Abstract
AbstractMaize (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.
Highlights
Maize (Zea mays L.) is of great importance in sub-Saharan Africa (SSA)
The predominance of the general combining ability (GCA) effects over the specific combining ability (SCA) effects for grain yield (GYLD) and northern corn leaf blight (NCLB) disease severity scores across the test environments implied the predominance of additive gene action in the inheritance of GYLD and resistance to NCLB in whiteand yellow-endosperm extra-early maize (EEM) maize hybrids
TZEEI 13 and TZEEI 51 were identified as inbred testers, whereas TZEEI 51 × TZEEI 8 was identified as a single-cross tester for the white kernel EEM hybrids
Summary
Maize (Zea mays L.) is of great importance in sub-Saharan Africa (SSA) It plays an important role as a staple food crop in combating food insecurity and malnutrition problems confronting the subregion (Badu-Apraku et al, 2015). Northern corn leaf blight causes grain yield (GYLD) losses ranging from 50% when infection occurs at the grain-filling stage (Human et al, 2016), to 100% when infected at the seedling stage (Hooda et al, 2017). These losses have serious economic implications for farmers in SSA
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