The following passage is vague, but troubling. It is from A Sierra Nevada Flora by Dr. Norman Weeden, Professor of Plant Genetics at Montana State University.
"The reader may be aware that even in common crops such as squash (Cucurbita pepo) or potato (Solanum tuberosum) genetic or environmental variation can make the crop extremely toxic. In much the same way, selenium accumulators such as locoweed (Astragalus spp) can be poisonous on some soils and relatively innocuous on other soils. Although the author is not aware of specific instances where the toxicity of a Sierran species has been demonstrated to vary as a result of genetic differences, such variation certainly exists."
Is anyone aware of an example of an edible plant being toxic when found growing in a different soil?