Switchgrass (Panicum virgatum L.) has ability to induce germination of Orobanche cumana

Orobanche cumana Wallr. (sunflower broomrape) is a devastating root parasitic weed, causing enormous crop losses worldwide. The question was whether or not switchgrass has the potential to be a 'trap crop' for O. cumana control. To answer this question, the field experiments, pot experiments, and laboratory experiments were conducted in this study. The ability of nine switchgrass (Panicum virgatum L.) cultivars to induce O. cumana seeds germination was tested. Results indicated that root extracts shoot extracts, rhizosphere soil, and root exudates from switchgrass induced O. cumana germination. Ability to induce germination varied significantly among growing stages, with the earlier part of growing season (grown for 2 weeks) generally inducing the highest O. cumana germination rates. The methanol was a more suitable solvent than distilled water for extracting germination stimulants from switchgrass plants. Ten-fold dilutions of the extracts generally induced higher germination rates than either undiluted or 100-fold dilutions. The germination rates of O. cumana seeds in shoot extracts treatments were positively correlated with those in the root extracts (R-2 = 0.6397; p < 0.01) and negatively correlated with those in the rhizosphere soil treatments (R-2 = 0.4433; p < 0.05). In conclusion, it is believed that switchgrass is a potential trap crop for the control of root parasitic weed O. cumana.