School of Agricultural Sciences (SAS)

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Browsing School of Agricultural Sciences (SAS) by Author "Agaba, Rolland"
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    Genotype-by-environment interaction of yam (Dioscorea species) for yam mosaic virus resistance, dry matter content and yield in Uganda
    (MDPI, 2022-08-23) Amponsah, Emmanuel Adjei ; Esuma, Williams ; Alicai, Titus ; Boache, Emmanuel Chamba ; Edema, Richard ; Onziga, Isaac Dramadri ; Adebo, Alfred Ozimati ; Agaba, Rolland ; Odong, Thomas L.
    Often, yam cultivars grown in different agro-ecologies show differential responses across production environments, a term known as "genotype-by-environment interaction. Such genotype-by-environment interaction makes the selection of the best genotypes under varied production environments more complex. This study evaluated twenty yam genotypes in six test environments to assess genotype, environment, and their interaction effects on tuber yield, response to yam mosaic virus, and dry matter content. The experiments were conducted over two seasons across three locations in Uganda, using a randomized complete block design with three replications. There were significant effects (p 0.001) for genotype (G), environment (E), and genotype-by-environment interaction for all key traits assessed. Serere (2021) and Namulonge (2021) were identified as the most discriminating and representative environments for testing responses to yam mosaic virus, respectively. Serere (2021) was recognized as the most discriminating environment, whereas Arua (2021) emerged closest to an ideal environment for assessing yam tuber yield. The tested genotypes also exhibited resistance to yam mosaic virus disease, had high tuber yields and dry matter content. Genotypes UGY16020, UGY16034, UGY16042, and UGY16080 demonstrated highest resistance to yam mosaic virus disease, along with high yield and dry matter content, and are thus potential parents for yam genetic improvement. Further evaluation of the four genotypes should be carried out within farmers’ production systems for selection, improvement, and release as new yam varieties for Uganda.
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    Phenotypic diversity within Ugandan yam (Dioscorea species) germplasm collection
    (Hindawi, 2022-12-19) Amponsah, Emmanuel Adjei ; Esuma, Williams ; Alicai, Titus ; Bhattavharjee, Ranjana ; Onziga, Isaac Dramadri ; Agaba, Rolland ; Boache, Emmanuel Chamba ; Odong, Thomas L.
    A proper understanding of the diversity of the available germplasm is an initial step for the genetic improvement of a crop through breeding. However, there is limited information on the diversity of Uganda’s yam germplasm. &e study sought to characterize the diversity of yam germplasm utilized for decades in Uganda together with germplasm recently introduced from West Africa using phenotypic traits. A germplasm collection of 291 genotypes was characterized using 28 phenotypic traits. Data were subjected to multivariate analysis using principal component analysis and cluster analysis. &e traits assessed were informative and discriminating, with 62% of the total variation explained among the 7rst six principal components. Results showed that the important phenotypic traits contributing to most of the variability among the genotypes were leaves, flowering, and tuber traits. Ugandan genotypes were identified with amorphous tuber shapes compared to West African genotypes. &e study has shown that there is ample phenotypic variability within the major yam genotypes in Uganda yam germplasm that can be used for genetic improvement. More in-depth molecular and biochemical studies to further understand the diversity are recommended. &e preprint was made available by research square in the following link: “https://www.researchsquare.com/article/rs-1518551/v1.”
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    Trench layering technologies for rapid multiplication of Elite Apple Germplasm (Malus domestica) in Kabale, Western Uganda.
    ( 2012-02) Agaba, Rolland
    Apples greatly contribute to farmers’ livelihoods in tropical highlands. However, there has been limited access to quality planting materials associated with poor rooting of apple rootstocks. To improve rooting ability, this experiment was setup at Bugongi Research Station Orchard to examine the effects of TsaOm (Top forest soil +Sand+ Organic matter) and TsdOm (Top forest soil + Saw dust +Organic matter) substrate mixtures and IBA concentrations [0 (control), 4000 ppm and 8000 ppm] on the rooting success and survivability of M106, M109, MM793 and Bitten felder Apple rootstocks. A completely randomized design with three replicates in factorial arrangement was used. The rooting percentage increased markedly to 76.02% in bitten felder and up to100% in M106. The highest (37.39±0.12) and lowest (13.04±0.3) rooting percentages were obtained in M109 and MM793 respectively with TsdOm. While TsaOm and TsdOm resulted in higher rooting percentages in MM793, it was the reverse in bitten felder. The application of TsdOm on M106 and M109 resulted in significant increases in root numbers and a reduction in the survivability of M106. The survivability of M109, MM793 and Bitten felder layers increased significantly in TsaOm and TsdOm mixtures, but the highest survival rate (45.1± 0.2) was obtained in M109 under TsaOm mixture. With IBA concentrations, 8000 ppm gave the highest (41.22 ± 0.11%) in M109 as and the lowest rooting percentage (8.4 ± 0.0%) in M106 respectively. IBA concentrations had significant effect on root lengths with the longest (9.9 ± 2.2 cm) recorded in M106 after treatment with 4000 ppm. The lowest root length was obtained in MM793 after treatment with 8000 ppm. A significantly difference in survival rates was exhibited by the interaction of apple rootstocks and IBA concentrations. These results indicate that trench layering technologies that incorporate appropriate organic substrate mixtures (TsaOm and TsdOm) and IBA at 4000 ppm are suitable for rapid multiplication of apple rootstocks which could increase farmer’s access to quality germplasm.