Nano-chitosan encapsulated Pseudomonas fluorescens greatly reduces Fusarium wilt infection in tomato

Pseudomonas sp. is a well-known rhizosphere growth-promoting bacterium. Our objectives were to investigate the synergetic effect of using nanochitosan to deliver Pseudomonas fluorescens on its stability in the soil and induction resistance against fusarium wilt in tomato plants. A greenhouse study includes four different treatments, tomato seedlings without treatment, tomato seedlings treated with nano-Pseudomonas fluorescens, tomato seedlings treated with free P. fluorescens, and tomato seedlings treated with nano-chitosan. The four groups of tomato seedlings were grown in two sets of soil one is infested with Fusarium oxysporum, and the second is uninfected soil for four weeks. The defense enzymes were determined in the tomato leaves after 2 and 4 weeks from transplanting, and at the same time, the soil enzymes were demonstrated. Results showed that nano-Pf treatment resulted in the highest growth percent (46.62%), disease reduction percent (115.85%). This enhancement because of the significant increase in soil enzymes activity under the nano-Pf treatment, this increase percent was about 411% in urease, 488% in phosphatase, 765% in catalase, 194% in glucosidase and antifungal enzymes (1666% in chitinase and 89% in glucanase) in compared to non-treated infected soil. Also, nano-Pf treatment upregulated defense enzymes in tomato plants under infection, the increase percent was about 64% in superoxide dismutase, polyphenol oxidase, 80% in cell wall bound peroxidase, and 180% in phenylalanine ammonia-lyase. Interestingly the increase percent of the antifungal enzymes chitinase and glucanase in the nano-Pf treated plants was about 231% and 260% respectively in compared to infected non-treated tomato plants. Nano-chitosan encapsulated P. fluorescens successfully mitigated Fusarium wilt infection and is a promising approach for a larger greenhouse study.