Pseudomonas putida WH-B3 degrades benzoic acid and alleviates its autotoxicity to peach (Prunus persica L. batsch) seedlings grown in replanted soil

Abstract

Autotoxins play important roles in problems with peach replanting. Benzoic acid (BA), one of the major autotoxins, is identified in peach root exudates and rhizosphere soil, leading to stunted seedling growth or even death. In this research, we aimed to screen the most efficient BA-degrading strain (BDS) from peach rhizosphere soil and assess its potential as a biodegradation strain that could relieve peach replant stress. In the work, three BDSs (WH-B1, WH-B2 and WH-B3) were isolated and identified as Pseudomonas denitrificans, Acinetobacter calcoaceticus and P. putida, respectively. Through bacterial growth and BA degradation tests, the strain WH-B3 was found to show the highest growth rate and the greatest degradation capacity and was selected for soil inoculation. Meanwhile, the phytotoxicity analysis revealed that the BA degradation products of the three BDSs were almost completely nontoxic to seedlings. Moreover, the pot experiments indicated that a high concentration of soil BA (≥ 40 mg kg−1) significantly restrained an increase in peach seedling height, stem diameter, and biomass, while the WH-B3 inoculum distinctly decreased the soil BA content and fully counteracted the BA-mediated inhibition of seedling growth. Furthermore, to investigate the performance of the potent strain under authentic replanted soil (RS) conditions, WH-B3 was inoculated into the RS for peach seedling growth. The results demonstrated that the WH-B3 inoculum degraded approximately 65% of the BA in RS and significantly improved replant-stressed seedling growth. Altogether, the characteristics of P. putida WH-B3 show that it is a potential strain for BA biodegradation and has promise for alleviating problems in peach replanting.