Effect of Mycorrhizal Fungus on Pathogenicity of Root-Knot Nematode (Meloidogyne incognita) and Histopathological Changes in Tolerant and Susceptible Cucumbers

Root knot nematodes (Meloidogyne spp.) are one of the most important plant parasitic nematodes that cause damage to most agricultural crops. In this study, the effect of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae on root knot nematode M. incognita on two cucumber cultivars; tolerant and susceptible was investigated. This experiment was conducted in a completely randomized design with four treatments and four replications. The results showed that adding mycorrhizal fungus one month before inoculation of nematode caused a significant decrease in nematode pathogenicity factors (number of galls, number of eggs, eggs per egg mass and number of second stage juveniles) in both tolerant and susceptible cultivars (cv). Although the pathogenicity of the nematode in tolerant cultivars was lower than that of susceptible cvs, inoculation of susceptible roots with mycorrhizal fungus significantly reduced the pathogenicity of the nematode. The reproductive factor decreased in mycorrhizal plants in tolerant and susceptible cultivars in 50 and 66.6%, respectively. The presence of mycorrhizal in tolerant and sensitive cultivar reduced 64 and 63.3% of the second larval population in the soil, respectively. Also, the comparison of the mean number, size and area of giant cells and the number and diameter of the nucleus in 2 cvs showed a significant difference between the plants with or without mycorrhizal fungus. Since mycorrhizal fungus reduces the pathogenicity of the root knot nematode and increases the resistance of the cv susceptible to nematode, it can be considered as an option for biologic control of the root knot nematode.