Deterministic Process Dominated Belowground Community Assembly When Suffering Tomato Bacterial Wilt Disease

Soil microbial communities are closely associated with ecosystem functions. However, unravelling the complex nature of the microbial world and successfully utilizing all positive interactions for multipurpose environmental benefits is still a major challenge. Here, we describe the soil bacterial communities in different niches of healthy and diseased tomatoes under natural conditions. A higher abundance of the pathogen Ralstonia solanacearum and lower bacterial diversity were observed in the disease samples. The healthy tomato rhizosphere harbored more plant-beneficial microbes, including Bacillus and Streptomyces. Also, the co-occurrence network in the healthy rhizosphere samples was more complicated, so as to better adapt to the soil-borne pathogen invasion. Both the beta nearest-taxon-index (beta NTI) and normalized stochasticity ratio (NST) analyses demonstrated that healthy rhizosphere communities were less phylogenetically clustered and mainly dominated by dispersal limitation, while homogeneous selection was the major assembly process driving the rhizosphere community of diseased samples. The results obtained with community assembly methods and co-occurrence network analysis revealed that healthy rhizosphere bacterial communities possessed potentially broader environmental stress (soil-borne pathogen stress) adaptability compared with diseased rhizosphere bacterial communities. In conclusion, this study contributed to widening our understanding of the potential mechanisms of soil bacterial community composition and assembly responding to soil-borne pathogen invasion.