The INTEFLAVI project: gene expression changes induced by abiotic stress treatment in grapevines affected by Flavescence dorée Il progetto INTEFLAVI: effetti di stress abiotici su viti affette da flavescenza dorata

Within the INTEFLAVI (Un approccio integrato alla lotta contro la Flavescenza dorata della vite) project, different research lines (phytoplasma genetics, epidemiology of the vector and its interactions with FDp, grapevine physiology and molecular biology) jointly focused to obtain novel biological knowledge on the mechanisms controlling FD. The grapevine biology studies included gene expression changes following FDp infection in leaves of the highly susceptible Vitis vinifera cv Barbera. Leaf samples were collected in field from healthy, infected, and recovered plants at three time points along the vegetative season. Samples from the second time point (late July), the moment of maximum infection on the basis of molecular diagnosis, were used for RNA extraction, RNA library preparation and high throughput sequencing. In parallel, we studied the evolution of recovery mechanisms in potted grapevines, infected and maintained under controlled conditions, and subjected to heat, water stress, and girdling treatments. We monitored physiological responses, quantifying phytoplasma concentration and assessing expression of selected genes by RT-qPCR. Elaboration of sequencing data showed that expression of genes involved in sugar metabolism and transport, and in the flavonoid biosynthetic pathway, were significantly affected. Flavonoids and stilbenes were in parallel identified and quantified by UPLC and preliminary results confirm that stilbene accumulation was differently modulated in infected and recovered plants. Stress treatments in controlled conditions, in particular girdling, affected the phytoplasma titre in plant leaf veins and expression of sugar metabolism and flavonoid biosynthetic genes, with significant differences in terms of recovery rate, suggesting that physiological conditions impact on phytoplasma multiplication or diffusion.