Irradiated chitosan nanoparticles and biological agent: a novel approach for management of sesame wilt disease

These results highlight irradiated Ch-NPs as a promising, eco-friendly, and sustainable component of integrated disease management strategies, offering a viable alternative to conventional chemical fungicides for controlling Fusarium oxysporum f. sp. sesami in sesame cultivation. Fusarium wilt, caused by Fusarium oxysporum f. sp. sesami, poses a major limitation to sesame productivity. To develop a more efficient control approach, chitosan nanoparticles (Ch-NPs) were synthesized and exposed to 24 kGy of gamma irradiation, a process that improves their structural uniformity and enhances their functional properties. The antifungal activity was tested under laboratory, greenhouse, and field conditions, either alone or in combination with Trichoderma reesei, Bacillus subtilis, and the commercial fungicide Maxim-XL. The nanoparticles were characterized using UV, FTIR, and TEM analysis. UV analysis confirmed the nanoparticle spectrum with a maximum absorbance at 224 nm. Using transmission electron microscopy, it was found that by gamma irradiation, Ch-NP size was reduced from 89.08-113.63 nm to 48.11-56.22 nm, which, in turn, made it more uniform and bioactive. Irradiated Ch-NPs (250 µL L⁻¹) demonstrated the ability of almost complete inhibition of F. oxysporum growth in vitro, along with controlling the disease incidence and severity in greenhouse and field tests, which is equal to that of Maxim-XL. Among the biological agents tried, T. reesei was the best in giving an antagonism of 76.3% inhibition. Treatment with irradiated Ch-NPs and T. reesei enhanced sesame growth and productivity, reflected in greater plant height, more capsules, and higher seed yield, and also elevated the activities of defense-related enzymes-peroxidase, polyphenol oxidase, chitinase, and phenylalanine ammonia-lyase. The study therefore sought to assess the effectiveness of gamma-irradiated chitosan nanoparticles, used in combination with biological control agents, as eco-friendly alternatives to chemical fungicides for managing the disease.