Combined effects of vermicompost and vermicompost leachate on the early growth of Meloidogyne incognita stressed Withania somnifera (L.) Dunal

Roots of Withania somnifera, an important medicinal herb, are prone to the infection of Meloidogyne incognita (a root parasitic nematode). The infection lowers the quality and quantity of plant material and poses a challenge in crop cultivation and obtaining desirable yield. In the present study, in vitro inhibitory activity of vermicompost leachate (Vcom-L) was assessed against % hatch and survival of M. incognita in a 96 h assay. Then, Vcom-L was used as soil supplement in combination with vermicompost (Vcom) to evaluate their nematode inhibitory and stress alleviating effect in W. somnifera, in a pot experiment. Root galling intensity and growth performance of nematode-stressed W. somnifera raised from seeds pre-soaked in distilled water (DW), Vcom-L, vermicompost tea (Vcom-T) and different dilutions of Vcom-L were assessed. We observed 79% suppression of egg hatching and 89% juvenile (J2) mortality after 96 h compared to control, at 100% concentration of Vcom-L. Significant reduction in gall formation with increase in growth parameters of seedlings was observed after combined application of Vcom (60% or 100%) + Vcom-L and was evident as enhancement in seedling biomass and contents of chlorophyll and protein. However, proline, total phenolics and malondialdehyde (MDA) content declined significantly in these combinations compared to the control (0% Vcom). Activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidise (APX), guaiacol peroxidise (GPX) and glutathione reductase (GR) declined with Vcom as well as Vcom + Vcom-L and corresponded with decline in the accumulation of reactive oxygen species in leaves. Further, 1:5 and 1:10 dilutions of Vcom-L in combination with Vcom (60%) proved beneficial in mitigating the nematode-induced stress in W. somnifera. Present results showed the potential of Vcom and Vcom-L in standardised combination as an effective strategy in controlling the pathogenicity of M. incognita in medicinal plants such as W. somnifera.