Soybean aphid feeding increases soybean cyst nematode reproduction

Soybean cyst nematode (SCN) is the leading pathogen of soybean in the United States. Current management is heavily reliant on resistant cultivars to suppress populations in order to protect soybean yield in the current year and sustain high yields for future years. Recent research suggested feeding by the soybean aphid increases SCN reproduction. A greenhouse experiment was conducted to discern the effect of soybean aphid feeding on SCN survival and reproduction. Soybean seed of a SCN-susceptible cultivar, Kenwood 94, and a PI 88788-derived SCN-resistant cultivar Dekalb 27-52 were grown in SCN infested soil for 30 d. Ten days after planting, plants were infested with either zero, five, or ten aphids. Aphids were allowed to increase for the remainder of the experiment. At 30 d after planting the number of SCN cysts and eggs per plant were counted. Soybean aphids facilitated SCN reproduction on the SCN-resistant cultivar increasing SCN eggs and cysts by 33% in the ten and five aphid treatments compared to the zero aphid treatment. However, soybean aphids created competition for resources on Kenwood 94, decreasing both SCN eggs and cysts by 50% across both the five and ten aphid treatments compared to the zero aphid control. Future research will investigate under diverse field conditions whether soybean aphid feeding leads to facilitation or competition with the soybean cyst nematode and the effect of various aphid and nematode host plant resistance genes on the interaction.