Maize (Zea mays L.) is a food security crop in sub-Saharan Africa (SSA). Incidence of northern corn leaf blight (NCLB), caused by Exserohilum turcicum, in lowlands of SSA during the past decade has caused 30–70% reduction in maize yield. This study (a) examined the combining abilities of extra-early maize (EEM) inbreds and classified them into heterotic groups; (b) elucidated gene action controlling resistance to NCLB; (c) assessed grain yield (GYLD) and yield stability of EEM hybrids under NCLB infection; and (d) identified testers. One hundred and fifty EEM hybrids, obtained by crossing 15 inbreds each of white- and yellow-endosperm maize using the North Carolina Design II, plus six checks, were evaluated in nine environments, six of which were inoculated with an isolate of E. turcicum and three of which were non-inoculated in 2018 and 2019. The white and yellow inbreds were placed in three heterotic groups using the heterotic grouping based on general combining ability (GCA) of multiple traits and stability of GYLD using the genotype plus genotype × environment (GGE) biplot analysis. The GCA, specific combining ability (SCA) and genotype × environment (G×E) interactions were significant for GYLD, disease severity, and other measured traits. The GCA effects were more important than the SCA effects for GYLD and NCLB severity scores across environments, implying that recurrent selection could facilitate improvement for GYLD and NCLB resistance. Three inbred testers and four single-cross testers were identified for developing high-yielding NCLB-resistant hybrids. Four white and five yellow single-cross hybrids were identified for on-farm testing and possible commercialization.

中文翻译：

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超早熟玉米自交系对北方玉米叶枯病的产量及抗性遗传分析

玉米（Zea mays L.）是撒哈拉以南非洲（SSA）的粮食安全作物。在过去十年中，由Exserohilum turcicum引起的北方玉米叶枯病 (NCLB)在 SSA 低地的发病率已导致玉米产量减少 30-70%。本研究 (a) 检查了超早熟玉米 (EEM) 近交系的配合能力，并将它们分为杂种优势组；(b) 阐明了控制 NCLB 抗性的基因作用；(c) 评估 NCLB 感染下 EEM 杂种的谷物产量 (GYLD) 和产量稳定性；(d) 确定测试人员。在九个环境中评估了 150 个 EEM 杂种，这些杂种是通过使用北卡罗来纳州设计 II 杂交 15 个自交系的白色和黄色胚乳玉米，加上六次检查获得的，其中六个接种了分离株E. turcicum其中三个在 2018 年和 2019 年未接种。 使用基于多性状一般配合力 (GCA) 和 GYLD 稳定性的杂种优势分组将白色和黄色自交置于三个杂种优势组中，使用基因型加基因型×环境(GGE) 双标分析。GCA、特异性结合能力 (SCA) 和基因型 × 环境 (G×E) 相互作用对 GYLD、疾病严重程度和其他测量性状具有显着意义。对于跨环境的 GYLD 和 NCLB 严重性评分，GCA 效应比 SCA 效应更重要，这意味着重复选择可以促进 GYLD 和 NCLB 抗性的改善。确定了三名自交测试员和四名单交测试员用于开发高产 NCLB 抗性杂种。