Alkaloidal variation in seedlings of Annona purpurea Moc. & Sessé ex Dunal infected with Colletotrichum gloeosporioides (Penz.) Penz. and Sacc.

Abstract

Annona purpurea is a species of the Annonaceae family that more than 50 alkaloids. Some alkaloids carry out defense functions and can be grouped from an ecological perspective as constitutive and induced metabolites. The latter are expressed in response to changes in abiotic or biotic conditions that trigger stress in a plant. However, there are few systematic studies of constitutive metabolite profiles and their responses to biotic stress, despite the relevance of this concept. This work analyzed the differences in constitutive and induced alkaloids in A. purpurea seedlings infected with the phytopathogen Colletotrichum gloeosporioides. For this study, methanolic extracts of seedling leaves, stems, and roots inoculated with the fungus and not inoculated with the fungus were obtained and analyzed by gas chromatography coupled to mass spectrometry. The richness and abundance of alkaloids between the treatments and between organs were represented using the Margalef, Shannon, and Simpson ecological indices and the analysis of principal components, PERMANOVA, and paired PERMANOVA. Twenty-one alkaloids were detected from two biosynthetic pathways distributed in the seedling organs, and 15 of these alkaloids were considered constitutive because they are also found in adults. Most of the constitutive alkaloids in the seedlings were observed in the roots (15 compounds), followed by the stems (11 chemicals) and leaves (9 chemicals). The diversity indices also showed differences between the organs. Infection with the fungus modified the constitutive profile of the alkaloids by inducing an increase in lirinidine (61%) and papaverine (403%) in the roots and N,N-dimethyl, 2-(methylamino) 3-phenylindole (143%) in the leaves. Due to the infection, no new alkaloids were detected in any organ.