Photosynthetic and antioxidant responses of Mexican lime (Citrus aurantifolia) plants to Citrus tristeza virus infection

Abstract

The effect of Citrus tristeza virus (CTV) infection on photosynthetic activity and antioxidant metabolism was analysedin plants of the highly susceptible citrus genotype Mexican lime (Citrus aurantifolia). Two virus isolates differing intheir virulence (the severe T318 and the mild T385) were used in the experiments. CTV infection caused a reduction inphotosynthetic capacity in infected plants. This limitation was mainly due to a reduction in the carboxylative efficiencywhereas the limitation of CO2diffusion through the stoma had lower impact. The virus did not damage the antennaeand did not reduce the efficiency of light harvesting complexes. Oxidative damage occurred in infected plants, as evi-denced by the increase in malondialdehyde levels. Indeed, CTV infection caused an increase in ascorbate peroxidaseactivity in new shoots developed in infected plants during the 2 years of the experiment. Data suggest that the H2O2removal machinery was not damaged as a result of stress but the defence mechanism was overwhelmed with time dueto the continuing pressure of biotic stress