Non-sterile soil extract solution (1.5%)

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Contents 1 Purpose 2 Ingredients 3 Instructions 4 Notes 5 References 6 Contributed by

Purpose

Stimulating sporangia formation.

Ingredients

Ingredient	1 L	500 ml
Distilled water	1000 ml	500 ml
Field soil	15 g	7.5 g

Instructions

1. Collect field soil (preferably a loam or silt loam) from an area where plants are growing; Phytophthora should not be present in this soil.
2. Mix soil and water in a flask with a magnetic stirrer for at least 4hrs.
3. Allow suspension to passively settle for at least 4hrs or, preferably, overnight.
4. Decant supernatant and centrifuge in 250ml or 500ml Nalgene bottles for 10min at 8000 rpm; this is a force of approximately 10,000 g.
5. Filter through 2 layers of Whatman No. 1 filter paper (with vacuum); this removes floating organic debris.
6. Store the extract solution in a glass bottle in the refrigerator (at approximately 4 °C).
7. The soil extract solution can be used for several months although it is best when “fresh”; although, aging for several days to a week before using it works most effectively.

Notes

• This solution can be sterilized by filtration or autoclaving if necessary, however, the sterile soil extract solution is not as effective as non-sterile solution for stimulating sporangia.

References

• Jeffers, S. N., and H.S. Aldwinckle. 1987. Phytopathology 77:1475-1482.

Contributed by

From the Culture Media for Plant Pathogenic Fungi and Bacteria, University of Massachusetts: Contributed by Robert L. Wick