Browsing by Author "HABTAMU GEBRESELASSIE ADDO"

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    GENETIC DIVERSITY AND TRAIT VARIABLITY IN SOME COFFEE [Coffea arabica L.] GENOTYPES FROM SOUTH ETHIOPIAN
    (Hawassa University College of Agriculture, 2025) HABTAMU GEBRESELASSIE ADDO
    DIVERSITY OF SOUTH ETHIOPIAN COFFEE [Coffea arabica L.]: AGROMORPHOLOGICAL, BIOCHEMICAL AND MOLECULAR ASPECTS Ethiopia is the center of origin and genetic diversity for Coffea arabica, a crop that plays a central role in the country's economy, culture, and identity. Coffee provides a livelihood to about 25 million people. Despite Ethiopia's favorable climate, soil, and rich genetic resources, national coffee productivity remains low as compared to leading producer and world average. This is partly due to our incomplete knowledge of the wider adaptability and stability, morphological, biochemical, and molecular diversity among characteristics of the plant and the relevant agricultural traits of the plant in general, and South Ethiopian genotypes, in particular. To address this gap, five integrated studies were conducted to evaluate the morphological, biochemical, and molecular diversity of South Ethiopian Arabica coffee genotypes and their relationship to yield and quality performance. These studies aimed to support genetic improvement efforts through better trait characterization, genotype selection, and understanding of genotype × environment interaction (GEI). The first two studies involved the evaluation of 17 genotypes (14 selections and 3 released varieties) at Awada, Wonago, and Shebedino using a randomized complete block design (RCBD). A total of 26 quantitative and 15 qualitative traits were recorded. Results revealed wide phenotypic variation, with Shannon-Weaver diversity indices ranging from 0.22 to 1.12. Significant differences (p<0.05) were found for most qualitative traits, confirming high morphological diversity. Quantitative trait analysis showed significant variation among genotypes, environments, and their interaction for several yield-related traits. Traits such as number of branches, canopy diameter, fruit size, and seed traits exhibited moderate-to-high heritability and genetic advance, indicating potential for improvement via selection. Principal component and cluster analyses grouped the genotypes based on trait similarities, highlighting key contributors to phenotypic diversity. Genotypes AW7705 and AW105 showed superior yield performance (1.37 t/ha), with AW7705 also demonstrating yield stability across environments. The third study analyzed GEI effects using AMMI and GGE-biplot models across 12 environments. The interaction was significant, accounting for 17.5% of total variation. Genotype AW7705 (G16) was identified as both high-yielding and stable, making it a best candidate for xxii variety development in Sidama, Gedeo, and similar agro-ecologies. Conversely, AW105 (G7) was high-yielding but less stable, suggesting potential for targeted environments. These results emphasize the importance of multi-location trials in coffee breeding to capture GEI effects and ensure stability. In the fourth study, 30 genotypes were assessed for physical traits, cup quality, and biochemical composition using RCBd design. Significant variation was found among genotypes and environments almost all the studied traits. Most genotypes scored above 80%, qualifying them as specialty coffee. Biochemical diversity included a wide caffeine range (0.52%–1.53%), offering opportunities to develop low-caffeine varieties. PCA and cluster analyses identified key traits contributing to quality variation, including caffeine, trigonelline, chlorogenic acid, acidity, and flavor. Genotype AW9648 consistently exhibited high-quality scores, making it suitable for both quality breeding and specialty market promotion. The fifth study, the genetic diversity of 40 accessions from Sidama, Guji, Amaro, and Jinka and 10 improved varieties analyzed using four ISSR markers. A total of 74 bands were generated, with private bands and higher polymorphism observed in improved varieties. Genetic diversity indices showed considerable variation among populations, with AMOVA revealing 67% of total variation occurring among populations. Principal coordinate analysis explained 43% of the genetic variation across the first three axes. UPGMA clustering grouped genotypes into four major clusters, often reflecting geographic origin. These findings confirm the rich genetic base in southern Ethiopian coffee and support its use in breeding and conservation programs. The integrated results of these five studies confirm the presence of significant agromorphological, quality, and molecular diversity among South Ethiopian coffee genotypes. Significant GEI effects further underline the need for multi-environment testing to develop widely adaptable and stable varieties. AW7705 and AW105 were high yielder and found to be promising candidate for yield competitive variety development; whereas, AW9648 was identified as superior quality. These results provide a foundation for selection, hybridization, and conservation strategies in Arabica coffee improvement. Future research should include more accessions and high-resolution molecular markers to enhance the precision of genetic diversity studies and guide sustainable crop improvement.