Parasitic Plants as a New Target Plant for Screening Rice Allelopathic Potential

Allelopathy becomes important to be considered as an alternative weed management measure. Screening or evaluating the allelopathic potential rice varieties is the first step toward implementing an allelopathic component of weed management. In this study, the parasitic plant Triphysaria versicolor was investigated as a new target plant for allelopathic potential assays by using extracts from 3 rice cultivars, Kouketsumuchi (potent allelopathic cultivar), Dongjinbyeo (non-allelopathic cultivar) and K21 (progeny of Dongjinbyeo crossed with Kouketsumochi). The effects of three rice cultivars on the haustorium induction rate of Triphysaria versicolor, and phytotoxicity activity on target plant barnyard grass and lettuce were determined. Experiments of assay cinnamic acid 4-hydroxylase (CA4H) activity and identification the amounts of total 14 phenolic compounds in the three rice cultivars were conducted by Bradford method and HPLC analysis respectively. Results indicated that Kouketsumochi caused the highest rate of haustorium induction followed by K21 and Dongjinbyeo. The different phytotoxicity activity and haustorium induction rates of rice cultivars were related to allelopathic potential. CA4H activity and total 14 phenolic compounds in the rice cultivars proved that there is a close relationship between haustorium inducing factors and phototoxic activity, which are structurally related to phenolic compounds. Thus, T. versicolor can be used as a new target plant for evaluating the allelopathic potential of plant species.