Heterotic responses among crosses of IITA and CIMMYT early white maize inbred lines under multiple stress environments

Abstract

Two major constraints militating against the achievement of food security in West Africa (WA) are recurrent drought and poor soil fertility. Seventeen early maturing maize inbreds from IITA and CIMMYT were used as parents to produce 136 diallel crosses which were evaluated along with four checks in contrasting environments at four locations for 2 year in Nigeria. The objectives of the study were to (i) examine the combining ability of the lines under drought, low soil nitrogen (low N), optimal and across environments; (ii) classify the inbreds into heterotic groups using the specific combining ability (SCA) effects of grain yield, heterotic group's specific and general combining ability (HSGCA), the heterotic grouping based on general combining ability (GCA) of multiple traits (HGCAMT) and the molecular-based genetic distance methods; (iii) compare the efficiencies of the four heterotic grouping methods in classifying the inbreds and identifying the best testers; and (iv) examine the performance of the inbreds in hybrid combinations across environments. Sum of squares for GCA of inbreds for grain yield and other measured traits were larger than those of the SCA in all environments. The relative importance of GCA to SCA effects for grain yield and other traits increased from stress to nonstress environments with the additive genetic effects accounting for the major portion of the total genetic variation under all research environments. The HSGCA method classified the lines into three groups and was the most efficient because it had the highest breeding efficiency (40 %) in the test environments followed by the HGCAMT, SNP marker-based and the SCA effects of grain yield methods. Inbred TZEI 19 was identified as the best tester across research environments based on HSGCA method. Hybrids ENT 11 9 TZEI 19 and TZEI 1 9 TZEI 19 were the most outstanding and should be tested extensively in on-farm trials and commercialized.

Genetic studies of extra‐early provitamin‐A maize inbred lines and their hybrids in multiple environments

“…For details on the observations made on traits and the appropriate scoring scales used in this research, refer to Badu‐Apraku et al. ().…”

“…The statistical model employed for the combined analysis in the present study has been previously described by Badu‐Apraku et al. (). Broad‐sense heritability (H 2 ) of the traits was estimated as the proportion of the phenotypic variance contributed by the genetic variance based on the hybrid means, following the method of Hallauer, Carena, and Filho ().…”

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

“…The authors found the HSGCA method to be superior to the SCA effect of grain yield method. In a similar study involving IITA and CIMMYT early-maturing white maize inbreds evaluated under multiple stress environments, the HSGCA method classified the lines into three groups and was the most efficient because it had the highest breeding efficiency in the test environments followed by the HGCAMT, SNP marker-based GD and the SCA effects of grain yield methods (Badu-Apraku et al, 2015b). Similarly, Akinwale et al (2014) identified HSGCA as the most efficient method in classifying early-maturing tropical maize inbreds under Strigainfested and Striga-free environments.…”

Genetic analysis of resistance to post flowering stalk rot in tropical germplasm of maize ( Zea mays L.)

“…SCA variance was found to be non-significant, suggesting the preponderance of additive gene action for FSR resistance at this location. It suggests that early generation testing would be effective and selection of hybrids could be solely based on the prediction of GCA effects (Badu-Apraku et al, 2015). The relative importance of GCA and SCA effects was estimated by the ratio of GCA effects to the total genetic effect (Baker, 1978).…”