How effective are plant bioestimulants to alleviate drought stress in grapevine?

Abstract

There is currently an increasing demand for innovative agronomic tools able to enhance crop resilience against environmental stresses caused by climate change. Even though plant biostimulants (PBs) have been found able to increase water stress tolerance of several crops under different growing conditions, research on the use of these natural compounds in viticulture is still incomplete and results are often inconsistent. The aim of this study was therefore to assess the ability of different commercial PBs to mitigate the adverse effects of water limitation in grapevine. PBs, including arbuscular-mycorrhizal fungi (AMF), protein-hydrolysate (PH), seaweed extracts (SEA) and silicon (SI) were tested on potted cv. Sauvignon Blanc grown in controlled conditions under two water regimes: well-watered (WW) and water-stress (WS). Vine growth performances, during and after the drought period, as affected by the different PBs applications were monitored at daily basis by measuring several physiological and biometric parameters. During WS, AMF and SEA-treated plants showed a slower decreased (-0.2 MPa, corresponding to 36% less) than the untreated WS plants. Moreover, the PBs pre-stress application accelerated the leaf gas exchange recovery to WW values. Upon rewatering, SI-WS-treated plants showed increments of leaf gas exchanges rates that were around 30% higher than those of the control-WS vines. As for the seasonal biomass accumulation, it resulted lower in WS-vines, independenlty of the PBs. Overall, the application of selected PBs before the water stress allow to slow down the the buildup of the drought stress in grapevine, therefore enhancing the possibility for the crop to overcome the negative physiological consequences of periods of water scarcity. Further evidence of PBs effectiveness are nevertheless needed especially under vineryard (open field) conditions.