Changes in soil bacterial community structure as a result of incorporation of Brassica plants compared with continuous planting eggplant and chemical disinfection in greenhouses

RESEARCH ARTICLE Changes in soil bacterial community structure as a result of incorporation of Brassica plants compared with continuous planting eggplant and chemical disinfection in greenhouses a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 Tianzhu Li1☯, Tongtong Liu1☯, Chengyu Zheng1, Chunsheng Kang2, Zichao Yang1, Xiaotong Yao1, Fengbin Song1, Runzhi Zhang1, Xuerong Wang1, Ning Xu1, Chunyi Zhang1, Wei Li1*, Shumin Li1* 1 Resource and Environmental College, Northeast Agricultural University, Harbin, China, 2 Research Development and Evaluation Center of Laboratory, Harbin, China ☯ These authors contributed equally to this work. * (WL); (SML) Abstract OPEN ACCESS Citation: Li T, Liu T, Zheng C, Kang C, Yang Z, Yao X, et al. (2017) Changes in soil bacterial community structure as a result of incorporation of Brassica plants compared with continuous planting eggplant and chemical disinfection in greenhouses. PLoS ONE 12(3): e0173923. https://doi.org/ 10.1371/journal.pone.0173923 Editor: Sabrina Sarrocco, Universita degli Studi di Pisa, ITALY Received: August 24, 2016 Accepted: February 28, 2017 Published: March 27, 2017 Copyright: © 2017 Li et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was financially supported by the Special Fund for Agro-scientific Research in the Public Interest, China (201503109), and Heilongjiang Natural Science Foundation, China (C2015016). Greenhouse eggplant monocropping in China has contributed to the aggravation of soilborne diseases, reductions in crop quality and yield, and the degradation of physical and chemical soil properties. Crop rotation is one effective way of alleviating the problems of continuous cropping worldwide; however, few studies have reported changes in soil bacterial community structures and physical and chemical soil properties after Brassica vegetables had been rotated with eggplant in greenhouses. In this experiment, mustard-eggplant (BFN) and oilseed rape-eggplant (BFC) rotations were studied to identify changes in the physicochemical properties and bacterial community structure in soil that was previously subject to monocropping. Samples were taken after two types of Brassica plants incorporated into soil for 15 days to compare with continually planted eggplant (control, CN) and chemical disinfection of soil (CF) in greenhouses. MiSeq pyrosequencing was used to analyze soil bacterial diversity and structure in the four different treatments. A total of 55,129 reads were identified, and rarefaction analysis showed that the soil treatments were equally sampled. The bacterial richness of the BFC treatment and the diversity of the BFN treatment were significantly higher than those of the other treatments. Further comparison showed that the bacterial community structures of BFC and BFN treatments were also different from CN and CF treatments. The relative abundance of several dominant bacterial genera in the BFC and BFN treatments (such as Flavobacteria, Stenotrophomonas, Massilia and Cellvibrio, which played different roles in improving soil fertility and advancing plant growth) was distinctly higher than the CN or CF treatments. Additionally, the total organic matter and Olsen-P content of the BFC and BFN treatments were significantly greater than the CN treatment. We conclude that Brassica vegetables-eggplant crop rotations could provide a more effective means of solving the problems of greenhouse eggplant monocultures. Competing interests: The authors have declared that no competing interests exist. PLOS ONE | https://doi.org/10.1371/journal.pone.0173923 March 27, 2017 1 / 17 Brassica plants incorporated changes continuous eggplant soil bacterial community structure Introduction A common phenomenon in eggplant (Solanum melongena L.) cropping systems is “continuous monoculture”, which means growing the same crop year after year in the same field. This practice exists in China due to the opposing forces of high market demand and limited cultivated land [1]. However, a series of problems result from the eggplant monoculture in China, such as the aggravation of soil-borne disease, reductions in crop quality and yield [2], and degraded soil physical and chemical properties [3]. In the Mediterranean region, the continuous cropping of eggplant has had negative effects on soil and plant growth due to an uneven supply of nutrients and increasingly widespread populations of nematodes and soil-borne pathogens [4]. Vanlauwe et al. (2001) found that there was an increase in soil acidification when nitrogen fertilizers were used excessively, affecting the microbial diversity of the soil. Long term monoculture with a single plant also harmed the rhizosphere of crop microorganisms [5] and eliminated soil biological diversity. Soil is a complex and dynamic environment, and its biological activity is mostly governed by microorganisms [6]. Continuous cropping alters soil composition and microbial community structures [7] which are important indicators of soil fertility [8]. Crop rotation is an effective way to alleviate problems with continuous cropping worldwide. If rotated crops are selected properly, the effectiveness of rotation can be maximized. Tian et al. (2009) found that in both tomato-onion and chrysanthemum-tomato rotations, tomato yield, organic C, total N and total microbial population significantly improved compared with continuous planting and were positively correlated [9]. Winter cover crops (oilseed rape) and their residue were beneficial to eggplant growth; eggplant yield increased by 46.19% in 2011 since nitrogen utilization efficiency was enhanced [10, 11]. Rice-rapeseed and cottonrapeseed crop rotations further improved N-use efficiency and increased the yields of seeds from previous crops [12]. The tissues of the rotated vegetables are beneficial to the elemental composition of the soil, subsequently improving plant growth. Therefore, crop soil quality could be improved by selecting crops based on their chemical composition to influence soil carbon content [13]. Furthermore, incidences of soil-borne diseases can be reduced by influencing microbial structures and its activities [14]. Therefore, it is important to explore how strongly crop rotations alter the diversity and composition of bacterial and fungal communities [15]. Several beneficial bacterial strains isolated from the rhizosphere of Brassica species [16] are associated with plant growth and promoting rhizobacteria (PGPR), such as Agrobacterium, Azospirillum, Bacillus, Enterobacter, Pseudomonas and Rhizobium [17]. These microorganisms can promote plant growth by regulating nutritional and hormonal balances, producin (...truncated)