The effect of amino acid Methionine on β- 1,3 glucanase gene expression and activity of effective enzymes in induced resistance to citrus canker disease in lime

Citrus bacterial canker, caused by Xanthomonas citri subsp. citri, is one of the most important diseases of citrus in tropical and subtropical regions. Accumulation of pathogenesis-related proteins such as β -1, 3 glucanase against plant pathogen attack, as plant defense mechanisms against plant pathogens is considered. To investigate the expression of PR-2 genes related β -1, 3 glucanase and the effective enzymes in induced resistance to citrus canker, an experiment was conducted in a completely randomized design. The amino acid methionine at a concentration of 25 mM and distilled water as control, were used for this study. After 48 hours post treatment, plants were inoculated with 5 ml of bacterial suspension (at a concentration of 108 colonies per ml) by syringe without needle and contained under greenhouse conditions. Based on phenotypic tests results, there were significant difference in the level of 0.05 between the amino acid methionine treated plants and control plants treated with sterile distilled water. The molecular test results indicated an increase in the expression of PR-2 at 24, 48 and 72 h after inoculation. Based on the results of antioxidant enzymes activity study in stressed plants, plants treated with the amino acid methionine significantly increased the enzyme activity of peroxidase and phenylalanine, however, did not affect on catalase activity.