Integrated use of chitosan and arbuscular mycorrhizal fungi mitigates Verticillium dahliae infection in Tomato: Comparison with conventional fertilization

This study aimed to evaluate the efficiency of chitosan and arbuscular mycorrhizal fungi (M) (Ch), individually or combined, in enhancing tomato resistance to Verticillium dahliae (V) compared to conventional chemical fertilizer (NPK). The application of biostimulants reduced the progression of disease symptoms and lowered the leaf alteration index as well as the severity and incidence of Verticillium wilt compared to the control. Specifically, the combination of chitosan, arbuscular mycorrhizal fungi and Verticillium dahliae (ChMV) reduced the area under disease progress curve (AUDPC) and final mean severity (FMS) by 50.42 % and 49.46 %, respectively in comparison with control. Furthermore, ChMV treatment improved photosynthetic pigments such as chlorophyll a (196.5 %), chlorophyll b (155.4 %), and total chlorophyll (173.2 %), respectively. Additionally, the biostimulants helped maintain higher total soluble sugar (TSS), proline and protein levels. ChMV protected the photosynthetic machinery, alleviated the deleterious effects of stress markers and enhanced the activity of antioxidant system. These included ascorbate peroxidase (APX) (50.11 %), peroxidase (POX) (286.10 %) and polyphenol oxidase (PPO) (186.30 %). Notably, the SOD activity showed the highest increase in the MV treatment (165.02 %), followed by ChMV (145.6 %) and ChV (97.1 %), in comparison with control (V). Chitosan and M applied alone or in combination, proved to be a promising strategy for strengthening the antioxidant defense systems and mitigating the progression of plant diseases in tomato plants.