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Mwimali, M.

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Mwimali
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Mwimali, M.

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    Resistance of Bt-maize (MON810) against the stem borers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) and its yield performance in Kenya
    (Elsevier, 2016) Tadele Tefera; Mugo, S.N.; Mwimali, M.; Bruce, A.Y.; Tende, R.; Beyene, Y.; Gichuki, S.T.; Oikeh, S.O.; Nang’ayo, F.; Okeno, J.; Njeru, E.; Pillay, K.; Meisel, B.; Prasanna, B.M.
    A study was conducted to assess the performance of maize hybrids with Bt event MON810 (Bt-hybrids) against the maize stem borer Busseola fusca (Fuller) in a biosafety greenhouse (BGH) and against the spotted stem borer Chilo partellus (Swinhoe) under confined field trials (CFT) in Kenya for three seasons during 2013e2014. The study comprised 14 non-commercialized hybrids (seven pairs of near-isogenic Bt and non-Bt hybrids) and four non-Bt commercial hybrids. Each plant was artificially infested twice with 10 first instar larvae. In CFT, plants were infested with C. partellus 14 and 24 days after planting; in BGH, plants were infested with B. fusca 21 and 31 days after planting. In CFT, the seven Bt hybrids significantly differed from their non-Bt counterparts for leaf damage, number of exit holes, percent tunnel length, and grain yield. When averaged over three seasons, Bt-hybrids gave the highest grain yield (9.7 t ha1), followed by non-Bt hybrids (6.9 t ha1) and commercial checks (6 t ha1). Bt-hybrids had the least number of exit holes and percent tunnel length in all the seasons as compared to the non-Bt hybrids and commercial checks. In BGH trials, Bt-hybrids consistently suffered less leaf damage than their non-Bt near isolines. The study demonstrated that MON810 was effective in controlling B. fusca and C. partellus. Bt-maize, therefore, has great potential to reduce the risk of maize grain losses in Africa due to stem borers, and will enable the smallholder farmers to produce high-quality grain with increased yield, reduced insecticide inputs, and improved food security.
    Publication
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    Response to S1 recurrent selection for resistance to two stem borers, Busseola fusca and Chilo partellus, in two tropical maize populations
    (Springer, 2015) Mwimali, M.; Derera, J.; Mugo, S.N.; Tongoona, P.
    Stem borers, Busseola fusca and Chilo partellus, are among the key devastating lepidopteran insect pests ofmaize causing grain yield losses.Recurrent selection studies for stem borer resistance in maize are limited. However, maize populations carrying resistance genes to these stem borers have not been exploited fully in breeding programmes. The objective of the study was to separately improve resistance to B. fusca and C. partellus stem borers for two maize populations CML395/MBR C5 Bc and CML444/MBR/MDR C3Bc and therefore grain yield after two cycles of S1 progeny recurrent selection. Cycle 0 and the advanced generations (cycle 1-susceptible, cycle 1-resistant and cycle 2-resistant) were evaluated at three locations in Kenya using a 35 9 12 a-lattice design with 2 replications. The net reductions in cumulative tunneling, number of exit holes and leaf feeding damage scores ranged from0 to 69 %for both populations after two cycles of selection. In the two populations, each cycle of selection for borer resistance improved grain yield by 0.5–0.8 t ha-1. Actual net gains in grain yield with reference to cycle 0 were 43 % for population CML395/MBRC5 Bc under B. fusca infestation and 70 % under C. partellus infestation. For population CML444/MBR/MDR C3Bc, the actual net gains in grain yield were 25 %under B. fusca infestation and 36 % under C. partellus infestation. The reductions in the injurious effects attributable to leaf feeding damage, cumulative stem tunneling and number of exit holes contributed towards the 43 and 70 % net genetic gain in grain yield under B. fusca and C. partellus infestation respectively, for both populations. Broad sense heritability (H2) for grain yield ranged from 2 to 98 % in both maize populations. The study showed that two cycles of S1 progeny recurrent selection was effective in accumulating favourable alleles for B. fusca and C. partellus stem borer resistance.
    Publication
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    Testing public Bt maize events for control of stem borers in the first confined field trials in Kenya
    (Academic Journals, 2011) Mugo, S.N.; Mwimali, M.; Taracha, C.; Songa, J.M.; Gichuki, S.T.; Tende, R.; Karaya, H.; Bergvinson, D.J.; Pellegrineschi, A.; Hoisington, D.A.
    Transgenic maize (Zea mays L), developed using modified genes from the bacterium Bacillus thuringiensis (Bt), controls stem borers without observable negative effects to humans, livestock or the environment, and is now sown on 134 million hectares globally. Bt maize could contribute to increasing maize production in Kenya. Nine public Bt maize events of cry1Ab and cry1Ba genes were tested in confined field trials site (CFTs) to assess the control of four major Kenyan stem borer species. Leaf damage rating, number of exit holes and tunnel length were scored in the field evaluations. Leaf area consumed and mortality rates among stem borers were scored in the leaf bioassays in a Biosafety Level II laboratory, located at the Kenya Agricultural Research Institute (KARI), National Agricultural Research Laboratories (NARL). Field evaluations showed that Bt maize controlled Chilo partellus with mean damage scores of 1.2 against 2.7 for the non-Bt CML216 control. Laboratory bioassays showed high control for Eldana saccharina and Sesamia calamistis, with mean larval mortality of 64 and 92%, respectively. However, substantial control was not observed for Busseola fusca. These results showed that Bt maize could control three of the four major stem borers in Kenya with mortality records of 52.7% for B. fusca, 62.3% for E. saccharina and 85.8% for S. calamistis. Additional Bt genes need to be sought and tested for effective stem borer control in all maize growing ecologies in Kenya.
    Publication
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    Experiences with the biosafety regulatory system in Kenya during the introduction, testing and development of Bt maize
    (Academic Journals, 2011) Mugo, S.N.; Gichuki, S.T.; Mwimali, M.; Taracha, C.; Macharia, H.
    The introduction of genetically modified (GM) crops in Kenya is governed by a biotechnology policy, a biosafety law, and a biotechnology awareness strategy to enable research and development of GM crops. In addition, Kenya has the National Biosafety Authority (NBA) that regulates plant biosafety through technical institutions including the Kenya Plant Health Inspectorate Services (KEPHIS). Bacillus thuringiensis (Bt) maize for stem borer pest control was imported and tested under this regulatory system. The Insect Resistant Maize for Africa (IRMA) project aimed at developing and deploying transgenic Bt maize for stem borer control in Kenya. The IRMA project developed and implemented an internal biosafety strategy. To comply with and implement the biosafety regulations, IRMA set-up biosafety facilities to develop, maintain and test the Bt maize. These included a biosafety level 2 laboratory, a biosafety level 2 greenhouse containment and a confined field trial site, which also provided valuable models to national and international interests. IRMA also developed protocols for the use and disposal of transgenic plant materials, and also generated data for guidance on post-harvest monitoring at Bt-maize trial sites. IRMA also trained Kenyan administrators, scientists, technicians and regulators on conducting and handling GM trials. Training included informal courses, seminars, scientists? visits to established institutes, and support to research for degree related training. The project, therefore, provided major inputs in the development and advancement of biotechnology framework in Kenya. This paper reports on the achievements realized, challenges encountered by IRMA, and lessons learnt in research and development of GM crops in Kenya
    Publication