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The Rating System
The laboratory is given an in-round rating for every particular test meaning that the laboratory is given an in-round rating for germination, for purity, for OSD, for moisture, and for tetrazolium testing. In addition, each test has an overall rating derived from the performance over six rounds. A laboratory may have an overall A for germination but an overall BMP for OSD for instance.
The In-Round Rating for Purity, Germination, Moisture, and Tetrazolium
The in-round rating system for purity, germination, moisture, and tetrazolium is based on the sum of absolute Z-scores. Only normal seedlings and pure seeds are taken into consideration for germination and purity. Z-scores for abnormal seedlings and ungerminated seeds are also reported but do not affect the in-round rating. A, B, C and BMP ratings are given. The in-round rating system for these tests is shown in Table 1.
Table 1: In-round rating system for purity, germination, moisture, and tetrazolium
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The In-Round Rating for Other Seed Determination
The performance in OSD is reported as a percentage of retrieved and identified seeds to genus level of seeds added to a round's sample. Identification to species level is expected. The species names must be reported in accordance with the current version of the ISTA List of Stabilized Plant Names. Synonyms will not be accepted. Samples sent to the participants have not been purified before adding the other seed inclusions. Therefore, seeds other than those that were added can also be found but they are not considered in the rating.
The in-round rating is based on the actual retrieval rate of a distinct species. The percentage of retrieved seeds for each species among all participants is calculated (Table 2). Based on the actual retrieval rate, a factor is assigned to each added species to take the relative difficulty into account. This factor is multiplied by the total number of seeds added for this species. Then the factor is multiplied by the number of seeds found by the laboratory. The percentage of retrieved and identified seeds determine the in-round rating.
The thresholds for assigning a factor are given in Table 2.
Table 2: Thresholds defining the factor assigned to each species based on the actual retrieval rate of all seeds added of a distinct species |
The thresholds for the OSD ratings are given in Table 3.
Table 3: In-round rating for OSD based on retrieval and identification rate |
An example for this rating system is presented in Table 4.
Table 4: Example laboratory results (Test round 04-1 B.nap, Brassica napus) |
* The retrieval rate [%] is the mean for all participants
The Overall Rating
The determination of the overall rating is the same for all tests to have a uniform system that can be applied for all tests once the in-round rating system is defined. Numerical values are attributed to the different in-round ratings. The values are then added for each test over the last six rounds as given in Table 5.
Table 5: Overall rating for all tests based on the in-round ratings over the last six rounds
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ISTA / ISF Experiment on Herbage Seed Lot Size
Technical Protocol and participating companies
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Next issue of
SEED TESTING INTERNATIONAL (ISTA News Bulletin) No. 139 April 2010
coming up soon!
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Outcome on the
World food security: urgent measures on seed needed
Second World Seed Conference 2009
held September 8-10,
in Rome, Italy
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ISTA Seed Mixture Experiment
to collect information that may be used to determine the reliability of seed mixture test results and establish tolerances.
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Universal List of Species
ISTA list of 130 plant species that accredited laboratories may wish to include in their seed collections
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Position Paper on
ISTA's view regarding the units for the reporting of quantitative results on presence of seeds with specified traits in conventional seed lots
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Accreditation Documents for the Testing of Specified Traits
Related Documents for download
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ISTA's Memorandum of Understanding with FAO
Read the full Press Release
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REPORTS from the
ISTA Annual Meeting June 15-18, 2009 Glattbrugg, Switzerland
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