Root colonization with arbuscular mycorrhizal fungi (AMF) enhances plant resistance particularly against soil-borne pathogenic fungi. In this study, mycorrhizal inoculation with Glomus mosseae (Gm) significantly alleviated tomato mould disease caused by the air-borne fungal pathogen, Cladosporium fulvum (Cf). The disease index (DI) in local leaves (receiving pathogen inoculation) and systemic leaves (just above the local leaf without pathogen inoculation) was 36.4% and 11.7% in mycorrhizal plants, respectively, whereas DI was 59.6% and 36.4% in the corresponding leaves of AMF noninoculated plants, after 50 days of Gm inoculation, corresponding to 15 days after Cf inoculation by leaf infiltration. Foliar spray inoculation with Cf also revealed that AMF pre-inoculated plants had a higher resistance against subsequent pathogen infection, where the DI was 41.3% in mycorrhizal plants vs. 64.4% in AMF non-inoculated plants.AMF-inoculated plants showed significantly higher fresh and dry weight than noninoculated plants under both control (without pathogen) and pathogen treatments.AMF-inoculated plants exhibited significant increases in activities of superoxide dismutase and peroxidase, along with decreases in levels of H 2 O 2 and malondialdehyde, compared with non-inoculated plants after pathogen inoculation. AMF inoculation led to increases in total chlorophyll contents and net photosynthesis rate as compared with non-inoculated plants under control and pathogen infection. Pathogen infection on AMF non-inoculated plants led to decreases in chlorophyll fluorescence parameters. However, pathogen infection did not affect these parameters in mycorrhizal plants. Taken together, these results indicate that AMF colonization may play an important role in plant resistance against air-borne pathogen infection by maintaining redox poise and photosynthetic activity. K E Y W O R D Santioxidative defence, arbuscular mycorrhiza, Cladosporium fulvum, disease index, Glomus mosseae, photosynthesis, tomato | INTRODUCTIONThe biotrophic pathogen fungus Cladosporium fulvum Cooke infects its only host tomato causing leaf mould disease, which is one of the most severe diseases threatening tomato yield and quality, especially in protected cultivation. For example, a yield loss of 10%-25% in normal years and even over 50% in bad years occurred in China (Sun, 2006). In conventional agricultural management, a large amount of synthetic fungicide is applied to control mould disease, which could cause serious environmental contamination and harm human health.In addition, new races of C. fulvum frequently emerge raising a problem of fungicide tolerance.*These authors contributed equally to this work. Control plants were sprayed with sterile distilled water. | MATERIALS AND METHODS | Plant culture and fungal treatment | Analyses of disease index and mycorrhizal colonizationThe DI was analysed after 15 days of pathogen inoculation accord- | Determination of plant growthThe effect of AMF colonization, pathogen infection, alone or in combinat...

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