Interactive effects of scion and rootstock genotypes on the root microbiome of grapevines

Diversity and community structure of soil microorganisms are increasingly recognized as important contributors to sustainable agriculture and plant health. In viticulture, grapevine scion cultivars are grafted onto rootstocks to reduce the incidence of the grapevine pest phylloxera. However, it is unknown to what extent this practice influences root-associated microbial communities. A field survey of bacteria in soil surrounding the roots (rhizosphere) was of 4 cultivars x 4 rootstock combinations was conducted to determine whether rootstock and cultivar genotypes are important drivers of rhizosphere community diversity and composition. Differences in a-diversity was highly dependent on rootstock-cultivar combinations, while bacterial community structure primarily clustered according to cultivar differences, followed by differences in rootstocks. Indicator genera (i.e., those that differed significantly in abundance) differed between rootstocks and cultivars, but did not differ in abundance between the different genotypes in each group. Bacterial diversity in grafted grapevines was affected by both cultivar and rootstock identity, but this effect was dependent on which diversity measure was being examined (i.e., a- or ß-diversity) and specific rootstock-cultivar combinations. These findings have potential functional implications, for instance, by differences in the ability of specific combinations to attract beneficial microbial taxa with the ability to control pathogens and/or assist plant performance.