Browsing by Author "Nkalubo, Stanley T."

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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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    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.