Tree breeding seeks to improve yield and quality through:
- Controlled pollination
- Breeding
- Extensive provenance and progeny testing and selections
- Reduction in rotation period
- Improvement in stem form
- Increased profitability for the forest industries
- Introduction of new species for both commercial and social forestry
- Introduction of latest propagation technologies
Contribution of Tree Breeding to Climate Change Mitigation
Climate change presents new challenges for tree improvement programs. The Tree Breeding Unit focuses on fast-growing species that can adapt to changing environments, primarily exotic softwoods (Pines) and hardwoods (Eucalyptus).
Promising softwood species:
- Pinus maximinoii
- Pinus tecunumanii (high and low elevation populations)
These outperform P. taeda, P. elliottii, and P. oocarpa. To mitigate monoculture risks in high altitudes, species like P. greggii and P. maximinoii are also introduced.
In low rainfall areas, P. roxburghii is under evaluation from 3 provenances.
For tobacco-growing regions, Eucalyptus hybrids offer fast growth and adaptability, providing sustainable fuelwood alternatives.
Eucalyptus Hybrids for Climate Adaptation
| Hybrid Cross (Eucalyptus) | Breeding Objective |
|---|---|
| E. grandis × E. camaldulensis | Drought, frost resistance |
| E. grandis × E. tereticornis | Drought, disease resistance |
| E. grandis × E. saligna | Fast growth |
| E. grandis × E. europhylla | Disease resistance |
| E. grandis × E. pellita | Fast growth, disease resistance |
Vegetative propagation has been adopted to address poor seeding performance. FRC has established a clonal hedge with:
- 21 individuals of E. grandis × E. tereticornis
- 24 individuals of E. grandis × E. camaldulensis
Vegetative Propagation at JMFRS
| Species | Growth Medium | With Seradix | Without Seradix |
|---|---|---|---|
| P. caribaea × P. tecunumanii | Pine bark/Sand | 220 | 348 |
| P. caribaea × P. tecunumanii | Pine bark/Sand | 52 | 96 |
| P. tecunumanii | Pine bark/Sand | 59 | 96 |
| P. patula | Pine bark/Sand | 711 | 7,519 |
| P. taeda | Pine bark/Sand | 48 | 35 |
| P. elliottii | Pine bark/Sand | 16 | 303 |
| P. maximinoii | Pine bark/Sand | — | 1,211 |
Total Cuttings: 14,290
Dry Zone Research Trials
| Trial No | Type | Species | Location |
|---|---|---|---|
| EV133A | Provenance | Azadirachta indica | Matopos |
| EV133B | Provenance | Azadirachta indica | Ntabazinduna |
| EV133C | Provenance | Azadirachta indica | Gwanda |
| EV133D | Provenance | Azadirachta indica | Forest Hill |
| EX132 | Progeny/Provenance | Faidherbia albida | Matopos |
| EV128C | Provenance | Acacia aneura | Ntabazinduna |
| EV131 | Provenance | Acacia erioloba | Matopos |
| EV136B | Provenance | Acacia auriculiformis | Kosi |
| EV138 | Provenance | Sesbania sesban | Matopos |
| EV139 | Provenance | Sesbania goetzii | Matopos |
| EB45 | Breeding Orchard | E. tereticornis | Forest Hill |
| EB46 | Breeding Orchard | E. tereticornis | Forest Hill |
National Tree Improvement Programme
F. albida progeny/provenance trials are established at: Matopos, Chesa, Chibhero, Makaholi, Middle Sabi, Kadoma, and Chesa.
Primary research is on E. camaldulensis and E. tereticornis at Chesa Forest Station (Alt: 1460m, Region V, Rainfall: 546mm).
Breeding Strategies
Focus on both genetic improvement and gene conservation across 13 pine species and 10 eucalyptus species.
Seed Orchards in Zimbabwe
| Species | No. of Orchards | Generation | Area (ha) |
|---|---|---|---|
| E. grandis | 6 | 2nd, 4th | 15 |
| E. camaldulensis | 17 | 1st–4th | 33 |
| E. tereticornis | 9 | 2nd, 3rd | 10 |
| E. citriodora | 1 | 1st | 0.6 |
| P. patula | 26 | 1st, 2nd | 46 |
| P. taeda | 24 | 1st, 2nd | 33 |
| P. elliottii | 28 | 1st, 2nd | 61 |
| P. kesiya | 17 | 1st, 2nd | 53 |
| P. oocarpa | 7 | 1st | 22 |
| P. pseudostrobus | 1 | 1st | 0.7 |
| P. maximinoii | 4 | 1st | 19 |
| P. tecunumanii | 14 | 1st | 18 |
| P. caribaea var. hondurensis | 1 | 1st | 0.6 |
| P. caribaea var. bahamensis | 1 | 1st | 0.6 |
| P. caribaea var. caribaea | 1 | 1st | 0.6 |
| P. palustris | 1 | 1st | 0.5 |
| P. chiapensis | 4 | 1st | 6 |
| Pinus spp hybrids | 2 | — | 1.4 |
| Cupressus lusitanica | 1 | — | 0.6 |
Total: 165 orchards on 321.6 hectares