n this section we provide technical/practical information that seed sector staff may find useful. It is simple to follow instructions for technical staff in seed production and quality control.

How to No 23: Verification of Seed Testing Media
Under the ISTA laboratory accreditation program, using well-documented procedures is one of the important features of quality assurance system. In this issue, the verification of seed testing media is explained.
        For testing seed for viability and germination a wide range of chemicals and substrates are used such as tetrazolium (TZ), sand, soil and filter paper. Each time a new batch of these materials is obtained, their suitability for use and possible effect on the test results has to be tested and checked. This is a routine procedure in quality assurance programs to ensure the quality and reliability of test results. The method described in the ISTA bulletin for quality assurance in seed testing is summarized as follows:
* Take standard working samples from submitted samples of the seed lots and one
   sample from a seed lot of a crop species that is known to show irregularities in test
   results.
* From each of the working samples, plant one set of four replicates of 100 seeds using
   the old and another set of four replicates using the new batch of material.
* At the end of the normal test period, make evaluation and calculation of the results
   according to the standard ISTA procedures for germination or TZ test.
* Compare the percentage viability or germination from the same seed lots using new
   and old batches of media.
* Based on a tolerance level, accept or discard the new batch. The tolerance table for
   comparing whole working samples in the ISTA rules may be used as a guide.

Abdoul Aziz Niane, Seed Unit, ICARDA, P.O. Box 5466, Aleppo, Syria; E-mail: A.Niane@cgiar.org