The problem. A couple of weeks ago an email was forwarded to me from another Extension employee that had fielded a call from a local ag service provider. The service provider was seeking guidance after having visited a client’s soybean field and encountering plants exhibiting unfamiliar symptoms. What was particularly puzzling (and worrying) to the service provider was that plants appeared to have symptoms caused by Phytophthora sojae but the soybean variety had both field or adult-plant resistance and pathotype or race-specific resistance genes to P. sojae . Bacterial cells and either spores of true fungi or fungus-like organisms like Phytophthora are individuals in a much larger population. During processes such as the genetic recombination that occurs during sexual reproduction and the random mutations that occur during cell division, new spores will be genetically different from their siblings. Some may be better able to survive and cause disease on plants that have g...