SA wine farmers, when establishing a new vineyard, are aware of the importance of using the right scion, clone and rootstock combination for a specific locality / soil type as well as the best plant material if the vineyard has to stand any chance of being sustainable and profitable in the course of its lifetime.
|South Africa also boasts one of the best plant improvement schemes in the world, managed and controlled by the Vine Improvement Association (VIA). The VIA is composed of representatives from producers, nurseries and plant improvement organisations.
Even so there are annual complaints about the quality of the vines and accusations by producers on the one hand and nurseries on the other hand about who is to blame if the vines do not take properly or if they display virus symptoms at an early stage. The producers accuse / suspect the nurseries of supplying poor quality plant material and infection in nurseries, while the nurseries contend that the producers’ handling of the vines and establishment practices are still not up to scratch.
The question is therefore: “Are there really problems in our industry with regard to the availability and quality of our plant material, is it an erroneous perception, or merely a matter of being poorly informed”
To find out more and get some answers, Francois Viljoen, Manager of VinPro : Consultation Service asked Nico van Rensburg, secretary of the VIA, to comment on the most common questions with regard to plant material that have to be dealt with by VinPro’s viticultural consultants. In Part I of two articles the focus is on the VIA and the certification scheme, inter alia the guarantees.
Question 1: What guarantees are there if I order certified material
Certification is a process and certified plant material means that plant material was propagated, following prescribed processes, from a nucleus plant with known virus status and viticultural characteristics, that it is true to varietal type, complies with the requirements of the scheme and has been inspected. Certified plant material therefore means that plant material with a known virus status and from a known source was handled and controlled in accordance with a prescribed process.
Question 2: For what do you test
Plant material within the Scheme is subject to various tests.
Varietal authenticity – Ampelographic controls are conducted to ensure that the nucleus plant complies with the typical characteristics of the variety.
Viticultural – New clones are compared with existing clones of the same variety on a scientific basis to ensure that a new clone will perform better or at least as well as existing clones.
Phytosanitary – During the candidate clone phase, nucleus plants are subjected to ELISA tests for Fanleaf and Leafroll, while ISEM and PCR tests are also used as optional tests.
Nucleus plants from registered clones are subjected to hard wood indicator tests, namely:
Question 3: What is meant by:
Material has been tested for all harmful viruses – It sounds like there are many other viruses
So far 54 viruses and/or virus-like diseases have been identified in vines throughout the world, although the causative organism has not yet been identified in all instances. With the annual expansion of scientific knowledge and the development of new testing techniques, new discoveries are being made each year or new strains of existing viruses identified. In terms of our Scheme testing takes place for 8 viruses/virus-like diseases that are of the biggest economic importance in South Africa at this stage. Consequently only those viruses that cause symptoms on grapevines and are of economic importance, are considered as pathogens. Although viruses are super-parasitic and always harmful, the greatest dangers are where viruses occur in varieties that are symptomless carriers and where complexes of viruses result from the grafting of scions and rootstocks of unknown status.
Question 4: How does the VIA ensure that nurseries comply with the certification requirements
By comparing the quantity of plant material received by nurseries from the PIOs (Plant Improvement Organisations) to the quantity of vines grafted for each clone; and the nurseries themselves are subject to 3 annual inspections, namely summer, autumn and winter inspection. During the winter inspection the vines are checked and finally certified as presented in bundles.
Question 5: What action does the VIA take, or is the VIA able to take, in the case of non-compliance
Nursery vines that do not comply with the requirements of the scheme are provisionally rejected and if the shortcoming can be rectified through reselection of the vines, they may be presented again for certification. If the shortcoming is such that it cannot be rectified, or does not comply with the scheme requirements at the second submission, the vines are finally rejected.
Question 6: What does a vine that complies with the certification requirements look like (physical standards)
Nursery vines should comply with the requirements of the scheme according to the following schematic representation:
Question 7: What should I, as a farmer, do to make sure I obtain the best plant material in our wine industry
Due to reinfection and the presence of latent viruses, the best practice is to start with the cleanest possible plant material and keep it clean for as long as possible in order to achieve the maximum productive lifetime of the vineyard.
Nursery vines with the highest possible phytosanitary status should be ordered from a registered nursery at least 18 months prior to planting. Two years ago a system was implemented whereby plant material in foundation and mother units is graded according to the phytosanitary status of the nucleus plant and the risk profile of the unit.
3 star plant material comes from a nucleus plant that tests clean of all the prescribed viruses, has been planted in a low risk unit and is tested for leafroll every three years on an individual vine basis.
2 star plant material comes from a nucleus plant that tests clean of all the prescribed viruses, has been planted in a risk unit and is tested for leafroll every year on an individual vine basis.
1 star plant material comes from a nucleus plant that does not yet test clean of all the prescribed viruses, but is free of fanleaf and leafroll, and the unit is only visually clean of the prescribed viruses.
Uncertified plant material may be propagated and planted in terms of the Plant Improvement Act, seeing that the scheme is voluntary and that the proclamation of the scheme did not prohibit the use of uncertified plant material. Although it is not recommended, the producer and nursery are free to use uncertified plant material from untested and uncontrolled sources and run the risk themselves.
Question 9: Can I import my own material/clones
Any person or body is free to import plant material. However, any import application should comply with rules in terms of the Plant Improvement Act as well as the Agricultural Diseases Act. Import requirements differ from country to country and depending on the risk profile of the plant material, as well as the area from which the plant material derives, additional requirements may have to be complied with. Some grapevine diseases such as “Pierce disease” and Flavesence Dore do not occur in South Africa yet. Consequently it is absolutely essential for all imported plant material to be subjected to strict quarantine measures. Importation of large quantities of grafted or rooted plant material is generally not recommended due to the inherent risks. If it is allowed on special conditions in cases with merit, the vines may only be planted on the importer’s premises and not propagated or distributed in the industry. Improved plant material should preferably be imported as unrooted shoots from a nucleus unit at recognised overseas instances and be further propagated and distributed by a Plant Improvement Organisation under the controls of the scheme.
Question 10: Can we still lay claim to having one of the world’s best schemes – In which ways are the other countries better than us
Our Scheme is considered to be one of the best in the world because it is very dynamic in the sense that it makes provision for the continuous upgrading of clones and units, while clones and units that have becomeobsolete are phased out when new improved clones become available.
Our Scheme is also unique in that it is administered by an industry organisation which is managed according to strict guidelines that are controlled on an ongoing basis. Over the past 14 years, since the proclamation of the Scheme in the Government Gazette, it has shown that it is able to keep up with current demands and that the principles on which it is based are as valid as in the past.
Conditions differ from country to country and each country’s Scheme is written according to its own particular requirements and risks. Consequently it is difficult to compare the Schemes of different countries directly with each other. The International Virus Congress held in South Africa in 2006 revealed that our requirements for nucleus plants are much higher than in the European Union and better than most other countries.
Our biggest problems, however, are that our new vineyards become reinfected due to the high risk of mealybug from old vines, especially the white varieties that are symptomless carriers of the leafroll virus and act as a source of infection.
Question 11: Is the material from all nurseries equally good as long as they comply with the certification requirements
Nurseries receive the certified scion and rootstock plant material from mother units of the Plant Improvement Organisations. Consequently the nurserymen have no control over the quality of the plant material, except that they can decide on the category of plant material that is ordered in terms of the grading system i.e. 1 star, 2 star or 3 star plant material.
Plant material within the Scheme should comply with the prescribed requirements and there are differences between the status of the various clones and sources. Consequently one may expect plant material to perform differently depending on the clone and the source.
Differences in grafted vines from different nurseries may be ascribed mainly to the cultivation and care of the nursery vines, especially in the first year of the vineyard’s lifetime. Thereafter grapevines from the same clones in the same area that have been properly taken care of, should perform the same.