Effect of an ectomycorrhizal fungus on fruit tree micropropagation

Some mycorrhizal fungi have proved to enhance the cutting rooting ability of some fruit rootstocks through the release of factors interacting with the endogenous hormones of these cuttings. Experiments designed to ascertain similar effects on microcuttings were performed on pear cv Bartlett which is very difficult to root in vitro without the addition of auxin to the medium. The addition of the mycelia of Hebeloma sinapizans to the auxin-free medium markedly increased the rooting ability of pear microcuttings. By contrast, no or slight enhancement occurs when the ectomycorrhizal fungus was added to the media containing IBA. In any case the H.S. mycelium has proved to increase the root number per plantlet and sharply reduced the shoot length at all the tested IBA concentrations.