The interplay between hormone signaling and defense gene expression in grapevine genotypes carrying genetic resistance against Plasmopara viticola

The present study aimed to investigate plant defense related pathways during Plasmopara viticola infection in Vitis vinifera varieties. Plant material consisted of 'Chardonnay' (no Rpv), 'Regent' (Rpv3-1), 'Bronner' (Rpv3-3+Rpv10), 'Calardis Blanc' (Rpv3-1+Rpv3-2), and the breeding selection GF15 (Rpv1+Rpv3-1). Gene expression analysis was carried out for the varieties 'Regent', GF15, 'Bronner', and 'Chardonnay'. Hormonal quantification was performed for jasmonic acid (JA), salicylic acid (SA), abscisic acid (ABA), indole-3-acetic acid (IAA), and trans-zeatin-ribose (tZR). The samples were collected from plants cultivated in vitro inoculated with Plasmopara viticola sporangia, and collected at 0, 1-, 3-, 5-, and 7-days post inoculation (DPI) for gene expression; and 0, 3, 5, and 7 DPI for hormonal quantification. The results showed an interaction between genotype and time post inoculation in gene expression and hormonal pathways linked with pathogen recognition. Both jasmonate and salicylic acids were involved in the resistance response. The role of stilbenes acting against the pathogen at different times was also confirmed. Changes in the expression of genes linked to cell defense were observed in all evaluated genotypes; however, genotypes with R-loci responded more quickly than the variety without R-loci, activating mechanisms of cell death, resulting in symptoms of hypersensitivity.