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Maize is one of the most important staple food crops in many parts of Ethiopia. However, it is not used extensively due to its poor nutritional quality and low productivity. It lacks two essential amino acids, namely, lysine and tryptophan. Knowledge of the interrelationships of grain yield and its various causal (contributory) components is very helpful to improve the efficiency of breeding programs using appropriate selection indices. This article reports the findings of a study conducted to determine the nature of relationships of grain yield and its contributing components and to identify those components with significant effects on yield with the intention of using them as selection criteria using path coefficient analysis (PCA). Therefore, PCA has shown that yield per hectare had a significant and positive phenotypic correlation with plant height, ear height, number of kernels per row, and 100-grain weight. Moreover, PCA had a significant and positive genotypic correlation with days to 50% tasseling, plant height, ear height, and 100-grain weight. The highest direct positive effect on yield per hectare was exhibited by ear height. The findings of this study showed that most genotypes are early maturing and are suitable for areas with short rainy seasons and prone to drought.

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Ethiopia, the probable center of origin and diversity for sorghum (Sorghum bicolor L. [Moench]) and with unique eco-geographic features, possesses a large number of sorghum landraces that have not been well studied. Increased knowledge of this diverse germplasm through large-scale genomic characterization may contribute for understanding of evolutionary biology, and adequate use of these valuable resources from the center of origin. In this study, we characterized genetic diversity, population structure and selection signature in 304 sorghum accessions collected from diverse sorghum growing regions of Ethiopia using genotyping-by-sequencing (GBS). We identified a total of 108,107 high-quality single nucleotide polymorphism (SNPs) markers that were evenly distributed across the sorghum genome. The average gene diversity among accessions was high (He = 0.29). We detected a relatively low frequency of rare alleles (26%), highlighting the potential of this germplasm for subsequent allele mining studies through genome wide association studies (GWAS). While we found no evidence of genetic differentiation among administrative regions (FST = 0.02, p = 0.12), population structure and cluster analyses showed clear differentiation among six Ethiopian sorghum populations (FST = 0.28, p = 0.01) adapting to different environments. Analysis of SNP differentiation between the identified genetic groups revealed a total of 40 genomic regions carrying signatures of selection. These regions harbored candidate genes potentially involved in a variety of biological processes, including abiotic stress tolerance, pathogen defense and reproduction. Overall, a high level of untapped diversity for sorghum improvement remains available in Ethiopia, with patterns of diversity consistent with divergent selection on a range of adaptive characteristics.

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