The arbuscular mycorrhizal fungi (AM fungi) as mixture of Glomus spp. was used to induce resistance in Phaseolus vulgaris against root rot disease caused by Rhizoctonia solani. Results showed that % disease incidence was significantly reduced in AMinoculated plants as compared with infected and AM-free control. Production of hydrogen peroxide (H 2 O 2 ) and level of lipid peroxidation increased in both roots and shoots bean plants with increasing the time of infection. AM fungi markedly alleviated oxidative stress in infected bean plants, thus, levels of H 2 O 2 and lipid peroxidation was markedly reduced. Also, activity of antioxidant enzymes (catalase, ascorbate peroxidase and superoxide dismutase) significantly increased in bean tissues in response to both R.solani and/or AM fungus. The highest enzyme activity was recorded in shoots of 14 days old plants inoculated with AM fungi. Total phenolic compounds and various phenolic acids especially cinnamic and ferulic acids greatly increased in roots of bean plants infected with R.solani and/or inoculated with AM fungi. However, coumarin was found only in AM-treated plants. But quercetin markedly increased in bean roots infected by R.solani and decreased in AM-treated plants, as compared with non-infected control. Finally, activity of lignification enzymes (polyphenol oxidase, peroxidase and phenylalanine-ammonia lyase) increased in all infected plants. Our results indicate that AM fungi increased resistance in infected bean plants by inducing both antioxidant system and phenolic compounds pathway.
Application of 10 µM of Jasmonic acid (IA) as seed soaking significantly reduced % of root rot incidence in bean plants. Production of reactive oxygen species especially H 2 O 2 was highly increased in both roots and shoots of R. solani infected-plants, as compared with non-infected control. JA significantly decreased the level of H 2 O 2 in roots of 14 and 28 days old plants. Lipid peroxidation decreased in JA-treated plants, as compared with infected control. Activity of antioxidant enzymes (catalase, ascorbate peroxidase and superoxide dismutase) significantly increased in bean tissues in response to both pathogenic fungi (R.solani) and/or elicitor JA. JA-treated plants significantly increased total phenolic compounds and various phenolic acids except gallic acid in bean roots as compared with infected or noninfected control. Coumarin was induced only by JA. Additionally, activities of POX, PPO and PAL were greatly increased in both roots and shoots of bean plants infected by Rhizoctonia solani. JA treated plants showed the highest enzymes activity.
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