Heterotic Patterns of IITA and CIMMYT Early‐Maturing Yellow Maize Inbreds under Contrasting Environments

Abstract

Drought and low soil nitrogen (low-N) constitute major constraints to maize (Zea mays L.) production in West Africa (WA). Th e International Institute of Tropical Agriculture (IITA) and International Center for Maize and Wheat Improvement (CIMMYT) have developed drought and low-N tolerant inbreds for Africa. Combinations between selected IITA and CIMMYT inbreds could produce outstanding hybrids. Diallel crosses of 12 IITA and fi ve CIMMYT early yellow inbreds plus four checks were evaluated under drought, low-N and optimal conditions at four locations in Nigeria for 2 yr. Th e objectives were to examine the combining ability of the inbreds for grain yield and other traits, classify the lines into heterotic groups, identify best testers under the contrasting environments, assess genotype × environment interactions and evaluate the yield performance and stability of single-cross hybrids. Grouping of the inbred lines was done with heterotic group's specifi c combining ability (SCA) and general combining ability (GCA) (HSGCA), single nucleotide polymorphism based genetic distance (SNP-GD) and GCA eff ects of multiple traits (HGCAMT) methods. Th e GCA mean squares for all traits were greater than SCA mean squares in all environments. Th e inbreds were classifi ed into four heterotic groups each across environments by HSGCA and SNP-GD while HGCAMT method placed them into three groups. HGCAMT was the most effi cient followed by HSGCA and then SNP-GD method. Th e HGCAMT identifi ed inbreds ENT 17, ENT 15, and ENT 8 as best testers for heterotic Groups 1, 2, and 3. Hybrids TZEI 17 × ENT 15, and TZEI 149 × ENT 15 were outstanding across environments.

Inheritance of Striga hermonthica adaptive traits in an early‐maturing white maize inbred line containing resistance genes from Zea diploperennis

“…Generation mean analysis is useful in determining gene effects for polygenic traits (Mather & Jinks, ) by allowing the computation of digenic genetic effects such as additive × additive [ i ], additive × dominance [ j ] and dominance × dominance [ l ] interactions (Singh & Singh, ). The preponderance of additive gene action over dominance gene action for grain yield and Striga traits has been documented in maize (Akaogu et al., ; Badu‐Apraku et al, ,). Partitioning of the genetic effects into its components including additive, dominance gene effects ( d and h ) and the three types of digenic gene actions, that is, additive × additive ( i ), additive × dominance ( j ) and dominance × dominance ( l ) effects will provide invaluable information for planning an efficient gene deployment schemes in Striga resistance enhancement programmes of SSA.…”

Plant Density and Nitrogen Responses of Maize Hybrids in Diverse Agro-ecologies of West and Central Africa

“…and International Maize and Wheat Improvement Centre (CIMMYT) researchers, along with their national programs collaborators are now developing low-N (about 30 kg N) tolerant maize germplasm. Studies by Badu-Apraku et al, showed that, in addition to being low-N tolerant, the resulting germplasm had the value addition of being high yielding at a high level of N, usually 90 kg ha -1 [4,33]. The present study was the first attempt at evaluating such material at N rates higher than 90 kg ha -1 .…”

Potential in a collection of adapted and exotic tropical maize inbred lines as resistance source for stem borers

“…Following combining ability studies involving inbreds from IITA and CIMMYT, some CIMMYT lines were identified to have potentials for improving IITA's early maturing and intermediate maturing germplasms for drought and low nitrogen tolerance (Adebayo et al, 2013;Ifie et al, 2015;Badu Apraku et al, 2016). However, limited studies have been conducted to examine the potentials of adapted and exotic non-borer maize inbred lines for their direct use in hybrid combinations aimed at stem borer resistance efforts.…”