Plant-associated bacterial communities are important contributors towards plant health and productivity, and are increasingly acknowledged for having the potential to alter plants' response to climate extremes, such as drought. Viticulture is generally conducted in areas that are prone to seasonal water deficit, and irrigation is the common way to counter this. In addition, soil conservation measures, such as cover cropping and no-tillage, are increasingly used. However, the effect of these management practices, in particular in viticulture, on soil bacterial communities remains unclear. Therefore, the objective was to examine the effect of irrigation and tillage on shaping soil bacterial communities associated with different grapevine cultivars, at different plant phenological stages.
We conducted an experiment whereby we examined the soil bacterial community of three Vitis vinifera L. (grapevine) cultivars (two indigenous and one international, grown at different locations in the same vineyard) under different management practices (irrigated and non-irrigated, tillage and no-tillage). Since there is evidence that plant phenology can also affect soil microbial communities, we sampled soil at three different plant developmental stages (flowering, veraison and harvest).
Soil bacterial communities primarily correlated with cultivar and location. At harvest we observed a link between bacterial communities and grape quality and yield measures and at all stages with soil physicochemical properties. A number of taxa were enriched in one or two cultivars, but these were generally in low abundance in our dataset. We also found an effect of plant phenology and management practices within each cultivar. For the two indigenous cultivars, soil bacterial communities at the flowering stage were most distinct, while for the international cultivar it was at the veraison stage. However, for all three cultivars, this effect differed by tillage treatment: bacterial communities in the tillage treatment varied by plant phenology, but in the no-tillage treatment less difference was observed, suggesting a buffering effect. While irrigation did lead to changes in bacterial communities, the effect was not as strong as that of the other factors.
Our results show that soil bacterial communities in grapevines are shaped by both plant-associated effects (i.e. cultivar and plant phenological stage) and environmental variables (i.e. soil management and soil physicochemical properties), and importantly, that these factors have an interactive effect. Future research on soil bacterial communities in grapevines should take this variability into account, as well as focusing on its functional implications.