Effects of strawberry root rot on rhizosphere bacterial community structure and screening and identification of strains with biocontrol potential

Abstract:

Objective We investigated the characteristics of rhizosphere bacterial communities of healthy and root rot-infected strawberry plants across different plots, as well as their correlations with soil physicochemical properties, aiming to discover and isolate beneficial rhizosphere bacteria with significant inhibitory effects against strawberry root rot pathogens to support disease management.Methods We utilized high-throughput sequencing combined with bioinformatics analysis to elucidate the differential characteristics and influencing factors of rhizosphere bacterial communities between healthy and diseased strawberry plants. Then, we employed the dilution plate method and dual culture assay to isolate antagonistic bacteria. Subsequently, we determined the taxonomic status of these beneficial strains by combining morphological observation with multi-gene phylogenetic analysis.Results The bacterial community diversity varied across different cultivation bases. Compared with that of healthy plants, the rhizosphere soil samples of diseased strawberry plants from the Xinzhuang and Kangshou bases showed decreased bacterial InvSimpson, Chao1, and Shannon evenness indices (P>0.05). Conversely, the rhizosphere soil samples of diseased strawberry plants from the Taolin base showed increased InvSimpson and Shannon evenness indices (P<0.05). Beta diversity analysis revealed that root rot significantly altered the microbial community structure. The complexity and stability of the rhizosphere bacterial co-occurrence network decreased in the diseased samples. Redundancy analysis indicated that soil total organic carbon, available phosphorus, and total potassium were the primary physicochemical factors shaping the bacterial community structure in strawberry rhizosphere. We isolated two bacterial strains, N2-10 and N2-18, that exhibited significant antagonistic activity from the healthy strawberry rhizosphere. The two strains demonstrated inhibition rates ranging from 55.6% to 62.2% and 54.5% to 66.7%, respectively, against the tested strawberry root rot pathogens. We identified strains N2-10 and N2-18 as Bacillus cereus and Bacillus velezensis, respectively.Conclusion We clarify how root rot affects strawberry rhizosphere bacterial communities and identify two beneficial rhizosphere bacterial strains with strong biocontrol potential. These findings provide a theoretical basis and valuable strain resources for elucidating the mechanisms of strawberry root rot and developing microbial-based green control technologies.