|
A Technical Guide for Wine Producers
|
|
RECENT ARTICLES | WYNBOER HOME
Certification of Plant Material according to Status
In terms of the SA Plant Certification Scheme for Wine Grapes all plant material must comply with the minimum requirements as determined by the Scheme and the certification of plant material that does indeed comply is confirmed by affixing the blue certification label.
In order to realise our main goal of plant improvement, plant material has been improved over the years and more exact scientific tests have been developed with which to test plant material. This development has made so much progress that the stage has been reached in which plant material is already being handled within the Scheme that complies with standards that exceed the minimum requirements.
Consequently it was decided to distinguish the plant material which already complies with these higher standards from that which complies with the minimum requirements only and to indicate this distinction on the certification labels.
This categorisation of the plant material is based on the phytosanitary status of the Nucleus plants from which it derives and whether the unit where the plant material is being produced, is a low risk or a risk unit. Furthermore specific tests are being prescribed to confirm that the plant material has retained its status and has not become reinfected in the mean time.
As a point of departure it was decided that there would be 3 statuses in the case of plant material issued to nurseries in 2004, namely:
THREE star status
In the case of rootstocks the Scheme has stipulated right from the start that the Nucleus plants must test free of Fanleaf using the serological test and must test free of Leafroll, Stemgrooving, Corky Bark, Fleck en Shiraz-disease using hard wood indicators. Consequently this prescription has been retained as is.
In the case of scions the Scheme has stipulated right from the start that the Nucleus plants must test free of Fanleaf using the serological test and must be visually free of the other virus diseases. These requirements have been extended, however, and determine that Nucleus plants of the scions must comply with the following requirements, namely:
1) THREE STAR STATUS is plant material planted in a low risk unit and deriving from a Nucleus plant that tests free of Fanleaf using the serological test and tests free of Leafroll, Stemgrooving, Corky Bark, Fleck and Shiraz-disease using hard wood indicators. (CATEGORY A)
2) TWO STAR STATUS is plant material planted in a risk unit and deriving from a Nucleus plant that tests free of Fanleaf using the serological test and tests free of Leafroll, Stemgrooving, Corky Bark, Fleck and Shiraz-disease using hard wood indicators. (CATEGORY A)
3) ONE STAR STATUS is plant material planted in a low risk or risk unit and deriving from a Nucleus plant that tests free of Fanleaf using the serological test and
According to these definitions it is therefore indeed possible to manage mother units in traditional viticultural areas so that no vectors occur and that the plant material tests free of viruses using the serological tests.
Since this is the first season that these new standards are being applied and with the ELISA tests having only a limited application, only a small percentage of scion and rootstock plant material that comply with the THREE STAR STATUS will be available this year.
Especially in the case of the rootstocks, the percentage of plant material that complies with the THREE STAR STATUS will be very small, seeing that the current ELISA tests for the Leafroll associated viruses 1,2 and 3 only give reliable results in the case of rootstock varieties that are hybrids of Vitis vinifera. Consequently this test cannot be used with certainty on most rootstock varieties for the time being.
Special provision has been made to indicate the status of the plant material on the existing certification and candidate labels.
Seeing that candidate plant material has not been fully evaluated, it will always fall in the lowest category, namely ONE STAR STATUS. Certified plant material only will therefore enjoy THREE STAR AND TWO STAR STATUS.
Plant material will be issued to the nurseries this year according to these statuses and the nurseries have been requested to plan their grafting programmes in order to graft the maximum amount of THREE STAR and TWO STAR STATUS scion plant material on THREE STAR and TWO STAR STATUS rootstock plant material. The first limited amounts of THREe stAr status grafted vines will therefore only be made available to producers in 2005.
Despite the preventative measures that are being taken to protect mother units against reinfection, it is very important for nurseries and producers to realise that an absolute guarantee cannot be given that the plant material will retain its virus status for the rest of its productive lifetime. Mainly due to reinfections and the distribution pattern of the Leafroll in the plant material, it is impossible to give such a guarantee in the light of the scientific knowledge that is currently available. It should also be taken into account that the plant material in the units was tested the year before being issued.
Although it is a modest beginning, it should be seen as a big step forward that will serve as a basis for further upgradings in future.
Status
of Scion Plant Material
Phytosanitary
Requirements
Status
Unit Requirements
Nucleus Plant Virus Profile
***
Low risk with tests
• Fanleaf
Sample at 5% level
Once off
• Leafroll (GLRaV1-3)
Sample Vine-by-Vine
Every third year
Category A (Registered Clones)
**
Risk with tests
• Fanleaf
Sample at 5% level
Annually
• Leafroll (GLRaV1-3)
Sample Vine-by-Vine
Annually
Category A (Registered Clones)
*
Low risk without tests but with visual
inspection
Or
Risk without tests but with visual
inspection
Category A (Registered Clones)
Category B (Registered Clones)
Category C (Candidate Clones)
Status
of Rootstock Plant Material Phytosanitary
Requirements Status Unit
Requirements Nucleus
Plant Virus Profile *** Low
risk with tests •
Fanleaf
Sample at 5% level
Once-off •
Leafroll (GLRaV1-3)
Sample Vine-by-Vine
Every third year
Only Vinifera hybrids Category
A (Registered Clones) ** Risk
with tests •
Fanleaf
Sample at 5% level
Annually •
Leafroll (GLRaV1-3)
Sample Vine-by-Vine
Annually
Only Vinifera hybrids Category
A (Registered Clones) * Low
risk without tests but with visual inspection
or Risk
without tests but with visual inspection Category
A (Registered Clones)
|
|
Wynboer is incorporated in WineLand, magazine of the SA wine producers.
Visit our sister sites:
|
||||||||||||||||||||||||||||||||||||||
| UP |
COPYRIGHT (C) 2000 WineLand |