Effects of different technical substitutions on reducing replant disease of and the underlying mechanism.

is a traditional Chinese medicinical herb, with tuberous roots being used as a medicine. Serious continuous monoculture problems were suffered from process of artificial and intensive cultivation. To explore the effective technical methods to overcome the monoculture problems, the effects of different technical substitution patterns on soil environment remediation, photosynthetic physiology and yield performance of were assessed under continuous cropping system with four technical substitution treatments in the phase between two crops after the newly harvested (first crop): fallow (RP-F-RP), fallow treated with microbial fertilizer (RP-F-BF), water flooding (RP-WF), and water flooding treated with specific microbial fertilizer (RP-WF-BF). Results showed that RP-WF-BF pattern was the single one that could effectively restore yield under two-year monoculture and three-year monoculture to more than 90% and 70% of the newly planted respectively. All the other patterns did not significantly improve yield under two-year monoculture. The contents of polysaccharide and total saponin in under RP-WF-BF treatment were significantly increased by 15.3% and 16.5% compared with those of the newly planted, respectively. The abundance of beneficial microorganisms in the rhizosphere soil of significantly increased. A reverse pattern occurred for pathogens under RP-WF-BF pattern. Moreover, soil nitrogen cycling was improved. The expression of , and was increased by 931%, 124% and 100% compared with those in the RP-F-RP pattern, respectively. Soil acidification under RP-WF-BF pattern was alleviated. The alleviation of soil biological and abiotic stress enhanced the stability of the antioxidant enzyme system, thereby improving the growth and development of at the seedling and the early expand stages. The chlorophyll content, leaf area index and photosynthesis rate of leaves were increased, with the dry matter translocation improved and accumulation of underground dry matter accelerated, which ultimately increased yield and quality under RP-WF-BF pattern. In this study, the separate water flooding treatment (RP-WF) and microbial fertilizer treatment (RP-F-BF) failed to significantly reduce the continuous cropping obstacles of , while the combination of them could produce a multiplication effect of sustainable strengthening on rhizosphere environment. The findings suggested that effective technical substitution could reduce replant disease of .