Long- term grapevine cultivation and agro-environment affect rhizosphere microbiome rather than plant age

- Difference in rhizosphere microbiome was estimated in adult and replaced grapevines.
- Ten long-term vineyards across four geographic areas were investigated.
- Rhizosphere microbiome did not differ between adult and replaced plants.
- Geographic origin mainly affected composition of rhizosphere bacteria.
- Rhizosphere fungi varied both according sites and geographic areas.

Single plant replacement is one of the most commonly adopted practices to overcome vineyard crop decline associated with grapevine trunk diseases. A study was undertaken in long-term cultivated vineyards of an important wine producing district in northern Italy to investigate whether rhizosphere microbiome differed between adult and young replaced plants.Fungal and bacterial communities in adult and young replaced plants were investigated in ten vineyards across four geographic areas within the district. General and specific fungal and bacterial primers were used for PCR-DGGE and qPCR analysis. Moreover, quali-quantitative evaluation of Cylindrocarpon-like fungi, agents of foot rot belonging to the disease complex involved in vineyard decline, was performed with specific primers using nested PCR.Fungal and bacterial communities did not differ between adult and young plants, conversely they differed in geographic areas. While Pseudomonas and Bacillus communities varied mostly according to geographic origin, Ascomycota (microfungi) and Basidiomycota (white-rot fungi) also varied between the vineyards within each area. Furthermore, Cylindrocarpon-like species showed an ubiquitous occurrence, regardless plant age.Results show that long-term plant growth legacy overcomes plant age in shaping rhizosphere microbiome. Although composition of rhizosphere microbiome does not seem to represent a bio-indicator of vineyard decline according to findings of this study, the site-dependent variation of microbiome indicates that part of the complex phenomenon of crop decline may be due to a variable interaction between a series of soil biotic components and physiological state of grapevines.