Bonkoungou Tégawendé Odette, Badu-Apraku Baffour, Adetimirin Victor Olawale, Nanema Kiswendsida Romaric, Adejumobi Idris Ishola
Pan African University Life and Earth Sciences Institute (including Health and Agriculture), University of Ibadan, Ibadan, Oyo State, Nigeria.
International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria.
Front Plant Sci. 2024 Nov 29;15:1463924. doi: 10.3389/fpls.2024.1463924. eCollection 2024.
Orange maize genotypes are sources of provitamin A (PVA) carotenoids, which are precursors of vitamin A. PVA deficiency and drought constitute major challenges causing increasing food and nutritional insecurity in sub-Saharan Africa (SSA). Breeding of drought-tolerant provitamin A hybrid maize can mitigate these challenges. This study was undertaken to determine the combining ability of newly developed extra-early orange inbreds for grain yield and related traits under managed drought stress and rain-fed conditions, determine the mode of gene action conditioning the inheritance of the traits, and classify the inbreds into heterotic groups.
One hundred and ninety-six extra-early orange hybrids comprising 180 testcrosses, 10 single crosses, and 6 commercial checks were evaluated under managed drought and rain-fed conditions at Ikenne. In addition, 41 inbreds comprising 36 orange lines and 5 PVA testers involved in the hybrid development were assessed under drought and rain-fed conditions.
The means square for general combining ability (GCA) and specific combining ability (SCA) were significant for grain yield and most other traits under both growing conditions. The contributions of GCA to performance were larger than SCA in each growing condition. Broad-sense and narrow-sense heritability estimates for grain yield were 66% and 37% under managed drought and 88% and 32% under rain-fed conditions, respectively. Mid-parent heterosis and better-parent heterosis for grain yield were 338% and 247% under managed drought, while 173% and 137% under rain-fed conditions. Significant positive correlations existed among grain yield of hybrids, heterosis, and specific combining ability under managed drought. The 41 inbred lines were classified into three heterotic groups under both growing conditions. Sixteen testcross hybrids out-yielded the best commercial check under managed drought.
The testcross hybrids have great potential for commercialization to address the problem of drought and PVA deficiency in SSA. Inbred TZEEIOR 510 showed desirable GCA effects for grain yield and 04 other traits under drought.
橙色玉米基因型是维生素A原（PVA）类胡萝卜素的来源，而PVA是维生素A的前体。PVA缺乏和干旱是撒哈拉以南非洲（SSA）地区造成粮食和营养不安全状况加剧的主要挑战。培育耐旱的维生素A原杂交玉米可以缓解这些挑战。本研究旨在确定新培育的特早熟橙色自交系在可控干旱胁迫和雨养条件下对籽粒产量及相关性状的配合力，确定控制这些性状遗传的基因作用模式，并将自交系划分为杂种优势群。
在伊凯内对196个特早熟橙色杂交种进行了评估，其中包括180个测交种、10个单交种和6个商业对照品种，试验设置了可控干旱和雨养两种条件。此外，对参与杂交种培育的41个自交系（包括36个橙色系和5个PVA测验种）在干旱和雨养条件下进行了评估。
在两种生长条件下，籽粒产量和大多数其他性状的一般配合力（GCA）和特殊配合力（SCA）的均方均显著。在每种生长条件下，GCA对表现的贡献都大于SCA。在可控干旱条件下，籽粒产量的广义遗传力和狭义遗传力估计值分别为66%和37%，在雨养条件下分别为88%和32%。在可控干旱条件下，籽粒产量的中亲杂种优势和高亲杂种优势分别为338%和247%，在雨养条件下分别为173%和137%。在可控干旱条件下，杂交种的籽粒产量、杂种优势和特殊配合力之间存在显著的正相关。在两种生长条件下，41个自交系被划分为三个杂种优势群。在可控干旱条件下，16个测交杂交种的产量超过了最好得商业对照品种。
测交杂交种具有很大的商业化潜力，可解决SSA地区的干旱和PVA缺乏问题。自交系TZEEIOR 510在干旱条件下对籽粒产量和其他4个性状表现出理想的GCA效应。
