Browsing by Author "Gibson, Paul T."
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Item 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, AmsalEarly-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.Item Harnessing genotype-by-environment interaction to determine adaptability of advanced cowpea lines to multiple environments in Uganda(Journal of Plant Breeding and Crop Science, 2020) Abiriga, Francis; Ongom, Patrick O.; Rubaihayo, Patrick R.; Edema, Richard; Gibson, Paul T.; Dramadri, Isaac; Orawu, MartinThis study was conducted to determine the yield stability of advanced cowpea lines in diverse agroecological zones of Uganda in order to facilitate documentation requirements for national performance trials (NPT). Thirty cowpea genotypes were evaluated against six checks in three localities, over three growing seasons, making a total of 9 unique environments. The trials were laid in a 6x6 alpha lattice design with three replications and grain yield was the principal trait measured. Single-site and multilocation data were summarized using analysis of variance. Further analysis of stability was visualized using the genotype and genotype by environment interaction (GGE) biplot and the additive main effect and multiplicative interaction (AMMI) models. ANOVA depicted highly significant differences among the genotypes, locations, seasons and GEI for grain yield. Based on AMMI analysis, environmental effect accounted for the most variation (84.7%) in the phenotype followed by GE (9.45%) and genotypes (4.45%), alluding to the complex inheritance of grain yield in cowpea. The polygon view and the average environment coordination view of the GGE biplot revealed Ayiyi as the wining genotype in the major mega environment and the most stable and high yielding across environments respectively. The genotypes Ayiyi, WC64 and ALEGIxACC2 yielded higher than the checks and were very stable. The other genotypes G36 (WC 36), G3 (ACC12xSECOW3B), G32 (WC16), and G14 (MU9) did not outperform the checks but displayed high yield stability and the mean yields were above the overall average. These genotypes were considered desirable for advancement to National Performance Trial for potential release as new improved cowpea cultivars.Item 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, PatrickStenocarpella 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.Item 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, PatrickThis 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.