Abstract

CUERVO, Diana C.; MARTINEZ, Sixta T.; ARDILA, Harold D.  and  HIGUERA, Bianca L.. DIFFERENTIAL INDUCTION OF PEROXIDASE ENZYME AND ITS RELATIONSHIP WITH LIGNIFICATION IN CARNATION DEFENSE (Dianthus caryophyllus L.) MECHANISM AGAINST Fusarium oxysporum f. sp. Dianthi. Rev.Colomb.Quim. [online]. 2009, vol.38, n.3, pp.379-393. ISSN 0120-2804.

Peroxidase (POD) enzymatic activity and lignin content in carnation stems (Diant-hus cayophyllus L.) infected with the fungus Fusarium oxysporum f.sp. dianthi race 2 were evaluated with the purpose of determining the possible enzyme participation in the plant defense response and in the resistance to the vascular wilting. Initially, the conditions for extraction and determination of enzymatic activity were selected. It was found that when citrate buffer 100 mM pH 5.0 with 3% PVPP was employed, the results of POD activity in enzyme extract obtained from carnation stems were higher. Best conditions were set for POD activity measure through oxidation reaction of o-dianisidine and H₂O₂ at 460 nm. A reaction mixture with a concentration of o-dianisidine 0,6mM and H₂O₂ 2.0 mM in citrate buffer 100 mM pH 5.5 at 45 ^oC displayed the best results for enzyme quantification. Once conditions were established, tolerant and susceptible vascular wilting carnation cuttings were inoculated with the pathogen. In each treatment at stem level, different postinoculation times were evaluated for enzyme activity levels and lignin accumulation. Tolerant variety (Barbara) showed a POD induction at 8 and 48 h pos-inoculation and an increase in lignin content at 48 and 72 h. At the same time, in susceptible variety (Delphi) there were no significant changes in POD levels or lignin contents. Therefore, it was established that POD activity induction is associated to lignification which, at stem level, is part of the mechanisms associated to defense in carnation (Dianthus caryophyllus L.) against Fusarium oxysporum f. sp. dianthi.

Keywords : carnation; Fusarium oxysporum; plant defense; peroxidase; lignin.

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