MICROBIAL ACTIVITY AND COMMUNITY DIVERSITY IN TOBACCO RHIZOSPHERIC SOIL AFFECTED BY DIFFERENT PRE-CROPS

In this study, we used both culture-dependent physiological profiling and culture-independent DNA-based approaches to characterize the bacterial communities of tobacco rhizospheric soils affected by different pre-crops (soybean, maize and tobacco). Using Biology-Eco plates, we found that the bacterial metabolic activity in soybean-tobacco and maize-tobacco rotation soils were higher than in tobacco monocropping soil. Across all soil samples, bacterial communities were dominated by Proteobacteria, Acidobacteria and Actinobacteria at the phylum level. However, the diversity and composition of the bacterial communities varied significantly between tobacco rotations and monocropping soil. The estimated bacterial diversity (Shannon diversity index) was higher in the maize-tobacco and soybean-tobacco soils than in tobacco monocropping soil. The populations of Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes were found in variable proportions, depending on the different pre-crops. The highest percentages of Proteobacteria, Actinobacteria and Bacteroidetes were found in soybean-tobacco soil, whereas Acidobacteria occurred at higher percentages in tobacco monocropping soil. Collectively, crop rotation influenced soil biodiversity by change of composition and abundance of individual species, and soils under cereal-tobacco rations had higher bacterial activity and diversity than soils under tobacco monocropping.