Discrimination of different prickly pear (Opuntia spp.) accessions by NMR-based metabolomics

Abstract

Mexico is one of the main producers of prickly pear worldwide and has around 50 registered accessions. Despite its great nutritional value, there are no reports on its metabolite profile. The objective of this study was to analyze 12 accessions of prickly pear (TAC, TNL, TCB, TCO, TV, TZ, TRI, TRP, TRR, TS, TSH and TT) of different colors using nuclear magnetic resonance (NMR) spectroscopy to identify their metabolic profiles. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to compare the metabolome. In total, 34 primary metabolites were identified in the 1H NMR spectra. The PCA model used to compare the 12 accessions did not show a clear separation between the groups. The OPLS-DA model made it possible to discriminate the TRI and TCB accessions. The heatmap showed that these accessions have a higher concentration of some metabolites. The TCB accession has high concentrations of sugars and amino acids while the TRI accession has high concentrations of organic acids. In addition, The TCO accession has a lower concentration of primary metabolites. The OPLS-DA model made it possible to classify the prickly pears by color. For orange prickly pears, the TNL accession has a higher concentration of primary metabolites than the TAC accession. In green prickly pears, the accession with the highest concentration of primary metabolites is the TCB accession, while it is the TRI accession in red prickly pears. This work demonstrated that NMR-based metabolomics is a highly reproducible and robust methodology to classify prickly pear accessions.