CULTIVARS AND BREEDING
In the previous issue of Landscape SA (May/June 2011), an article entitled 'From Breeder to Consumer' was featured, extracted from a new book, Cut Flowers of the World, by Johannes Maree and Ben-Erik van Wyk. In this issue and subsequent ones, further extracts from the book, published by Briza, will appear.
A comparison of cultivated flowers and their original (wild) counterparts shows the remarkable effect of human selection and breeding on the size, shape and colour of flowers. More subtle differences include a longer vase life, improved resistance against diseases, transportability, uniformity of growth and higher productivity (more stems with more buds per unit area of greenhouse). There is a natural tendency to select unusual colour forms (pigment mutants). In earlier years, breeders would pamper new potential selections but nowadays they select the ones that show maximum vigour and resistance to stresses such as diseases and temperature fluctuations. A new cultivar has to stay true to type once propagated and cultivated. This is especially of concern in flowers that are propagated from seed.
Breeding of new cultivars
Breeding is a specialised activity that calls for patience, dedication and hard work over many years. Commercial flower growers often have a small greenhouse on the side where they experiment with new hybrids and selections. Hybrid breeding is the most common and obvious way to create new forms. Hybrid seed is produced on the so-called 'pod parent' after cross-pollination from the 'pollen parent'. A common strategy in breeding is to create two distinct lineages of heavily inbred plants - the plants are repeatedly hybridized with themselves until they are genetically (and morphologically) absolutely uniform. When two such inbred lines are finally crossed, exceptionally vigorous hybrids are often produced - a phenomenon known as hybrid vigour. The more deeply inbred the two parental lines, the more likely and more pronounced the hybrid vigour effect. The resultant plants are called F1 hybrids. The seeds of F1 hybrids are not useful because the offspring usually lack uniformity and show a random combination of the traits present in the two parental lineages. This means one has to buy F1 seed from the breeder.
New cultivars can also be developed by subjecting seeds or cuttings to non-lethal levels of radiation. This cause a higher rate of mutation than would normally occur in nature. The vast majority of such random mutants have to be discarded but a few of them typically show interesting new traits that can be used in further breeding work. These changes are totally unpredictable and may include new colour patterns in flowers and foliages, increased stem length, larger flowers or taller plants. Nowadays it is also possible to create new cultivars by genetic engineering, where the desired traits re introduced by way of gene transfer. This process occurs totally randomly when we hybridise plants but can be highly predictable when specific target genes (for flower colour, for example) ae transferred. There is some resistance to genetically modified organisms but most people have no objections when the new organism is used for decoration only and not for food.
Botanical and cultivar names
It may be useful to consider here the correct terminology and the correct way of writing plant material and cultivar names. In botanical nomenclature, the correct scientific name for a plant species is a combination of the genus name e.g. Rosa and a descriptive term known as the specific epithet, e.g chinensis. Rosa chinensis is therefore the Latin botanical name that translates to 'Chinese Rose'. Sometimes species is subdivided into naturally occurring varieties (e.g Rosa chinensis var.alba - the white form/variety of the Chinese rose). The abbreviation var.means a botanical variety but this term is often also used for artificial or cultivated varieties. We recommend that the term 'cultivar' (derived from the words cultivated and variety) be used for all forms of a species that do not occur in nature but which resulted from selection and breeding.
The correct way to write a cultivar name is to combine the botanical name with the 'fancy' (non-botanical) name of the cultivar, such asRosa chinensis 'Emperor's Gold'. In the case of hybrids, many different species may be involved and then we simply write the genus name (e.g. Rosa 'Peace'). Hybrids are sometimes described as new botanical genera or species. The hybrid origin is indicated by a multiplication sign (x) placed before the genus name (in the case of inter-generic hybrids) or before the specific epithet in the case of inter-species hybrids. For example, the name x Cattleytonia is used for the new genus by creating crossing a Cattleya orchid with a Broughtonia orchid. The name Lilium x testaceum is used for the nankeen lily, a hybrid between Lilium candidum and L chalcedonicum.
Registration of cultivars
Breeders often register their cultivars in order to be granted 'plant breeder's rights', also called 'plant variety rights' in some countries. This is a form of intellectual property rights that are closely related to patent law, although it is not possible to patent a living organism such as a plant. The International Union for the Protection of New Varieties of Plants (UPOV) is responsible for an international convention on plant breeder's rights. Most countries of the world are signatories to the convention and have national laws aimed at protecting breeder's rights.
Plant breeder's rights
Plant breeder's rights are typically granted for a period of 20 years (or 25 years for woody vines and trees). In order to register a new cultivar, the breeder has to prove that it is:
- new and distinct (different form all forms found in nature and different from all other cultivars);
- uniform (that all individuals are the same - often a problem with seedlings); and
- stable (that it retains the unique traits through several generations).
After a lengthy process of evaluation by a special registrar usually residing in the National Department of Agriculture, the new cultivar may then be listed and registered. This process usually takes one to three years. National or international plant breeder's rights are then granted to the breeder, or to someone assigned by the breeder in the form on a deed of assignment, and a registration certificate is issued. There is an annual fee to keep the plant breeder's right in force. The holder of the rights is obliged to issue licenses to all producers who wish to use the cultivar and is entitled to collect a royalty payment per plant or stem sold in order to recover the costs of research and development.