Metabolome of Vanilla planifolia (Orchidaceae) and related species under Cymbidium mosaic virus (CymMV) infection

The genus Vanilla which belongs to the Orchidaceae family comprises more than 110 species of which two are commercially cultivated (Vanilla planifolia and Vanilla xtahitensis). The cured pods of these species are the source of natural vanilla flavor. In intensive cultivation systems the vines are threatened by viruses such as Cymbidium mosaic virus (CymMV). In order to investigate the effect of CymMV on the growth and metabolome of vanilla plants, four accessions grown in intensive cultivation systems under shadehouse, CR01 (V. planifolia), CR17 (V. xtahitensis), CR03 (V. planifolia × V. xtahitensis) and CR18 (Vanilla pompona), were challenged with an isolate of CymMV. CymMV infected plants of CR01, CR03 and CR17 had a reduced growth compared to healthy plants, while there was no significant difference in the growth of CR18 vines. Interestingly, CR18 had qualitatively more phenolic compounds in leaves and a virus titre that diminished over time. No differences in the metabolomic profiles of the shadehouse samples obtained by nuclear magnetic resonance (NMR) were observed between the virus infected vs. healthy plants. However, using in- vitro V. planifolia plants, the metabolomic profiles were affected by virus infection. Under these controlled conditions the levels of amino acids and sugars present in the leaves were increased in CymMV infected plants, compared to uninfected ones, whereas the levels of phenolic compounds and malic acid were decreased. The metabolism, growth and viral status of V. pompona accession CR18 contrasted from that of the other species suggesting the existence of partial resistance to CymMV in the vanilla germplasm.