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Murenga M.,University of KwaZulu - Natal | Murenga M.,Kenya Agricultural and Livestock Research Organization KALRO | Derera J.,University of KwaZulu - Natal | Mugo S.,International Maize and Wheat Improvement Center | Tongoona P.,University of KwaZulu - Natal
Maydica | Year: 2016

This paper provides a review on the context for the research in maize improvement for resistance to stem borers (Chilo partellus and Busseola fusca) in tropical environments. The following aspects are reviewed a) major productions constraints in East Africa, b) the stem borer problem in maize, c) genetic studies on maize resistance to stem borers. The explanations of key technical issues on progress and challenges in breeding for stem borer resistance in maize, inheritance of stem borer resistance and combining ability in maize, maize heterotic patterns, determination of heterotic orientations, application of the line x tester mating design, screening methods, selection indices, genotype x environment interactions, and response to selection for resistance to stem borers are addressed. Therefore, this paper forms a setting of reference for the study. © 2016, Consiglio per la Ricercame la sperimentazione in Agrcoltura. All rights reserved.

Mwimali M.,University of KwaZulu - Natal | Mwimali M.,Kenya Agricultural and Livestock Research Organization KALRO | Derera J.,University of KwaZulu - Natal | Mugo S.,International Maize and Wheat Improvement Center | Tongoona P.,University of KwaZulu - Natal
Euphytica | Year: 2015

Stem borers, Busseola fusca and Chilo partellus, are among the key devastating lepidopteran insect pests of maize 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 × 12 α-lattice design with 2 replications. The net reductions in cumulative tunneling, number of exit holes and leaf feeding damage scores ranged from 0 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. © 2015, The Author(s).

Muthoni J.,University of KwaZulu - Natal | Muthoni J.,Kenya Agricultural and Livestock Research Organization KALRO | Shimelis H.,University of KwaZulu - Natal | Melis R.,University of KwaZulu - Natal
Australian Journal of Crop Science | Year: 2015

In potatoes (Solanum tuberosum L. 2n=4x=48) both the general combining ability (GCA) effects of parents and specific combining ability (SCA) effects of crosses are important in conditioning traits of economic importance. The objective of this study was to determine the combining abilities for tuber yield, its components and bacterial wilt resistance on selected potato varieties and clones. Fourteen parents [eight male varieties that are commonly grown in Kenya and six female clones with moderate tolerance to bacterial wilt from the International Potato Center (CIP)] were crossed using the North Carolina II mating design. The resultant 48 families were evaluated for yield and yield components and bacterial wilt resistance in inoculated fields at Kenya Agricultural Research Institute, National Agricultural Research Laboratories (KARI-NARL) and at a farmer's field at Kinale using a 6 × 8 alpha lattice experimental design with three replications. Generally, crosses tested at Kinale took a longer time to start wilting, had lower values for the area under the disease progress curve (AUDPC), percentage of symptomatic tubers based on tuber numbers (PSTTN) and percentage of symptomatic tubers based on weight (PSTTW) than at KARI-NARL. Significant (P≤0.001) GCA effects were observed for males for total tuber weight (TTW) and days to maturity (DTM) while the GCA effects for females were significant (P≤0.001) for TTW and total tuber numbers ha-1(TTN)(P<0.01) at KARI-NARL.

Bajgain P.,Purdue University | Bajgain P.,University of Minnesota | Rouse M.N.,U.S. Department of Agriculture | Rouse M.N.,University of Minnesota | And 5 more authors.
PLoS ONE | Year: 2016

We combined the recently developed genotyping by sequencing (GBS) method with joint mapping (also known as nested association mapping) to dissect and understand the genetic architecture controlling stem rust resistance in wheat (Triticum aestivum). Ten stem rust resistant wheat varieties were crossed to the susceptible line LMPG-6 to generate F6 recombinant inbred lines. The recombinant inbred line populations were phenotyped in Kenya, South Africa, and St. Paul, Minnesota, USA. By joint mapping of the 10 populations, we identified 59 minor and medium-effect QTL (explained phenotypic variance range of 1%- 20%) on 20 chromosomes that contributed towards adult plant resistance to North American Pgt races as well as the highly virulent Ug99 race group. Fifteen of the 59 QTL were detected in multiple environments. No epistatic relationship was detected among the QTL. While these numerous small- to medium-effect QTL are shared among the families, the founder parents were found to have different allelic effects for the QTL. Fourteen QTL identified by joint mapping were also detected in single-population mapping. As these QTL were mapped using SNP markers with known locations on the physical chromosomes, the genomic regions identified with QTL could be explored more in depth to discover candidate genes for stem rust resistance. The use of GBS-derived de novo SNPs in mapping resistance to stem rust shown in this study could be used as a model to conduct similar markertrait association studies in other plant species.This is an open access article, free of all copiright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Nyongesa D.,Kenya Agricultural and Livestock Research Organization KALRO | Mwirigi M.K.,Institute of Biotechnology | Yongo D.,Ministry of Agriculture | Makokha S.,Institute of Biotechnology
International Journal of Agricultural Resources, Governance and Ecology | Year: 2016

Smallholder dairy farming is a key economic activity for improving rural livelihoods. This paper reports a study on six smallholder dairy groups that evaluated the importance of gender-concerns in the dairy value-chain towards improved livelihoods. Longitudinal study design was applied for two years from April 2012. Purposive and multistage sampling techniques were used. Data collection was through focus group discussions and evaluations. Data analyses encompassed descriptive statistics, value-scale ranking and gender-analyses. Men dominated decision-making and resource-control, indicating gender-inequality. Women performed all the nine activities in the three counties, over 70% while men and youths shared about 30%. Percentage change in milk handled and incomes generated ranged from 15.3 to 100 and 13.3 to 102 respectively after intervention (especially training on gender issues) within the groups. Hence, gender-concerns indeed mattered. Copyright © 2016 Inderscience Enterprises Ltd.

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