Combined application of allantoin and strain JIT1 synergistically or additively promotes the growth of rice under 2, 4-DCP stress by enhancing the phosphate solubility, improving soil enzyme activities and photosynthesis

Environmental pollution by 2, 4 dichlorophenol (2, 4-DCP) has become a widespread concern due to its detrimental influence on human and natural ecosystem. With the increasing accumulation of 2, 4-DCP in soil, it is of great significance to explore some appropriate approaches for enhancing plant tolerance to 2, 4-DCP stress. In the current study, a strain resistant to 2, 4-DCP was obtained from the tall fescue rhizosphere soil and named as Pseudomonas sp. JIT1. The strain JIT1 exhibited several remarkable plant growth-promoting traits, including the production of IAA, fixation of biological nitrogen and solubilization of phosphate. The inoculation of strain JIT1 significantly increased biomass, photosynthesis, antioxidant levels, chlorophyll contents and the osmotic substance contents in rice seedlings exposed to 2, 4-DCP. Meanwhile, inoculation of strain JIT1 also enhanced activities of soil alkaline phosphatase, urease, sucrase and cellulase. Moreover, under 2, 4-DCP stress, the content of allantoin in seedlings significantly increased and the pretreatment of exogenous allantoin noticeably ameliorated the negative effects caused by 2, 4-DCP stress in rice seedlings. Interesting, allantoin treatment also enhanced phosphate solubilization properties of strain JIT1. The chlorophyll contents, photosynthesis and osmotic substance further increased by combination use of strain JIT1 and allantoin, which improved the growth of seedlings, most likely to be attributed to the synergistic or additive effect between allantoin and strain JIT1. The results of this study highlight the important roles of combined use of strain JIT1 and allantoin for improving the tolerance of rice to 2, 4-DCP to stress.