Shift in rhizospheric and endophytic bacterial communities of tomato caused by salinity and grafting

Saline water has to be used as an alternative resource in modern agriculture due to the increasing lack of fresh water. Approaches that promote the growth of crops under saline conditions have, therefore, become crucial. Grafting has been reported to be effective for this; however, the associated bacterial community remains unclear. To obtain a deeper understanding of the underlying microbial mechanisms, both grafted and non-grafted tomatoes were irrigated with three types of water having different electrical conductivity values. The experiment lasted 2.5 months, after which, the soil chemical properties and tomato heights were assessed. The rhizospheric and endophytic bacterial communities of samples from the different treatments were assessed by Illumina sequencing. The results showed that saline water significantly affected leaf-associated endophytic bacterial communities, whereas rhizosphere and root- and stem-associated bacterial communities were not affected. Increasing salinity increased the abundance of Gammaproteobacteria, but decreased the abundance of Actinobacteria, Alphaproteobacteria, Bacilli, and Acidobacteria at the class level of the leaf-associated bacterial community. Moreover, under higher salinity levels, grafting increased the diversity of the leaf-endophytic bacterial community. Overall, this study provides a comprehensive understanding of the rhizosphere and endophytic bacterial communities of tomato under saline conditions. The results highlight the importance of leaf-endophytic bacteria for salt response in plants. This is an important complementary finding to previous studies on the effect of salinity, which mainly focused on plant rhizosphere and root bacterial communities.