Pyramiding R genes is a common strategy used by breeders to enhance resistance and increase durability of resistance in crops. However, the molecular mechanisms that mediate R gene interactions are not known. Kamphuis et al. (2019) analyzed Medicago truncatula plants carrying two genes that confer resistance to bluegreen aphids. They identified a potential phytohormone crosstalk triggered by the combined R gene action in response to aphid feeding that enhances resistance and minimizes R gene-associated fitness costs to the plant.