Person: Njoroge, K.
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Njoroge
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K.
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Njoroge, K.
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- Performance and adaptability of doubled haploid maize testcross hybrids under drought stress and non-stress conditions(International Research Journals, 2014) Odiyo, O.; Njoroge, K.; Chemining’wa, G.N.; Beyene, Y.
Publication - Combining ability of maize (Zea mays) inbred lines resistant to Striga hermonthica (Del.) Benth evaluated under artificial Striga infestation(Academic Journals, 2014) Karaya, H.; Njoroge, K.; Mugo, S.N.; Ariga, E.S.; Kanampiu, F.; Nderitu, J.
Publication - Molecular characterization of tropical maize inbred lines using microsatellite DNA markers(Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2014) Sserumaga, J.P.; Makumbi, D.; Ji, H.; Njoroge, K.; Muthomi, J.; Chemining’wa, G.N.; Si-myung, L.; Asea, G.; Kim, H.An insight on diversity and relationships among germplasm is important in any breeding program for crop improvement. The main objectives of our study were to: (i) determine the level of genetic diversity within mid altitude maize inbred lines resistant to weevils, aflatoxin accumulation and drought, (ii) to suggest potential heterotic groups using their genetic structures and distance based on cluster analysis with the aim to generate broad based source germplasm for mid altitude maize breeding program with combined traits of importance against Aflatoxin accumulation. In this study, 25 SSR markers were used to finger print forty two maize inbred lines to assess the genetic diversity, genetic relationships, and their population structure. A total of 184 alleles were identified at all the loci with an average of 7.36 and a range between two and 19 alleles per locus. The major allele frequency varied from 0.17 to 0.90 with an average of 0.49 while the minor allele frequency varied from 0.10 to 0.83 with an average of 0.51. The gene diversity values varied from 0.18 to 0.92 with an average of 0.65. Average heterozygosity percentage of the inbred lines was 4%, ranging from 0% to 2%, indicating the low level of heterozygosity within the inbred lines. The average polymorphism information content (PIC) was 0.61. A dendrogram constructed using unweighted Neighbour Joining algorithm suggested three heterotic groups among the inbred lines. The three heterotic patterns based on the SSR markers need to be verified by field testing to confirm what appears to be promising alternative heterotic patterns. The fixed pattern detected using SSR markers could potentially contribute towards effective utilization of the inbred lines for the exploitation of heterosis and formation of genetically diverse sources population.
Publication - Combining ability of maize inbred lines resistant to Chilo partellus (Swinhoe) in the mid-altitude environment of Kenya(Academic Journals, 2012) Gakunga, J.; Mugo, S.N.; Njoroge, K.; Olubayo, F.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.
Publication - Determination of levels of Striga germination Stimulants for maize gene bank accessions and elite inbred lines(Gorgan University of Agricultural Sciences, 2012) Karaya, H.; Njoroge, K.; Mugo, S.N.; Ariga, E.S.; Kanampiu, F.; Nderitu, J.Parasitism by Striga hermonthica (Del) Benth is a severe constraint in maize production in sub-Saharan Africa. Varying levels of tolerance to Striga attack have been identified and exploited in breeding programs of several crops. However, the level and stability of the tolerance is generally unacceptable in field-practice. Only limited exploration has been undertaken among the farmers? landraces to find the presence of viable sources of resistance to Striga. The objective of this study was to examine and document the presence of the Striga germination stimulants from a collection of some 420 maize landraces, populations and elite inbred lines. The genotypes were variously sourced from International Maize and Wheat Improvement Center (CIMMYT), International Institute for Tropical Agriculture (IITA) and Kenya Agricultural Research Institute (KARI). The ability to effect germination as a measure of the amount of germination stimulant produced was used to assess the materials, using the standard procedures. Data were recorded on Striga germination by counting Striga seeds with protruding radicle. Highly significant (P=0.001) differences were observed among the germplasm screened. Several landraces were found to stimulate low levels of Striga germination compared to the commercial checks. Landraces CRIC 51, CUBA T-31, BRAZ 1758, BRAZ 1279 and VERA 217 exhibited the lowest Striga germination, an indication of high level of resistance to Striga. The inbred lines were found to have a higher Striga germination percent compared to the landraces, a likelihood of a higher concentration of strigol, the stimulant causing chemical. CIMMYT lines CML 202 IR, CML 445 IR and CML 204 IR induced the least amount of Striga seeds to germinate. Higher levels of germination of Striga seeds were found in the IITA lines which are known to beresistant, depicting a probable avoidance root architecture mode of resistance as opposed to low production of strigol. It was concluded that the landraces with low Striga germination percent can be used by breeders in the extraction of new Striga resistant inbred lines. The resistant inbred lines can be recommended for direct use in the formation of maize synthetics and hybrids resistant to S. hermonthica.
Publication - The seed industry for dryland crops in Eastern Kenya(CIMMYT, 2003) Muhammad, L.; Njoroge, K.; Bett, C.; Mwangi, W.M.; Verkuijl, H.; De Groote, H.The development and promotion of improved crop varieties as well as efficient seed production, distribution, and marketing systems have contributed significantly to increased agricultural production and food security in Kenya. However, these impacts have not been replicated in the semi-arid midlands due to climatic, soil, and institutional factors. Following the liberalization of agriculture in the late 1980s, there has been greater participation of the private sector, non-governmental organizations, and voluntary agencies in the area. This study examined the extent to which these developments affected farmers’ access to dryland crops. The study found that the low quantity of seed traded, high cost of production, and high seed supply prices constrained the development of local seed trade. It recommended developing and offering a range of varieties to farmers to increase demand, training to strengthen farmers’ capacity to manage seed onfarm, and reduction of high production and distribution costs through further research and institutional improvements. In addition, the “seed loans” model, which has been very effective in the area, should be strengthened.
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