NRU :: Browsing by Author "Okori, Patrick"

Browsing by Author "Okori, Patrick"

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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.
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.
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.
Genotype by Environment Interaction in Sesame (Sesamum indicum L.) Cultivars in Uganda
(African Journal of Plant Science, 2016-10-31) Okello-Anyanga, Walter; Rubaihayo, Patrick; Paul, Gibson; Okori, Patrick
Sesame (Sesamum indicum L.) is an important and ancient oilseed crop cultivated in hot, dry climates for its oil and protein rich seeds. On the African continent, Uganda ranks seventh in sesame production. The improvement of new genotypes with the desired yield stability and performance in different environments is an important issue in breeding programs. In order to identify high yielding and stable sesame genotypes across environments, field experiments were conducted with 16 genotypes for four seasons (2011-2013) at three locations, viz. Serere, Kaberamaido and Ngetta. The objective of the study was to use additive main effects and multiplicative interaction (AMMI) and genotype by genotype environment interaction (GGE) biplot statistical analysis to identify the stability and yield potential of sixteen sesame genotypes. The results of AMMI analysis of variance for seed yield (kg/ha) showed that all the sources of variations that included treatments, genotypes, environments, blocks, interactions, IPCA1 and IPCA 2 were highly significant (P<0.001). The combined analysis of variance indicated that season, season x location, genotype and location x genotype had highly significant (P<0.001) variation. The GGE biplot suggested the existence of only one sesame mega-environment with genotype G9 (Local 158-1) best adapted in that mega-environment followed by G1 (Ajimo A1-6//7029)-1-1. The mega-environment had environments K2011B, K2012A, K2012B, N2012B and K2013B. The vertex genotypes which indicated that they were the most responsive in their respective environments were G2 (Ajimo A1-6//7029)-1-9, G3 (Local 158//6022)-1-2-1, G8 (EM15-3-2), G9 (Local 158-1), G12 (Renner 1-3-1-16) and G14 (Renner 1-3-1-17-1). Genotypes G2 and G12 performed poorly in poor environments. Genotypes were categorized into stable and high yielding, stable but poor yielding, unstable but good yielding and unstable and poor yielding. Environment K2013B was the most discriminating environment. According to the ideal-genotype biplot, genotype G9 (Local 158-1) was the best performing genotype and Kaberamaido was the nearest to ideal environment. It was officially released as Sesim 3 variety for commercial production because of its yield, stability, tolerance to pests and high oil content.
Identification of Blast Resistant Genotypes among Drought Tolerant Finger Millet in Uganda
(East African Nature and Science Organization, 2020-11-03) Aru, John Charles Aru; Wanyera, Nelson; Okori, Patrick; Gibson, Paul
Finger millet is an important food security crop among many subsistence farmers living in marginal and especially semi-arid regions of Eastern Africa. However, crop production is affected mainly by terminal drought and blast disease caused by fungus Pyricularia grisea. Both collectively lead to over 90% grain yield loss depending on environmental conditions, cropping systems and varietal differences. Therefore, resistance breakdown remains high owing to variability in the blast pathogen and weather conditions. Stable varieties should possess both blast resistance and drought. In order to initiate breeding for multiple resistance to blast on drought-tolerant background, a study was conducted to identify variability for blast resistance from adapted germplasm as an initial step in developing a breeding strategy for incorporating resistance. Thirty genotypes from drought-prone agro-ecologies and including mini core germplasm from NARO-NaSARRI national Finger Millet improvement programme were assessed. They were screened using a local virulent pathogen isolate (NGR1) from Ngora, representing Teso major farming system and is a hot spot for the blast. The screening was under controlled conditions from in Makerere University Agricultural Research Institute (MUARIK) in 2012b. The results showed significance (p<0.01) for Area Under Disease Progressive Curve (AUDPC). Subsequently, the study identified IE927, Seremi1, Seremi3, Sec220 and Kabale as highly resistant to foliar blast infection comparable to Gulu-E a standard broad-spectrum resistant check and they could be used to improve finger millet for blast resistance. Meanwhile DR33, IE9 and IE2576 as most susceptible compared to non-race -specific susceptible check E11 from Uganda.
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.
Interactive effects of host, pathogen and mineral nutrition on grey leaf spot epidemics in Uganda
(European Journal of Plant Pathology, 2004-02-08) Okori, Patrick; Rubaihayo, Patrick R.; Ekwamu, Adipala; Christina, Dixelius
Grey leaf spot incited by Cercospora zeae-maydis is a new devastating foliar disease of maize in East Africa. For effective control, elucidation of the most critical elements of the grey leaf spot disease pyramid is important. This study investigated the role of mineral nutrition, pathogen variability and host resistance in the epidemic. Trials were conducted under field and controlled environments. The 28 isolates used in the controlled environment varied significantly (P ≤ 0.05) in parasitic fitness measured indirectly as disease efficiency, but no infection pattern could be attributed to known C. zeae-maydis pathotypes. Data from field trials showed that host resistance and mineral nutrition significantly (P ≤ 0.05) affected disease efficiency, with highest disease development occurring in nitrogen-augmented plots. Exclusive phosphorus application had no clear effect on grey leaf spot epidemics but combined application with nitrogen significantly (P ≤ 0.05) reduced the predisposition effects of nitrogen to the disease. Overall, treated plots had less disease than unfertilised plots. Fertiliser application had no effect on sporulation capacity, while cultivars significantly affected it. Geographic differences in amount of disease were observed, suggesting environment influences on grey leaf spot incidence. The results suggest that the current grey leaf spot epidemics in East Africa are due to favourable cultivars, poor mineral nutrition and environmental interactions.
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.
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.
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.

Browsing by Author "Okori, Patrick"

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