Agricultural and Biological Research

Extracellular biosynthesis of silver nanoparticles using entamopathogenic bacteria against Meloidogyne incognita

A. Vinothini and S. Iruthaya Kalai Selvam*

Background: Root-knot nematode Meloidogyne incognita represents one of the most significant genera of plant-parasitic nematodes on various crops, as it is widespread and poses a threat to thousands of plant species. As a result of their infection of the root system, which absorbs water and nutrients, the entire plant is harmed. Their population expands at a quick rate as a result of the fact that at least two life cycles can be completed within the span of a particular growing season and that females have a high rate of fertility. The use of chemical nematicides to control the pathogen has been restricted due to adverse environmental and health effects. Now widely accepted as a substitute for agrochemicals, silver eliminates unwanted microorganisms in planter soils and hydroponics systems. Silver nanoparticles are also an excellent stimulant of plant growth. Silver nanoparticles have potent antibacterial, antifungal, insecticidal, and nematicidal properties.

Methods: The supernatant of symbiotic bacteria Photorhabdus luminescens ON929969 from the entamopathogenic was employed for the synthesis of silver (PsAgNPs) nanoparticles. UV–visible spectrophotometer, X-ray diffraction analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy studies were used to characterize the produced AgNPs. To examine the larvicidal impact of bio PsAgNPs, each treatment was duplicated three times in CRD. Observations were made on the mortality of M. incognita juveniles every 24 hours, and the percentage mortality of juveniles was calculated after confirming the irreversible reaction of M. incognita upon exposure to the bio-synthesised PsAgNPs.

Results: UV-visible spectroscopic investigation has revealed that PsAgNPs have a prominent SPR peak at 430 nm. Synthesized AgNPs exhibited frequency bands at 3398.50, 2960.04, 1641.39, 1540.52, 1387.38, 1230.45, 1077.11, and 607.03 cm^-1, as confirmed by FTIR. The Debye–Scherrer equation reveals that the average crystallite size of produced AgNP is 22.38 nm. The results clearly demonstrate that the majority of AgNPs were aggregated spherical nanoparticles with a distinct size distribution and an average diameter of approximately 15.5 nm. The effect of bio PsAgNPs had a direct correlation between the death rate of J2 of M. incognita and exposure concentrations/duration. There was 100 percent death of M. incognita juveniles at higher concentrations of 2 and 3 g/ml of bio-synthesized AgNPs during the shortest duration of time of 24 hours, and this tendency was maintained throughout the exposure period.

Conclusion: The results clarified the positive effect of bio synthesized PsAgNPs on M. incognita juveniles. More research needs to determine the long run effect.