Northern corn leaf blight (NCLB) incited by the fungus Exserohilum turcicum is a foliar disease that significantly limits maize production and productivity in West and Central Africa (WCA), particularly in the mid-altitudes but during the last decade it has become a menace in lowland agro-ecologies. The most economical and environmentally friendly disease management strategy is the cultivation of maize varieties resistant or tolerant to NCLB. However, no early maturing (EM) and extra-early maturing (EEM) NCLB resistant varieties are commercially available in WCA. One hundred inbred lines each of EM and EEM derived from tropical maize germplasm were inoculated with a virulent isolate of E. turcicum at five locations in Nigeria during the 2017 and 2018 growing seasons. The objective of the study was to identify promising NCLB resistant lines and to investigate inter-relationships among the traits. Analysis of variance revealed highly significant genotype and genotype by environment (G × E) interactions for disease severity, grain yield (GYLD), and other agronomic traits. The average disease severity (TURC) values ranged from 1.9 to 5.8 and 2.9 to 5.7 for the EM and EEM inbred lines, respectively. The levels of reaction of the inbred lines to NCLB ranged from highly resistant to highly susceptible. Stepwise regression analysis showed that ears per plant, ear and plant aspects were significantly influenced by the disease scores. Ears per plant, ear and plant aspects, TURC and GYLD traits were employed to develop a base index (BI) for selecting NCLB resistant inbred lines for hybrid development. TZEI 135 and TZEEI 1 were outstanding in GYLD and also had the highest positive BI values in the EM and EEM inbred lines, respectively. The identification of NCLB resistant lines in this study has set the premise for development of NCLB resistant hybrids for WCA as well as the improvement of tropical maize breeding populations for NCLB resistance.

中文翻译：

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鉴定撒哈拉以南非洲早熟和超早熟热带玉米自交系对 Exserohilum turcicum 具有抗性

由真菌 Exserohilum turcicum 引起的北方玉米叶枯病 (NCLB) 是一种叶面病害，严重限制了西非和中非 (WCA) 的玉米产量和生产力，尤其是在中海拔地区，但在过去十年中，它已成为威胁低地农业生态。最经济和环境友好的病害管理策略是培育对 NCLB 具有抗性或耐受性的玉米品种。然而，WCA 中没有早熟 (EM) 和超早熟 (EEM) NCLB 抗性品种在商业上可用。在 2017 年和 2018 年的生长季节期间，在尼日利亚的五个地点，分别对来自热带玉米种质的 EM 和 EEM 各 100 个自交系接种了 E. turcicum 的毒性分离株。该研究的目的是确定有前景的 NCLB 抗性品系，并调查这些性状之间的相互关系。方差分析显示，对于疾病严重程度、谷物产量 (GYLD) 和其他农艺性状，基因型和环境基因型 (G × E) 相互作用非常显着。EM 和 EEM 自交系的平均疾病严重程度 (TURC) 值分别介于 1.9 至 5.8 和 2.9 至 5.7 之间。自交系对 NCLB 的反应水平从高度抗性到高度敏感。逐步回归分析表明，单株穗数、穗数和植株方面受病害评分显着影响。每株穗数、穗数和植株方面、TURC 和 GYLD 性状被用来制定基础指数 (BI)，用于选择 NCLB 抗性自交系进行杂交开发。TZEI 135 和 TZEEI 1 在 GYLD 中表现出色，并且分别在 EM 和 EEM 自交系中具有最高的正 BI 值。本研究中NCLB抗性品系的鉴定为开发用于WCA的NCLB抗性杂种以及改进NCLB抗性热带玉米育种群体奠定了前提。