College of Agriculture

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The College of Agriculture is committed to advancing agricultural education, research, and community service. It serves as a center for knowledge creation and dissemination in crop science, animal production, natural resource management, and sustainable agriculture.

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    GENETIC DIVERSITY AND DROUGHT TOLERANCE IN ETHIOPIAN DURUM WHEAT (Triticum turgidum subsp. durum) GENOTYPES
    (Hawassa University College of Agriculture, 2025) BANTEWALU HAILEKIDAN DUKAMO
    Durum wheat (Triticum turgidum subsp. durum), the second most widely cultivated wheat species after common wheat, plays a crucial role in global food security. Ethiopia, recognized as a secondary center of origin and diversity for durum wheat, harbors a broad and unique genetic reservoir well adapted to diverse agroecological conditions. However, productivity remains low due to limited availability of improved, drought-tolerant varieties and insufficient exploitation of genetic diversity. This study aimed to characterize Ethiopian durum wheat landraces, identify drought-tolerant genotypes, and assess their potential for breeding programs by integrating field, greenhouse, and molecular analyses. The research involved three interlinked components. The first was a field experiment conducted at Dera (1500 masl) and Debrezeit (1920 masl), where 104 genotypes (100 landraces and 4 checks) were evaluated under drought-stressed and non-stressed conditions using an augmented design. Thirteen agronomic traits related to yield, phenology, and canopy status were measured across both environments. Additional data were collected from an extended growing season, and drought tolerance was assessed using various indices. ANOVA, correlation, principal component analysis (PCA), and clustering were used to identify promising genotypes and trait associations. The second component involved a greenhouse experiment at Hawassa University using 20 top-performing landraces and four checks selected from the field study. Genotypes were grown under well-watered (70% field capacity) and drought-stressed (35% field capacity) conditions in a completely randomized design with three replications. Data on morphological, physiological, and biochemical traits were collected, including grain yield, relative leaf water content (RLWC), chlorophyll content, canopy temperature, and proline accumulation. Statistical analyses were employed to evaluate drought responses, including correlation, PCA, cluster, and path coefficient analysis. The third component focused on the molecular characterization of 94 genotypes (86 landraces and 8 improved varieties) using SNP markers generated through DArTSeq technology. Genotyping was performed by SEQART AFRICA, producing 17,092 highquality SNPs. Genetic diversity, population structure, and linkage disequilibrium (LD) were analyzed to assess genome-wide variation and support genotype selection. Field results revealed significant genetic variation among landraces across all measured traits. Genotypes ETDW/15DZ23, 34493, ETDW/15DZ4, 34522, MCD3-14, 34217, and 31831 demonstrated superior grain yield under stress and non-stressed conditions. High heritability (h²b = 32.84–97.87) and genetic advance estimates for traits such as spike length, kernel number per spike, and tiller number indicated strong potential for selection. Drought indices, including stress tolerance index (STI), mean productivity (MP), and yield stability index (YSI), identified ETDW/15DZ23, 34493, and ETDW/15DZ4 as topperforming, drought-resilient genotypes. Strong positive correlations (r = 0.88) between grain yields under stressed and non-stressed conditions further confirmed their stability and xviii adaptability. The greenhouse experiment revealed significant effects of genotype, treatment, and their interaction (P<0.001) for most traits. Under stress, grain yield decreased by up to 68%, RLWC dropped from 93.07% to 44.91%, and proline content increased markedly, indicating drought response. Cluster analysis grouped genotypes based on resilience, with one cluster showing the highest yield (5.99 t/ha) under well-watered conditions, while another showed superior RLWC (65.80%) and yield (2.90 t/ha) under stress. Path analysis underscored the importance of RLWC, proline, and chlorophyll content in drought tolerance. Molecular analysis revealed 14,136 informative SNPs distributed across the A and B genomes, with chromosome 2B having the highest marker density. Population structure analysis indicated considerable variation within and among landraces, with AMOVA showing 51.75% of genetic variation within populations and 48.15% within individuals. The genome-wide LD decay threshold was 4.58 Mbp, with the highest LD values on chromosome 4B. Average polymorphic information content (PIC) and gene diversity values were moderate, indicating a diverse and informative marker set for future breeding applications. This study highlights the significant phenotypic and genotypic diversity within Ethiopian durum wheat and identifies promising genotypes for drought tolerance and yield stability. The integration of field performance, physiological traits, and genomic data provides a robust platform for developing improved durum wheat cultivars. These findings support the use of landraces in breeding programs targeting climate resilience and food security. Future work should focus on multi-environment trials, genome-wide association studies (GWAS), and marker-assisted selection to accelerate genetic improvement and enhance drought tolerance in Ethiopian durum wheat