| dc.description.abstract | Maize (zea mays. L.) is t b.e most important
food crop in Kenya. It is consumed as roasted cobs
and ground flour for making !!Ugali", a staple food
for over 50% of Kenya's population.
Although several hybrids and synthetic
varieties are available for cultivation in Kenya,
little effort has been made to study the genetics
of yield and its components in local maize. The
study was undertaken primarily to find out the
genetics of yield ,and other economic traits such
as bare tip in ears, whicn is directly associated
wi t h. the quality of Ute maize while still in the
field, and to suggest suitable breeding methods for
further improvement of the yielding potential.
A dialleI cross was made among six selected
maize inbred lines. All 15 possible crosses (excluding
reciprocals) and six parents were planted at two locations
in Kitale, in a randomized block design with two
replications during the 1985 rainy season. Normal
agronomic practices, were followed and data were recorded
'on twelve randomly selected plants for the following
traits; bare tip ears (incomplete husk cover of ears),
ear husk leaf number, leaf number per plant, plant
height, ear height (ear placement), kernel weight
and grain yield. For days to pollen shed, the whole
plot per entry was used to determine when 50\ 6f the
plants were shedding pollen~
Diallel analysis was carried out according ~o
Hayman{19 54ab1and Jone s (1965). Bo th additive and
dominance gene effects significantly influenced the
inheritance of all the traits except gr&in yield.
Dominance gene effects played a greater role than the
additive effects-in the expression of plant ~~light,
ear height, days to pollen shed, bare tip and husk
leaf number, while additive effects were of major
importance in the expression of leaf number and
kernel weight. Dominance~ effects accounted for all
the significant genetic variation in the inheritance
of grain yield. Over dominance gene action was
involved in the expression of all traits except leaf
number and kernel we i gh.t whose expression was
governed by partial dominance gene action. Symmetry
of dominant and recessive allele distribution in the
parents was indicated for kernel weight, days to
pollen shed and bare tip traits, while for the other
traits, asymmetry ~f allele distribution was suggested.
Effective factors' and gene or gene groups that
exhibited some degree of dominance in gene action
were estimated. The effective factors ranged from
one to six for the various traits and larger numbers
of genes or gene groups than those of effective
factors were obtained for most traits. High values
of n arrow and broad sense ,heritability were obtained
for all traits (tINS:: 46.6% - 84%, HBS:: 67.5% -
97.3%) except for plant height, ear height and grain
yield, for which low narrow sense heritability
values (HNS = 1.1% - 17.9%) we re obtained.
Progress under selection is possible for traits
largely governed by additive gene action. However,
better yielding hybrids can be obtained when parents
which carry highest numbers of dominant alleles for
yield and its components are used in crosses. | en |
