Water stress affects the frequency of Firmicutes, Clostridiales and Lysobacter in rhizosphere soils of greenhouse grape

The objective of this study was to identify the microbial community structures in rhizosphere soils of grapevine in protected cultivation and to assess the effects of soil water regulation on the main bacteria. Based on a two-year field test, soil samples from mild water stress and control (CK)treatments were collected during the flowering (FS) and early fruit development stages (ES) of grapes. Soil microbial community structures were analyzed using 16S rRNA gene sequencing method. The species composition (Observed species), species diversity index (Shannon, Simpson and PD_whole_tree), and community richness values (Chaol, ACE) under the mild water stress treatments a t FS and ES were all significantly higher than under the CK treatment (P < 0.05). Proteobacteria, Firmicutes, Actinobacteria were the main types of microbial phyla in grapevine rhizosphere soils. The relative abundance of Firmicutes under the mildwater stress treatments at FS and ES was significantly lower than under the CK treatment. Xanthomonadales and Clostridiales were the main orders, and the frequency of Clostridiales under the mild water stress treatments at FS and ES were significantly lower than under the CK treatment. Clostridium_sensu_stricto_1 was the dominant genus, the relative abundance of which reduced under the mild water stress, both at the two sampling stages. However, water stress had little effect on the relative abundance of Lysobacter. Meanwhile, a compensatory effect on grape growth was detected after re-watering. Results show that Firmicutes, Clostridiales, Clostridium_sensu_stricto_1 werethe main drought sensitive microorganisms a t phylum, order and genus levels, respectively. Mild water stress was an appropriate water management which can increase the diversity and richness of soil microorganisms in greenhouse grape soils, and can save water resources compared with the traditional irrigation regimes.