Browsing by Author "Okori, Patrick"

Now showing 1 - 7 of 7
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    Assessment of Groundnut (Arachis hypogaea L.) Genotypes for Yield and Resistance to Late Leaf Spot and Rosette Diseases
    (Journal of Experimental Agriculture International, 2018) Elsiddig Mohammed, Khalid; Afutu, Emmanuel; Odong, Thomas L.; Okello, David K.; Nuwamanya, Ephraim; Grigon, Olupot; Rubaihayo, Patrick R.; Okori, Patrick
    Groundnut which is a major staple food crop in Uganda is constrained by late leaf spot (LLS) and groundnut rosette disease (GRD), accounting for major economic yield loss. This study was conducted to identify sources of resistance to LLS and GRD and yield potential of selected groundnut genotypes that could be used in breeding programs. Thirty-eight groundnut genotypes were evaluated at the National Semi Arid Resources Research Institute (NaSARRI)-Serere, Eastern Uganda during the first and second seasons of 2015. The experiment was arranged in randomized complete block design with four replications. The results showed highly significant (P < 0.01) genotype-by-season interaction for most of the traits studied. There were significant differences among the genotypes for 100 seed weight (P < 0.01), and dry pod yield and unshelled sample of 100 pods at P < 0.05. Late leaf spot severity (at harvest), GRD incidence (at 12 weeks) and severity (at harvest) were significantly (P < .01) different and positively correlated with Area Under Disease Progress Curve (AUDPC). GRD severity at harvest showed highly significant (P < 0.001) negative correlation with shelling percentage. Both 100 seed weight and unshelled sample of 100 pod showed highly significant (P < 0.01) negative correlations with LLS at harvest, LLS AUDPC, GRD at 12 weeks, GRD AUDPC, and GRD severity. Genotypes susceptible to both LLS and GRD recorded the lowest 100 seed weight. Nine genotypes (Serenut.2, SGV 0001, SGV 0005, SGV 0006, SGV 0019, SGV 0071, SGV 0082, SGV 0083, and SGV 89751T) showed resistance to both diseases with high yield potential. These genotypes could be used to introgress resistance to both diseases in acceptable cultivars which are susceptible.
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    Azadirachta indica reduces black sigatoka in east african highland banana by direct antimicrobial effects against Mycosphaerella fijiensis without inducing resistance
    (Journal of Agricultural Science, 2017) Kumakech, Alfred; Jørgensen, Hans Jørgen Lyngs; Collinge, David B.; Edema, Richard; Okori, Patrick
    Black Sigatoka is a major disease of East African highland cooking bananas in Uganda. Aqueous extracts of Azadirachta indica, Cinnamomum zeylanicum and Capsicum annuum have shown the potential to reduce Black Sigatoka in banana plantlets. The mechanisms by which plant extracts confer protection against plant pathogens has previously been reported to involve activation of defence and direct antimicrobial activity. In the current study, both antimicrobial activities of selected extracts were studied as well as expression of three defence-related genes using quantitative real-time PCR. Gene expression was compared in susceptible (cv. Musakala, genomic group AAA-EA) and resistant (cv. Kayinja, genomic group ABB) banana cultivars. Additionally, Musakala treated with A indica extract at 1 day before inoculation (DBI) was tested for induction of defence-related genes at 0, 10 and 20 days after inoculation (DAI). Pathogenesis-related genes (PR-1 and PR-3) and non-expressor of PR-genes (NPR1B) were up-regulated in the resistant cultivar. The genes analysed responded at late time points to M. fijiensis inoculation in both extract-treated and control plants in the susceptible cv. Musakala. On the other hand, A. indica and C. annuum completely inhibited mycelial growth of M. fijiensis at 30% (w/v). These findings suggest that the effect of plant extracts on Black Sigatoka is strongly associated with the direct antimicrobial effects.
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    Exploiting Grain-Filling Rate and Effective Grain-Filling Duration to Improve Grain Yield of Early-Maturing Maize
    (Crop Science, 2013) Gasura, Edmore; Setimela, Peter; Edema, Richard; Gibson, Paul T.; Okori, Patrick; Tarekegne, Amsal
    Early-maturing maize (Zea mays L.) genotypes yield 15 to 30% less than late-maturing genotypes. One strategy for improving grain yield in the early-maturing group involves assessment of grain-filling traits as secondary traits for selection for high grain yield. In this study, we investigated the possibility of using grainfilling rate and duration for improving grain yield in early-maturing tropical maize. Forty-four hybrids generated using North Carolina design II were evaluated at CIMMYT-Zimbabwe during the 2011/2012 season under irrigated and nonirrigated environments. Although grain-filling rate and effective grain-filling duration were negatively correlated, several hybrids were distinctly above the trend line. The earliest-maturing hybrid took 127 d to reach physiological maturity and produced grain yields comparable to those of the medium-maturing genotypes (7 t ha-1). It had a high grain-filling rate of 2.40 g per plant d-1 (18% higher than those of the lowyielding hybrids) and a relatively longer effective grain-filling duration. Grain-filling rate and effective grain-filling duration had high coefficients of genetic determination, positive correlations with grain yield, low error terms, and low genotype × environment interactions, making them appropriate selection traits for improved grain yield. The study shows that it is possible to develop high-yielding early- to medium-maturing maize hybrids based on favorable combining ability values for grain-filling rate and duration.
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    Indirect selection for resistance to Stenocarpella maydis and Fusarium graminearum and the prospects of selecting for high-yielding and resistant maize hybrids
    (Plant Breeding, 2016) Tembo, Langa; Asea, Godfrey; Gibson, Paul T.; Okori, Patrick
    Stenocarpella maydis and Fusarium graminearum affect grain yield and quality as a result of mycotoxins produced. A negative association of yield with resistance to cob rots has been reported. The objectives of this study were therefore to investigate the influence of cob characteristics on the response to F. graminearum and S. maydis disease reaction and evaluate the prospects of direct selection for high-yielding and resistant maize hybrids. In this study, the pathogens were directly introduced to the cob through toothpick inoculation. Correlation of husk cover to diseaseseverity of each pathogen, separately toothpick inoculated, was significant(P < 0.01). However, the low r values (<0.45) of traits associated with the response to inoculation by S. maydis and F. graminearum imply that indirect selection would not be beneficial for obtaining the type of resistance shown under inoculation. Several hybrids combined good yields with at least moderate resistance to both pathogens.
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    A New Cheap and Efficient Single-Grain Shatter Tester for Use in Rice Breeding
    (Crop science, 2011) Lamo, Jimmy; Tongoona, Pangirayi; Okori, Patrick; Derera, John; Hendricks, Roelof; Laing, Mark
    Grain shattering, also called grain shedding, is the relative ease with which rice (Oryza sativa L.) seed is dislodged from the pedicel at maturity. Several qualitative methods have been used to assess grain shattering and they tend to underestimate yield loss. Equipments available for quantitative assessment of grain shattering are mostly laboratory based. However, a recently developed prototype in Japan for fi eldwork can be used, but the cost is prohibitive. An improved grain-shattering tester that uses a hand-held device has been developed and reported here. It is an improvement over the stationary laboratory device. It has the following modifi cations: a crocodile clip instead of a bench clamp and a helical spring for testing tensile material instead of tension gauge. The new device is affordable, handy for fi eldwork, and effective for large experimental trials. This equipment was designed and developed at the University of KwaZulu-Natal (UKZN) mechanical workshop (Pietmeritzburg, South Africa). Its effi ciency was tested at the National Crops Resources Research Institute (NaCRRI) at Namulonge, Uganda. The effi ciency was tested by fi rst estimating yield loss in selected test plants using a method that involves shaking panicles. This fi nding was compared with the minimum force required to dislodge the grains using this new device and a high correspondence of R2 = 99.9% was found. This new equipment has therefore been recommended for fi eld assessment of grain shattering.
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    Reaction of Waxy and Opaque-2 Inbreds and their Derived Progenies to Multiple Foliar Diseases of Maize in Uganda
    (Journal of Agricultural Science, 2012) Bombom, Alexander; Okori, Patrick; Gibson, Paul; Edema, Richard; Asea, Godfrey; Rubaihayo, Patrick
    Specialty maize lines possessing important endosperm genes waxy and/or opaque-2 enhance processing and nutritional qualities of the grain. However, production and utilization of specialty maize varieties for food, feeds and various industrial end-uses are constrained by endemic foliar diseases of maize including turcicum leaf blight, gray leaf spot and maize streak virus disease. The purpose of this study was to investigate the reaction of two specialty maize genotypes (waxy and opaque-2) and their derived F1, F2 and backcross progenies to multiple foliar diseases of maize. A randomized complete block design was used to evaluate these materials under field conditions in Uganda. Significant differences among populations were observed for susceptibility to turcicum leaf blight and maize streak virus disease. The opaque-2 inbred CML182 did not manifest any maize streak virus disease symptoms during the assessment period. Significant differences were observed for susceptibility to maize streak virus disease between reciprocal crosses but not for turcicum leaf blight suggesting possible maternal effects associated with maize streak virus disease resistance. Susceptibility to turcicum leaf blight and maize streak virus disease was associated with the recessive endosperm genes (waxy and opaque-2). These results show that developing waxy and opaque-2 specialty maize varieties with good agronomic and grain quality attributes is dependent on the choice of parents carrying important resistance as well as endosperm modifying genes.
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    Variability of grain-filling traits in early maturing CIMMYT tropical maize inbred lines
    (Crop Science, 2019) Gasura, Edmore; Setimela, Peter S.; Tarekegne, Amsal; Icishahayo, David; Edema, Richard; Gibson, Paul T.; Okori, Patrick
    This paper examines the relationship between positive deviance and entrepreneurial networking among small and medium enterprises (SMEs). Using a mixed method approach combined self-administered questionnaires and interview guide covering 228 SMEs in Uganda, the cross-sectional nature of this study revealed key nuances about SMEs. The research findings confirmed a significant positive relationship between positive deviance and entrepreneurial networking among SMEs in Uganda. The findings also revealed that: SME owner/ managers should create enabling environment for people with divergent views to interact with each other to innovate new practices, such as accessing resources from the networks; managers should initiate new policies for error management to allow employees room to learn from mistakes; managers should acquire new skills of leadership skills to manage and utilize the knowledge and skills of positive deviants. This research therefore contributes to existing scholarship by providing nuances in the study of positive deviance and entrepreneurial networking among SMEs in Uganda through employing a complexity approach that transcends previous academic focus on social network theory.