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.
Source: Resistance of Bt-maize (MON810) against the stem borers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) and its yield performance in Kenya
Authors: Mwimali, M., Derera, J., Mugo, S.N., Tongoona, P.
Published in: Euphytica, In Press.
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.
Published in African Journal Biotechnology 12 (11) : 1229-1235, 2013
Munyiri, S.W.; Mugo, S.N.; Otim, M.; Tadele Tefera; Beyene, Y.; Mwololo, J.K.; 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.
Published in African Journal of Biotechnology 12 (34) : 5370-5374, 2013
Mutisya. D.L.; Tadele Tefera; Mugo, S.
The quality of laboratory reared stem borer species for screening of maize varieties is usually questioned by end user cereal breeders. A quality check study was performed in a screen house at KARI-Katumani to evaluate the quality of eight-year old laboratory reared stem borer, Chilo partellus (Swinhoe). The evaluation was aimed at finding out the performance of the laboratory borers subjected to six-month interval of gene infusion in comparison with wild F1 generation of the same species collected from the field. One hundred (100) maize seedlings were grown on plastic pots of 5 by 5 cm and of 12 cm-height. The maize seedlings were infested with five first instar larvae on eight plants replicated four times for each borer ecotype. The wild ecotypes were collected from two different localities for comparison with eight-year old laboratory reared borers. Foliar damage, tunnel length on the maize stems and the recovered number of C. partellus larvae from the maize plants were used as the parameters for quality measure of the borer ecotypes. The laboratory-reared stem borer species had been subjected to frequent six-month gene-infusion interval from the wild. The results indicated feedvoracity drop of 3.8 and 21.5% for stem and foliar damage on the laboratory borer ecotype. The study established the need for continuous gene infusion to maintain high quality maize stem borer species as test organisms.
J. Gakunga, S. Mugo, K. Njoroge and F. Olubayo
Gene action conditioning important traits in maize is useful to breeders in order to design appropriate breeding methods. A study was conducted to determine the combining ability of 10 maize inbred lines adapted to Kenya’s mid-altitude environment and being resistant to spotted stem borer, Chilo partellus. The inbred lines were crossed in a diallel scheme and the resulting 45 single crosses were evaluated under conditions of artificial infestation at four locations in Kenya in 2008 and 2009. Data were recorded on grain yield, foliar damage, exit holes and tunnel length to plant height ratio. Significant differences (P<0.001) for foliar damage, exit holes, tunnel length to plant height ratio, and grain yield were found. General combining ability (GCA) and specific combining ability (SCA) gave significant differences for grain yield and exit holes. There was discord in GCA between grain yield and resistance traits among lines. The most favorable SCA for grain yield occurred in hybrid 5 × 7, while hybrids 7 × 10, 3 × 5 and 4 × 8 were superior in resistance. Our results suggest that the development of C. partellus resistant maize varieties should consider both grain yield and stem borer resistance traits. This study identified additive gene action as important in controlling stem borer resistance, stem borer resistant inbred line donors and elite single crosses.
Published in African Journal of Biotechnology 10(23):4725-4731, 2011
Levels of control of Chilo partellus stem borer in segregating tropical Bt maize populations in Kenya
Mwimali G. Murenga, Stephen M. Githiri, Stephen N. Mugo and Florence M. Olubayo
In Kenya, stem borers destroy an estimated 400,000 metric tons, or 13.5%, of farmers’ annual maize harvest costing about US$80 millions. Bacillus thuringiensis (Bt) maize controls stem borers without harming humans, livestock and the environment and was sown to 140m ha-1 globally in 2009. Two public Bt maize lines of cry1Ab::ubi gene (Event 216 and Event 223) were crossed with two non-Bt maize inbred lines, CML144 and CML159. The efficacy in the control of Chilo partellus stem borers in the parents, F1 and F2:3 successive generations were studied in a biosafety level 2 greenhouse. The Bt-gene effectively reduced stem borer damage with lower values for number of exit holes, tunneling length, proportion of stalk tunneled, number of larvae and number of pupae than the non Bt-maize and the check cultivars. The F1 generations values for all damage parameters studied were comparable to those for the Bt-maize inbred lines as expected. The F2:3 generations showed a spread of damage parameters from resistant to susceptible. These results suggest that the Cry1A(b) genes in the study was inherited following the Mendelian segregation.
Published in Crop Protection 29(2):115-120, 2010
Evaluation of Chilo partellus and Busseola fusca susceptibility to Delta-endotoxins in Bt maize
Regina M. Tende, Stephen N. Mugo, John H. Nderitu, Florence M. Olubayo, Josephine M. Songa, David J. Bergvinson
Susceptibility of Chilo partellus (Lepidoptera, Crambidae) and Busseola fusca (Lepidoptera, Noctuidae) populations to Cry proteins from the bacterium, Bacillus thuringiensis (Bt), the δ-endotoxins Cry1Ab and Cry1Ba in Bt-maize, were evaluated under biosafety greenhouse conditions. Larval feeding on Bt-maize was adjusted to deliver sub-lethal doses of δ-endotoxins from the two events; survivors were reared on artificial diet to obtain successive generations. Eight generations of three C. partellus populations and five generations of a B. fusca population were screened for susceptibility on each event. Mean proportion of surviving larvae from Bt-maize plants, and the corresponding pupal weights of survivors for each population, were lower for individuals exposed to δ-endotoxins. Both Bt Cry proteins expressed in maize leaves controlled C. partellus and showed stability in control, with no indication of a change in susceptibility among generations. Neither toxin, however, provided complete control of B. fusca, but no changes in susceptibility were observed after five generations of selection. Implications for development of future transgenic Bt maize events, and research for East Africa are discussed