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International Seed Testing Association
International Seed Testing Association
Richtiarkade 18
8304 Wallisellen, CH
+41 44 838 60 00
International Seed Testing Association

Calculator for adding working weights to Table 2C of the ISTA Rules

The International Rules for Seed Testing, hereafter refers as ISTA Rules, are the standard procedures or methods for sampling and testing seeds. With more diverse or new crops becoming more popular in the world seed trade, new species are needed to add to the ISTA Rules. In the ISTA Rules, Chapter 2, Table 2C provided the minimum submitted sample weights and working weights for purity analysis and Other Seed Determination (OSD). Also, Orange International Certificate (OIC) can only be issued if a species is listed in Table 2C as stated in 1.3.b ISTA Rules “the seed tested must be of a species listed in Table 2C (Lot and sample weights) of the ISTA Rules”. However, there is a gap in how to determine the working weights to add to Table 2C for new species or revisions made to existing species listed in Table 2C. 

Although the principle is to use a thousand seed weights to estimate working weights for purity analysis and OSD, and thereafter submitted sample weight, the method and weights of other influential factors are not clear or specified. For example, how many varieties of a crop species, seed lots within a variety, and replications are needed to get a reliable determination to meet the testing method and accuracy needs. How to collect data from how many laboratories for the representation of the estimation. To provide a uniform and statistically sound method, the purity committee worked with the statistics committee and bulking and sampling committee and developed a standard tool Calculator for adding working weights to Table 2C. The calculator also provides standard experiment designs for the estimation trials.

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