Comparison of the metabolites profiles between a Graft Chimera ‘Hongrou Huyou’ ( Citrus changshan-huyou + C. unshiu Marc.) and Two Donors

Abstract

Background: Chimeras synthesized artificially by grafting are crucial to breeding of perennial woody plants. 'Hongrou Huyou' ( Citrus changshan-huyou + C . unshiu Marc.) was a new grafting chimera originated from the junction where a scion Citrus changshan-huyou ("C") was top-grafted onto a stock Satsuma mandarin 'Owari' ( C . unshiu Marc., "O"). The chimera was simplified as OCC because the cell layer constitutions were O for L1 and C for L2 & L3, respectively. In this study, profiles of primary metabolites, volatiles and carotenoids derived from different tissues were investigated between OCC and two donors, aiming to figure out the relationship between layer donor and metabolites. Results:Comparison of the metabolite profiles showed that the amount and composition of metabolites were different between the peels and the juice sacs, as well as between OCC and two donors. Metabolites (such as violaxanthin and β -cryptoxanthin in carotenoids, germacrene D in volatiles, citric acid and sorbose in primary metabolites) specifically present or absent in the certain tissue were identified in three phenotypes. According to the principal component analysis (PCA), the total metabolites of chimeric peel properties were derived from the donor C, whereas those of chimeric juice sac properties came from the donor O. Conclusion: Profiles of primary metabolites, volatiles and carotenoids derived from the peels and the juice sacs were systematically compared between OCC and two donors. The content and composition of metabolites differed in tissues as well as between OCC and two donors. Donor dominant metabolite inheritance was dramatic in the different tissues of OCC and basically consistent with the layer origin that the chimeric peels were derived from C and the chimeric juice sacs came from O. These profiles provide potentially chemical markers for genotype differentiation and citrus breeding assessment, more than that, for donor selection during chimera synthesis artificially. BackgroundPlant chimeras refer to those plants composed of more than two genotype cells. According to the theory of 'Tunica-Corpus', the shoot apical meristem (SAM) of dicotyledonous plants are composed of three cell layers, that is L1, L2 and L3, from the outermost layer [1]. For citrus fruits, the juice sacs and epidermal pericarps are derived from cell layer L1; the color and aroma of the fruit rind, seeds 4 and segment walls are developed from L2; L3 produces vascular bundles, and fruit shape was determined by L2 and/or L3 [2]. Up to now, there have been some reports on the discovery and identification of citrus chimeras. Zhou et al. found that the interaction between cells derived from different genotypes caused the mutation of DNA levels in periclinally chimeric fruits NFF (L1-L2-L3=N-F-F) and FNN [2]; Wu et al. found that the fruit characteristics of chimera Ekuliku were inconsistent with source donor and cross-sectional structure of the blade was quite different from two donors [3] Zhang and his colleagues investigated two citrus chimeras named...