Infection by Heterodera glycines Elevates Isoflavonoid Production and Influences Soybean Nodulation

High-performance liquid chromatography and Sinorhizobium fredii USDA191 nodC-lacZ gene fusion were used to monitor changes in the isoflavonoid content of soybean roots infected with Heterodera glycines isolate TN1. Isoflavonoid concentrations in infected roots of both H. glycines-resistant Hartwig and susceptible Essex soybean were two to four-fold higher than those of uninfected roots 2 and 3 days after inoculation. The isoflavonoids produced activated the transcription of nodC-lacZ fusion. The most abundant isoflavonoids were identified as daidzein and genistein by HPLC and GC/MS. Heterodera glycines increased the number of nodules formed on Essex roots inoculated with B. japonicum (USDA110) but reduced shoot weight and decreased the net nitrogenase activity of the nodules. Heterodera glycines infection of resistant Hartwig did not affect the total number of nodules or their nitrogen- fixing capacity.