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Seed vigour measurement getting closer

Compounds linked to strong emergence under environmental stress will be identified and seed vigour will be assessed using quick, specific tests.


November 15, 2007
By Helen McMenamin

9aSeed quality has meant purity, appearance and germination, but growers and
seed companies want information on seed vigour, especially for small-seeded
crops like canola.

As economic conditions make it essential to optimize every part of the cropping
system, each input, including seed, must meet high quality standards. Strong
crop emergence and growth, especially under adverse conditions, can make as
much as a 60 percent difference in yield. Seed vigour also predicts storage
life of seed. Seeds with high vigour withstand storage better.

Some laboratories use low temperature germination tests to judge seed vigour.
Special training is needed to assess the strength of the emerging radicle, so
the test is subjective, time consuming and costly. Less subjective tests have
not proven reliable.

Larry Gusta, a molecular biologist at the Crop Development Centre at the University
of Saskatchewan in Saskatoon, plans to use tomography and proteomics to develop
a rapid and repeatable test for seed vigour.

Tomography uses light of a special wavelength to create a three-dimensional
image of internal structures. The principle is used in medical CAT scans and
can be adapted to examine individual seeds without destroying them.

Proteomics involves extracting proteins from cells and separating them by taking
advantage of the different rates at which they move along a medium, like dye
travelling through a fabric. Once the proteins have been separated, each one
can be identified and linked to activities in the cells when the proteins were
extracted.

Gusta will use these analytical tools to look at seed with high and low vigour
to find proteins that are associated with seed vigour, possibly at a particular
stage in germination. It is likely that the proteins involved are only produced
at a particular point in germination as the genes that control them are switched
on or off by other genes.

Likely sources of high vigour seed are fall seeded canola crops, hybrid seed
and transgenic crops carrying a universal stress gene which emerge very strongly.
Gusta will also use primed seed. Priming involves wetting the seeds with water,
a chemical solution or plant hormones to initiate the chemical changes of germination.
The seed is dried before the radicle breaks through the seed coat. The primed
seed is then stable and can be stored and handled like untreated seed.

Priming is used in horticulture to improve seedling health. The process boosts
seed vigour and increases seed storage life. Primed seed has higher germination
and emergence, earlier flowering and higher yields than untreated seed. Because
the biochemical events induced by priming are fixed by drying the seed, priming
provides an excellent system in which to find genes and proteins involved in
seed quality.

Once the Saskatoon researchers have identified some potential markers for high
quality seed, they will develop a test to measure one of them. One likely system
is a DNA test in which the appropriate part of the seed's genetic material is
increased by cloning, then separated in a DNA fingerprint. An alternative is
an ELISA test. In this system an antibody to the protein is prepared and attached
to a marker. When the antibody attaches to the protein, the marker is fixed,
along with the antibody, and identifies the protein.

The leading seed laboratories are supporting Gusta's work, so it will likely
be available for commercial tests soon after his work is complete. -30-