Abstract

Gibberellins (GA) are the most used growth regulator for table grape production in Chile which is the main exporter worldwide. GA increases berry size through pericarp cell expansion. However, these treatments are linked to negative postharvest berry drop. Studies have suggested that molecular changes in table grape pedicel derived from GA treatment would have a role on this disorder. Here we performed the first transcriptomic analysis of pedicel response towards GA in two genotypes with contrasting phenotypes for berry drop. Characterization of response in genotype L23 towards GA treatments was up to 10-fold more susceptible than cv. Thompson Seedless in terms of berry drop. GA induced several morphological changes in the pedicel with higher size dimensions. Under these conditions, quantitative analysis of lignin showed lower levels of this due to increased cell wall yield on treated groups. Differential expression analysis showed upregulation of 1098 and 1525 genes by GA on L23 and cv. Thompson Seedless, respectively (FDR≤0.05, logFC≥2). Test for set enrichment in gene ontology annotation showed interesting biological processes as phenylpropanoid, cell wall metabolism and xylem development elicited by GA treatments, after seven days of application. Validation of DE genes exclusive to highly susceptible phenotype could be used as response markers and provides further insight into gene variation across differential susceptibility for berry drop. In summary, postharvest berry drop in table grape is related to GA treatments which increases pedicel dimensions and changes structural properties due to promotion of cell wall and phenylpropanoid metabolism. Furthermore, variation between responses from different genotypes towards GA treatment should contribute to identify molecular factors underlying berry drop. This is the first study to investigate the effects of GA treatments on the pedicel transcriptomic response in contrasting models for berry drop