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Gakunga, J.

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Gakunga
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Gakunga, J.

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    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.
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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.
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