up to 58 and 26%, respectively, relative to the panel mean and commercial check hybrids. Secondary traits, such as anthesis and silking days, had gains ranging from 1 to 37%. Negligible gains were attained for stalk and root lodging and grain moisture content at harvest. Despite the need for further improvement, introgressed inbred lines performance inter se indicated significant grain yield potential improvements following one breeding cycle. The following experimental single-cross hybrids 12C22785, 12C20628, 11C1774, 12C20264, 12C20595, 11C1645 13XH349 outperformed the best commercial check hybrid PAN6Q445B, a leading hybrid on the South African market for grain yield performance potential. These seven selected single-cross hybrids also combined high grain yield potential performance with good ear prolificacy, in particular, experimental single-cross hybrids 12C20628, 11C1774 and 12C202595. Two experimental single-cross hybrids 12C2064 and 13XH349, combined high grain yield performance potential with low grain moisture content at harvest and improved standing ability relative to commercial check hybrids. Parents of these selected experimental single-cross hybrids will be advanced in the breeding program and will be the basis of future breeding for adaptation to South African environments. However, the general trend showed that many of the selected experimental single-cross hybrids did perform poorly for standability data depicted by plant aspects such as plant and ear height, stalk, and root lodging. Therefore, there is a need to improve these plants further to enhance the adaptability of tropical germplasm in South African environments. In conclusion, the introgression strategy effectively enhanced tropical elite inbred lines for the desired economic traits, to the extent that several of their combinations resulted in superior hybrids that are highly desired for South African markets.

中文翻译：

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从温带供体自交系渗入热带优良玉米自交系对谷物产量和成分的遗传增益评估：II. 表演之间

在玉米育种计划中，温带种质可用于将基因从温带自交系导入优良热带玉米自交系，以提高粮食产量及其跨环境的组成部分。本研究的目的是确定通过将温带玉米种质渗入热带优良玉米自交系以适应南非环境而实现的谷物产量及其组成部分的遗传增益。使用系谱育种方法开发的 122 个渐渗自交系与 4 个热带精英自交系测试者使用系 x 测试者交配设计杂交，获得 488 个实验单杂交杂种。在有足够的种子可供评估的情况下，在南非环境中的三个地点定义为种群 A 和 B 的两个实验中，使用增强设计对一组 444 个实验性单杂交杂种进行了评估。相对于面板平均和商业检查杂种，谷物产量和穗多产分别实现了高达 58% 和 26% 的正实现遗传增益。次要性状，如开花期和落丝日，增加了 1% 到 37%。收获时的茎和根倒伏以及谷物水分含量的收益可以忽略不计。尽管需要进一步改进，但渗入自交系的性能本身表明在一个育种周期后谷物产量潜力显着提高。以下实验性单交杂种 12C22785、12C20628、11C1774、12C20264、12C20595、11C1645 13XH349 在谷物产量性能潜力方面的表现优于南非市场上领先的杂交品种 PAN6Q445B。这七个选择的单交杂种还结合了高籽粒产量潜力性能和良好的穗多产性，特别是实验单交杂种 12C20628、11C1774 和 12C202595。两个实验性单交杂种 12C2064 和 13XH349，结合了高谷物产量性能潜力和收获时低谷物水分含量以及相对于商业对照杂种改善的站立能力。这些选定的实验性单交杂种的亲本将在育种计划中取得进展，并将成为未来适应南非环境的育种基础。然而，总体趋势表明，许多选定的实验性单交杂种在植物方面表现不佳，如植物和穗高、茎和根倒伏。因此，需要进一步改良这些植物，以增强热带种质在南非环境中的适应性。总之，基因渗入策略有效地增强了热带精英自交系的所需经济性状，以至于它们的几种组合产生了南非市场非常需要的优良杂种。需要进一步改进这些植物，以增强热带种质在南非环境中的适应性。总之，基因渗入策略有效地增强了热带精英自交系的所需经济性状，以至于它们的几种组合产生了南非市场非常需要的优良杂种。需要进一步改进这些植物，以增强热带种质在南非环境中的适应性。总之，基因渗入策略有效地增强了热带精英自交系的所需经济性状，以至于它们的几种组合产生了南非市场非常需要的优良杂种。