Breeding
Prima Bio's main activity is the development of new varieties of ornamental eucalyptus that are suited to the UK climate.
Background
Eucalyptus trees have become a familiar feature of gardens in the British Isles since they began to be planted in the 1850s. At least 20 species have proved sufficiently hardy to withstand very cold winters in much of Britain, and many other species will grow happily in milder coastal areas. Only a few of the hardier species have been planted in significant numbers, either because other hardy species grow much too large for typical gardens, or because seed supplies are scarce.
The more familiar species grown in Britain are valued for their attractive foliage (especially in winter), their general freedom from pests and diseases, and the attractive bark of certain species. The 'juvenile' foliage of some species is particularly attractive, and is grown commercially in both the UK and Ireland, and on a large scale elsewhere, for cut foliage for the floristry market.
However, the eucalyptus species familiar in Britain represent only a small proportion of the species that exist in Australia. Furthermore, the majority of species are not large trees, but multi-stemmed shrubs (usually called mallees in Australia), or small trees. These occur in every habitat imaginable, including cold exposed mountain-tops, cool windswept coasts, humid forests, and semi-deserts. Many of these species have large, showy flowers, which are often strikingly-coloured and borne in prominent clusters. Others have very distinctive foliage and bark. Unsurprisingly, many of these have become widely planted in streets and gardens, particularly in Australia but also in other countries with Mediterranean or sub-tropical climates.
The reason that most of these ornamental species are not grown in Britain is of course the climate, and the effect of this on soil conditions in winter. However, in the hands of enthusiastic gardeners, some of these species can grow and flower in seemingly unlikely places in Britain, both in gardens and in containers that are over-wintered in cool greenhouses. While this does not indicate that these species could be grown more widely in Britain, it does suggest that they are not so far from an acceptable environment as might be supposed.
Many eucalyptus species are very variable in nature. Some species exist both as large trees in favourable locations, and as dwarf mallee forms on cold, exposed sites. Many species hybridise naturally with one another, creating many taxonomic difficulties but also some fascinating opportunities to study evolution in action! Many other species will hybridise with man's assistance, often simply by being planted together. Such hybridisation, initially by chance and more recently by design, has become very important in the development of commercial eucalyptus forestry, most notably in Brazil and South Africa. Thus there is a considerable amount of information available on successful hybrid combinations, and the techniques for producing these. Coupled with selection of suitable individual parents, this offers the potential to create new hybrids having desirable features as ornamentals.
Since early 2004, a project to create such hybrids has becomePrima Bio's principal activity. The project received a significant boost in March 2004 with the award of a DTI Grant for R&D from the South East Small Business Service, which is now managed by the South East England Development Agency (SEEDA). This grant has allowed investment in facilities that are already allowing the breeding and selection to take place unusually quickly for a woody plant breeding programme.
Breeding Programme
The fundamental features of the breeding and selection programme are the same as in any such programme aimed at producing new varieties of woody plants. A key point is that each seedling produced will be genetically unique. The emphasis of Prima Bio's work is to create hybrids between species, with the aim of producing cold-tolerant shrubs and small trees having a wide range of ornamental qualities. Populations of hybrid seedlings are likely to be particularly variable, and such populations will need to be grown in the field in order to assess their potential as ornamentals. Candidate seedlings will also need to be propagated as rooted cuttings, to allow variety trialling
The ability to root cuttings from selected individuals is important, because otherwise it will be difficult to produce plants commercially, and impossible to register the new varieties.Prima Bio's breeding and selection therefore places considerable emphasis on selecting some parents for good rooting ability, in addition to ornamental attributes and cold hardiness. From work in eucalyptus species and selections important in forestry, it is known that certain ones will root very readily and confer this ability to hybrid progenies, while others cannot be rooted at all. But rooting of less vigorous ornamental species has hardly been studied. Therefore, an important part ofPrima Bio's programme is to examine rooting of candidate parental species, and to use individuals identified as having good rooting as parents. See rooting of selections for more details.
Prima Bio's first hybrids were made in 2004. The mother trees were some E. gunnii trees selected for particularly attractive bark and foliage, and some E. pulverulenta 'Baby Blue'. The latter is a dwarf variety of a shrubby species grown commercially for its striking cut foliage, though its growth habit is untidy. Pollen for other crosses has come from a wider variety of species and locations, and includes some of the spectacular red-flowered species. Many other sources of pollen have been collected and are stored for future use.
Two outdoor breeding arboreta were established in 2004. One of these is in north Kent, and the other is in a mild location in south Cornwall. The latter has been planted predominantly with relatively tender species. Further shrubby species have been established in a protected polytunnel at East Malling Research station. This location is used for mainly for tender species, including some from Western Australia, that are unlikely to survive cold wet winters outdoors. It is also used for species that flower in winter in the UK, to facilitiate hybridisation.
Some of the species planted have been bought as containerised stock from nurseries in the UK. However, many of the species are not available commercially in the UK, or are not available from seed provenances of greatest interest. These species have been grown by Prima Bio from seed, or have been raised in nurseries in Spain and Portugal in winter and imported as young seedlings. The experience of growing and over-wintering seedlings of diverse species has been invaluable as a means of learning about likely cultural requirements of different hybrid types. Certain species have been exceptionally free of pests and diseases. Many supposedly tender species were apparently undamaged by the 2004/05 winter despite their foliage being white with frost and their pots at least partly frozen on many mornings. Some have also been covered with snow on several mornings! Temperature loggers have been installed to allow cold tolerances to be quantified.
Prima Bio intends to work with other companies to bring its varieties with significant commercial potential through the evaluation and registration phases, and obtain royalties. Companies interested in such partnerships are welcome to discuss possibilities, at any stage.
One of the Eucalyptus caesia ssp magna that has flowered prolifically in the polytunnel used for breeding at East Malling. The polytunnel is frost-free in winter, and solar gain keeps it approximately 5° above ambient daytime temperatures in summer. Many eucalypts from Western Australia grow well and have initiated flower buds in the tunnel, but E. caesia has been the most easily-grown and free-flowering species.
Software for breeding
Existing software to support plant breeders appears not well suited to breeders of woody crop varieties. Prima Info has developed a plant breeding software package designed to support the needs of the ornamental eucalyptus breeding programme. This package may be of interest to other plant breeders, both professionals and amateurs. If you would like more information on this package, please contact at Prima Info.