A commentary and development perspective on the consecutive monoculture problems of medicinal plants

The consecutive monoculture problem, also known as replant disease, is a common disorder from modern agricultural practices. It has been reported that more than 70% of medicinal plants, especially those tuberous roots, have been affected. This disease has become a key factor restricting the quality and development of medicinal plants. This study analyzed three common problems with the formation of continuous cropping obstacles in medicinal plants, which includes the acidification of rhizosphere soil induced by root exudates, microbial community structure imbalance in the rhizosphere, and the severity of plant virus disease. The primary factors include:differentiation and evolution of microorganisms mediated by root exudates in rhizosphere soil, allelopathic interactions of soil-borne pathogens, soil acidification induced by rhizosphere bacterial community imbalance, increased rhizosphere soil-borne pathogens, decrease of beneficial microorganisms aggravating soil fungal diseases, and concomitant development of viral diseases. We analyzed the potential advantages of new rhizosphere management strategies on abating continuous cropping obstacles such as soil sterilization, microbial fertilizer application, diverse crop cultivation, and biochar management. This study recommended researchers to focus on rhizosphere ecological processes in continuous cropping obstacles by selecting the soil food web as the starting point, utilizing modern system biology and chemical ecology technology to analyze the interaction and mechanisms among plant-soil-microorganisms mediated by root exudates under continuous monoculture regimes. Therefore, we need to focus on the niche relationship between soil nematodes and viruses during the occurrence and development of continuous cropping obstacles, and elucidate the ecological mechanisms of soil acidification mediated by continuous cropping, as well as the co-evolution mechanism of pathogens responding to root exudates. Furthermore, several strategies can be combined to alleviate the continuous cropping obstacles. Overall, we should consider the economic, social, and ecological benefits to achieve "prevention-oriented" and "comprehensive management".