Abstract
Vitis vinifera, one of the most cultivated fruit crops, is susceptible to several diseases particularly caused by fungus and oomycete pathogens. In contrast, other Vitis species (American, Asian) display different degrees of tolerance/resistance to these pathogens, being widely used in breeding programs to introgress resistance traits in elite V. vinifera cultivars. Secondary metabolites are important players in plant defence responses. Therefore, the characterization of the metabolic profiles associated with disease resistance and susceptibility traits in grapevine is a promising approach to identify trait-related biomarkers. In this work, the leaf metabolic composition of eleven Vitis genotypes was analysed using an untargeted metabolomics approach. A total of 190 putative metabolites were found to discriminate resistant/partial resistant from susceptible genotypes. The biological relevance of discriminative compounds was assessed by pathway analysis. Several compounds were selected as promising biomarkers and the expression of genes coding for enzymes associated with their metabolic pathways was analysed. Reference genes for these grapevine genotypes were established for normalisation of candidate gene expression. The leucoanthocyanidin reductase 2 gene (LAR2) presented a significant increase of expression in susceptible genotypes, in accordance with catechin accumulation in this analysis group. Up to our knowledge this is the first time that metabolic constitutive biomarkers are proposed, opening new insights into plant selection on breeding programs.
Highlights
Vitis vinifera, one of the most cultivated fruit crops, is susceptible to several diseases caused by fungus and oomycete pathogens
Principal component analysis (PCA) and hierarchical clustering, were applied to the untargeted metabolomics data to verify the analytical reproducibility and to infer inter-genotype metabolic profile similarities among the various Vitis samples (Fig. 1)
As seen from the clustering of replicates together, was very high, an indicating that metabolome profiling of Vitis leaves appears to be sufficiently sensitive to distinguish the different species and cultivars. In both ionization modes, a trend of separation between wild Vitis and V. vinifera cultivars can be observed in the principal component analysis (PCA) score plots (Fig. 1a,b)
Summary
One of the most cultivated fruit crops, is susceptible to several diseases caused by fungus and oomycete pathogens. The characterization of the metabolic profiles associated with disease resistance and susceptibility traits in grapevine is a promising approach to identify trait-related biomarkers. Several compounds were selected as promising biomarkers and the expression of genes coding for enzymes associated with their metabolic pathways was analysed. Reference genes for these grapevine genotypes were established for normalisation of candidate gene expression. The selection for pathogen resistance traits is only possible 2 to 3 years after plant crossing, after which the more resistant seedlings are kept[10,11]. Stilbenoids were already reported as key defense compounds involved in grapevine resistance to Plasmopara viticola, Erysiphe necator and Botrytis cinerea[16,21]
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