Agriculture Reference
In-Depth Information
Seedling Spray
. Seedling spray methods involve growing seedlings in a laboratory or greenhouse and
spraying the normal seedlings with the herbicide solution. After several days, the susceptibility or tolerance
to the herbicide can be determined. The advantage of this test is that it relates well to ield application since
only emerged seedlings are sprayed. Disadvantages include the increased cost of a laboratory/greenhouse
test and the additional time required for seedling development (Fig 9.6).
It is worthy to note that the above techniques can also be used for Clearield crops which have toler-
ance to imidazolinone herbicides.
Figure 9.6. Seedling spray tests of Roundup Ready
TM
soybeans (courtesy of Iowa State Seed Laboratory).
Testing for the presence of genetic traits is conducted on seeds as well as plant parts such as leaves.
Table 9.2 shows the major genetically modiied crops, e.g., corn, soybean, cotton and canola as well as
some genetic traits, e.g., glyphosate tolerance (Roundup Ready
TM
) and corn borer and root worm resistance
(Bt). It also lists the method of detecting the presence of transgenes. Genetic traits can be detected by one
or more tests such as PCR testing, immunoassay (e.g., ELISA and Lateral Flow Strips) and/or bioassay
(i.e., exposing seeds or seedlings to herbicide to determine the presence of genetic tolerance). For more
information, check the AOSA Cultivar Purity Testing Handbook. It is worthy to note that various genetic
traits are currently available in many ield crops.
other Tests, and the future of Variety Testing
As future genetic modiications are developed, state-of-the-art of variety testing will continue to evolve.
New tests will need to be developed to accommodate the need for distinguishing the new generation of
varieties that are released. It is not necessarily the purpose of this chapter to provide detailed protocols
for all variety tests, although protocols for many tests are presented for broad tests as well as classic vari-
ety tests in the following sections. For more detailed tests, especially as new tests are developed, readers
are referred to the AOSA Cultivar Purity Testing Handbook and the SCST Seed Technologists Training
Manual.
