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Assessment of genetic purity of parental inbred lines and their resultant F1 hybrids is an essential quality control check in maize hybrid breeding, variety release and seed production. In this study, genetic purity, parent-offspring relationship and diversity among the inbred lines were assessed using 92 single-nucleotide polymorphism (SNP) markers. A total of 188 maize genotypes, comprising of 26 inbred lines, four doubled haploid (DH) lines and 158 single-cross maize hybrids were investigated in this study using Kompetitive Allele Specific Polymerase Chain Reaction (KASP) genotyping assays. The bi-allelic data was analyzed for genetic purity and diversity parameters using GenAlex software. The SNP markers were highly polymorphic and 90% had polymorphic information content (PIC) values of > 0.3. Pairwise genetic distances among the lines ranged from 0.05 to 0.56, indicating a high level of dissimilarity among the inbred lines. A maximum genetic distance of (0.56) was observed between inbred lines CKDHL0089 and CML443 while the lowest (0.05) was between I-42 and I-40. The majority (67%) of the inbred lines studied were genetically pure with residual heterozygosity of <5%, while only 33% had heterozygosity levels of >5%. Inbred lines, which were not pure, require purification through further inbreeding. Cluster analysis partitioned the lines into three distinct genetic clusters with the potential to contribute new beneficial alleles to the maize breeding program. Out of the 68 hybrids (43%) that passed the parent-offspring test, seven hybrids namely; SCHP29, SCHP95, SCHP94, SCHP134, SCHP44, SCHP114 and SCHP126, were selected as potential candidates for further evaluation and release due to their outstanding yield performance.

Provitamin A maize (Zea mays L.) biofortification is an ideal complementary means of combating vitamin A deficiency (VAD) in sub-Saharan Africa where maize consumption is high coupled by high VAD incidences. However, drought remains a major abiotic constraint to maize productivity in this region. Comprehensive drought screening of initial breeding materials before advancing them is important to achieve genetic gain. In this study, 46 provitamin-A inbred lines were screened for drought tolerance in the greenhouse and field under drought and optimum conditions using β-carotene content (BCC), grain yield (GY), and selected morphophysiological and biochemical traits. The results revealed that BCC, morphophysiological and biochemical traits were effective in discriminating among genotypes. Number of ears per plant (EPP), stomatal conductance (Gs), delayed leaf senescence (SEN), leaf rolling (RL), chlorophyll content (CC) and free proline content (PC) proved to be ideal traits to use when indirectly selecting for GY by virtue of having relative efficiency of indirect selection values that are greater than unity and considerable genetic variances under either or both conditions. The findings of this study form the basis of initial germplasm selection when improving provitamin A maize for drought tolerance.

Core Ideas In a drought and non‐stress breeding program, secondary traits are important in contributing to the identification of high yielding and stability maize genotypes.Designing selection strategies that enhance grain yield gains and stability.The traits tassel size, ear aspect, ear diameter, and kernel weight per ear were found to have high broad sense heritability and can effectively aid simultaneous for selection for high grain yield and stability. Information is needed on the contribution of secondary traits to grain yield and stability in maize (Zea mays L.). This study aimed at identifying stable and high yielding hybrids as well as traits contributing to high yield and stability in tropical maize. Twenty‐two test hybrids and six check hybrids were evaluated under five environments in Karnataka, India, using a 4 × 7 α‐lattice design with two replications. Genotype main effect plus genotype × environment interaction biplot model was used to ascertain genotype stability and yield across environments. Genotype × trait biplot, t test, and step‐wise regression analyses were used to determine trait expression differences between high yielding and stable, and low yielding and unstable hybrids. Genotypic correlations and heritability were used to estimate correlated response to selection for grain yield via each secondary trait. Mean grain yield under drought was 20% of that across environments, thus selection in both drought and non‐drought stress environments is required. Hybrids GH‐12444 and GH‐12408 were high yielding and stable across environments, and should be tested widely. Some traits, such as tassel size, had correlated response to selection values of near unity making them unsuitable for indirect selection. However, such traits could be used to supplement selection for grain yield given their high heritability and that they are relatively easy to measure. Different traits were associated with grain yield under different conditions thus suggesting that both drought and non‐drought stress conditions must be used as selection environments using secondary traits specific to a given environment.

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