Induction of Systemic Resistance to Erysiphe orontii Cast in Tobacco by Application on Roots of an Isolate of Gliocladium roseum Bainier

Induced systemic resistances (ISR) response is related to several biochemical changes in plants. Gliocladium roseum is a powerful biological control agent (BCA) as first emerged in controlling Botrytis cinerea in strawberry and later on diseases of raspberry and tomato. Enzymatic activities were measured on leaves of tobacco plants inoculated on roots with an isolate of G. roseum. Leaf extracts were analysed for 1,3-b-glucanases, 1,4-b-glycosidases, chitinases, N-acetyl-b-dglucosaminidase and -b-d-N-N¢-diacetyl-chitobiosidase activities; peroxidase isozymes were examined by polyacrylamide gel electrophoresis. Plants inoculated with G. roseum showed: (i) an increased activity of 1,3-bglucanases, 1,4-b-glycosidases and chitinases; (ii) two new bands and a major expression of two other isoforms in peroxidase isozymes pattern. Bioassays were carried out making a challenge inoculation with Erysiphe orontii on leaves of plants previously treated with Gliocladium on roots. Leaves of these plants showed a reduced number of colonies and less severe symptoms of powdery mildew compared with the control ones. This is the first time that this effect has been demonstrated for G. roseum