Assessing genetic, racial, and geographic diversity among Ethiopian sorghum landraces and implications for heterotic potential for hybrid sorghum breeding.

The wealth of sorghum genetic resources in Africa has not been fully exploited for cultivar development in the continent. Hybrid cultivars developed from locally evolved germplasm are more likely to possess a well-integrated assembly of genes for local adaptation, productivity, quality, as well as for defensive traits and broader stability. A subset of 560 sorghum accessions of known fertility reaction representing the major botanical races and agro-ecologies of Ethiopia were characterized for genetic, agronomic and utilization parameters to lay a foundation for cultivar improvement and parental selection for hybrid breeding. Accessions were genotyped using a genotyping by sequencing (GBS) generating 73,643 SNPs for genetic analysis. Significant genetic variability was observed among accessions with Admixture and Discriminant Analysis of Principal Components where 67% of the accessions fell into K=10 clusters with membership coefficient set to > 0.6. The pattern of aggregation of the accessions partially overlapped with racial category and agro-ecological adaptation. Majority of the non-restorer (B-line) accessions primarily of the bicolor race from the wet highland ecology clustered together away from two clusters of fertility restorer (R-line) accessions. Small members of the B accessions were grouped with the R clusters and in vice-versa while significant numbers of both B and R accessions were spread between the major clusters. Such pattern of diversity along with the complementary agronomic data based information indicate the potential for heterosis providing the foundation for initiating hybrid breeding program based on locally adapted germplasm. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01483-8.

Genome-wide association analysis reveals seed protein loci as determinants of variations in grain mold resistance in sorghum.

KEY MESSAGE: GWAS analysis revealed variations at loci harboring seed storage, late embryogenesis abundant protein, and a tannin biosynthesis gene associated with sorghum grain mold resistance. Grain mold is the most important disease of sorghum [Sorghum bicolor (L.) Moench]. It starts at the early stages of grain development due to concurrent infection by multiple fungal species. The genetic architecture of resistance to grain mold is poorly understood. Using a diverse set of 635 Ethiopian sorghum accessions, we conducted a multi-stage disease rating for resistance to grain mold under natural infestation in the field. Through genome-wide association analyses with 173,666 SNPs and multiple models, two novel loci were identified that were consistently associated with grain mold resistance across environments. Sequence variation at new loci containing sorghum KAFIRIN gene encoding a seed storage protein affecting seed texture and LATE EMBRYOGENESIS ABUNDANT 3 (LEA3) gene encoding a protein that accumulates in seeds, previously implicated in stress tolerance, were significantly associated with grain mold resistance. The KAFIRIN and LEA3 loci were also significant factors in grain mold resistance in accessions with non-pigmented grains. Moreover, we consistently detected the known SNP (S4_62316425) in TAN1 gene, a regulator of tannin accumulation in sorghum grain to be significantly associated with grain mold resistance. Identification of loci associated with new mechanisms of resistance provides fresh insight into genetic control of the trait, while the highly resistant accessions can serve as sources of resistance genes for breeding. Overall, our association data suggest the critical role of loci harboring seed protein genes and implicate grain chemical and physical properties in sorghum grain mold resistance.

A comprehensive phenotypic and genomic characterization of Ethiopian sorghum germplasm defines core collection and reveals rich genetic potential in adaptive traits.

Understanding population genetic structure and diversity of a crop is essential in designing selection strategies in plant breeding. About 2010 Ethiopian sorghum accessions were phenotyped for different traits at multiple locations. A subset of the collection, 1628 accessions, predominantly landraces, some improved varieties, and inbred lines were genotyped by sequencing. Phenotypic data revealed association of important traits with different sorghum growing agro-climatic regions, high genetic diversity and the presence of rare natural variation in the Ethiopian sorghum germplasm. Subsequent genotypic analysis determined optimum number of sub-populations, distinct cluster groups and ancestries of each sorghum accessions. To improve utilization of germplasm, a core subset of 387 lines were selected following posteriori grouping of genotypes based on cluster groups obtained through GBS analysis followed by stratified random sampling using quantitative traits. In order to evaluate how well this new sorghum and millet innovation lab (SMIL) collection from Ethiopia is represented within the largest world sorghum collection at United States Department of Agriculture - National Plant Germplasm System (USDA-NPGS) and the sorghum association panel (SAP), comparisons were conducted based on SNP data. The SMIL collection displayed high genetic diversity with some redundancy with the USDA-NPGS germplasm but SAP showed clear distinction. Furthermore, genome-environment association analysis identified candidate genes associated with adaptation to abiotic factors, that will be important for exploitation of adaptive potential to different environments. In summary, our results described the diversity and relationship of sorghum collections, representativeness of developed core and provide novel insights into candidate genes associated to abiotic stress tolerance.