Screening and Identification of Lignocellulase-Producing Endophytic Bacteria from Tomato Roots

Plant endophytes with abundant diversity are excellent strain resources for developing new microbial fertilizers and green biocontrol agents. In this study, 135 tomato root endophytic bacteria preserved in the laboratory were used to explore functional strains with strong root colonization potential and reveal the correlation between lignocellulose-degrading capacity and root colonization. The transparent circle method with CMC and xylan plates was applied to qualitatively detect cellulase and xylanase activities via primary and secondary screening, so as to systematically evaluate their lignocellulose degradation potential. The results showed that most strains exhibited lignocellulose-degrading activity; 67.4% of strains produced cellulase and 68.8% produced xylanase, with high synergism of the two enzymes matching the demand for plant cell wall degradation. The identified strains of Bacillus and Pseudomonas generally exhibit enzyme-producing ability. As the predominant strains for current microbial inoculants, these two genera indirectly verify that their prominent degrading capacity is tightly correlated with their colonization competence in the rhizosphere and root endosphere. In summary, lignocellulose-degrading traits widely exist in tomato root endophytes, which serve as a key basis for microbes to adapt to the root microenvironment and achieve persistent colonization. This property can be adopted as a vital index for rapid screening of high-efficiency endophytic biocontrol strains.