Table 3.

Functional predictions of grafted and ungrafted grape bacterial community plant growth-promoting (PGP) traits. Statistical results (p value) have been reported for each of the six PGP functional trait carried by grape bacterial communities to evaluate the effect of ‘Fraction’ (comparing root vs rhizosphere, t test) and the effect of ‘Rootstock’ (comparing rootstocks in both root and rhizosphere fractions, ANOVA). Significant values are reported in italics

Functional prediction of PGP traits	Fraction effecta	Rootstock effectb
	Root vs rhizosphere	Root (df = 4,10)	Rhizosphere (df = 4,10)
ACC deaminase activity	0.291; t = 1.0937	0.0006; F = 12.77	0.0538; F = 3.380
Auxin production	0.038; t = 2.141	0.0720; F = 3.005	0.3988; F = 1.123
Nitrogen Metabolism	0.259; t = 1.0923	0.2955; F = 1.24	0.4616; F = 0.978
Phosphate solubilization	0.235; t = 1.2452	0.0119; F = 5.681	0.3389; F = 1.286
General PGP (VOCs production)	0.350; t = 0.9454	0.6981; F = 0.558	0.5278; F = 0.844
Siderophore synthesis	0.296; t = 1.0649	0.4891; F = 0.920	0.6096; F = 0.699

^aT test statistical analysis was performed to compare the functional prediction of PGP traits in the two fractions. The p and t values have been reported to evaluate statistical significance

^bOne-way analysis of variance (ANOVA) was performed to evaluate the rootstock effect on the functional prediction of PGP traits in root and rhizosphere fractions. The p and F values have been reported to evaluate statistical significance