Fatoumata Ouattara

Background: Understanding the genetic diversity and population structure of maize inbred lines is fundamental for effective hybrid development and strategic heterosis exploitation. The objective of this study was to refine and validate heterotic groups within a diverse collection of extra-early and early maturing tropical yellow and orange maize inbred lines. A total of 1,437 elite tropical yellow and orange maize inbred lines spanning early and extra-early maturing groups were genotyped using a panel of 3,305 DArTag SNP markers. In addition, the study evaluated 280 hybrids comprising 276 hybrids (from 214 inbred lines crossed with four standard testers) and four commercial checks. The yield performance trials used a 14 × 20 alpha-lattice design with two replicates over two years. Results: Marker-based diversity analysis revealed average marker polymorphism of 0.328, minor allele frequency of 0.265, and expected heterozygosity of 0.315. Principal component analysis (PCA), discriminant analysis of principal components (DAPC), and ancestral admixture analysis revealed three genetic clusters, while phylogenetic analysis supported the existence of two major clusters with groups one and three from DAPC and admixture methods combined into a single phylogenetic group. Several sub-groups were identified within the main genetic pools and maturity rather than kernel color was the major driver of these sub-groups. For operational ease in breeding applications, the lines were assigned to two major heterotic groups. The average performance of the hybrid for grain yield and heterosis estimates from between maturity-based heterotic subgroups were consistently and significantly ( p < 0.001) higher than those from within maturity-based heterotic subgroups. Conclusion: These results provide a robust framework for parental line selection, heterotic grouping, and hybrid breeding strategies, facilitating the development of extra-early and early superior yellow/orange maize hybrids adapted to tropical environments.

Water yam ( Dioscorea alata L.) or greater yam, is an essential species of the Dioscoreceae family in tropical and subtropical regions. The wide geographical distribution is owing to its higher tuber yield, storability, and better nutritional and health benefits compared to many other species. Despite these promising characteristics, water yam remains less preferred by consumers for traditional food products, particularly boiled and pounded yam preparations. Fast and efficient development of superior genotypes that meet farmers and end-users needs have been challenging through classical breeding methods. The objective of the study was to use genome-wide associations to assess the genetics of post-harvest tuber quality, mainly targeting the consumer-preferred traits. A panel of 404 water yam genotypes were assessed to decipher the genomic regions associated with traits such as tuber oxidative browning, dry matter content, and boiled and pounded tuber quality. The Multiple Random Mixed Linear Model was employed for marker-trait association analysis using the naive, Q, and Q + K models, followed by gene annotation and marker or allele substitution effects. Fourteen SNP markers were significantly linked with the assessed tuber quality traits and r ² values ranged from 0.62 to 10.02%. The gene annotation analysis revealed presence of 32 putative candidate genes playing crucial roles in enzymatic browning and carbohydrate biosynthesis pathways for dry matter accumulation. The molecular information generated in the present study can be deployed for water yam improvement.

Water yam (Dioscorea alata L.) is the most widely cultivated yam species with good agronomic attributes. However, several biotic and abiotic constraints and its lower food quality such as poor pound ability limit its production and use. Therefore, the identification of superior genotypes with suitable characteristics is needed for water yam improvement. This study aims to assess a panel of half-sib (progenies with one parent in common) and full-sib (progenies with the same male and female parents) progenies as well as their parents for selection of desirable ideotypes based on their agronomic and quality characteristics. A total of 280 progenies from bi-parental populations as well as five parents were evaluated, and a significant variation was observed (p < 0.01) in their performances for the eight traits used in the study. A moderate to high broad-sense heritability (30% < H2–H2 ≥ 60%) was observed for all traits except for tuber pound ability (H2 < 30%). Positive correlations were displayed between the traits, while the hierarchical clustering grouped genotypes into three clusters indicating the potential for selection of diverse genotypes for multiple traits from the four families under study. Plant vigor and number of tubers per plant contributed (p < 0.01) positively to the yield per plant in the path coefficient analysis. Using the multi-trait genotype–ideotype distance index (MGIDI), a total of 39 most promising genotypes were identified. These promising genotypes could be further used as progenitors in D. alata improvement programs targeting good agronomic and quality traits targeted for farmers and end users.