Pinus patula is the most widely planted softwood species in Southern Africa and is utilised for various solid wood and pulp and paper products. Tree improvement programmes for forestry species started in Southern Africa during the 1950âs, with an initial focus on volume improvements. The focus for many advanced tree improvement programmes has moved to the improvement of wood properties.
This quantitative genetics study utilized half-rotation age P. patula progeny material from a 5 Ã 5 full diallel mating design and additional factorial crosses. A radial wood sample at 1.3 m above ground level from each of 300 trees was used to study a range of wood density, tracheid cross-sectional and -dimension characteristics. A large range of family variation was found for all wood properties. The combining ability analysis indicated that general combining ability was the most predominant effect and that specific combining ability effects were absent for nearly all the investigated wood density and tracheid traits. Reciprocal, maternal and non-maternal effects were also not significant for all but a few traits. Some of the wood properties were influenced by the specific site where trees were grown.
Heritability estimates for many of the important wood density and tracheid traits were moderate to high, indicating strong additive genetic control of these properties. Wood density traits were under strong genetic control, with a pith-to-bark increase in wood density traits. Latewood proportion and earlywood density had a strong effect on weighted mean wood density. There were also strong positive correlations for density traits between growth rings, indicating that early selection would be possible. Tracheid cross-sectional properties were also strongly inherited, and strong correlations were found between the cross-sectional traits and calculated pulp and paper traits. Tracheid dimension traits such as tracheid length, width and cellwall thickness had lower heritability estimates than those found for wood density and tracheid cross-sectional traits. These were, however, of higher magnitude than growth trait heritabilities.
Several strong positive and negative correlations were found between growth, wood density and tracheid property traits. These negative correlations would make multi-trait selections very problematic. Predicted gains for some of the studied wood properties were substantial, but correlated responses between primary and secondary selection traits were often negative. The structuring of genetic material into wood property specific sub-populations would ensure the improvement of selected important wood properties. These different properties can then be combined by means of controlled pollinations, and be deployed via vegetative propagation. This study has provided novel information on the genetic inheritance of physical wood properties of P. patula grown in Southern Africa, and will allow tree breeders to include some of these properties in breeding programmes.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08072014-105640 |
| Date | 07 August 2014 |
| Creators | Nel, André |
| Contributors | Dr A Kanzler, Prof JP Grobler, Prof A Fossey |
| 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-08072014-105640/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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