Microbial interference mitigates Meloidogyne incognita mediated oxidative stress and augments bacoside content in Bacopa monnieri L.

Abstract

Microbial interference plays an imperative role in plant development and response to various stresses. However, its involvement in mitigation of oxidative stress generated by plant parasitic nematode in plants remains elusive. In the present investigation, the efficacy of microbe's viz., Chitiniphilus sp. MTN22 and Streptomyces sp. MTN14 single and in combinations was examined to mitigate oxidative stress generated by M. incognita in medicinal plant, Bacopa monnieri. Microbial combination with and without pathogen also enhanced the growth parameters along with secondary metabolites (bacoside) of B. monnieri than the pathogen inoculated control. The study showed that initially the production of hydrogen peroxide (HO) was higher in dual microbes infected with pathogen which further declined over M. incognita inoculated control plants. Superoxide dismutase and free radical scavenging activity were also highest in the same treatment which was linearly related with least lipid peroxidation and root gall formation in B. monnieri under the biotic stress. Microscopic visualization of total reactive oxygen species (ROS), HO, superoxide radical and programmed cell death in host plant further extended our knowledge and corroborated well with the above findings. Furthermore, scanning electron microscopy confirmed good microbial colonization on the host root surface around nematode penetration sites in plants treated with dual microbes under pathogenic stress. The findings offer novel insight into the mechanism adopted by the synergistic microbial strains in mitigating oxidative stress and simultaneously stimulating bacoside production under pathogenic stress.

Insights into the Role of Streptomyces hydrogenans as the Plant Growth Promoter, Photosynthetic Pigment Enhancer and Biocontrol Agent against Meloidogyne incognita in Solanum lycopersicum Seedlings

“…It is attributable to the pathogenicity of nematodes in the form of elevated ROS within stressed plants. Moreover, a tremendous increase in ROS species in the Bacopa monnieri plants has also been reported upon nematode infestations [ 39 ]. Along with this, studies conducted by Khanna, et al [ 56 ] also formulated a paramount increase in oxidative stress markers in tomato plants infested with nematodes.…”

“…According to their study, this reduction is due to enhanced activities of defense enzymes in microbe inoculated plants [ 56 ]. Similarly, Gupta, et al [ 39 ] conducted research in nematode infected B. monnieri plants inoculated with Streptomyces sp. and Chitinphilus sp.…”

“…in which H 2 O 2 and MDA content was found to be considerably reduced. They speculated that this decrease is mainly due to the production of immunity developed signals via microbes in order to combat pathogen accumulated within plants [ 39 ]. Furthermore, microbes possess the ability to scavenge the ROS produced by plants through the ability to secrete chelating molecules like organic acids, siderophores, and other secondary metabolites.…”

“…In addition to these, many bacterial species have been reported to act as potential nematode killers. These bacterial species belonging to genera Bacillus , Pseudomonas , Burkholderia , Streptomyces , etc., show active responses against RKNs [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. Various Streptomyces species including S. hydrogenans strain DH-16, S. antibioticus strain M7 have been reported to produce active secondary biometabolites that have the capability to act as potential biocontrol agents against M. incognita .…”

Recent Advances in the Development of Environmentally Benign Treatments to Control Root-Knot Nematodes

“…strain MTN22 and Streptomyces sp. MTN14 on Brahmi ( Bacopa monnieri ) has been reported to mitigate the M. incognita mediated oxidative stress and augment the bacoside content of the plant ( Gupta et al., 2017 ). In greenhouse studies, fresh and dry biomass were improved by 1.7 and 2.1-fold respectively, upon treatment.…”