Browsing by Author "Kyamanywa, S."

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    Farmer-participatory Evaluation of Cowpea integrated Pest Management (IPM) Technologies in Eastern Uganda
    (Crop Protection, 2003) Nabirye, J.; Nampala, P.; Ogenga-Latigo, M.W.; Kyamanywa, S.; Odeke, V.; Adipala, E.
    A three-season study was conducted with the goal of verifying integrated pest management (IPM) technologies developed at Makerere University for management of cowpea field pests. Ten IPM-field schools with 10–20 farmers were run for three consecutive seasons of 2000 A (first rains), 2000 B (second rains), and 2001 A. Each school evaluated seven treatments that included farmers’ practices; cowpea monoculture and cowpea/sorghum intercrop mixtures, and five varying insecticide spray regimes. The key insect pests targeted by the sprays included aphids, Aphis craccivora Koch, flower thrips, Megalurothrips sjostedi Trybom, the legume pod borer, Maruca vitrata Fabricius (formerly M. testularis Geyer), and a range of pod sucking bugs (i.e., Nezera viridula Linnaeus, Clavigralla tomentosicollis Stal., Riptortus dentipes Fab.). The experiment was a randomized complete block design with farms (i.e., field schools) as replicates. Results indicated that combining cultural practices and spraying once each at budding, flowering, and podding stages was more effective and profitable than spraying cowpea weekly throughout the growing season. An IPM practice which combined early planting, close spacing cowpea (30×20cm2), and three insecticide applications once each at budding, flowering and podding stages, had the highest yields of 791kg/ha with a 51% yield gain over the farmers’ traditional practices. Farmer evaluation over the three seasons revealed that this practice was most preferred by farmers, with a farmer preference of 46.4%, 57.1%, 71.4%, and 89.3% at planting, vegetative, flowering and harvesting evaluation stages, respectively.
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    Genetic Basis of Maize Resistance to Multiple Insect Pests: Integrated Genome-Wide Comparative Mapping and Candidate Gene Prioritization
    (Genes, 2020) Badji, A.; Kwemoi, D. B.; Machida, L.; Okii, D.; Mwila, N.; Agbahoungba, S.; Kumi, F.; Ibanda, A.; Bararyenya, A.; Solemanegy, M.; Odong, T.; Wasswa, P.; Otim, M.; Asea, G.; Ochwo-Ssemakula, M.; Talwana, H.; Kyamanywa, S.; Rubaihayo, P.
    Several species of herbivores feed on maize in field and storage setups, making the development of multiple insect resistance a critical breeding target. In this study, an association mapping panel of 341 tropical maize lines was evaluated in three field environments for resistance to fall armyworm (FAW), whilst bulked grains were subjected to a maize weevil (MW) bioassay and genotyped with Diversity Array Technology’s single nucleotide polymorphisms (SNPs) markers. A multi-locus genome-wide association study (GWAS) revealed 62 quantitative trait nucleotides (QTNs) associated with FAW and MW resistance traits on all 10 maize chromosomes, of which, 47 and 31 were discovered at stringent Bonferroni genome-wide significance levels of 0.05 and 0.01, respectively, and located within or close to multiple insect resistance genomic regions (MIRGRs) concerning FAW, SB, and MW. Sixteen QTNs influenced multiple traits, of which, six were associated with resistance to both FAWandMW, suggesting a pleiotropic genetic control. Functional prioritization of candidate genes (CGs) located within 10–30 kb of the QTNs revealed 64 putative GWAS-based CGs (GbCGs) showing evidence of involvement in plant defense mechanisms. Only one GbCG was associated with each of the five of the six combined resistance QTNs, thus reinforcing the pleiotropy hypothesis. In addition, through in silico co-functional network inferences, an additional 107 network-based CGs (NbCGs), biologically connected to the 64 GbCGs, and di erentially expressed under biotic or abiotic stress, were revealed within MIRGRs. The provided multiple insect resistance physical map should contribute to the development of combined insect resistance in maize.
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    Genomic Prediction of Tropical Maize Resistance to Fall Armyworm and Weevils: Genomic Selection Should Focus on Effective Training Set Determination
    (ResearchGate, 2020) Badji, A.; Machida, L.; Kwemoi, D. B.; Kumi, F.; Okii, D.; Mwila, N.; Agbahoungba, S.; Ibanda, A.; Bararyenya, A.; Nghituwamhata, S. N.; Odong, T.; Wasswa, P.; Otim, M.; Ochwo-Ssemakula, M.; Talwana, H.; Asea, G.; Kyamanywa, S.; Rubaihayo, P.
    Genomic selection (GS) can accelerate variety release by shortening variety development phase when factors that influence prediction accuracies (PA) of genomic prediction (GP) models such as training set (TS) size and relationship with the breeding set (BS) are optimized beforehand. In this study, PAs for the resistance to fall armyworm (FAW) and maize weevil (MW) in a diverse tropical maize panel composed of 341 double haploid and inbred lines were estimated. Both phenotypic best linear unbiased predictors (BLUPs) and estimators (BLUEs) were predicted using 17 parametric, semi-parametric, and nonparametric algorithms with a 10-fold and 5 repetitions cross-validation strategy. n. For both MW and FAW resistance datasets with an RBTS of 37%, PAs achieved with BLUPs were at least as twice as higher than those realized with BLUEs. The PAs achieved with BLUPs for MW resistance traits: grain weight loss (GWL), adult progeny emergence (AP), and number of affected kernels (AK) varied from 0.66 to 0.82. The PAs were also high for FAW resistance RBTS datasets, varying from 0.694 to 0.714 (for RBTS of 37%) to 0.843 to 0.844 (for RBTS of 85%). The PAs for FAW resistance with PBTS were generally high varying from 0.83 to 0.86, except for one dataset that had PAs ranging from 0.11 to 0.75. GP models showed generally similar predictive abilities for each trait while the TS designation was determinant. There was a highly positive correlation (R=0.92***) between TS size and PAs for the RBTS approach while, for the PBTS, these parameters were highly negatively correlated (R=-0.44***), indicating the importance of the degree of kinship between the TS and the BS with the smallest TS (31%) achieving the highest PAs (0.86). This study paves the way towards the use of GS for maize resistance to insect pests in sub-Saharan Africa.
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    Maize resistance to stem borers and storage pests: The need for new genetic and functional genomics approaches in future research
    (African Journal of Rural Development, 2017) Badji, A.; Otim, M.; Machida, L.; Odong, T.L.; Kyamanywa, S.; Rubaihayo, P.
    Insect pests are primary constraints in maize (Zea mays) production in many places in sub-Saharan Africa. Stem borers and storage pests are responsible for severe yield losses and health hazards due to mycotoxin contamination. Integrated pest management (IPM) strategies have moved from control methods and transgenic resistance to recognizing the necessity of host plant resistance (HPR) especially in the context of an ever changing climate and its forecasted negative consequences. For that, a wealth of scientific knowledge has been generated over the years although the goals are far to be reached. Here, we first review current literature on maize resistance mechanisms as regards to insect herbivory. We show that there are numerous insect species that feed on maize before narrowing down to stem borers and storage pests. We also look at the basis of maize resistance in terms of its biochemical components and analyze the progress of genetic studies in terms of QTL mapping and trait genes identification. Finally, we highlight the usefulness of new genetic and functional genomic approaches in underpinning the genetic basis of maize resistance to insect pests in general and particularly stem borers and storage pests.
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    Oviposition preference and offspring performance of Crocidolomia pavonana (Lepidoptera: Pyralidae) on different host plants
    (Journal of Applied Entomology, 2010) Karungi, J.; Lubanga, U. K.; Kyamanywa, S.; Ekbom, B.
    The cabbage head caterpillar Crocidolomia pavonana (Fabricius) (Lepidoptera: Pyralidae) is an increasingly devastating pest on white cabbage (Brassica oleracea var. capitata) in Uganda. Screen house and field trials were used to assess oviposition preference and offspring performance of C. pavonana on six hosts in the genus Brassica: kale (B. oleracea var. acephala), cauliflower (B. oleracea var. botrytis), broccoli (B. oleracea var. italica), Chinese cabbage (B. campestris spp. pekinensis), Indian mustard (B. juncea (L.) Czern.) and white cabbage (B. oleracea var. capitata). To assess oviposition preference, the hosts were offered to C. pavonana in multiple-choice (all six); two-choice (cabbage with each of the other hosts) or cabbage-only situations. After specified oviposition periods, egg numbers on individual plants were recorded. To determine C. pavonana offspring performance on the six hosts, whole plants were placed in individual cages, where larvae were monitored for development time, pupal weight and foliage consumption. Results of the choice tests indicated that C. pavonana preferred Chinese cabbage and broccoli for oviposition. In two-choice arrangements, all the tested host plants were able to greatly reduce oviposition on white cabbage (69–100%) when compared with the monocrop. Chinese cabbage was the most suitable host with regard to C. pavonana offspring performance as demonstrated by the shortest development time and highest pupal weight. Chinese cabbage and broccoli can be used as traps for the pest but the resulting larvae should be destroyed regularly to prevent accumulation in the system.
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    Portable PCR field-based detection of sweetpotato viruses
    (African Crop Science Journal, 2020) Ssengo, J.; Wasswa, P.; Mukasa, S.B.; Okiror, A.; Kyamanywa, S.
    Sweetpotato (Ipomoea batatas Lam.) production is greatly constrained by viral infections, especially Sweet potato feathery mottle virus and Sweet potato chlorotic stunt virus that synergistically cause a severe sweetpotato virus disease. The impact of viruses is aggravated by the vegetative nature of the crop and inaccessibility to dependable diagnostic tools in rural areas where sweetpotato production is done. This makes it hard for seed inspectors to perform quality checks prior to use of vines for planting. The objective of this study was to develop a procedure that allows for detection of sweetpotato viruses on-site. This involved modification of the Lodhi et al. (1994) nucleic acid extraction procedure, by omitting some of the laboratory specific steps and varying the incubation time in liquid nitrogen, instead of the freezer. Incubation in liquid nitrogen for only 1.5 hours yielded as high quality RNA compared to that of the original protocol, when incubation was done at 4°C overnight in a freezer. Reverse transcriptase (RT) was run using a portable miniPCR thermocycler; and the resulting cDNA was amplified using this miniPCR machine instead of using a laboratory stationed conventional PCR thermocycler. The cDNA was efficiently amplified and amplicons were similar to those obtained with the original extraction protocol and subsequent amplification by the conventional RT-PCR. Our protocol reduced extraction time from about 16 hours for the original protocol, to about 2 hours and 45 minutes. If this tool is utilised by the crop protection departments, we believe it will contribute greatly towards sustainable sweetpotato production through making timely recommendations.
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    Relating shading levels and distance from natural vegetation with hemipteran pests and predators occurrence on coffee
    (Journal of applied entomology, 2015) Karungi, J.; Nambi, N.; Ijala, A. R.; Jonsson, M.; Kyamanywa, S.; Ekbom, B.
    The study was carried out to determine the effect of shading levels and/ or distance from the natural alpine vegetation (NAV) on the occurrence of two insect functional groups: hemipteran herbivores and generalist predators in farmers’ coffee fields in the Mt. Elgon region of Uganda. Three distance categories from the NAV, that is (i) 0–250 m; (ii) 250– 1000 m and (iii) 1000–1500 m, were used to demarcate farms in the first stage of selection, and within each distance category, three levels of shading, that is (i) no shade, (ii) moderate shade and (iii) full shade, were used for final selection of coffee farms for the study. A total of 90 individually owned coffee fields were studied; 30 for each distance category, of which 10 represented each shading level. In two separate rounds, inventories of scale insects (Coccus spp.), antestia bugs (Antestiopsis spp.), root mealybugs (Planococcus spp.) and aphids (Toxoptera aurantii) on coffee plants were made for the hemipteran herbivores, whereas ants (Formicidae) and spiders (Araneae) were recorded for the predatory taxa. The results showed that the interaction between distance from the NAV and shading level consistently influenced the occurrence of the insects in both functional groups. For scale insects, root mealybugs and ants, it was closest to the NAV that shading-level effects were most discernible and generally limiting. To the contrary, the occurrence of aphids and spiders increased with the increase in the level of shading for plants furthest from the NAV. These results indicate that if inclusion of shade trees is to be a strategy in ecological pest management, the level of shading should be determined basing on the insect taxa as well as other pertinent factors in the landscape.