Maize (Zea mays L.) is one of the most important food crops in sub-Saharan Africa (SSA);
however its production is constrained by many factors. Grain yield is compromised by poor
genetic performance and poor agronomic management. This calls for need to develop
hybrids and exploiting heterosis of single crosses which are adapted to challenging
environments. Currently, there is no popcorn hybrids developed in South Africa which is
adapted to local conditions. As such, there is need to develop hybrids that cater for smallscale
farmers in marginal environments. The objectives of the study were to determine i)
standard heterosis, levels of variation and heritability for phenotypic traits in dent and flint
maize hybrids; ii) the association between genetic distances and phenotypic traits in dent and
flint maize hybrids; iii) mid-parent heterosis in popcorn hybrids, iv) the effect of secondary
traits on grain yield in dent, flint and popcorn hybrids; v) genetic diversity and the relationship
between traits in widely grown selected hybrids in Southern Africa; and vii) to compare
effectiveness of phenotypic analysis models for determining genetic distances between
hybrids. Popcorn, dent and flint hybrids were evaluated at two sites. The data was analysed
using SAS, Genstat and Power marker statistical packages. The results revealed that the
relationship between genetic distance and heterosis is dependent on the environment.
Hybrids in top 10 at both sites were different indicating that there was a significant genotype x
environment interaction. 13 new heterotic patterns that performed better than the controls can
be utilized in heterosis breeding; however there is need to test them in different environments
to check on their stability. Grain texture cannot be used to discriminate hybrids for yield
because all patterns of dent x dent, dent x flint and flint x flint were present in the top 10
hybrids. Lines DXL124 and DXL158 dominated parentage of the top 10 hybrid rank for yield
qualifying them as potential testers for specific combining ability in future studies. Heterosis in
popcorn hybrids that performed better than the mid-parent can be utilized in heterosis
breeding to exploit vigour, though there is need to test the hybrids in a number of different
environments. The main direct factors contributing to yield were ear prolificacy, ear aspect,
number of plants and shelling percentages qualifying them to be selected to boost grain yield.
Phenotypic data and 91 SNP markers were used to estimate the genetic distance between
the hybrids. The results indicated that hybrids that were in the same cluster belong to the
same brand and were related in origin and pedigree. Both molecular and phenotypic data
were effective in discriminating the hybrids into different clusters according to genetic
background. SNP markers revealed nine clusters of hybrids, 12-trait model revealed eight
clusters and five-trait model revealed six clusters at 85% genetic distance. The study
indicates strategies that can be adopted to boost grain yield in dent, flint and popcorn hybrids. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/10931 |
| Date | January 2013 |
| Creators | Mhoswa, Lorraine. |
| Contributors | Derera, John., Odindo, Alfred Odour. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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