Peroxidase changes in Phoenix dactylifera palms inoculated with mycorrhizal and biocontrol fungi

Abstract

In Morocco, yields of date palms are highly decreased by the pathogen fungi Fusarium oxysporum. To solve this issue, mycorrhizal fungi and biocontrol agents could enhance plant resistance to pathogens. Here, we studied peroxidases in roots and leaves of Phoenix dactylifera in response to inoculation with the fungi Glomus mosseae and Trichoderma harzianum. Date palm plants were harvested 57 weeks after inoculation with mycorrhizal fungi and biocontrol fungi. We measured the dry biomass, arbuscular colonization, cytochemistry of peroxidase, and peroxidase forms and activities in roots and leaves. Our results show that mycorrhization increased the plant dry biomass by about 57%. The rate of mycorrhizal colonization ranged from 25% to 30%. Peroxidase activity in roots colonized by T. harzianum alone was 1.6 times higher than in control plants. Peroxidase activity in roots colonized by G. mosseae and T. harzianum was about 2 times higher than in control plants. Peroxidase activity in leaves increased by + 419% when plants were inoculated by both fungi. The cytochemical results show an accumulation of structural substances in root cell walls after inoculation with T. harzianum. These structural substances may increase the mechanical strength of the host cell walls in order to inhibit pathogen invasion. Peroxidase activities were found in plant cell walls; the tonoplast and host plasmalemma in the chloroplast; mitochondrial membranes; and intercellular spaces of plants inoculated with G. mosseae and T. harzianum. SDS-PAGE analyses of leaf extracts gave a main band at 54 kDa for all the treatments. The stimulatory effect of Trichoderma on the peroxidase activity is a resistance mechanism of date plants to pathogens. The use of Trichoderma could thus be an alternative to chemicals in crop protection.