| dc.description.abstract | Maize (Zea mays L.) is an important staple food crop in the developing world. The spotted
stem borer, Chilo partellus Swinhoe is an important stem borer causing significant maize
yield losses in the mid-altitude ecology of Kenya. Host plant resistance is a preferred option
to reduce yield losses among the available methods used to manage stem borers. Breeders
have developed inbred lines resistant to a number of stem borer species. The objectives of the
study included allocating ten putative Chilo partellus resistant maize inbred lines into their
heterotic groups, assess the biotic resistance present and measure the agronomic performance
of F I hybrids made from these lines.
The inbred lines were crossed in a diallel mating scheme to generate 45 single crosses, which,
together with five commercial checks, were used to form a trial with 50 hybrids. These were
evaluated at four sites for two rainfall seasons in 2009 and 2010. Ten plants in every plot
were artificially infested using first instar neonates of C. partellus while the rest were
protected using beta cyfluthrin (Bulldock). Data were recorded on grain yield, stem borer leaf
damage, and number of exit holes, tunnel length, and ratio of tunnel length to plant height,
anthesis and silking dates, plant and ear heights, ear and plant aspect. Analysis of variance
was carried out on the data using GLM procedure of SAS.
Results showed variability (P<0.001) among the ten lines for resistance to the spotted stem
borer, grain yield potential and agronomic performance. Six parents were classified into
heterotic group B while only one parent was classified into heterotic group A. Two parents
were placed into heterotic group AB. Grain yields ranged between 8.02 - 3.37 t/ha under
infestation. Additive gene effects were found to be more important than non-additive gene
effects for grain yield and leaf damage, number of exit holes, tunnel length and tunnel lengthplant
height ratio. However, genotypes x parameter interactions were observed between grain
yield and leaf damage, number of exit holes and tunnel length. GCA estimates ranged
between -1.2 and 1.1, with parents 1 and 2 showing significant (p=0.001) grain yield
superiority, 3 and 4 had significant (p=0.001) good expressions for stem borer resistance in
hybrids while parent 9 showed good performance for both grain yields and resistance. Thus,
inbreds 1, 2 and 9 were identified as being potentially good breeding stocks.
Results also showed parent 1 to flower significantly (p=0.05) earlier than the rest. There was
no variability in reaction to gray leaf spot, Exserohilum turcicum, and rust and maize streak
virus among the hybrids across the various environments.
It was concluded from this study that additive gene action was very important in controlling
stem borer resistance in the materials used. Future inbred lines with useful resistance to stem
borers were identified and single crosses useful in the development of high-yielding stem
borer-resistant hybrids formulated. It was further concluded that it would be possible to
develop viable F 1 hybrids resistant to C. partellus and with desirable agronomic traits through
recurrent selection. It was recommended that reaction of ten identified inbred lines resistant
to C. partellus and Busseolafusca (Fuller) should be confirmed through exposing them to
higher intensities of attack than those used in the study. | en |
