Changes in chitinase and β-1,3-glucanase transcript levels in sweet orange (Citrus sinensis) in response to treatment with Xanthomonas citri subsp. Citri

Asiatic citrus canker caused by Xanthomonas citri subsp. citri is a bacterialdisease with economic importance in tropical and subtropical citrus-producing areas.One of the potential reaction of plants to pathogens attack is an increased levels ofpathogenesis-related proteins such as chitinase and β - 1,3 -glucanase. The objectiveof present study was to investigate the expression of the PR proteins; β-1,3-glucanaseand chitinase in Washington Navel orange (Citrus sinensis) inoculated withXanthomonas citri sub sp.citri. Quantitative reverse transcription-polymerase chainreaction was used to quantify the mRNA level of chitinase and ß- 1,3 -glucanasegenes in early stage of plant defense response. For this purpose, total RNA wasextracted from inoculated and non inoculated citrus plants at different times postinoculation.Higher amounts of transcripts were detected 24 hours after pathogeninoculation of citrus leaves and four-fold more than the control citrus plant. Thetranscript levels of the two genes were reduced with the time after inoculation, anddecreased significantly at 96 hours post inoculation. This study indicated that the roleof chitinase gene is more than glucanase in early stage of citrus canker disease.