Nematicidal Potential of Green Chiretta Extracts Against Meloidogyne enterolobii and M. Incognita: In vitro Assessment for Agricultural Application

Abstract

Root-knot nematodes pose a persistent threat to various economically important crops in Thailand, with limited available management strategies for farmers. This study aimed to assess the efficacy of aqueous (AE), methanolic (ME), ethanolic (EE), ethyl acetate (EAE), and chloroform (CE) crude extracts derived from green chiretta in controlling Meloidogyne enterolobii and M. incognita under laboratory conditions. The results demonstrated significant inhibitory effects of all crude extracts, except for CE, against both nematode species. Notably, AE (10 and 20 mg/mL), ME (20 mg/mL), and EE (20 mg/mL) treatments exhibited maximum inhibition of hatching, leading to a considerable reduction in nematode hatch rates by 87.5 - 96.8 % for M. enterolobii and 88.5 - 96.5 % for M. incognita, compared with distilled water (DW). In terms of second-stage juveniles (J2s) mortality, AE (10 and 20 mg/mL), ME (20 mg/mL), and EAE (20 mg/mL) demonstrated the highest nematicidal activity, resulting in mortality rates of 94.2 - 100 % for M. enterolobii and 92.2 - 99.2 % for M. incognita. Chemotaxis assays revealed a repellent effect of all extracts on both nematode species, except for the ethyl acetate extract (EAE), which attracted M. incognita J2s without affecting M. enterolobii J2s. The observed efficacy was attributed to the higher concentrations of bioactive compounds, including flavonoids, phenolics, and terpenoids, in the extracts compared to CE. Based on these in vitro findings, it is suggested that AE, ME, EE, and EAE of green chiretta exhibit significant nematicidal activity against M. enterolobii and M. incognita. Further evaluation under greenhouse and field conditions is warranted to ascertain the practical applicability and effectiveness of these extracts in a real-world agricultural setting.