Effects of continuous cropping of sugar beet ( Beta vulgaris L.) on its endophytic and soil bacterial community by high-throughput sequencing

As a major sugar crop, sugar beet (Beta vulgaris L.) plays an important role in both sugar industry and feed products. Soil, acts as the substrate for plant growth, provides not only nutrients to plants but also a habitat for soil microorganisms. High soil fertility and good micro-ecological environment are basic requirements for obtaining high-yield and high-sugar sugar beets. This study aimed at exploring the effects of continuous cropping of sugar beet on its endophytic, soil bacterial community structures, and diversity. Using high-throughput sequencing technology which is based on Illumina Hiseq 2500 platform, the seeds of sugar beet (sample S), non-continuous cropping sugar beet (sample Bn) with its rhizosphere soil (sample Sr), and planting soil (sample Sn), continuous cropping sugar beet (sample Bc) with its planting soil (sample Sc), were collected as research materials. The results showed that the bacterial communities and diversity in each sample exhibited different OTU richness; 67.9% and 63.8% of total endophytic OTUs from samples Bc and Bn shared with their planting soil samples Sc and Sn, while sharing 36.4% and 31.8% of total OTUs with their seed sample S. Pseudarthrobacter and Bacillus as the two major groups coexisted among all samples, and other shared groups belonged to Achromobacter, Sphingomonas, Novosphingobium, Terribacillus, Planococcus, Paracoccus, Nesterenkonia, Halomonas, and Nocardioides. Genera, including Pantoea, Pseudomonas, Stenotrophomonas, Weissella, Leuconostoc, and Acinetobacter, were detected in each sugar beet sample but not in their corresponding soil sample. In this study, the bacterial community structures and soil compositions have significantly changed before and after continuous cropping; however, the effects of continuous cropping on endophytic bacteria of sugar beet were not statistically significant. This study would provide a scientific basis and reference information for in-depth research on correlations between continuous cropping and micro-ecological environment of sugar beet plant.