When seeds come in contact with a humid substrate, their coat will likely develop fungi growth. This is pretty normal, and it doesn’t necessarily compromise germination: most of the time the fungus stays on the outside of the seeds without penetrating into the inside. However, if the growing seedlings are affected by fungi, their survival is at risk.
Nursery germination in compost, sand, or other nursery substrates should reduce this problem, compared to lab germination on substrates like paper or agar.
One option to reduce fungal attack during germination tests is to sanitize the seeds prior to germination testing. To do so, soak the seeds for 5–10 minutes in a solution of 1% sodium hypochlorite. In general, homemade bleach comes at a concentration of 5% sodium hypochlorite. Add 80 ml of distilled water to 20 ml of bleach to obtain a solution at 1%. Rinse the seeds well before testing.
Be aware that the use of sodium hypochlorite could potentially affect the results of germination tests, and could constitute a threat to the health of those who analyze the seeds. That’s why we recommend using this technique only when essential.