Genetic analysis of grain yield and resistance of extra‐early‐maturing maize inbreds to northern corn leaf blight

Abstract

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.

A large‐scale survey reveals agro‐ecological factors influence spatio‐temporal distribution and epidemics of maize leaf blight: Implications for prioritizing sustainable management options

“…Similarly, the NLB is favoured by mild temperatures (15–25°C), high relative humidity (90%–100%), extended periods of leaf wetness, and frequent light showers as noticed by Ogliari et al (2007). It had also been reported that the distribution and development of NLB is favoured by long dew periods, and cool to moderate temperatures with high relative humidity across maize‐growing areas of the world (Ahangar et al, 2022; Badu‐Apraku et al, 2021). Hence, extreme impact of leaf blight on maize in the mid‐ and high‐land agro‐ecologies of Uganda, Kenya, Ethiopia, Zambia and South Africa have been reported (Ramathani et al, 2011).…”

“…Such environmental conditions may support sporulation and conidia germination, infection, establishment and development of NLB in maize. Other studies also reported that epidemic of NLB is influenced by weather variables, among other factors (Ahangar et al, 2022;Badu-Apraku et al, 2021;Camera et al, 2019;Wathaneeyawech et al, 2015).…”

“…In highly affected areas, maize grain yield losses of 15%-100% have been reported (De Rossi et al, 2022). The disease has caused 30%-70% reduction in maize yield in lowlands of sub-Saharan Africa during the past decade (Badu-Apraku et al, 2021).…”

“…In highly affected areas, maize grain yield losses of 15%–100% have been reported (De Rossi et al, 2022). The disease has caused 30%–70% reduction in maize yield in lowlands of sub‐Saharan Africa during the past decade (Badu‐Apraku et al, 2021). Similarly, grain yield loss of 40.7%–49.10% has been recorded on susceptible cultivars in Ethiopia (Debela et al, 2017).…”

Variation in the morphology and effector profiles of Exserohilum turcicum isolates associated with the Northern Corn Leaf Blight of maize in Nigeria

“…The photosynthetic potential of maize is significantly reduced by E. turcicum infection and this invariably affects grain yield [ 22 ]. The premature death of infected plants has been reported when the disease epidemic begins at an early stage [ 11 , 23 ]. This is consequent upon the alteration of the physiological activities of the infected host [ 24 ].…”