Purity is one aspect of a seed lot that must be reported on the seed label.
Purity is the percentage by weight of the pure seed present in a seed lot.
Contaminants like soil or stones in the seed lot must be recorded.
The determination of genetic purity requires a trained seed analyst usually from a state or private seed lab.
The Society of Commercial Seed Technologists provides training and testing to certify Registered Seed Technologists who are qualified to conduct purity analysis.
Pure seed must be separated from other physical contaminants such as soil particles, plant debris, inert material, and other crop or weed seeds.
Seed lots are also grown in the field or greenhouse to check for genetic purity.
To the right is a hybrid seed lot of petunia where the white flowers indicate that this seed crop is not pure and contains some seeds from the non-hybrid maternal parent.
Different cultivars will have a different pattern when a sample is run on an electrophoretic gel. On the DNA gel to the right, you can see plant samples that have the same banding pattern, while others show different banding patterns.
The banding patterns can be used by the geneticist or the seed technologist to show that a seed lot is "pure" and has the expected genetics.
A RAPD (randomly amplified polymorphic DNA) gel for cultivar identification. Lanes with the same letter have the same banding pattern. The lane marked with a W is the molecular weight reference lane.
