Browsing by Author "Mukankusi, Clare"

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    Genetic variation, Heritability estimates and GXE effects on yield traits of Mesoamerican common bean (Phaseolus vulgaris L) germplasm in Uganda
    (Plant Genetic Resources, 2018) Okii, Dennis; Mukankusi, Clare; Sebuliba, Sulaiman; Tukamuhabwa, Phinehas; Tusiime, Geoffrey; Talwana, Herbert; Odong, Thomas; Namayanja, Annet; Paparu, Pamela; Nkalubo, Stanley; Otim, Michael; Ugen, Michael; Buah, Stephen; Gepts, Paul
    Germplasm of common beans from the Mesoamerican gene pool races: Durango, Jalisco, Mesoamerica and Guatemala have highest genetic variation for the crop’s improvement. The objective was to assign 50 common bean germplasm in Uganda into its gene pool races based on analyses of population structure. Secondly, to estimate heritability and effects of genotype environment (GXE) interaction on common bean agronomic and yield traits in space and time. Sample genomic DNA was amplified in 2011 with 22 Simple sequence repeat markers (SSRs) and alleles separated using capillary electrophoresis. Field evaluations were conducted in 2010 and 2011 at NaCRRI and 2015 at CIAT – Kawanda. Multivariate analyses of SSRs data identified four subgroups within the germplasm: K4.1–K4.4, with corresponding Wrights fixation indices (FST) as 0.1829 for K4.1, 0.1585 for K4.4, 0.1579 for K4.2 and least for K4.3 at 0.0678. Gene pool race admixtures in the population (14%) were notable and attributed to gene flow. Four superior parents currently used in improving resistance to major diseases grouped as; Jalisco for MLB49-89A; Mesoamerica for MCM5001 and G2333; Durango for MEXICO 54. Heritability values for yield traits estimated using phenotypic data from above fixed parents, was above 0.81. Season and location had significant effect (P < 0.05) on numbers of: flower buds per inflorescence, pod formation and weight of 100 seeds. The findings will improve understanding of co-evolutionary relationships between bean hosts and pathogens for better disease management and will broaden the germplasm base for improving other tropical production constraints.
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    Inheritance of resistance to common bacterial blight in four selected common bean (Phaseolus vulgaris L.) genotypes
    (Journal of Plant Breeding and Crop Science, 2017) Alladassi, Boris M. E.; Nkalubo, Stanley T.; Mukankusi, Clare; Mwale, Eric S.; Gibson, Paul
    Common bacterial blight (CBB) is the most serious bacterial disease of common bean in Uganda. It causes severe yield losses of up to 62%. Genetic resistance is the most effective option for controlling CBB in smallholder common bean production systems. This study was carried out to determine the inheritance pattern of CBB resistance in leaf and pod of four new resistance sources. The four resistant and four susceptible genotypes were crossed in a half-diallel mating design. F1 individuals were advanced to F2 and evaluated with the parents, in a randomized complete block design replicated twice. Combining ability analysis was performed according to Griffing's (1956) method IV and model 1 using Genstat 12th. General combining ability effects were significant whereas specific combining ability was not suggesting that resistance to CBB in leaf and pod was primarily controlled by additive genes effects. The estimated narrow sense coefficient of genetic determination was moderately high (0.65) for the resistance in leaf and high (0.83) for resistance in pod suggesting that early-generation selection would be effective. Baker’s ratio estimates were relatively high for resistance in leaf (0.79) and pod (0.9) suggesting that hybrids’ performance can be predicted based on the parents’ general combining ability (GCA) effects.
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    Participatory farmers’ selection of common bean varieties (Phaseolus vulgaris L.) under different production constraints
    (Plant Breeding, 2018) Bruno, Awio; Katungi, Enid; Nkalubo, T. Stanley; Mukankusi, Clare; Malinga, G. Maxwell; Gibson, Paul; Rubaihayo, Patrick; Edema, Richard
    On-farm evaluation of 15 common bean varieties was undertaken with nine farmer groups under two fertilizer applications levels in four subcounties of Hoima and Rakai districts for two seasons to select farmers’ desired and undesired varieties. Farmers’ votes for acceptance and rejection of varieties at podding stage were converted to a preference index, and analysis of variance was conducted to examine differences in farmers’ preference indices among subcounties and combined across subcounties, seasons, management and gender. Management had no-significant influence on the way farmers selected varieties in the subcounties. Choice of varieties varied significantly (p ≤ .001) between seasons and gender in the different subcounties. Variety Masindi Yellow Long and Farmers’ seed (Kaduli), and the introduced KATB1 were accepted by farmers due to their medium seed size, desired seed colour and potential of varietal adaptability to their farm conditions. Varieties NABE2, ROBA1 and RWR719 were deselected due to possession of traits less desired in the market. These results demonstrate the need for breeding programmes to involve diverse stakeholders in capturing the diverse traits preferences in varietal development process.
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    Phenotypic and genotypic screening for rust resistance in common bean germplasm in Uganda
    (Euphytica, 2017) Odogwu, Blessing A.; Nkalubo, Stanley T.; Mukankusi, Clare; Odong, Thomas; Awale, Halima E.; Patrick, Rubaihayo; Kelly, James D.
    Rust caused by Uromyces appendiculatus (Pers., Pers.) Unger is one of the major foliar diseases of common bean (Phaseolus vulgaris) in Uganda. The use of host resistance remains the best option in managing this disease. The objective of this study was to identify sources of broad-spectrum rust resistance in common bean germplasm including landraces, commercial and introduced genotypes using a combination of phenotypic and genotypic screening with simple sequence repeats (SSRs) markers located on chromosome Pv04. A total of 138 cultivars were field screened from 2014 and 2015 using alpha lattice design. The variance and correlation of disease incidence, area under the disease progression curve (AUDPC) and total grain yield were computed using GenStat. The polymorphism information content of the cultivars was determined, and the association of the markers and the disease resistance traits were analyzed using PowerMarker and TASSEL respectively. Resistance of each cultivar was compared to the presence and absence of amplified markers. There were highly significant differences (P < 0.001) among the cultivars for disease incidence, AUDPC and total grain yield and a strong correlation (P < 0.001) between disease incidence and AUDPC in both years. The SSR markers, BARC_PV_SSR04725, bean_ssr_0778 and bean_ssr_2892 were observed to be associated (P ≤0.05) with rust resistance. The two screening methods identified cultivars which included local cultivars, Nabufumbo, Kapchorwa white, and NABE as new sources of rust resistance. This study identified sources of rust resistance that would be useful in the bean breeding programmes in Uganda.
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    Recombination fraction and genetic linkage among key disease resistance genes (Co-42/Phg-2 and Co-5/“P.ult”) in common bean
    (African journal of biotechnology, 2019) Okii, Dennis; Badji, Arfang; Odong, Thomas; Talwana, Herbert; Tukamuhabwa, Phinehas; Male, Allan; Mukankusi, Clare; Gepts, Paul
    Anthracnose (Colletotrichum lindemuthianum), Angular leaf spot (Pseudocercospora griseola) and Pythium root rot are important pathogens affecting common bean production in the tropics. A promising strategy to manage these diseases consists of combining several resistance (R) genes into one cultivar. The aim of the study was to determine genetic linkage between gene pairs, Co-42/Phg-2, on bean-chromosome Pv08 and Co-5/“P.ult” on-chromosome Pv07, to increase the efficiency of dual selection of resistance genes for major bean diseases, with molecular markers. The level of recombination was determined by tracking molecular markers for both BC3F6 and F2 generations. Recombination fraction r, among gene pairs, the likelihood of linkage, L(r), and logarithm of odds (LOD) scores were computed using the statistical relationship of likelihood which assumes a binomial distribution. The SCAR marker pair SAB3/PYAA19 for the gene pair Co-5/“P.ult” exhibited moderate linkage (r = 32 cM with a high LOD score of 9.2) for BC3F6 population, but relatively stronger linkage for the F2 population (r = 21 cM with a high LOD score of 18.7). However, the linkage among SCAR marker pair SH18/SN02, for the gene pair Co-42/Phg-2 was incomplete for BC3F6 population (r = 47 cM with a low LOD score of 0.16) as well as F2 population (r = 44 cM with a low LOD score of 0.7). Generally, the weak or incomplete genetic linkage between marker pairs studied showed that all the four genes mentioned earlier have to be tagged with a corresponding linked marker during selection. The approaches used in this study will contribute to two loci linkage mapping techniques in segregating plant populations.
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    Responses to selection for yield traits and key diseases among common bean genetic pyramids across locations
    (Journal of Crop Improvement, 2019) Okii, Dennis; Badji, Arfang; Odong, Thomas; Talwana, Herbert; Tukamuhabwa, Phinehas; Magdalena, William; Gepts, Paul; Mukankusi, Clare
    Knowledge of response to selection (R) helps to analyze the efficiency of crop-improvement programs and devise appropriate selection strategies. The objective of this study was to determine response to selection of common bean (Phaseolus vulgaris L.) genetic pyramids for diseases and yield traits. Populations evaluated included pyramided parents, climbing pyramided progenies, and checks. The trial was planted in 2016 in Uganda (Kabale and Kawanda) and Northern-Tanzania (Maruku and Kitengule) in randomized incomplete blocks with three replications. Summarized data and appropriate parameters were incorporated into the breeder’s equation (R = ih2S). R was positive for mean days to flowering (5 days) and negative for mean number of pods per plant (−9.5 pods) and 100-seed weight (−1.9 g). Diseases (anthracnose, angular leaf spot, and bean common mosaic virus) had positive, undesirable R. Generally, pyramided lines segregated at BC3F9 for disease resistance and yield traits, and thus, superior bean lines should be identified in subsequent generations, such as BC3F11.