Use of Trichoderma harzianum strain T-22 as a biocontrol agent in Prunus spp. nursery processes.

Trichoderma harzianum strain T-22 (T22) is one of the most effective strain and is able to colonize roots of the most of plant species across a wide range of soil types. This fungus is utilized as a biocontrol agent for crop production purposes, and for the improvement of plant nursery processes. Inoculation of T22 were applied on in vitro-cultured shoots of GiSeLa6® (Prunus cerasus x Prunus canescens) and GF677 (Prunus amygdalus x Prunus persica), two important varieties utilized as commercial rootstocks. The results showed that fungus inoculation (7 days after shoot transfer in the root-inducing medium), both GiSeLa6® and GF677 plants survived and showed significant increases in shoot growth and root development, particularly in root length (180 and 136% of non-inoculated controls, respectively). The microscopical analysis allowed to observe hyphae spreading on root cortex surface of GiSeLa6® (fungus colonization frequency of 20%) but not on GF677 roots. Our results demonstrated that the application of T22 during the rooting phase permits to have higher shoot length and leaves, number of roots and stem diameter and could be considered a natural product‐based biopesticide. These morphological characteristics could increase nursery plant material and give notable advantages during the following acclimation phase.