Differences in defence-related gene expression and metabolite accumulation reveal insights into the resistance of Greek grape wine cultivars to <i> Botrytis </i> bunch rot

Abstract

Berries of 13 Greek grape wine cultivars were evaluated for resistance to Botrytis bunch rot. Artificial inoculations on detached berries revealed that the Greek cultivars tested varied regarding their susceptibility to Botrytis cinerea. Cultivar (cv.) “Limnio” was found to be highly resistant, while higher susceptibility was observed on berries of cv. “Roditis”. To determine the molecular basis of the observed resistance or susceptibility of cv. “Limnio” and “Roditis”, an expression analysis of 12 defence-related genes, was carried out on artificially inoculated berries of the two cultivars at different time points after inoculation. Gene expression measurements in the resistant cv. “Limnio” showed that the artificial inoculation with the pathogen triggered the induction of genes encoding pathogenesis-related (PR) proteins such as chitinases (CHIT), polygalacturonase-inhibiting protein (PGIP), serine proteinase inhibitor (PIN) and enzymes involved in phytoalexin synthesis such as phenylalanine ammonia-lyase (PAL) and stilbene synthase (STS). In contrast, on the susceptible cv. “Roditis”, most of the same genes were down-regulated. Metabolomic analysis revealed significant differences in the initial metabolic profiles of “Limnio” and “Roditis” berries. Furthermore, in response to inoculation, the abundance of several metabolites increased in the resistant cultivar indicating intensification of metabolic processes. Proline and mannitol accumulation, as well as the modification of metabolites related to phenylpropanoid and lignin biosynthesis, are among the major players in defence responses of the “Limnio” cultivar. The above findings enhance our understanding of the resistance of Greek grape wine cultivars to B. cinerea and, at the same time, lay the foundation for breeding wine grape cultivars in the future.