ABSTRACT
Methanol, ethyl acetate, and water were used to extract the continuous cropping soils of Panax notoginseng, with the solution/soil ratios of 3:1, 6:1, and 9:1. We investigated the effects of those soil extracts on the growth and population of root-rot pathogens of P. notoginseng. Results showed that the methanol, ethyl acetate and water extracts all promoted mycelial growth of Fusarium oxysporum and Fusarium solani after 72 h of plate culture. The response indices of methanol and ethyl acetate extracts on the growth of F. oxysporum were 14.0%-19.8% and 16.2%-20.2%, being higher than that of water extract (8.9%-14.2%), but without significant difference between diffe-rent extraction ratios. However, methanol extract inhibited the mycelial growth of Alternaria spp. The inhibitory effect was highest at the extraction ratio of 3:1, reaching -33.2% to -38.5%. Ethyl acetate and water extracts did not affect the mycelial growth of Alternaria spp. After four weeks of soil culture, methanol, ethyl acetate and water extracts all increased the F. oxysporum populations. The positive effect of water extract was higher than that of methanol (1.68×104-6.73×104 copies·g-1 dry soil) and ethyl acetate (1.77×104-3.72×104 copies·g-1 dry soil) extracts, being 3.49×106-9.56×106 copies·g-1 dry soil. This increment was weakened along with the increase of extraction ratio. Both water extract and methanol extract with low extraction ratio could increase the F. solani populations, while there were no significant effects of methanol, ethyl acetate and water extracts on the population of Alternaria spp. Therefore, the extracts from continuous P. notoginseng cropping soil showed allopathically promoting effects on the growth and population of root-rot pathogens, F. oxysporum and F. solani, which may be one of the reasons for the occurrence of root rot and other soil-borne diseases in replanted P. notoginseng gardens.
Subject(s)
Fusarium , Panax notoginseng , Plant Diseases , Plant Roots , SoilABSTRACT
Replant failure has threatened the production of Sanqi ginseng (Panax notoginseng) mainly due to the accumulation of soil-borne pathogens and allelochemicals. Reductive soil disinfestation (RSD) is an effective practice used to eliminate soil-borne pathogens; however, the potential impact of RSD on the degradation of allelochemicals and the growth of replant Sanqi ginseng seedlings remain poorly understood. In this study, RSD was conducted on a Sanqi ginseng monoculture system (SGMS) and a maize-Sanqi ginseng system (MSGS), defined as SGMS_RSD and MSGS_RSD, respectively. The aim was to investigate the impact of RSD on allelochemicals, soil microbiomes, and survival rates of replant seedlings. Both short-term maize planting and RSD treatment significantly degraded the ginsenosides in Sanqi ginseng-cultivated soils, with the degradation rate being higher in the RSD treatment. The population of Fusarium oxysporum and the relative abundance of genus Fusarium were dramatically suppressed by RSD treatment. Furthermore, the RSD treatment, but not maize planting, markedly alleviated the replant failure of Sanqi ginseng, with the seedling survival rate being 52.7-70.7% 6 months after transplanting. Interestingly, RSD followed by short-term maize planting promoted microbial activity restoration, ginsenoside degradation, and ultimately alleviated the replant failure much better than RSD treatment alone (70.7% vs. 52.7%). Collectively, these results indicate that RSD treatment could considerably reduce the obstacles and might also act as a potential agriculture regime for overcoming the replant failure of Sanqi ginseng. Additional practices, such as crop rotation, beneficial microorganism inoculation, etc. may also still be needed to ensure the long-term efficacy of seedling survival.
