Browsing by Author "Odong, Thomas Lapaka"

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    Genetics of Resistance in F2 Soybean Populations for Adzuki Bean Bruchid (Callosobruchus chinensis)
    (J Agric Sci, 2018-11-15) Msiska, Ulemu Mercy; Miesho, Belay Weldekidan; Tukamuhabwa, Phinehas; Kyamanywa, Samuel; Odong, Thomas Lapaka; Ibanda, Angele Pembele; Rubaihayo, Patrick
    Adzuki bean bruchid (Callosobruchus chinensis) is a significant pest of soybean in Uganda. To sustainably manage this pest, utilization of resistant soybean varieties is the key solution. Development of resistant varieties needs knowledge on modes of inheritance which is crucial in selection of parent materials. To identify parents, a study was initiated to determine the gene action and mode of inheritance of resistance to bruchids in soybean. Nine parental lines were crossed in a full-diallel at Makerere University Agricultural Institute, Uganda. The generated F1s were advanced to F2 and seeds were evaluated for response to bruchid infestation in a randomised complete block design. Ten seeds were infested with 10 randomly selected unsexed 1-3 day old bruchids. Genotypes showed significant differences in seed weight loss (swl), adult bruchid emergence (ABE) and Dobie susceptibility index (DSI) indicating that these parameters could be used to screen genotypes in genetic analysis. Mean squares of general combining ability (GCA) were significant (P < 0.05) for swl, DSI and number of ABE from the F2 seeds indicating additive gene action. Susceptibility parameters ABE and DSI showed significant specific combining ability (SCA) indicating non-additive gene action. Resistance was influenced by maternal effects indicating that direction of the cross was important. Genotypes S-Line 9.2 and S-Line 13.2A showed negative significant GCA effects for at least two of the susceptibility parameters indicating that they were the best parents for bruchid resistance breeding. The study established that additive, non additive and maternal effects governed the gene expression in soybean resistance to bruchids.
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    Genome-wide Association study of Biological Nitrogen Fixation Traits in Mini-core Cowpea Germplasm
    (PLoS One, 2025-05-09) Nkurunziza, Gelase; Mbeyagala, Emmanuel K.; Tukamuhabwa, Phinehas; Ssemakula, Mildred Ochwo; Tumuhairwe, John Baptist; Odong, Thomas Lapaka
    Biological Nitrogen Fixation (BNF) efficiency in legume crops such as cowpea (Vigna unguiculata L. Walp) has been less documented yet is key in improving yield performance and restoring soil fertility in sub-Saharan Africa. Nevertheless, little progress has been made in understanding the gene control of the BNF traits in cowpea to sustain the development of smart agriculture in this part of the world. This study aimed to identify cowpea genotypes and map genomic regions for BNF traits for developing high nitrogen-fixing cultivars. A total of 241 mini-core cowpea genotypes were inoculated with Bradyrhizobium spp in a screen house for two cycles. Phenotypic data collected on the number of nodules (NN) per plant, nodule efficiency (NE) in percentage, and nodule dry weight (NDW) per plant revealed significant differences implying high genetic variability in the mini-core population for nodulation capacity. Fifteen significant association signals were identified for BNF traits on nine chromosomes except Vu02 and Vu09 when two multi-locus models were considered. Markers accounting for over 15% variation for BNF traits included 2_31410 (2.32Mb) on Vu05 and 2_45545 (24.93Mb) on Vu06 for NN, 2_06530 (56.64Mb) and 2_27028 (34.31Mb) on Vu01 for NE and 2_50837 (10.07Mb) on Vu01 and 2_11699 (34.41Mb) on Vu07 for NDW, respectively. Additionally, positional candidate genes near the peak markers that encode genes associated with BNF in cowpea included Vigun06g121800, Vigun01g160600, Vigun10g014400, Vigun07g221500, Vigun07g221300 and Vigun11g096700. The genotype TVu-1477 was identified to have favorable alleles for both three studied traits. The significant markers identified in this study can be converted to Kompetitive Allele Specific-PCR (KASP) markers to accelerate the development of high-yielding cowpea varieties that also enhance soil fertility.
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    Identifying Optimal Lines for Enhanced Symbiotic Performance in a Mini-Core Collection of Cowpea [Vigna unguiculata (L.) Walp]
    (Advances in Agriculture, 2025-09-10) Nkurunziza, Gelase; Odong, Thomas Lapaka; Mbeyagala, Emmanuel K.; Ssemakula, Mildred Ochwo; Tumuhairwe, John Baptist
    Cowpea (Vigna unguiculata L. Walp) is an important food security and climate-resilient legume grain crop grown in the semiarid regions of sub-Saharan Africa (SSA). It can symbiotically fix atmospheric nitrogen (N2) and improve soil fertility, which should be harnessed to increase its yield in the region. This study assessed the mini-core cowpea collection genotypes for effective and efficient nodulation, aiming to select the superior genotypes for further field evaluation in Ugandan agroecologies. A total of 252 cowpea genotypes were planted in pots in a screen house at Makerere University Agricultural Research Institute, Kabanyolo (MUARIK), in a randomized complete block design (RCBD) with two replications. Seeds were inoculated with Bradyrhizobium spp. (strain ICB756). At early pod formation stage, data were collected on plant vigor (based on plant height, leave greenness, and biomass) and nodulation-related traits including number of nodule (NN) per plant, proportion of active nodule (AN), and nodule dry weight (NDW) per plant. Results showed that NN and AN ranged from 0% to about 89% and 0% to 100%, averaging 25% and 44.6%, respectively. NDW ranged from 0 to 128.9 mg/plant, averaging 31.7 mg/plant. Analysis of variance (ANOVA) showed significant differences (p < 0.05) among genotypes for AN and NDW, indicating a genetic diversity between the genotypes which were grouped in four clusters. There was a positive correlation between symbiotic traits and plant vigor, implying a combined possible improvement of these traits. Genotypes such as TVu-14971, TVu-1477, and TVu-14691 were identified as best performers for both nodulation traits and plant vigor, while TVu-9259, TVu-14621, and TVu-7719 exhibited poor nodulation. After confirmation under standardized screening conditions, the present findings could contribute to cowpea breeding programs aiming at developing new cultivars, contributing to agricultural sustainability and food security while maintaining a healthy environment.