Root ACC and rhizosphere ACC deaminase producing bacteria affects apple root architecture under soil compaction stress

Abstract

Abstract Purpose To explore the relationship among root architecture, 1-aminocyclopropane-l-carboxylic acid (ACC) in roots and ethylene-modulating bacteria in rhizosphere and root endosphere under soil compaction stress, so as to provide theoretical reference for soil treatment. Methods One-year-old potted apple (Malus domestica Borkh 'Red Fuji') trees as experiment materials, whose rootstocks were Malus hupehensis and Malus robusta respectively. After maintaining soil compaction stress for one year, we detected root architecture, root activity, root ethylene production, ACC content and the activity of ACC synthase (ACS) and ACC oxidase (ACO) in roots. Furthermore, we quantified the abundance of ethylene-modulating bacteria including the bacteria of ACC deaminase and ethylene-forming enzyme (efe) in rhizosphere and root endosphere, and analyzed their relationship with ethylene biosynthesis and root characteristics. Results Soil compaction stress significantly changed root architecture, decreased root activity, enhanced ethylene production, increased ACC content and ACS activity in roots, regardless of whether the rootstock was M. hupehensis or M. robusta. The abundance of ethylene-modulating bacteria varied with rootstocks under compaction stress. Soil compaction stress decreased the abundance of ACC deaminase producing bacteria in M. robusta and increased that of efe in M. hupehensis both in rhizosphere and root endosphere. The changes of root characteristics were significantly correlated with ethylene production and ACC deaminase producing rhizobacteria. Conclusion The increase of ACC content in roots and the decrease of abundance of ACC deaminase producing rhizobacteria jointly lead to the increase of ethylene release from roots, which lead to the change of root architecture under soil compaction stress.