A new approach to manage phytoplasma diseases: field treatments with resistance inducers to contain grapevine Bois noir

Grapevine Bois noir (BN) is a phytoplasma disease that is widespread in most viticultural regions of the World, and it can result in heavy reductions to yields and grape juice quality. At present, there is no effective strategy to reduce the incidence of BN-infected grapevines. However, phytoplasma-infected plants can recover through spontaneous or induced symptom remission. Five elicitors (chitosan, two glutathione plus oligosaccharine formulations, benzothiadiazole, phosetyl-Al) were applied weekly to the canopy of BN-infected cv. Chardonnay grapevines, from early May to late July. The best and most constant recovery inductions were obtained with benzothiadiazole and the two glutathione plus oligosaccharine formulations. The plants that recovered naturally or following the elicitors showed qualitative and quantitative parameters of production no different from healthy plants. In another vineyard, diseased plants showed reduced shoot length and production, as compared to healthy plants, and there were no negative effects on these parameters for grapevines sprayed with a glutathione plus oligosaccharine formulation. The application of resistance inducers promoted the recovery of BN-infected grapevines with no adverse effects on the plants. Therefore, grapevine can be used as a model species to test this innovative strategy to contain phytoplasma diseases