Fecha de publicación: -- Fuente: WIPO "tomato" Disclosed herein are compositions comprising chitosan and at least 1% (w/v) nitrogen. In certain cases, at least 50% of the nitrogen is in chemical form of amine and/or nitrate and/or ammonia. Also disclosed herein are methods of producing chitosan nanoparticles by dissolving chitosan in acidic water, where the water is made acidic by an acid selected from the group of acetic acid, nitric acid, sulfuric acid, hydrochloric acid, and combinations thereof; and forming nanoparticles from the dissolved chitosan. Further disclosed is the treatment of plants or plant parts with the compositions disclosed herein.