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Otim, M.

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Otim
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Otim, M.
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AGROVOC: PEST RESISTANCE × Author: Mwololo, J. ×

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Now showing 1 - 3 of 3
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    Quantitative trait loci mapping in maize for resistance to larger grain borer
    (Consiglio per la Ricerca e la Sperimentazione in Agricoltura, 2018) Mwololo, J.; Mugo, S.N.; Otim, M.; Munyiri, S.W.; Okori, P.
    Storability of maize grain is constrained by the larger grain borer (LGB) (Prostephanus truncatus). Host plant resistance is the most feasible way to manage LGB among smallholder farmers. Breeding for resistance to this pest in maize is dependent on understanding genetic mechanisms underlying the resistance. The objective of this study was to map quantitative trait loci (QTL) associated with LGB resistance in tropical maize. A mapping population of 203 F2:3 derived progenies was developed from a cross between susceptible and resistant inbred lines. The F2:3 progenies were crossed to a tester and testcrosses evaluated across six environments followed by screening for resistance to LGB. Data was collected on husk cover tip length, and grain texture in the field. Biochemical traits were analyzed on the maize grain. Harvested grain was evaluated for resistance and data recorded on grain damage, weight loss and number of insects. Grain hardness was measured as a putative trait of resistance. Univariate analysis of variance for all the traits was done using the general linear model of statistical analysis system. Genetic mapping was done using Joinmap 4, while QTL analysis was done using PLABQTL. The QTL for resistance were mapped to 6 out of the 10 chromosomes. QTL for resistance traits were located in chromosomes 1, 5 and 9. Chromosome 1 had a common QTL linked to protein content, grain hardness and husk cover tip length. Additive genetic effects were prevalent in all detected QTL. Overall, the studies show that breeding for resistance to LGB is possible.
    Publication
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    Responses of tropical maize landraces to damage by Chilo partellus stem borer
    (Academic Journals, 2013) Munyiri, S.W.; Mugo, S.N.; Otim, M.; Tadele Tefera; Beyene, Y.; Mwololo, J.; Okori, P.
    The potential to manage insect pests using host-plant resistance exists, but has not been exploited adequately. The objective of this study was to determine the resistance of 75 tropical maize landraces through artificial infestation with Chilo partellusSwinhoe. The trial was laid in alpha-lattice design and each seedling was infested with five neonates three weeks after planting, over two seasons in 2009 and 2010. The number of exit holes, tunnel length, ear diameter, ear length, plant height, stem diameter, stem lodging and grain yield were measured and a selection index computed. GUAT 1050 was the most resistant with an index of 0.56, while BRAZ 2179 was the most susceptible with an index of 1.66. Ear characteristics were negatively correlated with damage parameters. The principal component biplot suggested that exit holes, cumulative tunnel length, leaf damage, cob diameter, stem lodging, selection index, ear and plant height contributed 71.2% of the variation in resistance. The mean number of exit holes and tunnel length for resistant landraces and resistant hybrid checks were similar; at 5.5 and 2.48 cm, respectively. The identified resistant landraces (GUAT 1050, GUAT 280, GUAT 1093, GUAT 1082, GUAT 1014, CHIS 114, and GUAN 34) could be used to develop C. partellus stem borer-resistant maize genotypes.
    Publication
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    Sources of resistance to the maize weevil Sitophilus Zeamais in tropical maize
    (Canadian Center of Science and Education, 2012) Mwololo, J.; Mugo, S.N.; Okori, P.; Tadele Tefera; Otim, M.; Munyiri, S.W.
    The maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), is among the major storage pests that enhance food insecurity among maize farmers. New sources of resistance to the maize weevil are critical in a successful breeding program to address grain damage by postharvest pests. The objective of the study was to evaluate resistance in maize genotypes to the maize weevil, and consequently their value for use in breeding programs. A total of 175 genotypes, including hybrids, landraces, open-pollinated varieties and checks, were tested for resistance to the maize weevil. The percentage grain damage, weight loss, flour weight and weight of damaged and undamaged grains were measured. Significant differences (P <0.001) were observed among the genotypes for all the traits evaluated. The distribution of the genotypes among the different categories of resistance was an indication of the existence of genetic variation. The most resistant genotypes were CKPH08003 and BRAZ 2451 while the most susceptible were PH 3254 and BRAZ 4, among the hybrids and landraces respectively. Genotypes that were superior to the resistant checks were identified. The percentage weight loss and flour weight were identified as the most important insect-resistance traits for discriminating genotypes as evident from the canonical discriminant analysis. Correlation coefficients among the traits evaluated were highly significant. The resistant hybrids identified can be recommended for release and adoption by farmers, whereas the resistant landraces can act as sources of resistance for use in breeding programs.
    Publication