A novel water-based chitosan-La pesticide nanocarrier enhancing defense responses in rice (Oryza sativa L) growth

To relieve the environmental pressure from overusing conventional pesticides formulations, the study of a new environmentally friendly and multifunctional formulation is so very urgent. Here, we firstly reported a lanthanum-modified chitosan oligosaccharide nanoparticles (Cos-La) prepared by a simple ionic cross-linking method to load avermectin (AVM). The loading capacity of AVM-loaded Cos-La was up to 46.3%. As a water-based formulation, Cos-La could effectively improve the persistence of AVM over 25% and reduce the photolysis rate of AVM around 20%. Furthermore, different concentrations of Cos-La were used to cultivate rice. The treated rice exhibited growth promotion effects in terms of plant height and fresh weight. With the increase in the treating concentration of Cos-La nanoparticles, the wettability of rice tended to reduce, which indicated it might lower the risk of plant diseases and pests. Further, Cos-La treated rice showed significant defense response for rice blast and the effect was two times more than equivalent Cos and LaCl₃·7H₂O mixture solution. These results showed that Cos-La not only could improve the stability and persistence of pesticides, but also could effectively promote the growth and improve the disease resistance of crops. Cos-La nanoparticles would be a promising and environmentally friendly nanocarrier of pesticides in agricultural scenarios.