Arbuscular mycorrhizal fungi provides enhanced development and reduced mite incidence in Phaseolus vulgaris L. by direct root colonization and via the common mycorrhizal network

Arbuscular mycorrhizal fungi (AMF) are important to agriculture due to positive effects on development and resistance to attack by herbivores in agricultural crops. AMF can affect a single plant by directly colonizing its roots and two or more plants through the common mycorrhizal network (CMN). This work aimed to analyze the influence of AMF on the development of Phaseolus vulgaris and on the incidence of the mite Tetranychus urticae in bean plants colonized directly by mycorrhizal propagules or linked by the CMN. The root systems of two plants were either separated by an impassable barrier so that one or both plants could be colonized by the mycorrhizal propagules without forming the RMC, or they were separated by a steel mesh that allowed the outer hyphae of the AMF on the roots of one of the plants to colonize the non-mycorrhizal roots of the other plant and form the RMC. The mite infestation occurred first on one plant and at the end of the experiment on all. Percentage of mycorrhizal colonization, dry mass of aerial part and roots, number of reproductive structures and mite incidence were analyzed. The colonization by the mycorrhizal propagules and the hyphae of the MRC positively influenced the vegetative and reproductive development of P. vulgaris and resulted in lower mite incidence on the leaflets of the plants. Therefore, direct colonization of P. vulgaris roots by AMFs and via CMR improves plant development and resistance of bean plants to T. urticae mite infestation.