Seed testing and sampling

it also contains content related to seed sampling. The various seed tests along with their explanation.

1. Seed Testing BY-ANSHUL PHAUGAT B.Sc (Hons) AGRICULTURE

2. SEED TESTING Seed testing is the cornerstone of all other seed technologies. It is the means by which we measure the viability and all the physical factors that regulate the use and maintenance of seeds. Everything that is done with seeds should have some test information to guide the work and ensure high quality. Seed tests tell if a crop of seeds is worth collecting, if handling procedures are correct, and how many potential seedlings are available for regeneration. Seed testing is the science of evaluating the planting value of seed. Seed quality in India is legally controlled by the Seed Act, 1966.

3. The seed Act is enforced by Govt. of India through the Central Ministry of Agriculture and Co-operation and State Department of Agriculture. According to this Act all the seeds of notified varieties / kinds when sold to farmers must meet the minimum standard of germination, genetic purity and physical purity. The seed should be packed in a suitable container and a label has to be affixed on the container. Information about germination, physical purity, variety, date of test and name of the seed producer has to be given on the label. The germination as given on the label is valid for 9 months and after which it has to be revalidated.

4. Objectives of seed testing To determine their quality, that is, their suitability for planting. To identify seed quality problems and their probable cause. To determine the need for drying and processing and specific procedures that should be used. To determine if seed meets established quality standards or labelling specifications. To establish quality and provide a basis for price and consumer discrimination among lots in the market.

5. Seed Testing Laboratory The seed testing laboratory is the hub of seed quality control. Seed testing services are required from time to time to gain information regarding planting value of seed lots. To carry out these responsibilities effectively, it is necessary that seed testing laboratories are established, manned and equipped in a manner such that whatever samples are received could be analyzed in the least possible time, so that the seed quality control work and the need of seed industry are effectively met.

6. Routine tests in STL Purity Germination Moisture Types of samples received at STL Service sample  - Sample received from the farmers Certified sample  - Sample received from certification agencies or officers Official sample  - Sample received from the seed inspectors.

7. Principle of Seed sampling Sample is obtained from seed lot by taking small portion at random from different places and combining them. From this sample smaller samples are obtained by one or more stages. In each and every stage thorough mixing and dividing is necessary.

8. Methods of sampling Hand sampling This is followed for sampling the non free flowing seeds or chaffy and fuzzy seeds such as cotton, tomato, grass seeds etc., In this method it is very difficult to take samples from the deeper layers or bag. To over come this, bags are emptied completely or partly and then seed samples are taken. While removing the samples from the containers, care should be taken to close the fingers tightly so that no seeds escape

9. B. Sampling with triers By using appropriate triers, samples can be taken from bags or from bulk. Bin samplers Used for drawing samples from the lots stored in the bins. b) Nobbe trier The name was given after Fredrick Nobbe father of seed testing. This trier is made in different dimensions to suit various kinds of seeds. It has a pointed tube long enough to reach the centre of the bag with an oval slot near the pointed end. The length is very small. This is suitable for sampling seeds in bag not in bulk. c) Sleeve type triers or stick triers It is the most commonly used trier for sampling: There are two types viz., 1. with compartments 2. Without compartments.

10. Types of samples Primary sample Each probe or handful of sample taken either in bag or in bulk is called primary sample. Composite sample All the primary samples drawn are combined together in suitable container to form a composite sample. Submitted sample When the composite sample is properly reduced to the required size that to be submitted to the seed testing lab, it is called submitted sample. Submitted sample of requisite weight or more is obtained by repeated halving or by abstracting and subsequently combining small random portions. Working sample It is the reduced sample required weight obtained from the submitted sample on which the quantity tests are conducted in seed testing lab.

11. Purity Test A purity test is conducted on approximately 2,500 seeds which are broken down into four components: Pure seed, Other crop seed, Weed seed, and Inert matter.  The components are then weighed from which percentages are calculated.  The percentage is based on the weight of each component, not the number of seeds. Information on actual seed lot composition is important; purity analysis serves as a guideline to determine the necessity of further cleaning. During purity analysis, each ‘pure’ seed fraction from the working sample is separated from the inert matter and other seeds.

12. WARM GERMINATION The  Warm germination  test is used to determine under optimum conditions, the percentage of seed able to germinate in a given lot. What Do the Results Mean?   Results are reported as a percentage, which represents the number of seedlings categorized as normal out of the 400 seed test. During analysis, the technician records the number of normal, abnormal and dead seedlings. A good warm germ result is 93% or higher. The germination percent is used for tagging and labeling purposes as determined by state, national and international seed law.

13. What Technique is Used?    Rolled Towel Method: The technician layers one heavy weight (76#) towel, one light weight (38#) towel and a sheet of waterproof paper.  400 seeds are laid on towels; 4-8 reps, depending on the crop. The rolled towels are placed in germination baskets, and placed in the germinator for the applicable length of time by crop. The towels remain in the germinator at 25ºC (77ºF) for 6 days (corn), 7 days (soybeans), 7 days (sorghum), and 20ºC (68ºF) for 7 days for wheat and small grains. Seedlings are evaluated on the final day.   *  Small seeds, forbes , natives, wildflowers and vegetables are handled separately - planted, grown and evaluated according to the protocols specific to the species.

14. Germination test

15. VIGOUR TEST Test results are mainly used as a quality assurance tool to rank seed lots for field and/or storage potential. Vigour tests can help predict: Rate and uniformity of seed germination and seedling growth Field performance, including extent, rate and uniformity of seedling emergence Performance after storage and transport, particularly the retention of germination capacity Vigour testing is not a substitution for germination testing. Both are tests of seed viability, but they measure different sides of that coin. A germination test tells you what percentage of your seed lot will start to grow under ideal conditions. A vigour test, on the other hand, is an indicator of how that seed will perform under less than perfect environmental conditions, taking into account the seeds’ genetic constitution, size, physiological maturity, and any effects related to production and storage the previous year.

16. VIGOUR TEST

17. Tetrazolium [ T-test ] TZ (Tetrazolium) test which provides an estimate of seed viability in a short amount of time. The TZ test identifies problems associated with damage due to mechanical, insect, freeze, heat, seed coat checking, disease, immaturity and sprouting. Although this test is most commonly conducted on soybeans, sorghum, wheat, barley, corn and oats; it can be performed on any species.

18. What Technique is Used?  Seeds are pre-conditioned overnight by soaking in water or on a damp germination towel. 100 seeds are placed in a small container and soaked in a staining solution and then each container is placed in a germinator at 35ºC (95ºF) for the appropriate staining period. Each seed is bisected through the embryo using a razor blade to allow the TZ chemical to stain the embryo. What Do the Results Mean?   A TZ test can determine cause and percentage of damage and the TZ score is most often very close to the warm germination test result. Potential germ is reported as a % based on normal seeds found.

19. Tetrazolium [ T-test ]

20. Electrical Conductivity Test This test is used to determine when seed should be planted, and applies mainly to pulses and large seeded legumes, but can also be used on canola. The test evaluates the integrity of cell membranes and their ability to repair themselves during the “soak period.” Seed is soaked in de-ionized water for a short period of time, allowing sugars, starches and amino acids to leach from the seed. The higher the conductivity value of the soak water, the lower the vigour . Seed with high E.C. values should be used with caution.

21. Electrical Conductivity Test

22. Seedling Growth Rate Test This test is closely related to the standard germination test and is useful to figure out field planting potential under optimal or near ideal conditions. Seeds are planted under optimum conditions and are allowed to grow for an extended period of time, usually several days past the typical germination period. The seedlings are evaluated by their growth characteristics, such as stem length, leaf development or root branching. The measurements determining strong or poor vigour are highly dependant on the particular cultivar being tested. Some varieties of lentil, for example, may naturally be longer than others. It means our seed analysts have to get very familiar with a lot of different growth characteristics!

23. X-RADIOGRAPHY X-ray  based imaging provides a method for the non-invasive analysis of the internal structures of  seeds . Already shortly after the discovery of  X -rays by Röntgen in 1895, the technology was applied to  seeds . Lundström (1903) was the first to use  X -rays to analyse coniferous tree  seeds .

24. The principle of the technique is based on differential absorption of X-rays by seed tissues, depending on the thickness, density, and composition of these tissues, in addition to the wavelength of the radiation. Seeds are placed between a low energy source of X-rays and a photosensitive film. When the X-rays cross through the seed and reach the film, a latent image is created. After the film is processed, an image of light and dark shadows is formed, a permanent image on the X-ray film. Darker areas of the X-ray correspond to the parts in which the X-rays penetrate more easily, whereas lighter areas represent denser parts of the seed. This same reasoning applies to interpretation of images obtained by digital X-ray equipment (without use of film), with the advantage of greater speed in acquiring images and better quality (contrast and resolution).

25. X-RADIOGRAPHY

26. THANK YOU For ppt on another topics drop me an email: [email protected] (topics related to Agriculture only)