Response of tomato root endophytic bacterial communities to water-oxygen coupling under micro/nanoaerated drip irrigation in slightly saline soils

Abstract

The aims of this study were to explore the effects of micro/nanoaerated drip irrigation on the root endophytic bacterial communities of crops in saline soils and to offer new insights into how to increase the productivity of such soils by regulating these communities using water-oxygen coupling. A tomato cultivation experiment was conducted in mildly saline soil to evaluate the responses of the root endophytic bacterial community to the soil microenvironment created by micro/nanoaerated drip irrigation. The results revealed that the total relative abundance of phyla, which accounted for 54.80–80.31% of the root endophytic bacterial communities, differed significantly among treatments. The tomato root volume, soil available nitrogen (N) and soil electrical conductivity (EC) were the top three factors that had the greatest influence on the composition and functions of the root endophytic bacterial communities. The ability of these factors to explain the composition differences in the root endophytic bacterial communities reached 0.169, 0.158 and 0.154, respectively. The top three factors were significantly correlated with 10, 13 and 10 functional groups, respectively, of the root endophytic bacterial communities. Furthermore, the structural equation model (SEM) suggested that root endophytic bacterial community functions were significantly correlated with tomato yield (r = 0.71). The combination of the high dissolved oxygen concentration with sufficient and excessive irrigation (A30W1 and A30W1.2) significantly reduced the soil EC and increased the soil available N and root volume, thereby significantly improving the metabolic functions of the root endophytic bacterial communities and the tomato yields. The combination of moderate dissolved oxygen concentration with sufficient and excessive irrigation (A15W1 and A15W1.2) had moderate effects on the metabolic functions of the root endophytic bacterial communities, leading to medium tomato yields. In conclusion, different water-oxygen coupling treatments significantly affected the environmental factors in the root zone and then regulated the metabolic functions of the root endophytic bacterial communities, thus affecting the tomato yields.