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Abstract
Survival, growth 2nd stem straightness were assessed at 7 years of age for F
1 hybrids of
E. grandis with
E. saligna,
E. pellita and
E. urophylla established at a high rainfall area, and the same traits were assessed at 6 years for F
1 hybrids of
E. grandis with both
E. camaldulensis amd
E. tereticornis established at two low rainfall sites in Zimbabwe. Survival was moderate to high in a11 taxa. Both
E. grandis x
E. saligna and
E. grandis x E. urophylla hybrids from controlled crosses outperformed the local control in growth and straightness with the former outperforming the local control by 41%, and the latter by 16% in volume. The natural hybrid
E. grandis x
E. pellita had similar growth to the local control, and the natural hybrid between
E. grandis and
E. saligna was outperformed by the control. The most productive hybrid at the low rainfall sites,
E. grandis x
E. camaldulensis, outperformed the conrrol by as much as 68% in volume. The other dry-zone hybrid,
E. grandis x
E. tereticornis, outperformed the control by 25% in volume. Heterosis was exhibited in all the hybrids and was expressed differentially at different sites, in different traits and in crosses involving different species. The fast growth rate of the hybrids in this study suggests that, with confirmation via further tests in more appropriate field designs with broadly-based controls, commercial planting of eucalypt hybrids both in high and low rainfall areas may be favourable in Zimbabwe. For the best eucalypt hybrids,
E. grandis x
E. saligna and
E. grandis x
E. camaldulensis, the best clones could be selected and coppiced, and then clonal tests from the c;oppices could be started. Given that all the controlled crosses reported in this study were from South Africa, there is a need to test the potential of locally produced hybrids.
Citation
Gwaze, D. P.; Bridgwater, Floyd E.; Lowe, W. J. 2000. Performance of interspecific F
1 eucalypt hybrids in Zimbabwe. Forest Genetics 7(4):295-303
