Leaf and stem galls of Schinus polygamus (Cav.) Cabr (Anacardiaceae): Anatomical and chemical implications

Galling insects commonly induce anatomical and metabolic changes in their host plant tissues, which is true for Schinus polygamus (Cav.) Cabr. (Anacardiaceae) in Chile. Currently, anatomical and chemical changes induced by galling insects in stems and leaves of S. polygamus were analyzed. Methanolic extracts of non-galled and galled tissues were analyzed by gas chromatography-mass spectrometry (GC-MS). Differences in the secondary metabolite profiles, and their relation with plant responses to gall development were evidenced. Transverse sections of non-galled host organs and galls were done, and observed under light and scanning electron microscopies. One stem gall (conical) and one leaf gall (globoid) morphotypes were identified. The globoid and conical galls have dense trichomes, large nymphal chambers, and develop mainly by tissue hyperplasia. The chemical profiles of stems, leaves and galls are distinct, except for the concomitant detection of pyrogallol in galls. The highest abundance of terpenes and phenols in gall tissues were identified, and two triterpenes were firstly reported for the non-galled tissues of S. polygamus. Host plant tissues are highly responsive to the Psyllidae stimuli toward the over development of a phenolic-rich parenchyma, which ends up favouring the Callophya sp. establishment and gall development.