Modification of competence for response to Fusarium oxysporum f. sp. lycopersici in tomato cells. IV. Increased tolerance of plants regenerated from high-polysaccharide-selected cells.

Our previous work had shown that cell lines from a tomato cv. susceptible to Fusarium oxysporum f. sp. lycopersici selected for high polysaccharide content have become "competent for active defense". This was assessed by a series of in vitro parameters which correlated with the defense response. The aim of this work is to extend these observations to plants regenerated from calli of the cv. Tondino which were selected for high polysaccharide content. These plants and their self-fertilized R2 and R3 progenies were analyzed for their tolerance to in vivo infection with pathogen as well as for inhibition of fungal growth in vitro and ion leakage in the presence of fusaric acid. Two out of six clones and their progenies were confirmed to be stably resistant to Fusarium. Genetic stability was assessed by RAPD analysis, which showed a higher degree of polymorphism in the selected clones, and led to the identification of three bands unique to the selected plants. Moreover, since two different phenotypes were observed, compact or thin, compared to the control, their IAA level was evaluated. In accordance with the known physiological effect of auxins, plants bearing the compact phenotype had a lower auxin content, while the thin plants showed a higher level as compared with the controls.