Grafting on resistant rootstock enhances pepper bacterial spot disease resistance and alters rhizosphere bacterial community

Bacterial spot of pepper, caused by Xanthomonas campestris pv. vesicatoria is a foliar disease that can cause serious yield loss and quality reduction. Grafting, an effective horticultural practice used to manage crop diseases, is reported to alter plant microbiota. However, the role of changes in plant microbiota in the enhanced disease resistance of grafted plants is unclear. Here, we found that the susceptible scion grafted onto the resistant rootstock showed enhanced resistance against bacterial spot. Moreover, 16S rRNA gene sequencing revealed that grafting susceptible scions onto resistant rootstocks and grafting resistant scions onto susceptible rootstocks altered the rhizosphere bacterial community composition. Specific bacterial taxa, such as Noviherbaspirillum sp. OTU6 and Piscinibacter sp. OTU9, were enriched in the rhizosphere of susceptible scions grafted onto resistant rootstocks, but were not enriched in the rhizosphere of resistant scions grafted onto susceptible rootstocks. This indicates that grafting with resistant rootstock promotes the enrichment of beneficial rhizosphere bacteria in pepper. Overall, grafting with a resistant rootstock enhanced susceptible scion resistance to bacterial spot, which was linked to the enrichment of beneficial rhizosphere bacteria.