Technology

Need for seed purity testing

Seed companies need to deliver seed varieties to the grower with a high percentage of seeds with particular trait, since there are mixtures of conventional seed as well. Hence there is necessity to analyze seed purity to determine how much per cent of the admixture is present in the seed lot. Buyer is protected against admixture in seed of a particular variety or crop by the seed regulation laws or acts in many countries, for this purpose seed testing by grow out test or “molecular GOT” are conducted before commercial sale & these facilities are accredited by governmental bodies (Ex. NABL).

Germination test

Reports the percentage of seed that germinated. Tests are usually made in 200 or 400 seed samples.

Purity test:

The percentage of seed described on the label that is actually found in the quantity of seed. This is tested by grow out test (GOT), results are observed after flowering and fruiting otherwise one crop cycle.

Tetrazolium seed viability test: A test for viability that involves three steps:

  1. Preconditioning (imbibition);
  2. Preparation and staining (sometimes cutting the seed and then soaking the seed
    in a 2, 3, 5 triphenyl tetrazolium chloride solution);
  3. Evaluation (examining the seed for a color change in the embryo).

Weed test:

Examines a sample of seed and identifies every seed that is different
from the labeled seed type.

Genetic seed Purity or Hybrid seed Purity:

Genetic purity of seeds refers to the trueness to type. If the seed possesses all the
genetic qualities that breeder has placed in the variety, it is said to be genetically
pure and is tested using molecular markers.

  • Molecular - based testing: brief description of Process and advantages
  • Tests both Genetic purity and Bt-purity
  • Genomic DNA isolated from 100 - 400 seed constitute single lot
  • 2 – 3 polymorphic STR to differentiate hybrids from parental line (not
    multiplexed)
  • Genomic DNA is quantified by Real-Time PCR or Spectrophotometer
  • PCR is performed under standardized condition using labeled primers
  • PCR products are analyzed on genetic analyzer
  • Results within 2-3 working days
  • Data would have ±0.5% error rate
  • Scalable model, can test large number of samples per day
  • Results represent purity for the sample provided only

Features:

  • Fast and high-throughput protocol
  • Error-free protocol
  • Economically viable

Comparison of Fields and Lab GOT

  Grow Out test Molecular Based Test
Time 120 day 5 Hours
Cost High Low
Manpower High Low
Sample 200-400 seed/Lot 100-400 seed/ Lot
Environmental Influence Yes No
Phenotypic Confusion Yes No
Seed Selling 3-4 Months
May be next season
After test results-
Same season

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