Image analysis – Applications – Animal – plant – or food inspection
Reexamination Certificate
1999-05-03
2001-05-22
Chang, Jon (Department: 2623)
Image analysis
Applications
Animal, plant, or food inspection
C382S286000
Reexamination Certificate
active
06236739
ABSTRACT:
FIELD OF THE INVENTION
The present invention provides a method for assessing the quality of a seed lot by determining the vigor rating of a sample of seedlings. The method employs the use of image analysis equipment, also known as machine vision, to determine the vigor rating.
BACKGROUND AND PRIOR ART
Seed Vigor Tests
In 1876, Nobbe in his “Handbook der Samenkunde” described his observations regarding the differences in seed vigor and “germination energy”. Since that time, the nature and importance of seed vigor has increased steadily.
Today, the Vigor Test Committee of the Association of Official Seed Analysts has adopted the following definition of seed vigor: “Seed vigor comprises those properties which determine the potential for rapid uniform emergence and development of normal seedlings under a wide range of field conditions.”
Seed Vigor Testing Handbook
Prepared by the Seed Vigor Testing Committee of the Association of Official Seed Analysts (1983).
Biologically, seed vigor is based on the genetic constitution of seeds which establishes their maximum physiological potential based on the fact that seeds begin to deteriorate at maturity and this deterioration proceeds until all of the seed tissues are dead. Id. The rate of deterioration, including loss of vigor, is determined not only by heredity, but also by events occurring during seed development, harvesting, conditioning, and storage. Id.
Several categories of seed vigor tests are known. These categories are: (1) seedling growth and evaluation tests (which are often referred to as “seedling vigor classification and seedling growth rate” tests); (2) stress tests; and (3) biochemical tests.
Germination Testing
In addition to vigor testing, germination testing is frequently conducted to determine seed quality. Germination (in laboratory practice) is defined by the AOSA as, “the emergence and development from the seed embryo of those essential structures, which, for the kinds of seed in question, are indicative of the ability to produce a normal plant under favorable conditions.” Id. Germination test results establish the maximum plant producing potential of seed lots and correlate quite well with emergence under favorable field conditions. Id.
Today, the germination test is the principal and accepted criterion for determining seed viability. The test results are typically obtained from seeds which have been placed under favorable germination conditions. Essentially, germination tests are made on artificial, standardized, essentially sterile media, in humidified, temperature controlled germinators for periods sufficiently long to permit rather “weak” seeds to germinate. Id. However, one problem with that prior art germination test is that it overestimates field emergence because rarely, if ever, are favorable conditions encountered in the field.
Another problem with the prior art germination test is that it is scaleless or dimensionless. Either a seed germinates or it does not. Thus, every germinable seed is by definition equal in plant producing ability. Id. The results of a germination test are expressed as a percentage from 1-100%. The problem with using such percentages is that it is very misleading. For example, a seed lot germinating 50% should produce the same stand as a seed lot germinating 100%, provided twice as many seeds are planted. Id. In a few situations it might, but mostly it will not.
Types of Vigor Tests
a. Seedling growth and evaluating tests
Some vigor tests are conducted under the same conditions as the standard germination test, except seedling growth is measured or evaluated in a different way. Seedling growth and evaluation tests are generally inexpensive and relatively rapid. However, the drawbacks of these tests are that conditions are tough to standardize between laboratories and the seed analyst must be able to determine whether the seed has germinated.
The seedling vigor classification is similar to the standard germination test. The only difference between the two tests is that normal seedlings are further classified as “strong” or “weak”. Id. A seedling is often characterized as weak if it is missing its primary root and/or cotyledon, if its hypocotyl has breaks, lesions, necrosis, twisting or curling. Id. In contrast, normal seedlings are characterized as “strong”. Based on this test, seedlings are divided into those with deficiencies and those without deficiencies. While this test involves very little work, careless handling of the test can result in errors.
The seedling growth rate test involves a measurement of seedling growth. Under this test, seeds are germinated according to the standard germination test with a more specific moisture content of paper towels. Id. At the end of the germination period, seedling growth is measured. Id. Usually, linear growth and dry weight are determined. Seeds which produce a single straight shoot or root can be measured to determine linear growth. The seedling growth rate test suffers from four limitations: (1) the seedling measurement and the removal of cotyledons or other storage tissues prior to oven drying are relatively time consuming; (2) seedling elongation can be inherently different among cultivars; (3) rate of germination is affected by moisture and temperature; and (4) seed size affects hypocotyl growth in soybeans. Id.
b. Stress tests
Various types of stress tests are known. Some of the stress tests simulate stresses seeds encounter in the field. The theory behind a stress test is that under sub optimum or stressed conditions, high vigor seeds have a greater potential for emergence.
In the accelerated aging test, for example, seeds are placed temperature of 40-45° C. and nearly 100% relative humidity for various lengths of time, after which a germination test is conducted. This test is relatively inexpensive.
The cold test simulates early spring field conditions by providing high soil moisture and low soil temperature. Typically, seeds are placed in soil in a plastic box or in paper towels lined with soil and incubated at 10° C. for a specified period. Id. At the end of the cold period, the tests are transferred to a favorable temperature for germination. Id. The emergence percentage is considered as an indication of seed vigor. Id. However, one problem with the cold test is microorganisms. Microorganisms frequently cause seed decay, fungus and other problems. In addition, specific soil conditions are often difficult to standardize from laboratory to laboratory.
The cool germination test involves germinating seeds in darkness at constantly low temperatures, such as 18° C. for several days. Basically, this test is a type of seed exhaustion test. This test is also referred to as the slant board test, which has been used to predict the field vigor in lettuce, carrots, cauliflower seeds and cotton. See O. E. Smith et al., “Studies on Lettuce Seed Quality: I. Effect of Seed Size and Weight on Vigor,”
J. Amer. Soc. Hort. Sci
. 98(b): 529-533 (1973). McCormac, A. C. et al., “Automated Vigour Testing of Field Vegetables Using Image Analysis,”
Seed Sci. and Technol
. 18: 103-112 (1990).
c. Biochemical Tests
Biochemical tests measure certain metabolic events in seeds that are associated with germination and can be used to assess vigor.
The tetrazolium test measures dehydrogenase enzyme activity. These enzymes reduce tetrazolium chloride salt, which is colorless, to form a water insoluble red compound, formazon, which “stains” living cells a red color. The dead cells remain colorless. See the
Seed Vigor Testing Handbook
Prepared by the Seed Test Committee of the Association of Official Seed Analysts (1983).
Conductivity tests involve measuring soak water conductivity. Low vigor seeds often have poor membrane structure and often leak. Seeds with such a poor membrane structure frequently lose electrolytes, such as amino acids and organic acids, when they imbibe water, thereby increasing the conductivity of the soak water.
Image Analysis
Image Analysis, which is also known as Machine Vision, is a computer based system that is being used in the pla
Ball Horticultural Company
Chang Jon
Marshall O'Toole Gerstein Murray & Borun
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