Dialiel analysis of bare tip, lusk leaf number and other agronomic traits in maize (Zea Mays l. )

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.