Studies on the relationship between Venturia inaequalis and Malus X domestica in vitroplants

A simple and effective method for the infection of Malus x domestica plantlets by apple scab [Venturia inaequalis] is described. Disease development was followed by macroscopic observation of symptoms and scanning electron microscopy observations. The infection of rooted and micropropagated plantlets of the susceptible cultivar Gala showed that rooting is a necessary precondition for the establishment of the host-pathogen relationship. On the nonrooted plantlets, there was no disease expression; hyphae remained over the leaf surface Without penetration or sporulation. Under these conditions, vitroplants of clones resistant by Vf and Vm genes expressed their resistance when inoculated with V. inaequalis race 1. The study of the overcoming of the Vm gene resistance by race 5 of the pathogen showed aspects similar to those observed in the greenhouse. One of the applications of this study will be the rapid in vitro characterization of different races of the fungus.