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Njoka, S.

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Njoka
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Njoka, S.

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    Participatory farmer evaluation of stem borer tolerant maize varieties in three maize growing ecologies of Kenya
    (Academic Journals, 2011) Ouma, J.O.; Odendo, M.; Bett, C.; De Groote, H.; Mugo, S.N.; Mutinda, C.J.M.; Gethi, J.; Njoka, S.; Ajanga, S.; Shuma, J.M.
    Insect resistant maize for Africa (IRMA) project aims at developing and deploying insect resistant maize varieties to reduce grain losses due to insect pests. As part of incorporating farmers? perceptions to improve the adoption of the developed varieties, participatory approaches were adopted. The paper analyses farmer?s preferences of maize germplasm developed through conventional breeding. This paper uses data collected from evaluations conducted at the end of 2006 April and October rains season. Nine stem borer resistant maize varieties were evaluated alongside six commercial checks in the moist transitional zones (East and West) at taselling and harvest stage, while in the dry transitional zone and dry mid altitude zones, six new varieties were evaluated together with four commercial checks at harvest stage. Each variety was assessed on a scale of 1(very poor) to 5 (very good) based on key criteria generated in earlier group discussions with farmers and overall score. Data was analyzed using ordinal regression model of Social Package for Social Sciences (SPSS). At the Dry Transitional (DT) zone, CKIR06007 and CKIR06008 were more preferred to the checks based on overall score. CKIR06008 was also more preferred on yield and tolerance to insect pest criteria, while CKIR04002, CKIR06009, and CKIR04003 were perceived more superior to local check based on tolerance to insect pests. In the DM altitude zone, CKIR06008 was better on yield attribute. Three varieties namely CKIR04002, CKIR06007, CKIR06009 were superior on stem borer tolerance attribute. In moist transitional zone Embu only CKIR06005 was more preferred (p<0.01) to the check at harvest stage in April 2006 and October rains season based on early maturity. While there was no preference for the new varieties at vegetative stage in Embu in October rains 2006 season, a number of new varieties CKIR06001, CKIR06002, CKIR06003, CKIR06004, and CKIR06005 were more preferred based on early maturity at harvest in October rains 2006 season. In the moist transitional zone (west) CKIR06004 had good attributes in terms of cob size at taselling stage in April rains 2006. We conclude that farmers perceive some varieties to have good tolerance to insect pests in addition to good yield and early maturity, which are critical attributes to the farmers in the adoption of new varieties.
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    Combining ability of maize (Zea mays L.) inbred lines resistant to stem borers
    (Academic Journals, 2011) Beyene, Y.; Mugo, S.N.; Gakunga, J.; Karaya, H.; Mutinda, C.J.M.; Tadele Tefera; Njoka, S.; Chepkesis, D.; Shuma, J.M.; Tende, R.
    Ten inbred parents with varying resistance levels to Chilo partellus and Busseola fusca were crossed in a half diallel mating scheme to generate 45 F1 hybrids. The hybrids and five commercial checks were evaluated across four locations in Kenya under artificial and natural infestation in 2009. Genotype (G) by environment (E) interaction (G x E) was non-significant for stem borer leaf damage, number of exit holes and tunnel length, suggesting that screening for stem borer resistance at one location would be adequate. On the other hand, G x E and general combining ability (GCA) x environment interactions were highly significant for gray leaf spot and turcicum leaf blight, indicating an inbred line resistance to a disease in one location may have a different reaction to the same disease in another location. The results of combining ability analysis showed that GCA effects were significant for stem borer resistance traits (leaf damage scores, number of exit holes, and tunnel length) while the opposite was true for specific combining ability (SCA) effects. Parents 5, 2, 6, 9 and 3, were good sources of genes for higher grain yield while parents 1 and 4 were good sources of resistance genes for stem borers. Hybrid 5 x 9 was the best performing hybrid in grain yield (6.53 t/ha) across the locations, while hybrid 1 x 4 was the least performing in grain yield (3.08 t/ha). The source of stem borer resistance identified in the study may be useful for improving levels of stem borer resistance in maize breeding programs in eastern and southern Africa.
    Publication