Effect of phytoplasma infection on metabolite content and antioxidant enzyme activity in lime (Citrus aurantifolia)

The objective of the present work was to study biochemical alterations in lime plants infected by the Candidatus Phytoplasma aurantifoliae. Changes in antioxidant activities, content of chlorophylls (Chl), carotenoids (Car), soluble proteins, sugars and auxin (IAA) in infected plant were investigated. The activities of polyphenol oxidase (PPO), peroxidase (POX) and superoxide dismutase (SOD) were observed to be greater in infected leaves than the healthy control. Also according to non-denaturing PAGE, in infected leaves all the antioxidative enzymes isoforms were stronger than that of the healthy control. These results suggest that antioxidant enzymes can be activated in response to infection by phytoplasma. The decrease in content of proteins, total soluble and reducing sugars in infected plants point out changes in host metabolism due to the phytoplasma infection. The reduction in chlorophylls and auxin content shows that the phytoplasma can interfere in photosynthesis and induces senescence in the leaf. In conclusion, this study provides new insights into the lime response to phytoplasma infection.