Activation of Glycosidases as a Consequence of Infection Stress in Fusarium Wilt of Tomato

Changes of β-1,3-glucanase, chitinase, β-1,4-glucosidase and N-acetylglucosaminidase activity have been investigated in relation to the development of symptoms and colonization by the pathogen in roots, stems and leaves of susceptible (‘Improved, Pearson’) and resistant (‘Improved Pearson VF11’) tomato plants infected by Fusarium oxysporum f. sp. lycopersici. Glycosidase activities increased after inoculation to different extents depending on the plant part and cultivar. Increases were always higher in susceptible than in resistant plants. Changes in the β-1,3-glucanase activity after inoculation were particularly large in stems of infected plants. In contrast, chitinase activity increased more in roots than in stems. The β-1,3-glucosidase and chitinase activity decreased slightly from the basal to the apical third of stems. The trend of changes of the glycosidase activity generally were well related with the severity of disease symptoms and the fungal colonization of basal stem segments. There was no evidence that the increase of glycosidase activity after the infection was directly related with the resistance to Fusarium wilt in tomato.