The Association of Official Seed Analysts (AOSA) approved a rule proposal on June 19, 2002, to include a reference in the “Rules for Testing Seeds” which provides an option to use a grow-out test as a supplement to the fluorescence test of ryegrass.  This test does not eliminate or replace the fluorescence test, but creates an option to grow-out the fluorescing seedling when the test fluorescence is above described values or appears to overestimate annual contamination.  This test requires special growing conditions, evaluation criteria  and calculations. An updated protocol will be published in the AOSA “Cultivar Purity Testing Handbook” by October 2002.

Although the fluorescence test is currently used to determine the annual  type in perennial ryegrass, in some cases it seems to overestimate the annual ryegrass contamination causing a reduction in the selling price of perennial seed lots. It is well documented that the fluorescence trait is not always associated with the annual form of ryegrass and that environmental conditions affect the level of fluorescence from year to year and from location to location. The new protocol will standardize test procedures and minimize variation among labs.

 The new supplemental grow-out test is the fruit of collective efforts of the Oregon Seed Council, ryegrass growers, grass seed industry, private Oregon seed testing labs, Oregon Department of Agriculture, USDA, laboratories in other states, and the Oregon State University Seed Laboratory. Special thanks should be expressed to all the laboratories from around the US who participated in the national ryegrass grow-out referee study that was coordinated by the OSU Seed Laboratory and contributed to the development of the grow-out test protocol. It is worthy to note that AASCO, AOSCA, and ASTA have supported this rule in their resolutions.

Although this test provides reliable supplemental seed purity information, it should be noted that it takes 6 weeks in the greenhouse after germination is completed. Therefore, in order to avoid unnecessary delays, it is best to order it with the initial germination/fluorescence. Recently some customers asked for the grow-out after the germination test had been completed and all seedlings had been thrown away. This resulted in higher charges (because the seeds had to be germinated again) and more delays (because germination takes 2-3 weeks). To avoid this situation, the OSU Seed Laboratory offers a sequential option, whereby a customer can indicate, ‘Grow-out  if test fluorescence exceeds (x%)’.

When the grow-out test is used to determine the percentage of annual and perennial ryegrass in a sample, the purity report should include the following statement:  “Pure seed is based on grow-out test”.

This test can also be provided by other laboratories. For specific information and arrangements, the customer should contact the specific laboratory.

If you have any question or comments concerning the ryegrass grow out test, please contact OSU Seed Laboratory at (541) 737-4464.