The effect of Glomus intraradices on the physiological properties of Panax ginseng and on rhizospheric microbial diversity

Effects of a co-bacterial agent on the growth, disease control, and quality of ginseng based on rhizosphere microbial diversity

BACKGROUND

The ginseng endophyte Paenibacillus polymyxa Pp-7250 (Pp-7250) has multifaceted roles such as preventing ginseng diseases, promoting growth, increasing ginsenoside accumulation, and degrading pesticide residues, however, these effects still have room for improvements. Composite fungicides are an effective means to improve the biocontrol effect of fungicides, but the effect of Pp-7250 in combination with its symbiotic bacteria on ginseng needs to be further investigated, and its mechanism of action has not been elucidated. In this study, a series of experiments was conducted to elucidate the effect of Paenibacillus polymyxa and Bacillus cereus co-bacterial agent on the yield and quality of understory ginseng, and to investigate their mechanism of action.

RESULTS

The results indicated that P. polymyxa and B. cereus co-bacterial agent (PB) treatment improved ginseng yield, ginsenoside accumulation, disease prevention, and pesticide degradation. The mechanism is that PB treatment increased the abundance of beneficial microorganisms, including Rhodanobacter, Pseudolabrys, Gemmatimonas, Bacillus, Paenibacillus, Cortinarius, Russula, Paecilomyces, and Trechispora, and decreased the abundance of pathogenic microorganisms, including Ellin6067, Acidibacter, Fusarium, Tetracladium, Alternaria, and Ilyonectria in ginseng rhizosphere soil. PB co-bacterial agents enhanced the function of microbial metabolic pathways, biosynthesis of secondary metabolites, biosynthesis of antibiotics, biosynthesis of amino acids, carbon fixation pathways in prokaryotes, DNA replication, and terpenoid backbone biosynthesis, and decreased the function of microbial plant pathogens and animal pathogens.

CONCLUSION

The combination of P. polymyxa and B. cereus may be a potential biocontrol agent to promote the resistance of ginseng to disease and improve the yield, quality, and pesticide degradation.

Arbuscular mycorrhizal fungal communities in soils where astragalus had grown for 2 years were similar to those in the abandoned farmland

Purpose

Astragalus-cultivated soils are enriched in arbuscular mycorrhizal fungi (AMF); however, the community changes of AMF between years in stragalus-cultivated soils are still unclear.

Methods

To illustrate this, using high-throughput amplicon sequencing and quantitative real-time PCR, we analyzed the AMF communities of the abandoned farmlands and interannual astragalus-cultivated soils for 1-, 2-, 3-, and 4-years, including community composition, dominant, core, specific and significantly fluctuating AMF, co-occurrence network, alpha diversity, and beta diversity.

Results

A total of 74 OTUs were classified into one phylum, Glomeromycota; one class, Glomeromycetes; four orders; four families; and six genera. The 2-year soil had the highest number of reads among the interannual soils. Only one OTU was shared among all interannual soils. The treatments significantly affected the Ace, Shannoneven, and Shannon estimators of the communities. The 2-year soil had the highest richness, evenness, and diversity among all interannual soils and was the closest to the abandoned farmland in terms of alpha diversity. Glomus of the family Glomeraceae was the dominant genus present in all treatments, and the composition of the dominant genus in interannual soils was different. Both Glomus and Diversispora were the core AMF in interannual soils, and specific AMF existed in different interannual soils. Glomus is a genus that exhibits significant interannual variation. The interannual time significantly affected the network connectivity. The results of the principal coordinate analysis showed that the community composition of the interannual soils was close to each other and separated from the abandoned farmland, and that the interannual time significantly affected the community composition.

Conclusion

Among the interannual soils, the 2-year soil may be more suitable for A. sinensis seedling rotation.

Effect the accumulation of bioactive constituents of a medicinal plant (Salvia Miltiorrhiza Bge.) by arbuscular mycorrhizal fungi community

BACKGROUND

Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with various terrestrial plants and have attracted considerable interest as biofertilizers for improving the quality and yield of medicinal plants. Despite the widespread distribution of AMFs in Salvia miltiorrhiza Bunge's roots, research on the impact of multiple AMFs on biomass and active ingredient accumulations has not been conducted. In this study, the effects of five native AMFs (Glomus formosanum, Septoglomus constrictum, Rhizophagus manihotis, Acaulospora laevis, and Ambispora gerdemannii) and twenty-six communities on the root biomass and active ingredient concentrations of S. miltiorrhiza were assessed using the total factor design method.

RESULTS

Thirty-one treatment groups formed symbiotic relationships with S. miltiorrhiza based on the pot culture results, and the colonization rate ranged from 54.83% to 89.97%. AMF communities had higher colonization rates and total phenolic acid concentration than single AMF, and communities also appeared to have higher root fresh weight, dry weight, and total phenolic acid concentration than single inoculations. As AMF richness increased, there was a rising trend in root biomass and total tanshinone accumulations (ATTS), while total phenolic acid accumulations (ATP) showed a decreasing trend. This suggests that plant productivity was influenced by the AMF richness, with higher inoculation benefits observed when the communities contained three or four AMFs. Additionally, the affinities of AMF members were also connected to plant productivity. The inoculation effect of closely related AMFs within the same family, such as G. formosanum, S. constrictum, and R. manihotis, consistently yielded lower than that of mono-inoculation when any combinations were applied. The co-inoculation of S. miltiorrhiza with nearby or distant AMFs from two families, such as G. formosanum, R. manihotis, and Ac. laevis or Am. gerdemannii resulted in an increase of ATP and ATTS by more than 50%. AMF communities appear to be more beneficial to the yield of bioactive constituents than the single AMF, but overall community inoculation effects are related to the composition of AMFs and the relationship between members.

CONCLUSION

This study reveals that the AMF community has great potential to improve the productivity and the accumulation of bioactive constituents in S. miltiorrhiza, indicating that it is an effective way to achieve sustainable agricultural development through using the AMF community.

Transcriptomics and metabolomics reveal the changes induced by arbuscular mycorrhizal fungi in Panax quinquefolius L

BACKGROUND

Panax quinquefolius L. is one of the most important foods and herbs because of its high nutritional value and medicinal potential. In our previous study we found that the ginsenoside content in P. quinquefolius was improved by arbuscular mycorrhizal fungi (AMFs). However, little research has been conducted on the molecular mechanisms in P. quinquefolius roots induced by AMFs colonization. To identify the metabolomic and transcriptomic mechanisms of P. quinquefolius induced by AMFs, non-mycorrhized (control) and mycorrhized (AMF) P. quinquefolius were used as experimental materials for comparative analysis of the transcriptome and metabolome.

RESULTS

Compared with the control, 182 metabolites and 545 genes were significantly changed at the metabolic and transcriptional levels in AMFs treatment. The metabolic pattern of AMFs was changed, and the contents of ginsenosides (Rb1, Rg2), threonine, and glutaric acid were significantly increased. There were significant differences in the expression of genes involved in plant hormone signal transduction, glutathione metabolism, and the plant-pathogen interaction pathway. In addition, several transcription factors from the NAC, WRKY, and basic helix-loop-helix families were identified in AMFs versus the control. Furthermore, the combined analysis of 'transcriptomics-metabolomics' analysis showed that 'Plant hormone signal transduction', 'Amino sugar and nucleotide sugar metabolism' and 'Glutathione metabolism' pathways were the important enriched pathways in response to AMFs colonization.

CONCLUSION

Overall, these results provide new insights into P. quinquefolius response to AMFs, which improve our understanding of the molecular mechanisms of P. quinquefolius induced by AMFs. © 2023 Society of Chemical Industry.

Developing Sustainable Agriculture Systems in Medicinal and Aromatic Plant Production by Using Chitosan and Chitin-Based Biostimulants

Chitosan is illustrated in research as a stimulant of plant tolerance and resistance that promotes natural defense mechanisms against biotic and abiotic stressors, and its use may lessen the amount of agrochemicals utilized in agriculture. Recent literature reports indicate the high efficacy of soil or foliar usage of chitin and chitosan in the promotion of plant growth and the induction of secondary metabolites biosynthesis in various species, such as Artemisia annua, Curcuma longa, Dracocephalum kotschyi, Catharanthus roseus, Fragaria × ananassa, Ginkgo biloba, Iberis amara, Isatis tinctoria, Melissa officinalis, Mentha piperita, Ocimum basilicum, Origanum vulgare ssp. Hirtum, Psammosilene tunicoides, Salvia officinalis, Satureja isophylla, Stevia rebaudiana, and Sylibum marianum, among others. This work focuses on the outstanding scientific contributions to the field of the production and quality of aromatic and medicinal plants, based on the different functions of chitosan and chitin in sustainable crop production. The application of chitosan can lead to increased medicinal plant production and protects plants against harmful microorganisms. The effectiveness of chitin and chitosan is also due to the low concentration required, low cost, and environmental safety. On the basis of showing such considerable characteristics, there is increasing attention on the application of chitin and chitosan biopolymers in horticulture and agriculture productions.

Sustainable Approaches to Boost Yield and Chemical Constituents of Aromatic and Medicinal Plants by Application of Biostimulants

INTRODUCTION

Biostimulants consist of natural ingredients, metabolites of fermentation, micro-organisms, algae or plant extracts, bacteria, mushrooms, humus substances, amino acids, biomolecules, etc. Methods: In this study, all relevant English-language articles were collected. The literature was reviewed using the keywords of biostimulant, medicinal plant, aromatic plant, natural products, and pharmaceutical benefits from Google Scholar, Scopus, and PubMed databases.

RESULTS

The significant and promoting impact of biostimulants has been reported for different medicinal and aromatic plants, such as salicylic acid for ajuga, artichoke, ajwain, basil, common rue, common sage, common thyme, coneflower, coriander, dendrobium, desert Indian wheat, dragonhead, fennel, fenugreek, feverfew, ginger, groundnut, guava, henna, Iranian soda, lavender, lemon balm, lemongrass, Malabar spinach; seaweed extract on almond, bird, s eye chili; amino acids on artemisia, broccoli, chamomile, beneficial bacteria on ashwagandha; humic acid on black cumin, cannabis, chicory, garlic, gerbera, Hungarian vetch, Moldavian dragonhead, niger plant; chitosan on dragon fruit, marigold, milk thistle, etc. The suggested mechanisms include the stimulatory impacts on the activity of enzymes involved in different biosynthetic processes, the hormone-like activity of biostimulant compounds and the improvement of nutrient uptake of plants.

CONCLUSION

The current manuscript gives many examples of the potential of biostimulants for medicinal and aromatic plant production. However, further studies are needed to better understand the effectiveness of different biostimulants and foliar applications in sustainable agriculture.

Arbuscular mycorrhizal fungi and production of secondary metabolites in medicinal plants

Medicinal plants are an important source of therapeutic compounds used in the treatment of many diseases since ancient times. Interestingly, they form associations with numerous microorganisms developing as endophytes or symbionts in different parts of the plants. Within the soil, arbuscular mycorrhizal fungi (AMF) are the most prevalent symbiotic microorganisms forming associations with more than 70% of vascular plants. In the last decade, a number of studies have reported the positive effects of AMF on improving the production and accumulation of important active compounds in medicinal plants.In this work, we reviewed the literature on the effects of AMF on the production of secondary metabolites in medicinal plants. The major findings are as follows: AMF impact the production of secondary metabolites either directly by increasing plant biomass or indirectly by stimulating secondary metabolite biosynthetic pathways. The magnitude of the impact differs depending on the plant genotype, the AMF strain, and the environmental context (e.g., light, time of harvesting). Different methods of cultivation are used for the production of secondary metabolites by medicinal plants (e.g., greenhouse, aeroponics, hydroponics, in vitro and hairy root cultures) which also are compatible with AMF. In conclusion, the inoculation of medicinal plants with AMF is a real avenue for increasing the quantity and quality of secondary metabolites of pharmacological, medical, and cosmetic interest.

Combined inoculation with dark septate endophytes and arbuscular mycorrhizal fungi: synergistic or competitive growth effects on maize?

BACKGROUND

Effects on maize were assessed of dual inoculation with arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) isolated from other plant species.

METHODS

Suspensions of DSE isolated from Stipa krylovii were prepared at different densities (2, 4, and 8 × 10⁵ CFU mL^- 1) and inoculated separately (AMF or DSE) or together (AMF + DSE), to explore their effects on maize growth.

RESULTS

Inoculation with AMF or medium and high densities of DSE and combined inoculation (AMF + DSE) increased plant above-ground growth and altered root morphology. Differences in plant growth were attributable to differences in DSE density, with negative DSE inoculation responsiveness at low density. AMF promoted plant above-ground growth more than DSE and the high density of DSE promoted root development more than AMF. Combined inoculation might lead to synergistic growth effects on maize at low density of DSE and competitive effects at medium and high DSE densities.

CONCLUSIONS

AMF and DSE co-colonized maize roots and they had positive effects on the host plants depending on DSE density. These findings indicate the optimum maize growth-promoting combination of AMF and DSE density and provide a foundation for further exploration of potentially synergistic mechanisms between AMF and DSE in physiological and ecological effects on host plants.

Fungicides alter the distribution and diversity of bacterial and fungal communities in ginseng fields

The present study was focused on comparison of four typical fungicides in ginseng field to evaluate the impact of the different fungicides on the soil bacterial and fungal communities’ composition and diversity by using high-throughput sequencing. Five treatments were designed comprising carbendazim (D), dimethyl disulfide (E), dazomet (M), calcium cyanamide (S), and control (C). The application of fungicide obviously altered the distribution of dominant fungal and bacterial communities and remarkably decreased the diversity (1099-763 and 6457-2245). The most abundant Proteobacteria obviously degenerate in fungicide-treated soil and minimum in E (0.09%) compared to control (25.72%). The relative abundance of Acidobacteria was reduced from 27.76 (C) to 7.14% after applying fungicide and minimum in E. The phylum Actinobacteria are both decomposers of organic matter and enemies of soil-borne pathogens, elevated from 11.62 to 51.54% and are high in E. The fungi community mainly distributed into Ascomycota that enriched from 66.09 to 88.21% and highin M and E (88.21 and 85.10%), and Basidiomycota reduced from 21.13 to 3.23% and low in M and E (5.27 and 3.23%). Overall, environmentally related fungicides decreased the diversity and altered the composition of bacterial and fungal communities, highest sensitivity present in dimethyl disulfide-treated soil.

Microbial Biostimulants as Response to Modern Agriculture Needs: Composition, Role and Application of These Innovative Products

An increasing need for a more sustainable agriculturally-productive system is required in order to preserve soil fertility and reduce soil biodiversity loss. Microbial biostimulants are innovative technologies able to ensure agricultural yield with high nutritional values, overcoming the negative effects derived from environmental changes. The aim of this review was to provide an overview on the research related to plant growth promoting microorganisms (PGPMs) used alone, in consortium, or in combination with organic matrices such as plant biostimulants (PBs). Moreover, the effectiveness and the role of microbial biostimulants as a biological tool to improve fruit quality and limit soil degradation is discussed. Finally, the increased use of these products requires the achievement of an accurate selection of beneficial microorganisms and consortia, and the ability to prepare for future agriculture challenges. Hence, the implementation of the microorganism positive list provided by EU (2019/1009), is desirable.

How to improve CHMs quality: Enlighten from CHMs ecological cultivation

Chinese herbal medicines (CHMs) are one of the important bioresources of medicine, which works by unlocking nature's ability to prevent diseases and recover from illnesses. Recently, it has ascended to the world stage and become a global icon. Nowadays, a considerable of researches have focused on the quality evaluation of CHMs. However, it is difficult to meet the reasonable needs of human beings for safe drug use to evaluate the quality of a huge number of inferior goods for the CHMs contaminated by pesticides and heavy metals. Hence to explore an eligible medicinal plant cultivation pattern, which can provide high quality CHMs sustainably, is most promising. This review analyzed the situation and characteristics of medicinal plant resources in different periods, including wild-harvested and cultivated resources during different stages, putting forward that ecological cultivation must be the way to develop medicinal plant cultivation and to obtain high quality CHMs.

Research Advances of Beneficial Microbiota Associated with Crop Plants

Plants are associated with hundreds of thousands of microbes that are present outside on the surfaces or colonizing inside plant organs, such as leaves and roots. Plant-associated microbiota plays a vital role in regulating various biological processes and affects a wide range of traits involved in plant growth and development, as well as plant responses to adverse environmental conditions. An increasing number of studies have illustrated the important role of microbiota in crop plant growth and environmental stress resistance, which overall assists agricultural sustainability. Beneficial bacteria and fungi have been isolated and applied, which show potential applications in the improvement of agricultural technologies, as well as plant growth promotion and stress resistance, which all lead to enhanced crop yields. The symbioses of arbuscular mycorrhizal fungi, rhizobia and Frankia species with their host plants have been intensively studied to provide mechanistic insights into the mutual beneficial relationship of plant–microbe interactions. With the advances in second generation sequencing and omic technologies, a number of important mechanisms underlying plant–microbe interactions have been unraveled. However, the associations of microbes with their host plants are more complicated than expected, and many questions remain without proper answers. These include the influence of microbiota on the allelochemical effect caused by one plant upon another via the production of chemical compounds, or how the monoculture of crops influences their rhizosphere microbial community and diversity, which in turn affects the crop growth and responses to environmental stresses. In this review, first, we systematically illustrate the impacts of beneficial microbiota, particularly beneficial bacteria and fungi on crop plant growth and development and, then, discuss the correlations between the beneficial microbiota and their host plants. Finally, we provide some perspectives for future studies on plant–microbe interactions.

Comparative study of the mycorrhizal root transcriptomes of wild and cultivated rice in response to the pathogen Magnaporthe oryzae

BACKGROUND

Rice, which serves as a staple food for more than half of the world's population, is very susceptible to the pathogenic fungus, Magnaporthe oryzae. However, common wild rice (Oryza rufipogon), which is the ancestor of Asian cultivated rice (O. sativa), has significant potential as a genetic source of resistance to M. oryzae. Recent studies have shown that the domestication of rice has altered its relationship to symbiotic arbuscular mycorrhizae. A comparative response of wild and domestic rice inhabited by mycorrhizae to infection by M. oryzae has not been documented.

RESULTS

In the current study, roots of wild and cultivated rice colonized with the arbuscular mycorrhizal (AM) fungus (AMF) Rhizoglomus intraradices were used to compare the transcriptomic responses of the two species to infection by M. oryzae. Phenotypic analysis indicated that the colonization of wild and cultivated rice with R. intraradices improved the resistance of both genotypes to M. oryzae. Wild AM rice, however, was more resistant to M. oryzae than the cultivated AM rice, as well as nonmycorrhizal roots of wild rice. Transcriptome analysis indicated that the mechanisms regulating the responses of wild and cultivated AM rice to M. oryzae invasion were significantly different. The expression of a greater number of genes was changed in wild AM rice than in cultivated AM rice in response to the pathogen. Both wild and cultivated AM rice exhibited a shared response to M. oryzae which included genes related to the auxin and salicylic acid pathways; all of these play important roles in pathogenesis-related protein synthesis. In wild AM rice, secondary metabolic and biotic stress-related analyses indicated that the jasmonic acid synthesis-related α-linolenic acid pathway, the phenolic and terpenoid pathways, as well as the phenolic and terpenoid syntheses-related mevalonate (MVA) pathway were more affected by the pathogen. Genes related to these pathways were more significantly enriched in wild AM rice than in cultivated AM rice in response to M. oryzae. On the other hand, genes associated with the 'brassinosteroid biosynthesis' were more enriched in cultivated AM rice.

CONCLUSIONS

The AMF R. intraradices-colonized rice plants exhibited greater resistance to M. oryzae than non-AMF-colonized plants. The findings of the current study demonstrate the potential effects of crop domestication on the benefits received by the host via root colonization with AMF(s), and provide new information on the underlying molecular mechanisms. In addition, results of this study can also help develop guidelines for the applications of AMF(s) when planting rice.

Effect of the biocontrol bacterium Bacillus amyloliquefaciens on the rhizosphere in ginseng plantings

Panax ginseng is an important medicinal herb due to its ability to strengthen the human immune system. However, due to the increasing needs of ginseng in medicine, the continuous cropping of ginseng has become more common and has resulted in increased problems with fungal decay. Thus, chemical fungicides are commonly used in ginseng plantings, which have caused fungicide residue problems. As an alternative control measure, biocontrol bacteria can be used to manage fungal pathogens. Additionally, these bacteria are environmentally friendly and can also improve stress tolerance in plants. In this study, an antifungal bacterial strain, TB6, that possesses ACC deaminase activity was isolated from the rhizosphere of ginseng plants. This strain was identified as Bacillus amyloliquefaciens. TB6 was applied to 2-year-old ginseng seedlings for a 2-year period, and its impact on the soil rhizosphere was evaluated. The results revealed that strain TB6 decreased fungal abundance and diversity; improved urease, catalase, and phosphatase activities; and decreased the cellulase activity of the rhizosphere soil. In addition, strain TB6 also promoted root growth and increased the fresh weight of ginseng roots, in addition to increasing polyphenol oxidase and catalase activities. These results may have practical implications for the use of biocontrol bacteria in ginseng plantings.

Co-evolutionary associations between root-associated microbiomes and root transcriptomes in wild and cultivated rice varieties

The plants and root-associated microbiomes are closely related. Plant metabolic substances can serve as a nutrient source for the microbiome, and in return, the microbiome can regulate the production of plant metabolic substances. Wild rice (Oryza rufipogon), as the ancestor of cultivated rice (Oryza sativa), has changed several metabolic pathways and root-associated microbiome during evolution. Thus, the study of the different associations between metabolic pathways and root-associated microbiomes in wild and cultivated rice varieties is important for rice breeding. In this article, the co-evolutionary association between metabolic pathways, which are based on transcriptome data, and root-associated microbiomes, which are based on 16S rRNA and internal transcribed spacer (ITS) amplicon data, in wild and cultivated rice was studied. The results showed that the enriched pathways were differentially correlated with the enriched microbiomes in wild and cultivated rice varieties. Pathways for 'Glutathione metabolism', 'Plant-pathogen interaction', 'Protein processing in endoplasmic reticulum' and 'Tyrosine metabolism' were positively associated with the improved relative abundance of bacterial and fungal operational taxonomic units (OTUs) in wild rice. On the other hand, 'Glycolysis/Gluconeogenesis', 'Brassinosteroid biosynthesis', 'Carbon metabolism', 'Phenylpropanoid biosynthesis' and 'Caffeine metabolism' were positively correlated with the improved relative abundance of bacterial and fungal OTUs in cultivated rice. Redundancy analysis showed that certain bacterial and fungal species could positively and significantly affect plant gene expression; for instance, Streptomyces, with 8.7% relative abundance in bacterial community, significantly affected plant gene expression in wild rice. This study can provide the theoretical basis for recognizing the associations between root-associated microbiomes and root transcriptomes in wild and cultivated rice varieties, and can provide practical significance for developing useful bacterial and fungal resources in wild rice.