Protective effect of Dryopteris crassirhizoma extracts in the control of the root-knot nematode Meloidogyne incognita

Root-knot nematodes (Meloidogyne spp.) are among the most damaging soilborne plant parasites and are responsible for large economic losses in a wide variety of crops worldwide. More recently attention has increased on the use of phytochemicals as natural and biodegradable control agents to control plant-parasitic nematodes. In this study the nematicidal activity of extracts from 13 cryptogamic species was tested against the root-knot nematode Meloidogyne incognita. Ten extracts caused more then 50% mortality of second-stage juveniles after 48 h in an in vitro assay at 1 mg.ml(-1). The extract from Dryopteris crassirhizoma displayed the highest activity, resulting in 100% mortality after 72 h at 1 mg.ml(-1). The extract of D. crassirhizoma was then separated into five fractions by sequential extractions with water, petroleum ether, chloroform, ethyl acetate, and n-butyl alcohol. The chloroform fraction contained the highest level of total phloroglucinols (64.4%) and also was the most bioactive, with the lowest LC50 value of 0.4 mg.ml(-1). In pot experiments, D. crassirhizoma was tested against M. incognita on tomato and applied in three ways: as a liquid extract for soil drenching and root-dip treatments, or as a powder applied as a soil additive. All of these treatments reduced root galling and the final population density of M. incognita and increased plant growth compared with the control. Of the three types of treatments, soil amendment with pulverized rhizomes from D. crassirhizoma was the most effective treatment against M. incognita.