MORPHO-PHYSIOLOGICAL, SEED OIL COMPOSITIONAL, AND MOLECULAR DIVERSITY IN ETHIOPIAN MUSTARD (Brassica carinata A. Braun) GERMPLASM

Abstract

Morpho-Physiological, Seed Oil Compositional and Molecular Diversity in Ethiopian Mustard (Brassica carinata A.Braun) Germplasm Ethiopian mustard (Brassica carinata A. Braun) is an economically significant selfpollinating oilseed crop valued for its adaptability and diverse industrial applications. Despite its long cultivation history in Ethiopia and the availability of extensive germplasms, a comprehensive understanding of its diversity is lacking, hindering effective breeding strategies. This study aimed to evaluate the morpho-physiological, seed oil, fatty acid, and genetic diversity of 386 collections of B. carinata accessions. Three independent experiments were conducted. First, 386 accessions were phenotypically characterized for 27 agro-morphological and physiological traits for two successive growing seasons in 2022 and 2023 using an augmented block design, replicated twice. Second, seed oil content and fatty acid profiles were analyzed using Nuclear Magnetic Resonance Spectroscopy (NMRS) and Near-Infrared Reflectance Spectroscopy (NIRS), respectively, to identify significant variation (P < 0.05) and promising accessions for industrial and edible oil applications. Third, genetic diversity was assessed in 188 accessions using 3793 DArTSeqgenerated single nucleotide polymorphism (SNP) markers. Phenotypic analyses revealed significant variation (P < 0.001) within accessions for all measured traits indicates substantial phenotypic diversity. Cluster analysis identified four distinct groups with significant inter-cluster divergence, indicating potential for selection. Promising accessions (n = 19) with high seed yields and oil contents were identified. Seed oil content ranged from 37.88% to 46.98%, with high heritability (85-94%) and genetic advance (22.30-59.29%) observed for all traits. Specific accessions (n = 19) were identified as valuable sources of high oil contents and desirable fatty acid profiles. Genetic diversity and population structure analysis using STRUCTURE, principal coordinate analysis (PCoA), and neighbor-joining trees identified two distinct subpopulations with limited genetic differentiation (PhiPT = 0.02) and high gene flow (Nm = 5.74). PCoA indicated low molecular variation, and genetic diversity indices (HE = 0.21, PIC = 0.13) suggested heterozygote deficiency, likely due to restricted cross-fertilization. Accessions did not cluster strictly according to geographical origin, indicating that other factors influence genetic diversity. Higher genetic variation was observed within populations (65.19%) than between populations (44.81%). In conclusion, this study revealed substantial phenotypic variability and medium genetic diversity in the Ethiopian mustard germplasm. These findings highlight the importance of intra-population diversity in breeding programs and suggest that geographic origin is not the primary determinant of genetic diversity. Promising accessions identified for high seed yield, oil content, and desirable fatty acid profiles provide valuable resources for future improvement and commercialization. This study contributes to a more comprehensive understanding of B. carinata diversity, informing efficient conservation and breeding strategies.