Study of catechin, epicatechin and their enantiomers during the progression of witches' broom disease in Mexican lime (Citrus aurantifolia)

• Infection of the plant by disease has a close relation to the level of catechin.
• The contents of metabolites are agreement with the activities of CHS.
• Infection has a high impact on the enantiomeric composition of catechin.
• Enantiomeric ratio can be as biomarker for the detection of infected plant.

Witches'broom diseases of Mexican lime (WBDL) caused by ‘Candidatus Phytoplasma aurantifolia, is a big threat to lime production in Southern Iran. In this investigation, concentration of catechin, epicatechin and their enantiomers were monitored during WBDL progression for 6 months. In addition, the activities of peroxidase (POD), phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) as well as the content of malondialdehyde (MDA) were assayed. The results showed that after 30 days of inoculation, levels of catechin and epicatechin were considerably increased up to 390% and 290% respectively, but both of them significantly decreased after 150 days. These changes in the levels of catechin and epicatechin are in well agreement with the activities of PAL, CHS and POD as well as the level of MDA. Does WBDL influence on biosynthesis of enantiomers in lime? The analysis of catechin enantiomeric ratio of infected leaves demonstrated that after 30 days of inoculation, the ratio of (+)-catechin changed from 61:39 to 79:21 and then remained almost constant. Finally, the infection of lime by WBDL, not only induced the production of resistance enzymes (PAL and CHS) as well as catechin and epicatechin but also enhanced the accumulation of (+)-enantiomer.

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