Effects of rotation and Bacillus on the changes of continuous cropping soil fungal communities in American ginseng.

The continuous cropping obstacle is the main factor in leading to difficulty in American ginseng replanting. The dormant microbiota in the soil may be the cause of American ginseng disease and eventually caused continuous cropping obstacles, but there are few studies on the dynamic changes of soil microenvironment after American ginseng planting. In this study, we tracked short-term variation in physicochemical properties, enzyme activities, and fungal communities over time-series in soils with continuous cropping obstacle under crop rotation and probiotic Bacillus treatments. Furthermore, we examined the relationships between the important fungal compositions and the soil properties. The results showed that sucrase, cellulase, urease and acid phosphatase activities were significantly increased, while catalase and dehydrogenase were decreased with treatments time. Rotation treatment significantly affected the diversity, dissimilarity degree and species distribution of soil fungal community with continuous cropping obstacle over a short-term. Moreover, beneficial fungal biomarkers such as Cladorrhinum, Oidiodendron, and Mariannaea were accumulated at 48 h under rotation treatments. Almost all fungal biomarkers were negatively correlated with hydrolases and positively correlated with oxidoreductases and acid phosphatase under crop rotation treatments. This study suggested that compared to probiotic Bacillus, crop rotation can significantly affect soil fungal community structure, especially the enrichment of specific potentially beneficial fungal species. Our findings provide a scientific basis for understanding the dynamic changes of fungal communities and soil properties with continuous cropping obstacle of American ginseng in initial stage of soil improvement.

Metagenomics insights into responses of rhizobacteria and their alleviation role in licorice allelopathy.

BACKGROUND: Allelopathy is closely associated with rhizosphere biological processes, and rhizosphere microbial communities are essential for plant development. However, our understanding of rhizobacterial communities under influence of allelochemicals in licorice remains limited. In the present study, the responses and effects of rhizobacterial communities on licorice allelopathy were investigated using a combination of multi-omics sequencing and pot experiments, under allelochemical addition and rhizobacterial inoculation treatments. RESULTS: Here, we demonstrated that exogenous glycyrrhizin inhibits licorice development, and reshapes and enriches specific rhizobacteria and corresponding functions related to glycyrrhizin degradation. Moreover, the Novosphingobium genus accounted for a relatively high proportion of the enriched taxa and appeared in metagenomic assembly genomes. We further characterized the different capacities of single and synthetic inoculants to degrade glycyrrhizin and elucidated their distinct potency for alleviating licorice allelopathy. Notably, the single replenished N (Novosphingobium resinovorum) inoculant had the greatest allelopathy alleviation effects in licorice seedlings. CONCLUSIONS: Altogether, the findings highlight that exogenous glycyrrhizin simulates the allelopathic autotoxicity effects of licorice, and indigenous single rhizobacteria had greater effects than synthetic inoculants in protecting licorice growth from allelopathy. The results of the present study enhance our understanding of rhizobacterial community dynamics during licorice allelopathy, with potential implications for resolving continuous cropping obstacle in medicinal plant agriculture using rhizobacterial biofertilizers. Video Abstract.

Application of UPLC-Orbitrap-HRMS targeted metabolomics in screening of allelochemicals and model plants of ginseng.

Continuous cropping of ginseng leads to serious declines in yield and quality because of self-toxicity of allelochemicals and other factors in soil. However, because of the long growth cycle and low survival rate of ginseng, rapid screening of autotoxic activity is difficult. Therefore, it is important to analyze the allelochemicals and identify a model plant with autotoxic responses similar to those of ginseng. In this study, UPLC-Orbitrap-HRMS targeted metabolomics and verification of autotoxic activity were used to analyze a problem soil from continuously cropped ginseng. Allelochemical markers were screened by OPLS-DA. Seeds and seedlings of maize, Chinese cabbage, cucumber, green beans, wheat, sunflower, and oats were selected to identify potential model plants. Model plants with autotoxic responses similar to those of ginseng were evaluated by comparing morphological, physiological, and biochemical characteristics. The n-butanol extract of the continuously cropped problem soil had the most significant autotoxic activity. Twenty-three ginsenosides and the contributions to autotoxic effects were screened and evaluated. Of potential model plants, seeds and seedlings of cucumber showed similar growth inhibition to that of ginseng under the action of allelochemicals. Thus, metabolomics can be used to screen allelochemicals in soil and predict the autotoxic effects, and the cucumber plant model can be used to rapidly screen allelopathic activity of ginseng. The study will provide reference for methodology in allelopathy research on ginseng.

[Correlation analysis between continuous cropping obstacle of Gastrodia elata and Ilyonectria fungi and relieving strategy].

The continuous cropping obstacle of Gastrodia elata is outstanding, but its mechanism is still unclear. In this study, microbial changes in soils after G. elata planting were investigated to explore the mechanism correlated with continuous cropping obstacle. The changes of species and abundance of fungi and bacteria in soils planted with G. elata after 1, 2, and 3 years were compared. The pathogenic fungi that might cause continuous cropping diseases of G. elata were isolated. Finally, the prevention and control measures of soil-borne fungal diseases of G. elata were investigated with the rotation planting pattern of "G. elata-Phallus impudicus". The results showed that G. elata planting resulted in the decrease in bacterial and fungal community stability and the increase in harmful fungus species and abundance in soils. This change was most obvious in the second year after G. elata planting, and the soil microbial community structure could not return to the normal level even if it was left idle for another two years. After G. elata planting in soils, the most significant change was observed in Ilyonectria cyclaminicola. The richness of the Ilyonectria fungus in soils was significantly positively correlated with the incidence of G. elata diseases. When I. cyclaminicola was inoculated in the sterile soil, the rot rate of G. elata was also significantly increased. After planting one crop of G. elata and one to three crops of P. impudicus, the fungus community structure in soils gradually recovered, and the abundance of I. cyclaminicola decreased year by year. Furthermore, the disease rate of G. elata decreased. The results showed that the cultivation of G. elata made the Ilyonectria fungi the dominant flora in soils, and I. cyclaminicola served as the main pathogen of continuous cropping diseases of G. elata, which could be reduced by rotation planting with P. impudicus.

[Effects of chloropicrin fumigation on soil and growth and development of Panax notoginseng].

The continuous cropping obstacle of Panax notoginseng is serious, and effective control measures are lacking. Soil disinfection with chloropicrin(CP) has been proven to be effective in reducing the obstacles to continuous cropping of other crops. In order to ascertain the effect of CP in the continuous cropping of P. notoginseng, this paper explored the influences of CP at different treatment concentrations(0,30,40,50 kg/Mu, 1 Mu≈667 m~2) on soil macro-element nutrients, soil enzyme activity, growth and development of P. notoginseng, and the accumulation of medicinal components. The results showed that CP fumigation significantly increased the content of total nitrogen, alkali-hydrolyzable nitrogen, ammonium nitrogen, nitrate nitrogen, and available phosphorus in the soil, but it had no significant effect on potassium content. The soil protease activity showed a trend of first increasing and then decreasing with the prolonging of the treatment time. Both the soil urease and acid phosphatase activities showed a trend of first decreasing and then increasing with the prolonging of the treatment time. The higher the CP treatment concentration was, the lower the urease and acid phosphatase activities would be in the soil. The protease activity was relatively high after CP40 treatment, which was better than CP30 and CP50 treatments in promoting the nitrogen-phosphorus-potassium accumulation in P. notoginseng. The seedling survival rates after CP0, CP30, CP40, and CP50 tratments in October were 0, 65.56%, 89.44%, and 83.33%, respectively. Compared with the CP30 and CP50 treatments, CP40 treatment significantly facilitated the growth and development of P. notoginseng, the increase in fresh and dry weights, and the accumulation of root saponins. In summary, CP40 treatment accelerates the increase in soil nitrogen and phosphorus nutrients and their accumulation in P. notoginseng, elevates the seedling survival rate of P. notoginseng, enhances the growth and development of P. notoginseng, and promotes the accumulation of medicinal components. CP40 treatment is therefore recommended in production.

Rhizosphere Exudate-mediated Synergistic Harm of Soil Microorganisms to Medicinal Plants in Continuous Cropping / 中国实验方剂学杂志

Continuous cropping obstacle is the bottleneck of medicinal plant cultivation, which seriously affects the quality and yield of medicinal materials. The research on the mechanism of continuous cropping obstacle has evolved from soil physical and chemical properties and allelopathy in the 1970s to the changes of rhizosphere microenvironment and plant response mechanism at present. According to the available studies in this field and our previous research work, we systematically analyzed the mechanism of rhizosphere exudate-mediated microbial community reconstruction in the soil of the medicinal plants in continuous cropping. Specifically, rhizosphere exudates, providing the carbon source and energy for microbial growth, act as inducers or repellents to induce microbial growth or transfer, thereby changing the physicochemical properties (such as acidity) of rhizosphere soil and further altering the structure of rhizosphere microbial community. Further, we comprehensively discussed the ways of synergism between rhizosphere exudates and soil microorganisms in causing harm to the medicinal plants in continuous cropping. That is, rhizosphere exudates mediate the infection of the rhizosphere by pathogenic microorganisms, increase the susceptibility of the nearby plants, inhibit the defense of the host plants, and protect the pathogens to occupy the dominant niche. The synergistic interaction results in the release of more pathogenic factors such as mycotoxins by rhizosphere pathogens, enhanced toxicity of rhizosphere allelochemicals, and deterioration of soil physical and chemical properties. This paper summarizes the role of interaction between rhizosphere exudates and soil microorganisms in the formation of continuous cropping obstacles, aiming to provide a new research idea for revealing the formation mechanism as well as the theoretical support for overcoming continuous cropping obstacles of medicinal plants.

Pinellia ternata (Thunb.) Breit: A review of its germplasm resources, genetic diversity and active components.

ETHNOPHARMACOLOGICAL RELEVANCE: The medicinal plant Pinellia ternata has been widely used in China, Korea, and Japan and has been demonstrated to be highly effective for treating cough, vomiting, infection, and inflammatory diseases. Modern pharmacological investigations have demonstrated its multiple activities, such as antitussive, expectorant, antiemetic, antitumor, antibacterial, and sedative-hypnotic activities. AIM OF THE REVIEW: This review aims to summarize the information about the biological traits, genetic diversity, active components, and continuous cropping obstacle of P. ternata in order to improve its use. MATERIALS AND METHODS: In this review, the relevant literature was gathered by using Pinellia ternata, genetic diversity, active components, and continuous cropping obstacle as the keywords from Google Scholar, PubMed, Springer Link, the Wiley online library, SciFinder, SCOPUS, Baidu Scholar, China national knowledge infrastructure (CNKI), and WANFANF DATA (up to April 2020). RESULTS: P. ternata is the most widely used herb in the Pinellia genus to treat several diseases. The genetic diversity of P. ternata has been extensively studied, and its high genetic diversity level in China has been demonstrated. Modern pharmacological research has indicated that amino acids, alkaloids, and polysaccharides are the main active components supporting P. ternata's medicinal effects. However, an efficient method for determining its active components is still unavailable. The method used to evaluate Pinelliae Rhizoma (PR) quality standards should be further optimized. The continuous cropping obstacle has a significant effect on the quantity and quality of P. ternata. The underlying mechanism of the continuous cropping obstacle needs to be further explored. CONCLUSIONS: P. ternata has emerged as a valuable source of traditional medicine. Some uses of P. ternata in medicine have been validated by pharmacological investigations. However, a more efficient analytical method should be established to evaluate the quality of PR based on multiple quality markers. Furthermore, high-performance liquid chromatography (HPLC) and DNA barcoding should be introduced to identify the authenticity of PR. In addition, the genes involved in the metabolic synthesis pathways of the main active components, population genetic relationships, the quality control of processed PR, and the continuous cropping obstacle need to be further elucidated. We hope this review will allow for better utilization of this valuable herb.

Advances in research on allelopathic autotoxicity effects of medicinal plants / 中草药

Allelopathic autotoxicity is one of the important factors for the continuous cropping obstacle of medicinal plants, which will reduce the yield and quality. With the development of medicinal plants industry, the problem of continuous cropping obstacle is becoming more and more serious. How to alleviate the continuous cropping obstacle of medicinal plants needs to be solved urgently. This paper combines the research status of allelopathic autotoxicity in medicinal plants. On the one hand, expounds the mechanism that the allelochemicals of medicinal plants inhibit the growth and development of medicinal plants by damaging the cell structures, interfering with the metabolism of reactive oxygen species and phytohormones, affecting photosynthesis and so on. On the other hand, based on the analysis of the relationship between allelochemicals and continuous cropping obstacle of medicinal plants, this paper elucidated some methods to alleviate the continuous cropping obstacle of medicinal plants, such as breeding antiallelopathic autotoxicity medicinal plants varieties, rational fertilizing, selecting proper cropping system and using microbial agents, in order to provide reference for the production of medicinal plants.

[Allelopathic effects of phenolic compounds of ginseng root rhizosphere on Cylindrocarpon destructans.] / äººå‚è¿žä½œæ ¹é™ åœŸå£¤ä¸­é šé ¸ç‰©è´¨å¯¹äººå‚é”ˆè ç— èŒçš„åŒ–æ„Ÿæ•ˆåº”.

In this study, five phenolic compounds of ginseng rhizosphere soil were identified by HPLC, including gallic acid, salicylic acid, 3-phenylpropionic acid, benzoic acid and cinnamic acid. The results show that five phenolic compounds inhibited mycelium growth and spore germination at high concentration, but promoted mycelium growth and spore germination at low concentration. Gallic acid, salicylic acid, benzoic acid of 0.5 mmol·L-1 and 3-phenylpropionic acid, cinnamic acid of 0.05 mmol·L-1 could significantly promote the spore germination, mycelium growth and disease severity of Cylindrocarpon destructans.

[Effects of two phenolic acids on root zone soil nutrients, soil enzyme activities and pod yield of peanut]. / ä¸¤ç§é šé ¸ç±»ç‰©è´¨å¯¹èŠ±ç”Ÿæ ¹éƒ¨åœŸå£¤å »åˆ†ã€é ¶æ´»æ€§å’Œäº§é‡çš„å½±å“.

In order to investigate the relationship between the accumulation of phenolic acids in peanut continuous cropping soil and the continuous cropping obstacle of peanut, the effects of p-hydroxy benzoic acid and cinnamic acid on peanut root zone soil nutrients, soil enzyme activities and yield of peanut were studied by pot experiment at three stages of peanut, i.e. the pegging stage of peanut (45 days after seedling), the early podding (75 days after seedling) and the end of podding (105 days after seedling) stages. The results showed that the peanut root zone soil nutrients and enzyme activities changed obviously under the two phenolic acids treatment, especially at the pegging stage of peanut. The soil alkali-hydrolyzable nitrogen, available phosphorus, available potassium, and soil enzyme activities (urease, sucrose, neutral phosphatase) were decreased significantly. At the early and end of podding stages of peanut, the effects of the two phenolic acids on peanut root zone soil nutrients and soil enzyme activities were under a weakening trend. The allelopathy of cinnamic acid was stronger than that of p-hydroxy benzoic acid at the same initial content. The pod yield per pot was reduced by 45.9% and 52.8%, while the pod number of per plant was reduced by 46.2% and 48.9% at higher concentration (80 mg·kg-1 dry soil) of p-hydroxy benzoic acid and cinnamic acid treatments, respectively.