Browsing by Author "Isaac Onziga Dramadri"

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Combining Ability of Cowpea (Vigna unguiculata (L) Walp) Genotypes for Resistance to Cowpea Bacterial Blight in Uganda
(American Journal of Agricultural Science, Engineering, and Technology (AJASET), 2023-01-28) Gauden Nantale; Peter Wasswa; Muhumuza Edgar; Tusiime Richard; Pamela Paparu; Isaac Onziga Dramadri
The low productivity of cowpea is partly attributed to a number of constraints including diseases such as cowpea bacterial blight (CoBB). Cowpea bacterial blight has the capacity to cause up to 92% yield loss under severe infections. The objective of this study was to determine the combining ability for resistance to CoBB among cowpea genotypes in Uganda. Nine selected parents were crossed to produce 63 progenies. F1 progenies were evaluated and data gathered included days to 50% flowering, CoBB disease scores and grain yield. The mean squares for rAUDPC due to GCA and SCA effects were significant (P≤0.001) and non-significant respectively. The broad sense coefficient of genetic determination (BCGD) and narrow sense coefficient of genetic determination (NCGD) were 44.3% and 29.1% respectively for rAUDPC. Parents WC 26 (-0.023) and NE 31 (-0.035) had highly significant negative GCA effects for rAUDPC and were therefore good general combiners for this trait. Crosses SECOW 3B x ACC 26 X SECOW 1T and WC 26 x NE 32 had negative significant SCA effect for rAUDPC with a values of -0.073 and -0.06, respectively while Crosses ACC 26 x SECOW 1T x NE 40 (-0.07) and NE 40 x WC 26 (-0.06) had significant negative reciprocal effects for rAUDPC. This study revealed that genetic inheritance for cowpea bacterial blight was controlled predominantly by additive gene effects. Parents WC 26 and NE 31 identified as good general combiners for resistance to CoBB could be utilized as sources of resistance while Crosses SECOW 3B x ACC 26 X SECOW 1T, WC 26 x NE 32, ACC 26 X SECOW 1T x NE 40 and NE 40 x WC 26 that were the best specific combiners for resistance to CoBB could be put under further evaluation as potential varieties.
Genetic clustering, and diversity of African panel of released common bean genotypes and breeding lines
(Springer Nature, 2023-03-08) Winnyfred Amongi; Stanley Tamusange Nkalubo; Mildred Ochwo‐Ssemakula; Arfang Badji; Isaac Onziga Dramadri; Thomas Lapaka Odongo; Ephraim Nuwamanya; Phineas Tukamuhabwe; Paulo Izquierdo; Karen Cichy; James Kelly; Clare Mukankusi
Common bean is a grain legume of global importance especially for proteins and micronutrients. The crop is a staple food in sub-Saharan Africa, where it has gained importance in iron bioforti cation for people prone to anemia. However, biotic and abiotic constraints, long cooking time, and high phytic acid and polyphenols both of which affect bioavailable iron, hinder the production and health benefits. To inform breeding decisions, the study determined genetic diversity and population structure within 725 breeding lines, varieties, or landraces mostly from Uganda and South America. Genotyping by sequencing and diversity array technology (DarTseq) were used to generate single nucleotide polymorphic markers on Set1 (427) and Set2 (298) germplasm, respectively. The germplasm were grouped into Andean and Mesoamerican gene pools, with the latter as the larger subpopulation. Analysis of molecular variance revealed 46% (Set1) and 50% (Set2) of genetic variation among the subpopulations, with fixation indices (FST) of 0.54 (Set1) and 0.71 (Set2) among Andean and Mesoamerican beans, respectively. The overall germplasm’s gene diversities were 0.206 (Set1) and 0.332 (Set2). Admixtures were the most diverse (0.193) in both sets of germplasm. The germplasm exhibited high genetic diversity and as a result they have a high potential for use in plant breeding. Inter- gene pool crosses within and across market classes are possible and considering both approaches is expected to increase diversity to realize genetic gain. The structure and polymorphic information generated provided useful perspectives for genomic breed- ing and genome-wide association study using the population.
Response of cowpea germplasm to bacterial blight in Uganda
(Journal of Scienti c Agriculture, 2023-02-07) Gauden Nantale; Peter Wasswa; Richard Tusiime; Edgar Muhumuza; Isaac Onziga Dramadri; Pamela Paparu
Cowpea (Vigna unguiculata (L.) walp) is a legume crop mainly grown on small scale in low–input farming systems in Uganda. Cowpea bacterial blight (CoBB) disease caused by Xanthomonas axonopodis pv. vignicola (Burkh.) Dye is increasingly becoming a major hindrance to cowpea productivity. Sixty-four cowpea genotypes were evaluated for their response to bacterial blight disease (CoBB). Field experiments were carried out during the first and second rainy seasons using alpha lattice design with three replications. Data on disease incidence and severity, grain yield, days to 50% flowering, number of seeds per pod, pod length, number of peduncles per plant, and number of branches per plant were collected. Disease severity and incidence data was used to determine relative Area Under Disease Progress Curve (rAUDPC). Results showed significant differences (P ≤ 0.001) among the genotypes for rAUDPC in each season. The rAUDPC across the seasons indicated that genotypes NE 32, WC 32A, WC 26 and NE 44 with rAUDPC values ranging from 0.22 to 0.26 were resistant to CoBB whereas genotypes NE 31 and NE 40 with rAUDPC values 0.44 and 0.46 respectively were susceptible. The rAUDPC did not show any significant correlation with days to 50% flowering, yield and its components. This study suggested that the genotypes NE 32, WC 32A, NE 44, and WC 26 be used as prospective parents in breeding initiatives to develop bacterial blight-resistant varieties due to their high yields and resistance to CoBB.