Single Inoculation Research Articles

Enhancing alfalfa photosynthetic performance through arbuscular mycorrhizal fungi inoculation across varied phosphorus application levels

This study evaluated the effects of arbuscular mycorrhizal fungi inoculation on the growth and photosynthetic performance of alfalfa under different phosphorus application levels. This experiment adopts two-factors completely random design, and sets four levels of fungi application: single inoculation with Funneliformis mosseae (Fm, T1), single inoculation with Glomus etunicatum (Ge, T2) and mixed inoculation with Funneliformis mosseae × Glomus etunicatum (Fm×Ge, T3) and treatment uninfected fungus (CK, T0). Four phosphorus application levels were set under the fungi application level: P2O5 0 (P0), 50 (P1), 100 (P2) and 150 (P3) mg·kg-1. There were 16 treatments for fungus phosphorus interaction. The strain was placed 5 cm below the surface of the flowerpot soil, and the phosphate fertilizer was dissolved in water and applied at one time. The results showed that the intercellular CO2 concentration (Ci) of alfalfa decreased at first and then increased with the increase of phosphorus application, except for light use efficiency (LUE) and leaf instantaneous water use efficiency (WUE), other indicators showed the opposite trend. The effect of mixed inoculation (T3) was significantly better than that of non-inoculation (T0) (p < 0.05). Pearson correlation analysis showed that Ci was significantly negatively correlated with alfalfa leaf transpiration rate (Tr) and WUE (p < 0.05), and was extremely significantly negatively correlated with other indicators (p < 0.01). The other indexes were positively correlated (p < 0.05). This may be mainly because the factors affecting plant photosynthesis are non-stomatal factors. Through the comprehensive analysis of membership function, the indexes of alfalfa under different treatments were comprehensively ranked, and the top three were: T3P2>T3P1>T1P2. Therefore, when the phosphorus treatment was 100 mg·kg-1, the mixed inoculation of Funneliformis mosseae and Glomus etunicatum had the best effect, which was conducive to improving the photosynthetic efficiency of alfalfa, increasing the dry matter yield, and improving the economic benefits of local alfalfa in Xinjiang. In future studies, the anatomical structure and photosynthetic performance of alfalfa leaves and stems should be combined to clarify the synergistic mechanism of the anatomical structure and photosynthetic performance of alfalfa.

Integrated use of Consortia-based Microbial Inoculants and Nutrient Complex Stimulates the Rhizosphere Microbiome and Soybean Productivity

Background: The effectiveness of soybean inoculants in field conditions may be improved through the joint application of rhizobia and plant growth-promoting bacteria (PGPB). Plant nutrients may also contribute to the higher efficacy of microbial inoculants as well as the growth and development of plants. Methods: A field experiment was performed to evaluate the responses of the rhizomicrobiome and soybean to seed treatments with multiple bacterial strains (Bradyrhizobium japonicum, Bacillus subtilis, Bacillus megaterium and Azotobacter chroococcum), applied individually or in consortia, with and without nutrient complex (S, Mg, Mn, Fe, Zn, Cu, B and Mo). Result: Seed treatments with microbial consortia of Br. japonicum, B. subtilis/B. megaterium, A. chroococcum strains and nutrients had the highest effect on the abundance of total bacteria, nitrogen-fixing bacteria, actinomycetes and activity of dehidrogenase in the soybean rhizosphere. The highest effect on plant height, plant weight, pod number, pod weight, seed number and seed weight was obtained from treatment with Br. japonicum strains with nutrients, followed by co-inoculation with B. megaterium and A. chroococcum. In comparison with the control and Bradyrhizobium single inoculation, a statistically significant increase in the seed yield was recorded in treatment with Br. japonicum, B. megaterium, A. chroococcum and nutrients, reflecting the highest increase in protein and oil yield. The interactive effects of microbial consortia and nutrients could be used as promising seed technology for sustainable soybean cropping.

Screening of high-efficiency nitrogen-fixing bacteria from the traditional Chinese medicine plant Astragalus mongolicus and its effect on plant growth promotion and bacterial communities in the rhizosphere

BackgroundAstragalus mongolicus Bunge is used in traditional Chinese medicine and is thus cultivated in bulk. The cultivation of A. mongolicus requires a large amount of nitrogen fertilizer, increasing the planting cost of medicinal materials and polluting the environment. Isolation and screening of plant growth-promoting rhizobacteria (PGPR) and exploring the nitrogen fixation potential of A. mongolicus rhizosphere microorganisms would effectively reduce the production cost of A. mongolicus.ResultsThis study used A. mongolicus roots and rhizosphere soil samples from Longxi County of Gansu Province, Jingle County, and Hunyuan County of Shanxi Province, China, to isolate and identify nitrogen-fixing bacteria. Through nitrogen fixation efficiency test, single strain inoculation test, and plant growth-promoting characteristics, three strains, Bacillus sp. J1, Arthrobacter sp. J2, and Bacillus sp. G4 were selected from 86 strains of potential nitrogen-fixing bacteria, which were the most effective in promoting the A. mongolicus growth and increasing the nitrogen, phosphorus, and potassium content in plants. The antagonistic test showed that these bacteria could grow smoothly under the co-culture conditions. The J1, J2, and G4 strains were used in a mixed inoculum and found to enhance the biomass of A. mongolicus plants and the accumulation of the main medicinal components in the field experiment. Mixed bacterial agent inoculation also increased bacterial diversity and changed the structure of the bacterial community in rhizosphere soil. Meanwhile, the relative abundance of Proteobacteria increased significantly after inoculation, suggesting that Proteobacteria play an important role in plant growth promotion.ConclusionsThese findings indicate that specific and efficient PGPRs have a significant promoting effect on the growth of A. mongolicus, while also having a positive impact on the structure of the host rhizosphere bacteria community. This study provides a basis for developing a nitrogen-fixing bacterial fertilizer and improving the ecological planting efficiency of A. mongolicus.

Virulence and Molecular Detection of Cassava Mosaic and Brown Streak Virus Genes on Elite Mutant Cassava Lines

Unavailability of germplasm with Cassava Brown Streak Disease (CBSD) and Cassava Mosaic Disease (CMD) tolerance genes remains the main bottleneck towards management of the two diseases in tropic and sub-tropic regions in Africa. We assessed the pathogenicity of two viruses and established the presence of genes linked to CBSD and CMD among some elite cassava lines using field techniques and PCR methods. The screen-house experiment was arranged in split plot in completely randomized block design replicated thrice. Severity data was done on a scale of 1 - 5 at an interval of 14 days post inoculation. Symptomatic fresh leaves were used in the extraction of genomic deoxyribonucleic acid and amplification done using markers linked to African cassava mosaic virus (ACMV), separated bands scored as present (+) or absent (-) and visualized under UV trans-illuminator. Virulence and pathogenicity results showed higher tolerance to CBSD and CMD under single inoculation. In contrast, dual inoculation synergistically increased severity expression leading defoliation at early stages of growth. DNA amplification found no CBSD and CMD alleles in CAS1. However, some traces of the alleles were amplified on CAS2, CAS3, KME3 and KME4. Mutant cassava lines exhibited low severity compared to parental lines which were genetically different in terms of viral genes detected by the ACMV linked markers.

Plant growth promoting activities of Pseudomonas sp. and Enterobacter sp. isolated from the rhizosphere of Vachellia gummifera in Morocco.

The Moroccan endemic Vachellia gummifera grows wild under extreme desert conditions. This plant could be used as an alternative fodder for goats, and camels, in order to protect the Argan forests against overgrazing in Central and Southwestern Moroccan semiarid areas. With the aim to improve the V. gummifera population's density in semiarid areas, we proposed its inoculation with performing plant growth-promoting bacteria. Hence, 500 bacteria were isolated from the plant rhizosphere. From these, 291 isolates were retained for plant growth-promoting (PGP) activities assessment. A total of 44 isolates showed the best phosphates solubilization potential, as well as siderophore and auxin production. The combination of REP-PCR (repetitive extragenic palindromic-polymerase chain reaction) fingerprinting, PGP activities, and phenotypic properties, allowed the selection of three strains for the inoculation experiments. The three selected strains' 16S rRNA sequencing showed that they are members of the Enterobacter and Pseudomonas genera. The inoculation with three strains had diverse effects on V. gummifera growth parameters. All single and combined inoculations improved the plant shoot weight by more than 200%, and the root length by up to 139%, while some combinations further improved protein and chlorophyll content, thereby improving the plant's forage value. The three selected strains constitute an effective inoculum for use in the arid and semiarid zones of southern Morocco.

Effect of Sequential Inoculation of Tetragenococcus halophilus and Wickerhamomyces anomalus on the Flavour Formation of Early-Stage Moromi Fermented at a Lower Temperature.

Microbial inoculation in moromi fermentation has a great influence on the physicochemical and flavour properties of soy sauces. This work investigated the effect of inoculating Tetragenococcus halophilus and Wickerhamomyces anomalus on the flavour formation of early-stage moromi (30 days) fermented at a lower temperature (22 °C) by determining their physicochemical and aroma changes. The results showed that single yeast or LAB inoculation increased the production of amino nitrogen, lactic acid and acetic acid, as well as free amino acids and key flavour components. Particularly, the sequential inoculation of T. halophilus and W. anomalus produced more free amino acids and aromatic compounds, and there might be synergistic effects between these two strains. More characteristic soy sauce flavour compounds, such as benzaldehyde, HEMF, guaiacol and methyl maltol were detected in the sequentially inoculated moromi, and this sample showed higher scores in savoury, roasted and caramel intensities. These results confirmed that sequential inoculation of T. halophilus and W. anomalus could be a choice for the future production of moromi with good flavour and quality under a lower temperature.

Ectomycorrhizal fungi and dark septate endophyte inoculation improve growth and tolerance of Pinus tabulaeformis under cadmium stress

Forest trees can establish symbiotic associations with dark septate endophytes (DSEs) and ectomycorrhizal fungi (ECMF) simultaneously. However, the combined effects of these two fungi on the growth and cadmium (Cd) tolerance of host plants remain largely unexplored. To address this knowledge gap, a pot experiment was conducted to examine the impact of the interaction between ECMF (Suillus granulatus) and DSEs (Pseudopyrenochaeta sp.) on Pinus tabulaeformis under Cd stress. Various growth and physiological indicators, nutrient uptake, and soil properties were assessed to evaluate the impact of the fungal strains. Notably, the colonization rates of both fungal strains were found to increase in response to Cd stress, with the extent of this increase being influenced by the specific fungal species and the level of Cd in the soil. Compared to the uninoculated treatment, single inoculation of P. tabulaeformis seedlings resulted in enhanced biomass, root development, and nutrient contents under Cd stress conditions. Furthermore, a synergistic effect was observed when these seedlings were simultaneously infected with S. granulatus and Pseudopyrenochaeta sp., as indicated by significantly greater measurements in various indicators compared to both the single-inoculated and uninoculated treatments. Fungal inoculation effectively regulated the antioxidant defense responses and photosynthesis of P. tabulaeformis seedlings subjected to excess Cd stress, particularly under mixed inoculation conditions. In addition, the fungal inoculation facilitated the accumulation of Cd in P. tabulaeformis, suggesting a promising potential for the implementation of bioremediation strategies in areas contaminated with heavy metals. The findings from this study indicate that the utilization of root symbiotic fungi obtained from stressed environments could potentially enhance the growth performance and tolerance of P. tabulaeformis towards heavy metals, and simultaneous inoculation of both fungal groups may result in even more pronounced synergistic effects on the overall fitness of the plant.

Effects of Phosphorus-dissolving Dark Septate Endophytes on the Growth of Blueberry.

Dark septate endophytes (DSEs) are widely distributed and improve plant growth. DSEs secrete large amounts of enzymes to mineralize insoluble phosphorus in soil and convert it into soluble phosphorus, promoting plant uptake of phosphorus. However, the effects of DSEs with phosphate-solubilizing ability on host plants need further study. In this study, phosphorus-dissolving DSEs were screened for growth-promoting effects. We isolated, identified and characterized three DSE species (Thozetella neonivea, Pezicula ericae and Hyaloscyphaceae sp.) showing phosphate-solubilizing ability. The impact of single, dual or triple inoculation of DSEs on blueberry plant characteristics was studied. Their effects on colonization intensity, seedling biomass, nutrients in plants and soil, and activities of plant resistance enzymes and soil enzymes were markedly upregulated relative to the control (P < 0.05). The available phosphorus and acid phosphatase levels in different combinations were significantly increased. These findings indicate that the application of the three DSEs may be valuable in facilitating the cultivation of blueberry with a higher biomass and improved plant quality.

Economic Analysis of Seed Inoculation and Phosphorus Doses Application in Cowpea (Vigna unguiculata L.)

The study about the economic returns of cowpea (Vigna unguiculata) by the use of rhizobium seed inoculation and different phosphorus doses was conducted at Bharatpur, Chitwan, from February to May 2022. The experiment was conducted in a two-factor randomized complete block design (RCBD) with three replications and eight treatments. Treatments were set as factor A: seed inoculation i.e., un-inoculated and inoculated; and factor B: four different phosphorus doses (20, 40, 60, 80 kg ha­-1). The cowpea variety ‘Prakash’ was used. Results revealed that the application of seed inoculation provides the highest returns compared to an un-inoculated one; similarly, in case of phosphorus dose of 40 kg P2O5 ha-1 gives the maximum economic returns compared to other phosphorus doses. Furthermore, the interaction of rhizobium inoculation with 40 kg ha­-1 gives the highest gross income (NRs. 216005), net return (NRs. 110829.39) and B: C (2.05) compared to all other single inoculation or phosphorus or interaction treatments ( 1 $ = NRs. 132.53) . From the result, it is concluded that the use of rhizobium inoculation along with 40 kg P2O5 ha­-1 would be economically profitable for the farmers under the Terai conditions of Nepal.

Bacteriophages targeting protective commensals impair resistance against Salmonella Typhimurium infection in gnotobiotic mice.

Gut microbial communities protect the host against a variety of major human gastrointestinal pathogens. Bacteriophages (phages) are ubiquitous in nature and frequently ingested via food and drinking water. Moreover, they are an attractive tool for microbiome engineering due to the lack of known serious adverse effects on the host. However, the functional role of phages within the gastrointestinal microbiome remain poorly understood. Here, we investigated the effects of microbiota-directed phages on infection with the human enteric pathogen Salmonella enterica serovar Typhimurium (S. Tm), using a gnotobiotic mouse model (OMM14) for colonization resistance (CR). We show, that phage cocktails targeting Escherichia coli and Enterococcus faecalis acted in a strain-specific manner. They transiently reduced the population density of their respective target before establishing coexistence for up to 9 days. Infection susceptibility to S. Tm was markedly increased at an early time point after challenge with both phage cocktails. Surprisingly, OMM14 mice were also susceptible 7 days after a single phage inoculation, when the targeted bacterial populations were back to pre-phage administration density. Concluding, our work shows that phages that dynamically modulate the density of protective members of the gut microbiota can provide opportunities for invasion of bacterial pathogens, in particular at early time points after phage application. This suggests, that phages targeting protective members of the microbiota may increase the risk for Salmonella infection.

Combined Application of Organic Fertilizer with Microbial Inoculum Improved Aggregate Formation and Salt Leaching in a Secondary Salinized Soil.

Greenhouse vegetable production provides significant quantities of vegetables throughout the year and improves farmers' income. However, over-fertilization with mineral fertilizer causes soil secondary salinization and decreases the stability of the soil structure. To improve aggregate formation and decrease salt accumulation in the soil profile, bio-organic fertilizers (Protaetia brevitarsis larvae frass with Bacillus amyloliticus and/or Trichoderma harziensis) were applied to partially substitute mineral fertilizer in a salinized vegetable soil. Soil nutrient condition, aggregate stability, and salt movement in the soil profile were measured in a greenhouse double-cucumber system. The results showed that soil organic matter (SOM), total nitrogen (TN), and available phosphorus (AP) increased significantly under bio-organic fertilizer treatments compared with control. Soil electrical conductivity (EC) and total salt content (TSC) decreased by 15.74-24.20% and 19.15-29.05%, respectively, with bio-organic fertilizers (p < 0.05). Cl-, NO3-, and SO42- content under double inoculation with B. amyloliticus and T. harziensis reduced by 31.19%, 26.30%, and 53.11%, respectively, compared to CK (p < 0.05). In addition, double inoculation was more efficient in reducing nitrate content in the soil profile than single inoculation. Soil microaggregates of 0.25-0.053 mm increased by 75.87-78.51% with bio-fertilizers compared with control, and double inoculation was the best for aggregate formation. In conclusion, the inoculation of plant-growth-promoting and salt-tolerant microorganisms with high humic acid larvae frass can alleviate salinization in vegetable soil, enhance soil nutrient content, and improve the soil structure.

Optimizing biomass yield of three herbaceous forage legumes through dual inoculation of Arbuscular Mycorrhizal Fungi and Rhizobia

The production of forage legumes under Sub-Saharan region of Eastern Cape Province (South Africa) had been limited by several factors which includes low levels of soil nitrogen and phosphorus. The current study aimed at investigating the effects of Arbuscular Mycorrhizal Fungi (AMF) and Rhizobium inoculation on growth and yield of three forage legumes, namely, Vigna unguiculata, Lablab purpureus and Mucuna pruriens. The field trials were established over two growing seasons (2017/2018 and 2018/2019) to measure growth parameters such as seedling survival, plant height, stem diameter and plant vigor as well as mycorrhizal dependency, nodulation and forage yield. The results showed that the dual inoculation of AMF and Rhizobia bacteria significantly increased (P ≤ 0.05) seedling survival, plant height, stem diameter, plant vigor, nodule numbers, active nodulation rate and dry matter yield. However, nodule dry weight and dry matter content of forage legumes were significantly reduced by the dual inoculation of AMF and Rhizobia. In conclusion, the dual inoculation resulted in high forage production compared to single inoculation and un-inoculated forages in both seasons. Therefore, the dual inoculation could be an ideal alternative in attempts to reduce the overreliance of chemical fertilizer application on forage production under semi-arid regions.

Promoting the growth of Sulla flexuosa L. by endophytic root nodule bacteria authors and affiliations.

Legume plants rely upon multipartite interactions between rhizobia and bacterial endophytes within root nodules to facilitate plant growth. This study aimed to isolate and identify indigenous endophytic bacteria from root nodules of Sulla aculeolata L. in Northeast Morocco. Based on their tri-calcium phosphate (TCP) solubilization capacity, five endophytes were chosen for further evaluation of their plant growth traits. All isolates were hydrogen cyanide (HCN) and siderophore producers, while only BCH24 tested positive for ACC deaminase activity. Indole-3-acetic acid (IAA) synthesis ranged from 1.27 mgL- 1 to 2.89 mgL- 1, while soluble phosphate concentrations was between 7.99mg L- 1 and 110.58mg L- 1. Additionally, all the endophytes were able to produce more than two lytic enzymes. Based on the analysis of 16S rRNA gene sequences five isolates were identified as Enterobacter sp (BCH13, BCH2), Pseudomonas sp (BCH16, BCH24), and Serratia sp (BCH10). The strains inhibited the growth of three phytopathogenic fungi, with BCH13 exhibiting the highest rate against Aspergillus ochraceus (45%), followed by BCH24 against Fusarium oxysporum (40%) and Botrytis cinerea (35%), respectively. In vivo inoculation of halotolerant strains Enterobacter hormaechei (BCH13) and Pseudomonas moraviensis (BCH16) under gnotobiotic conditions revealed that co-inoculation with Rhizobium sullae KS6 improved plant development compared to single inoculation, making it a promising eco-friendly bio-inoculant for legume Sulla flexuosa L. production.

First report ofFusarium meridionalecausing Fusarium head blight of wheat in Henan Province, China.

Fusarium graminearum and F. asiaticum have been found as a major cause of Fusarium head blight (FHB) of wheat (Triticum aestivum L.), especially in Henan Province of China (Zhang et al. 2014; Xu et al. 2021). In May 2021, a survey to determine the composition of Fusarium species infecting wheat heads was conducted in commercial fields in Henan. A total of 395 diseased spikes with premature whitening symptom were collected from 31 commercial fields in Henan. Symptomatic spikelets were excised, surface-sterilized for 10 s in 70% ethanol followed by 1 min in 3% sodium hypochlorite, rinsed three times with autoclaved distilled water, and then plated onto potato dextrose agar (PDA) medium. Isolated colonies that resembled Fusarium species were transferred to fresh PDA plates and purified using a single spore method. Species were identified based on sequence analysis of the translation elongation factor-1α (TEF) and trichothecene 3-Oacetyltransferase (Tri 101) gene (Proctor et al. 2009). The results indicated that F. graminearum (43.3%), F. asiaticum (47.8%), F. pseudograminearum (6.6%) were the main causal agents of FHB in Henan. However, nine isolates (2.3%) were found to be identical to F. meridionale by sequence comparison in GenBank, and eight isolates of which came from three fields with 1% to 2% diseased spikes near Reservoir Luhun (34.1255° N, 112.1111° E, altitude: 388 m above sea level), Songxian County of Henan. The isolates of F. meridionale were transferred onto carnation leaf agar (CLA) and incubated at 20℃ under black light blue illumination. Macroconidia were abundant, relatively slender, curved to almost straight, commonly six- to seven-septate, and 27.0 to 61.0 (average 44.0) μm × 3.2 to 6.8 (average 5.3) μm. Microconidia were not observed. The TEF sequences (Accession nos. OM460748 to OM460756) and the Tri 101 sequences (OM460759 to OM460767) of the nine isolates showed 99 to 100% similarity with the TEF and Tri 101 sequences of F. meridionale NRRL 28436 and NRRL 28723 (AF212435 and AF212436 (TEF); AF212582 and AF212683 (Tri 101)). To complete Koch's postulates, the pathogenicity of the fungus was tested by using the single floret inoculation method by injecting 20-μl conidial suspension (5 × 105 conidia per milliliter) into healthy inflorescences of wheat cultivar Bainong 207 at anthesis in the field. Another 30 healthy inflorescences were injected with sterile distilled water. The heads were covered with polyethylene bags that were removed after 2 days. Twenty days after inoculation, while control inflorescences were asymptomatic, the F.meridionale-inoculated inflorescences showed 12% bleached spikelets per spike. By using the methodology described above, the fungus was re-isolated from infected spikelets of inoculated wheat heads but not from the controls. Although F.meridionalehas frequently been reported in association with Fusariumear rot (FER) of maize in Chongqing City and Gansu Province (Zhang et al. 2014; Zhou et al. 2018), and riceFER in Sichuan Province (Dong et al. 2020), to our knowledge, this is the first report of F. meridionale from diseased wheat heads in Henan, China. Further investigation is needed to gain a better understanding of this species by collecting isolates from different cropping system in Henan, which maize-wheat and rice-wheat rotation fields have coexisted in the region.

Co-Inoculation with Arbuscular Mycorrhizal Fungi and Dark Septate Endophytes under Drought Stress: Synergistic or Competitive Effects on Maize Growth, Photosynthesis, Root Hydraulic Properties and Aquaporins?

Arbuscular mycorrhizal fungi (AMF) and dark septate fungi (DSE) were simultaneously colonized in the root cells of maize. Single AMF and DSE symbiosis have been proven to improve the drought tolerance of maize. However, the effects of both fungi coexisting in maize roots under drought stress are not yet known. In this study, pot experiments of maize seedlings were conducted through four inoculation treatments (single AMF inoculation of Rhizophagus irregularis, single DSE inoculation of Exophiala pisciphila, co-inoculation of AMF + DSE and non-mycorrhizal inoculation) under well-watered (WW) and drought-stressed (DS) conditions. AMF and DSE colonization status, maize physiology and aquaporin gene expression in maize roots were investigated. The objective of this paper was to evaluate whether AMF and DSE had competitive, independent or synergistic effects on regulating the drought tolerance of maize. When maize seedlings of three inoculation treatments were subjected to drought stress, single AMF inoculation had the highest shoot and root dry weight, plant height, root length, osmotic root hydraulic conductivity and hydrostatic root hydraulic conductivity in maize seedlings. However, co-inoculation of AMF + DSE induced the highest stomatal conductance in maize leaves and the lowest H2O2 and O2•- concentration, membrane electrolyte leakage, intercellular CO2 concentration and gene expression level of ZmPIP1;1, ZmPIP1;2, ZmPIP2;1, ZmPIP2;5 and ZmPIP2;6. In addition, co-inoculation of AMF + DSE also obviously down-regulated the GintAQPF1 and GintAQPF2 expression in R. irregularis compared with single AMF inoculation treatment. Under DS stress, there were competitive relationships between AMF and DSE with regard to regulating mycorrhizal colonization, maize growth, root hydraulic conductivity and the gene expression of aquaporins in R. irregularis, but there were synergistic relationships with regard to regulating membrane electrolyte leakage, oxidative damage, photosynthesis and the aquaporin gene expression of maize seedlings. The obtained results improve our knowledge about how the mechanisms of AMF and DSE coexist, promoting the drought tolerance of host plants.

Microorganisms and Biochar Improve the Remediation Efficiency of Paspalum vaginatum and Pennisetum alopecuroides on Cadmium-Contaminated Soil.

Phytoremediation can help remediate potential toxic elements (PTE) in soil. Microorganisms and soil amendments are effective means to improve the efficiency of phytoremediation. This study selected three microorganisms that may promote phytoremediation, including bacteria (Ceratobasidium), fungi (Pseudomonas mendocina), and arbuscular-mycorrhizal fungi (AMF, Funneliformis caledonium). The effects of single or mixed inoculation of three microorganisms on the phytoremediation efficiency of Paspalum vaginatum and Pennisetum alopecuroides were tested under three different degrees of cadmium-contaminated soil (low 10 mg/kg, medium 50 mg/kg, and high 100 mg/kg). The results showed that single inoculation of AMF or Pseudomonas mendocina could significantly increase the biomass of two plants under three different degrees of cadmium-contaminated soil, and the growth-promoting effect of AMF was better than Pseudomonas mendocina. However, simultaneous inoculation of these two microorganisms did not show a better effect than the inoculation of one. Inoculation of Ceratobasidium reduced the biomass of the two plants under high concentrations of cadmium-contaminated soil. Among all treatments, the remediation ability of the two plants was the strongest when inoculated with AMF alone. On this basis, this study explored the effect of AMF combined with corn-straw-biochar on the phytoremediation efficiency of Paspalum vaginatum and Pennisetum alopecuroides. The results showed that biochar could affect plant biomass and Cd concentration in plants by reducing Cd concentration in soil. The combined use of biochar and AMF increased the biomass of Paspalum vaginatum by 8.9-48.6% and the biomass of Pennisetum alopecuroides by 8.04-32.92%. Compared with the single use of AMF or biochar, the combination of the two is better, which greatly improves the efficiency of phytoremediation.

ENDOPHYTIC BACTERIA FROM BANANA PLANT IMPROVES THE GROWTH AND YIELD OF BLACK RICE PLANT

Three bacterial isolates selected as plant growth-promoting endophytic bacteria (PGPEB) from “Klutuk” banana (Musa balbisiana L.) gained scrutiny for first-time testing on black rice. The presented study pursued an investigation on the impact of endophytic bacteria inoculation obtained from “Klutuk” banana plants on the growth and production traits of black rice. For this research, the three bacterial isolates (K10, K324, and K111) served as inoculums for black rice seeds, testing for synergism. The three isolates inoculation into black rice plants used both single and consortium inoculation methods. With agar media, black rice growth observation began 14 days after plantation (DAP) while on soil, at 30 and 140 DAP with inoculation. Three isolates did not show any antagonistic reactions. Overall, isolate K10 showed less significant improvement in growth and yield traits of black rice compared with two other isolates, i.e., K324 and K111. With agar media, the endophytic bacteria inoculations did not show a significant effect on the growth of black rice, and even isolate K324 was inhibiting in action. However, on soil media, isolate K324 significantly enhanced the number of roots and shoot length in black rice compared with the control at 30 DAP. The single inoculation with isolate K111 has caused increased productivity based on the weight of the root, dry grain weight per clum, plant height, root length, leaf length, and panicle length in black rice. Isolate K324 promotes the growth of black rice on the soil media at 30 DAP, while isolate K111 improves the production traits on the soil media at 140 DAP. The study findings provide a significant basis for the positive impact of endophytic bacterial inoculation on black rice growth and yield traits.

Double trouble: Co‐infection of potato with the causal agents of late and early blight

AbstractGlobal potato production is plagued by multiple pathogens, amongst which are Phytophthora infestans and Alternaria solani, the causal agents of potato late blight and early blight, respectively. Both these pathogens have different lifestyles and are successful pathogens of potato, but despite observations of both pathogens infecting potato simultaneously in field conditions, the tripartite interactions between potato and these two pathogens are so far poorly understood. Here we studied the interaction of A. solani and P. infestans first in vitro and subsequently in planta both in laboratory and field settings. We found that A. solani can inhibit P. infestans in terms of growth in vitro and also infection of potato in both laboratory experiments and in an agriculturally relevant field setting. A. solani had a direct inhibitory effect on P. infestans in vitro and compounds secreted by A. solani had both an inhibitory and disruptive effect on sporangia and mycelium of P. infestans in vitro. In planta infection bioassays revealed that simultaneous co‐inoculation of both pathogens resulted in larger necrotic lesions than single inoculations; however, consecutive inoculations only resulted in larger lesions when A. solani was inoculated after P. infestans. These results indicate that the order in which these pathogens attempt to colonize potato is important for the disease outcome and that the influence of plant pathogens on each other should be accounted for in the design of future disease control strategies in crops such as potato.

Effects of Septoglomus constrictum and Bacillus cereus on the competitive growth of Ageratina adenophora.

Beneficial microorganisms play a pivotal role in the invasion process of exotic plants, including arbuscular mycorrhizal fungi (AMF) and Bacillus. However, limited research exists on the synergistic influence of AMF and Bacillus on the competition between both invasive and native plants. In this study, pot cultures of Ageratina adenophora monoculture, Rabdosia amethystoides monoculture, and A. adenophora and R. amethystoides mixture were used to investigate the effects of dominant AMF (Septoglomus constrictum, SC) and Bacillus cereus (BC), and the co-inoculation of BC and SC on the competitive growth of A. adenophora. The results showed that inoculation with BC, SC, and BC + SC significantly increased the biomass of A. adenophora by 14.77, 112.07, and 197.74%, respectively, in the competitive growth between A. adenophora and R. amethystoides. Additionally, inoculation with BC increased the biomass of R. amethystoides by 185.07%, while inoculation with SC or BC + SC decreased R. amethystoides biomass by 37.31 and 59.70% compared to the uninoculated treatment. Inoculation with BC significantly increased the nutrient contents in the rhizosphere soil of both plants and promoted their growth. Inoculation with SC or SC + BC notably increased the nitrogen and phosphorus contents of A. adenophora, therefore enhancing its competitiveness. Compared with single inoculation, dual inoculation with SC and BC increased AMF colonization rate and Bacillus density, indicating that SC and BC can form a synergistic effect to further enhance the growth and competitiveness of A. adenophora. This study reveals the distinct role of S. constrictum and B. cereus during the invasion of A. adenophora, and provide new clues to the underlying mechanisms of interaction between invasive plant, AMF and Bacillus.

Dual Inoculation of Rhizobium and Arbuscular Mycorrhizal Fungi Increases Soil-Total Nitrogen, Available Phosphorus, and Yield of Soybean in Vertisols

Soybean is a protein source food crop with high economic value. So far, national production has not been able to meet domestic demand resulting in continuing import of soybean. The use of rhizobium and arbuscular mycorrhizal fungi (AMF) as biological fertilizers could be an alternative to increase soybean production. The research aimed to investigate the effect of dual inoculation of rhizobium and arbuscular mycorrhizal fungi (AMF) on root nodules formation, AMF development, total-N and available P of Vertisols, and yield of soybean. This study was designed in a completely randomized design) with 4 treatments namely no inoculation (R0), rhizobium inoculation (R1), AMF inoculation (R2), and dual inoculation of rhizobium and AMF (R3), with four replications. The variables observed were the number of effective root nodules, AMF spore density, AMF colonization, soil total-N, available P, plant height, number of pods, and seed weight. The results showed that dual inoculation of rhizobium and AMF had a better effect on the number of effective root nodules, AMF spore density, AMF colonization, soil total- N, available P, plant height, number of pods, and seed weight compared to the single inoculation and un-inoculated treatments