In a citrus breeding programme, information on the breeding value of available parents and
the heritability of specific characters can be an important aid to the breeder when planning
controlled crosses for cultivar improvement. By quantifying the genetic variation in a
population the breeder can study the relationships between the hybrids and parents and
gain an understanding of how certain characteristics are inherited. Therefore a study was
undertaken to investigate the genetic variation in the progenies of six mandarin families,
where female parent Kiyomi tangor was crossed with male parents Dancy, Hansen, Rishon,
Roma, Shani and Sunburst mandarins. Data were collected over a two year period for the
fruit quality characteristics of rind colour, fruit size, fruit shape and fruit internal quality.
A significant level of variation was found between the families for all the fruit characteristics
studied. The within family variation was larger than the between family variation and
indicated a high level of genetic variation within the families, while the within tree variation
was found to be lower than the within family variation. Data collected over a two year period
showed significant year and year x family variation for many of the fruit characteristics. The
intraclass correlation coefficient, relevant to selection within the families, was found to be
fairly low for all the fruit characteristics studied and indicated that the variation found within
the families was only partly genetic and non-genetic factors contributed to the variation in the
phenotype. Therefore only two years of testing will not be reliable and a mean performance
over multiple years data is recommended for effective selection.
All the families showed an improvement in the population for rind colour, fruit shape and the
fruit internal quality while half of the families showed an improvement for fruit size. All the
families showed heterosis with some individuals being superior to both parents. Families
with male parents Hansen, Rishon, Shani and Sunburst had a rind colour superior to the
other families, while the Kiyomi x Rishon family had larger fruit with a more round fruit shape
and the Kiyomi x Roma family had a superior internal quality. This study revealed the male
parent to have a large influence on the progeny and male parents with a deeper orange rind
colour, larger fruit size, better fruit shape and superior internal quality resulted in families
with a greater improvement in the population. Therefore only male parents of the highest
quality should be used as parents in breeding programmes in order to increase the chance
of obtaining a superior new cultivar.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-07182013-102922 |
| Date | 18 July 2013 |
| Creators | Combrink, Nicola Kim |
| Contributors | Z Bijzet, Prof MT Labuschagne |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-07182013-102922/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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