Haustorium induction of parasitic plant: A new bioassay method to determine allelopathic potential

Allelopathy has the potential to reduce the herbicide use as a component of integrated weed management technology. To develop a new bioassay method, we studied the effects of extracts from 3 rice cultivars (Kouketsumochi, Dongjinbyeo and K21) on the haustorium induction rate, phytotoxicity and ROS (reactive oxygen species) activity of parasitic plant Triphysaria versicolor as the target plant. The three cultivars influenced the different rates of haustorium induction. Kouketsumochi caused the highest haustorium induction rate followed by K21 and Dongjinbyeo (lowest response at varying concentrations of rice tissue extracts). Application of UV irradiation to the rice cultivars increased the phytotoxic effects on root growth of T. versicolor. Activity of reactive oxygen species (ROS) was assayed by staining root tip of parasitic plant with probe CM-H2DCFDA [5-(and 6)-chloromethyl-2’, 7’-dichlorodihydro-fluorescein diacetate, acetyl ester] and monitoring the change of fluorrescence. The fluorescence increased when the dye was oxidized by ROS. Fluorescence appeared in the shortest time in Kouketsumochi (allelopathic cultivar), followed by K21 and Dongjinbyeo (non-allelopathic cultivar). Results indicated that different haustorium rates of rice cultivars were related to different ROS activity. Thus T. versicolor can be used as a new target plant to evaluate the allelopathic potential of plant species.