Nematicidal Action of Chitosan Nanoformulation: A Detailed Study

Biopolymers are naturally occurring materials formed during the life cycle of plants, animals, bacteria, and fungi. Chitosan is the second most abundant biopolymer available in the world, second only to cellulose. It is found in crustaceous shells, e.g., those of crabs, shrimps, prawns, and fungi, as well as insect exoskeletons. The use of nano-formulations for the management of pests and diseases is receiving increased interest with the advancement of nanotechnology. Here, chitosan nanospheres were obtained from chitosan using the ionic gelation technique. The nano-formulations obtained were characterized using a particle size analyzer, Fourier transform infrared spectroscopy, and a transmission electron microscope. The efficacy of chitosan nanospheres in suppressing the root-knot nematode Meloidogyne incognita was studied. The particle size of nanospheres formulated for this study was 380.2 nm, with a polydispersity index (PI) of 0.4 and zeta potential of 45.7 or 50.9 mV at pH 5.2. The chitosan nanospheres were spherical, and the particles did not agglomerate. FTIR spectra of the chitosan nanospheres peaked at 3334 cm-1, thereby indicating the stretching of the OH and NH groups. In in-vitro studies, chitosan nanospheres showed significant nematicidal activity against M. incognita. Under pot culture conditions, chitosan nanospheres (1% active compound chitosan) at 2 ml/plant decreased the nematode population in roots or soil. Compared to the control, the number of galls was reduced by 83.68%, the number of egg masses by 83.85%, the number of adult females by 66.56%, and the number of second-stage juveniles by 73.20%. In a field experiment, the application of chitosan nanospheres (1%) was followed by an 18.75% increase in fruit yield compared to the non-treated control. The study concluded that as chitosan nanospheres are synthesized from a biological source, the formulation is environmentally friendly and does not leave any toxic residues in the ecosystem.