Plant Growth-promoting Agents Research Articles

Wild again: recovery of a beneficial Cannabis seed endophyte from low domestication genotypes.

Beyond carrying the plant embryo, seeds harbour intricate microbial communities whose transmission across successive plant generations can significantly influence the ecological and evolutionary dynamics of plant-microbe symbioses. The process of plant domestication has potential repercussions in genes involved in plant-microbiome interactions. However, the extent to which breeding can impact the seed microbiome is sparsely explored. Cannabis is a high-value crop but sparsely subjected to agricultural innovations established in other crop species during the last century. Here, we conduct a large-scale analysis of the bacterial seed microbiome of Cannabis across different domestication grades and investigate the potential of seed-associated endophytes as plant growth-promoting agents under both controlled and field conditions. Analysis of Cannabis seed endophyte composition and diversity across 46 plant genotypes revealed 813 different bacterial genera with a predominance of Gammaproteobacteria, Bacilli, Actinobacteria and Alphaproteobacteria but a genotype-specific microbiome. The assessment of domestication and breeding on microbial assembly revealed a higher bacterial diversity in low domestication genotypes (Shannon index, H': 1.21 vs. 1.05) and a higher homogeneity in bacterial composition caused by line development. Further, a seed bacterial isolate (Bacillus frigoritolerans C1141) associated with low domestication genotypes, and with genes associated with bio-fertilization, bioremediation and phytohormone production, increased plant growth by 42.3% at the time of harvest, under field conditions. This study addresses critical knowledge gaps related to the assembly of the Cannabis seed-endophytic microbiome. It reveals that Cannabis breeding is linked to alterations of seed microbial communities, which potentially led to the loss of bacteria with functional significance. These results highlight the importance of preserving seed microbiomes in plant breeding to support sustainable plant health and growth enhancement in Cannabis. Video Abstract.

Study of Plant Growth Promoting Abilities of Rhizobium Strains Isolated from Mungbean Root Nodules

Background: Plant Growth Promoting Rhizobacteria (PGPR) are a type of bacteria that use biofertilizers and other plant growth-promoting agents to increase plant output and growth. In the last several decades, there has been a global surge in the usage of beneficial soil microorganisms like PGPR for safe and sustainable agriculture due to the detrimental effects of artificial fertilizers on the environment and their rising prices. Plant-beneficial rhizobacteria have the potential to reduce the world's reliance on dangerous agricultural chemicals that upset agro-ecosystems. Today a large part of yield is lost due to the various stress mechanisms of plants. It could be classified into biotic and abiotic stress. These are generally a group of microorganisms that is found either in the rhizosphere or in the root nodules of plants. PGPR has beneficial impact, they colonize in the plant roots and improve crop yields and agricultural productivity and also produce some useful growth promoting growth hormones viz., IAA, Auxins, Cytokinin and Gibberellins. Methods: The bacterial isolates were screened for plant growth promoting traits such as phosphate solubilization, IAA production and siderophore production was tested qualitatively by using pikovskayas media, TSB (Tryptone Soy Broth) agar and Chrome Azurol Sulphate (CAS) blue agar respectively. Results: In present study out of the eight rhizobial isolates, five exhibited the phosphate solubilization zones, three shows negative result. However out of eight isolates five isolates produced IAA and three showed negative result. Among all isolates seven isolates were able to produce siderophore, while one showed negative result.

Potentiality of Beneficial Microbe Bacillus siamensis GP-P8 for the Suppression of Anthracnose Pathogens and Pepper Plant Growth Promotion.

This study was carried out to screen the antifungal activity against Colletotrichum acutatum, Colletotrichum dematium, and Colletotrichum coccodes. Bacterial isolate GP-P8 from pepper soil was found to be effective against the tested pathogens with an average inhibition rate of 70.7% in in vitro dual culture assays. 16S rRNA gene sequencing analysis result showed that the effective bacterial isolate as Bacillus siamensis. Biochemical characterization of GP-P8 was also performed. According to the results, protease and cellulose, siderophore production, phosphate solubilization, starch hydrolysis, and indole-3-acetic acid production were shown by the GP-P8. Using specific primers, genes involved in the production of antibiotics, such as iturin, fengycin, difficidin, bacilysin, bacillibactin, surfactin, macrolactin, and bacillaene were also detected in B. siamensis GP-P8. Identification and analysis of volatile organic compounds through solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) revealed that acetoin and 2,3-butanediol were produced by isolate GP-P8. In vivo tests showed that GP-P8 significantly reduced the anthracnose disease caused by C. acutatum, and enhanced the growth of pepper plant. Reverse transcription polymerase chain reaction analysis of pepper fruits revealed that GP-P8 treated pepper plants showed increased expression of immune genes such as CaPR1, CaPR4, CaNPR1, CaMAPK4, CaJA2, and CaERF53. These results strongly suggest that GP-P8 could be a promising biocontrol agent against pepper anthracnose disease and possibly a pepper plant growth-promoting agent.

Paramixta manurensis gen. nov., sp. nov., a novel member of the family Erwiniaceae producing indole-3-acetic acid isolated from mushroom compost

There are numerous species in the Erwiniaceae family that are important for agricultural and clinical purposes. Here we described the Erwiniaceae bacterium PD-1 isolated from mushroom (Pleurotus eryngii) compost. Comparative genomic and phylogenetic analyses showed that the strain PD-1 was assigned to a new genus and species, Paramixta manurensis gen. nov., sp. nov. in the family Erwiniaceae. From the average amino acid index, we identified the five AroBEKAC proteins in the shikimate pathway as a minimal set of molecular markers to reconstruct the phylogenetic tree of the Erwiniaceae species. The strain PD-1 containing annotated genes for ubiquinone and menaquinone produced a higher level of ubiquinone (Q8) than demethylmenaquinone (DMK8) and menaquinone (MK8) in anaerobic condition compared to aerobic condition, as similarly did the reference strains from the genera Mixta and Erwinia. Results from fatty acid methyl ester and numerical analyses of strain PD-1 showed a similarity to species of the genera Mixta and Winslowiella. This study revealed that the strain’s ability to utilize polyols, such as glycerol, erythritol, and d-arabitol, distinguished the strain PD-1 from the nearest relative and other type strains. The analyzed genetic markers and biochemical properties of the strain PD-1 suggest its potential role in the process of mushroom compost through the degradation of carbohydrates and polysaccharides derived from fungi and plants. Additionally, it can produce a high concentration of indole-3-acetic acid as a plant growth-promoting agent.

Exploring stress-tolerant plant growth-promoting rhizobacteria from groundnut rhizosphere soil in semi-arid regions of Ethiopia

ABSTRACT The potential of rhizobacteria with plant growth promoting (PGP) traits in alleviating abiotic stresses, especially drought, is significant. However, their exploitation in the semi-arid regions of Ethiopian soils remains largely unexplored. This research aimed to isolate and evaluate the PGP potential of bacterial isolates collected from groundnut cultivation areas in Ethiopia. Multiple traits were assessed, including phosphate solubilization, indole-3-acetic acid (IAA) production, ammonia production, salt and heavy metal tolerance, drought tolerance, enzyme activities, hydrogen cyanide production, antibiotic resistance, and antagonistic activity against fungal pathogens. The identification of potent isolates was carried out using MALDI-TOF MS. Out of the 82 isolates, 63 were gram-negative and 19 were gram-positive. Among them, 19 isolates exhibited phosphate solubilization, with AAURB 34 demonstrating the highest efficiency, followed by AURB 12. Fifty-six isolates produce IAA in varying amounts and all isolates produce ammonia with AAURB12, AAURB19, and AAURB34 displaying strong production. Most isolates demonstrated tolerance to temperatures up to 40°C and salt concentrations up to 3%. Notably, AAURB12 and AAURB34 exhibited remarkable drought tolerance at an osmotic potential of −2.70 Mpa. When subjected to levels above 40%, the tested isolates moderately produced lytic enzymes and hydrogen cyanide. The isolates displayed resistance to antibiotics, except gentamicin, and all isolates demonstrated resistance to zinc, with 81–91% showing resistance to other heavy metals. AAURB34 and AAURB12 exhibited suppression against fungal pathogens, with percent inhibition of 38% and 46%, respectively. Using MALDI-TOF MS, the promising PGP isolates were identified as Bacillus megaterium, Bacillus pumilus, and Enterobacter asburiae. This study provides valuable insights into the potential of rhizobacteria as PGP agents for mitigating abiotic stresses and contribute to the understanding of sustainable agricultural practices in Ethiopia and similar regions facing comparable challenges.

Unlocking the growth-promoting and antagonistic power: A comprehensive whole genome study on Bacillus velezensis strains

Bacillus species are extensively documented as plant growth-promoting rhizobacteria, contributing significantly to the enhancement of soil fertility, nutrient recycling, and the control of phytopathogens. Utilizing them as biocontrol agents represents an environmentally friendly strategy, particularly within the rhizospheric community. This study presents the comprehensive genome sequences of three B. velezensis strains (LGMB12, LGMB319, and LGMB426) which were previously isolated from root samples of maize (Zea mays L.), along with a type strain FZB42. The research assesses the capability of the three strains for antagonizing fungi, specifically Fusarium graminearum, Fusarium verticillioides, Colletotrichum graminicola, and Stenocarpella sp. In paired cultures involving maize fungi, treatments containing bacteria B. velezensis exhibited statistically significant differences compared to both negative and positive treatments in terms of antagonism. Furthermore, genome mining techniques were employed to explore their inherent antagonistic potential. The assembly revealed that strains LGMB12, LGMB319, LGMB426, and FZB42 exhibit genome sizes of 4,187,541 bp, 4,244,954 bp, 3,976,537 bp, and 3,990,518 respectively. Their respective G + C content stands at 46.42 %, 46.50 %, 46.51 %, and 46.38 %. Moreover, the genomes present multiple gene clusters responsible for the synthesis of secondary metabolites and carbohydrate-active enzymes (CAZymes). These clusters highlight a diverse array of antibacterial and antifungal properties, complemented by numerous plant growth-promoting genes. These results highlight the potential of B. velezensis LGMB12, LGMB319, and LGMB426 strains as biocontrol and plant growth promotion agents, being promising candidates for further studies in agricultural production, including field trials.

Effects of Klebsiella michiganensis LDS17 on Codonopsis pilosula growth, rhizosphere soil enzyme activities, and microflora, and genome-wide analysis of plant growth-promoting genes.

We comprehensively evaluated the plant growth-promoting characteristics and heavy metal (HM) resistance ability of the LDS17 strain, as well as the effects of strain LDS17 inoculation on the Codonopsis pilosula seedling growth and the soil qualities in the Codonopsis pilosula rhizosphere. We conducted whole-genome analysis and identified lots of genes and gene clusters contributing to plant-beneficial functions and HM resistance, which is critical for further elucidating the plant growth-promoting mechanism of strain LDS17 and expanding its application in the development of plant growth-promoting agents used in the environment under HM stress.

Pseudomonas sp. AMGC1 takes on rice blast: Broad-spectrum antimicrobial activity underpins plant growth and disease tolerance.

A diverse group of gram-negative bacteria called Pseudomonas have been extensively researched for their ability to promote plant growth and suppress pathogens. The aim of the study was to identify the strain AMGC1 as a biocontrol agent against rice blast disease and a plant growth-promoting agent. The activity of AMGC1 against phytopathogens and its plant growth promotion activity were tested in vitro. Molecular identification by 16S rRNA gene sequencing, detection of antifungal antibiotic genes, biochemical characterization and antibiotic resistance testing were performed. Moreover, an in-planta biocontrol experiment with a blast susceptible rice cultivar was conducted to assess the effectiveness in managing the disease. Thin-layer chromatography was used to verify the presence of antifungal compounds. The results showed that AMGC1 had strong antimicrobial activity and multiple plant growth promotion traits. The strain was identified as Pseudomonas sp. and it contained genes for phenazine-1-carboxamide, hydrogen cyanide, and 2-hexyl, 5-propyl resorcinol antifungals. In the in-planta suppression experiment, applying AMGC1 strain two days before pathogen inoculation reduced the disease severity by 28% and disease incidence by 29% compared to control. Applying AMGC1 two days after pathogen inoculation resulted in lower reductions in disease severity (17.10%) and disease incidence (18.5%). Two putative bioactive compounds, phenazine-1-carboxamide and 2-hexyl, 5-propyl resorcinol, were isolated and purified from the AMGC1 growth medium. AMGC1 showed varied carbohydrate utilization patterns and both resistance and susceptibility to different antibiotics. The strain had multiple features that enhance plant growth and resistance against various phytopathogens, making it a potential biocontrol agent for sustainable agriculture.

Novel report of Acinetobacter johnsonii as an indole-producing seed endophyte in Tamarindus indica L.

Plant-microbe associations have been regarded as an exciting topic of research due to their potential as environment friendly alternatives for stimulating crop growth and development. Seeds of Tamarindus indica L. have been chosen for the present study as seed endophytes prefer larger or nutritive cotyledon and hard seed coats for their colonization. The main objectives of our study were to isolate and identify the seed endophytes, their bioefficacy, and responsible chemical compounds. In a dose-dependent experiment, tamarind seed exudates (TSE) showed plant growth-promoting properties on Oryza sativa (53-81%), Daucus carota (10-31%), and Raphanus sativa (21-42%). Identification of the bacterial load in TSE through 16S rRNA sequencing revealed the existence of two bacterial species, Acinetobacter johnsonii and Niallia nealsonii. This is the first report of these two bacteria as seed endophytes of Tamarindus indica L. HRLC-MS analysis of TSE confirmed the presence of indole derivatives, primarily indole-3-lactic acid (ILA). The quantitative phytochemical estimation of bacterial culture filtrates revealed that indole-like substances were present in the extracts only in A. johnsonii at a concentration of 0.005mg/ml of indole acetic acid equivalent. Experimental results suggested that the stimulatory activity of TSE was caused by the presence of A. johnsonii, a potential plant growth-promoting bacteria that produced indole-like compounds. This study suggests tamarind seed exudates with its endophytic microbiota as a potent plant growth-promoting agent that may find use as a cheap and sustainable source of metabolites useful in the agro-industries.

Diversity, Characterization, and Potential Applications of Bacterial Endophytes Isolated from the Halophyte Limonium axillare

Recently, there has been a worldwide call to explore nature-friendly compounds, which could enhance plant growth and substitute for chemically synthesized products. Endophytes are a group of microorganisms that lives in the plants and algae symbiotically. In this research, endophytes were isolated from leaves of the halophyte, Limonium axillare. A total of 280 bacterial isolates were obtained from the leaves of L. axillare. Strains displaying similarities in terms of morphology and biochemical reactions were categorized into 48 groups. One representative from each group was identified and subjected to enzymatic and plant growth-promoting tests. Forty-eight isolates were identified using a sequence similarity-based method based on the 16S rDNA gene. The identified strains were categorized into two genera: Bacillus and Staphylococcus. Our investigation uncovered 44 isolates from the Bacillus genus, representing 10 different species, including Bacillus sp., B. pseudomycoides, B. cereus, B. paramycoides, B. velezensis, B. subtilis, B. thuringiensis, B. wiedmannii, B. anthracis, and B. bacterium. Furthermore, we observed that only 4 isolates belonged to the Staphylococcus genus, encompassing 3 distinct species: S. bacterium, S. succinus, and S. saprophyticus. The isolated bacteria were screened for extracellular enzymes, plant growth promoting traits, antifungal activity, and salinity tolerance. From the previous screening, diverse responses were obtained. Most of the isolates were secreted at least one of the hydrolysis enzymes (protease, lipase and amylase). (93.8%) of the strains showed phosphate solubilization activity. (33.3%) produce (IAA). Siderophore production potential was present in 91.7% of isolates, while ACC deaminase and HCN production activities were identified in 52.1 and 41.7% of strains, respectively. Additionally, DNase activity was evident in 27.1%, and ammonia production was observed in 31.3% of the isolates. The isolates Bacillus velezensis (AL4QUA) strain showed positive effect in the greenhouse experiment in terms of plant growth promoter agent and biocontrol agent against Fusarium oxysporum pathogen of tomato seedling. Thus, endophytes have the potential to reduce chemical inputs in conventional agricultural practices, increase nutrient uptake and improve plant stress resilience.

Pseudoxanthomonas sp. JBR18, a halotolerant endophytic bacterium, improves the salt tolerance of Arabidopsis seedlings

Salinization of land is globally increasing due to climate change, and salinity stress is an important abiotic stressor that adversely affects agricultural productivity. In this study, we assessed a halotolerant endophytic bacterium, Pseudoxanthomonas sp. JBR18, for its potential as a plant growth-promoting agent with multiple beneficial properties. The strain exhibited tolerance to sodium chloride concentration of up to 7.5 % in the R2A medium. In vitro evaluation revealed that strain JBR18 possessed proteolytic, protease (EC 3.4), and cellulase (EC 3.2.1.4) activities, as well as the ability to produce indole-acetic acid, proline, and exopolysaccharides. Compared with the controls, co-cultivation of Arabidopsis seedlings with the strain JBR18 improved plant growth, rosette size, shoot and root fresh weight, and chlorophyll content under salinity stress. Moreover, JBR18-inoculated seedlings showed lower levels of malondialdehyde, reactive oxygen species, and Na+ uptake into plant cells under salt stress but higher levels of K+. Additionally, seedlings inoculated with JBR18 exhibited a delayed response time and quantity of salt-responsive genes RD29A, RD29B, RD20, RD22, and KIN1 under salt stress. These multiple effects suggest that Pseudoxanthomonas sp. JBR18 is a promising candidate for mitigating the negative impacts of salinity stress on plant growth. Our findings may assist in future efforts to develop eco-friendly strategies for managing abiotic stress and enhancing plant tolerance to salt stress.

Biological control of damping-off and plant growth promotion in soybean using Trichoderma virens

Rhizoctonia solani is soil borne pathogen that causes damping-off in legumes including soybean. To reduce disease infection of R. solani in soybean, seven isolates of Trichoderma virens were used as seed treatments. Soil was artificially infected using R. solani grown in organic media. Agronomic parameters and total phenolics were recorded at vegetative phase. Treatments with T. virens T.v6, T.v4, T.v7, and T.v3 showed lower disease incidence (22% to 34%) than that of the control (46%). T. virens T.v6 induced higher shoot and root length compared to plants grown in sterile soil. Phenolic in T. virens T.v7 treated plants showed the highest content (2.69 mg GAE/g) and the increase of this content was 13.7% compared to the control. Higher number of normal seedling growth and lower disease incidence than the control were observed in these treated plants. Another treatment with T. virens T.v6 showed lower amount of phenolic content (2.53 mg GAE/g) and lower increase of this content (7.2%) than those of T. virens T.v7 treated plants. However, the T. virens T.v6 treated plants performed higher normal seedling growth, lower disease incidence than the control. T. virens T.v6 and T.v7 were promising for plant growth promotion and biological control agents.

Candle soot colloids enhance tomato (Solanum lycopersicum) seed germination and seedling quality

The effect of candle soot colloids, a novel nanomaterial from candle combustion that we developed previously, on tomato (Solanum lycopersicum) seed germination and seedling vigor was investigated. Candle soot colloids were applied at different concentrations and hydrophobicities to tomato seeds and germination parameters and seedling vigor characteristics, such as length, fresh weight, dry weight, chlorophyll, and carotenoids, were measured. It was found that candle soot colloids significantly improved germination speed, seedling length, and seedling fresh weight compared to the control. The adherence of soot particles to the trichomes on the seed surface, which may help seeds retain moisture and stay hydrated, was observed. The chemical composition of the soot samples was analyzed using gas chromatography-time of flight mass spectrometry and two different chemical constituents in hydrophilic and hydrophobic soot samples that may affect seed germination were identified. A new potential use of candle soot colloids as plant growth-promoting agents and insights into the effects of nanomaterials on plant physiology and biochemistry were revealed by this study.

Insights into Endophytic and Rhizospheric Bacteria of Five Sugar Beet Hybrids in Terms of Their Diversity, Plant-Growth Promoting, and Biocontrol Properties

Sugar beet is the most important crop for sugar production in temperate zones. The plant microbiome is considered an important factor in crop productivity and health. Here, we investigated the bacterial diversity of seeds, roots, and rhizosphere of five sugar beet hybrids named Eduarda (ED), Koala (KO), Tibor (T), Tajfun (TF), and Cercospora-resistant (C). A culture-independent next-generation sequencing approach was used for the further investigation of seed-borne endophytes. Hybrid-associated bacteria were evaluated for their plant growth–promoting (PGP) characteristics, antagonistic activity towards Cercospora beticola and several Fusarium strains in dual culture assays, and drought and salinity tolerance. High-throughput sequencing revealed that the Proteobacteria phylum was most dominant in the seeds of all hybrids, followed by Cyanobacteria and Actinobacteriota. The predominant genus in all hybrids was Pantoea, followed by Pseudomonas, Acinetobacter, Chalicogloea, Corynebacterium, Enterobacter, Enterococcus, Glutamicibacter, Kosakonia, and Marinilactibacillus. Unique genera in the hybrids were Pleurocapsa and Arthrobacter (T), Klebsiella (TF), Apibacter (ED), and Alloscardovia (KO). The genera that were most represented in one hybrid were Weissella and Staphylococcus (TF); Streptococcus (T); Gardnerella, Prevotella, and Rothia (KO); and Gilliamella, Lactobacillus, and Snodgrassella (ED). Thirty-two bacteria out of 156 isolates from the rhizosphere, roots, and seeds were selected with respect to various plant growth–promoting activities in vitro, i.e., nitrogen fixation, phosphate solubilization, siderophore production, indole-3-acetic acid production, 1-aminocyclopropane-1-carboxylic acid deaminase activity, hydrogen cyanide production, exoenzymatic activity (amylase, protease, lipase, cellulase, xylanase, mannanases, gelatinase, and pectinase), mitigation of environmental stresses, and antifungal activity. Mixta theicola KO3-44, Providencia vermicola ED3-10, Curtobacterium pusillum ED2-6, and Bacillus subtilis KO3-18 had the highest potential to promote plant growth due to their multiple abilities (nitrogen fixation, phosphate solubilization, production of siderophores, and IAA). The best antagonistic activity towards phytopathogenic fungi was found for Bacillus velezensis C3-19, Paenibacillus polymyxa C3-36 and Bacillus halotolerans C3-16/2.1. Only four isolates B. velezensis T2-23, B. subtilis T3-4, B. velezensis ED2-2, and Bacillus halotolerans C3-16/2.1 all showed enzymatic activity, with the exception of xylanase production. B. halotolerans C3-16/2.1 exhibited the greatest tolerance to salinity, while two B. subtilis strains (C3-62 and TF2-1) grew successfully at the maximum concentration of PEG. The current study demonstrates that sugar beet–associated bacteria have a wide range of beneficial traits and are therefore highly promising for the formulation of biological control and PGP agents.

Serendipita indica as a Plant Growth Promoter and Biocontrol Agent against Black Rot Disease in Cabbage Grown in a Phytotron

Serendipita indica, a mutualistic root endophytic fungus, has gained attention for its potential to enhance plant health and resistance to various stresses. This study investigated the impact of S. indica (strain DSM 11827) on plant growth promotion and the management of black rot disease. This is a devastating bacterial ailment caused by Xanthomonas campestris pv. campestris, which affects cruciferous crops worldwide. The experiment was conducted under sterile conditions in a phytotron for 10 weeks. It involved the substrate and seed inoculation of S. indica in a cabbage crop. The findings suggested that S. indica establishes mutualistic relationships with cruciferous plants, positively influencing their growth while simultaneously reducing their susceptibility to black rot disease. Plant morphological and physiological parameters were enhanced by S. indica application. Additionally, bio stress markers were also enhanced in response to black rot disease. Moreover, disease severity was reduced by 27.9% and 18.8% in the substrate and seeds treated with S. indica, respectively. However, our findings did not report any antagonistic effect between S. indica and two pathogens, i.e., Xanthomonas campestris pv. campestris and Alternaria brassicicola under the in vitro test, suggesting that the suppression of black rot disease in cabbage seedlings was induced indirectly by S. indica. This study, therefore, underscores the promising prospect of utilizing S. indica to promote crop productivity and combat the destructive impact of black rot disease in cruciferous plants, contributing to more sustainable and resilient agriculture.

Evaluating the potential of Bacillus licheniformis YZCUO202005 isolated from lichens in maize growth promotion and biocontrol

Lichens exist in an organismal organization of mycobiont, photobiont, and non-photoautotrophic bacteria. These organisms contribute to the growth of lichens even in poor nutrition substrates. However, studies on the isolation and application of non-photoautotrophic bacteria in plant growth and biocontrol are scanty. Therefore, a study was conducted to isolate and evaluate the potential of non-photoautotrophic bacteria from lichen tissues in maize plant growth promotion and biocontrol of plant pathogens (fungi and bacteria). Five bacterial strains were isolated and tested for their ability to produce indole-3-Acetic Acid (IAA). One bacterium named YZCUO202005 produced IAA, siderophores and biofilms, solubilized phosphate and potassium and exhibited extracellular enzymes (cellulases, proteases, amylase, and β −1,3-Glucanase). Based on the 16S rRNA sequence analysis results, YZCUO202005 was identified as Bacillus licheniformis. The strain inhibited the growth of five pathogenic fungi with an inhibition percent of between 58.7% and 71.7% and two pathogenic bacteria. Under greenhouse conditions, YZCUO202005 was tested for its abilities to enhance maize seed germination, and vegetative growth. Compared with the control treatment, the strain significantly enhanced the growth of stem length (i.e. 18 ± 0.64 cm, 78 ± 0.92 cm), leaf length (i.e. 10 ± 0.36 cm, 57 ± 1.42 cm), leaf chlorophyll levels (i.e., 13 ± 0.40, 40 ± 0.43 SPAD), and root length (i.e, 9.8 ± 2.25 cm, 22.5 ± 6.59 cm). Our results demonstrated that B. licheniformis YZCUO202005 from lichens has the potential to promote plant growth and reduce fungal and bacterial pathogens’ growth. Furthermore, the results suggest that lichens are naturally rich sources of plant growth promotion and biocontrol agents that would be used in agriculture.

Biocontrol property of Streptomyces parvulus VRR3 in green gram plant (Vigna radiata L.) against Fusarium solani in greenhouse

Actinomycetes are isolated from various habitats including, plants, rhizospheres of.plant roots, terrestrial environment, and marine sediments. These Actinomycetes produce various secondary metabolites with antifungal, antibacterial, anticancer and antidiabetic properties. In the present study, a total of 31 endophytic Actinomycetes strains were isolated from the root of Vigna radiata L. (green gram plant). The antagonistic property of all strains was tested in vitro against Fusarium solani. The mycelia growth inhibition varied between 10.5 ± 1.4 and 80.5 ± 4.2% by Actinomycetes, whereas, the crude extract showed 14.2 ± 1.1 and 78.4 ± 3.1% growth inhibition (p < 0.01). The selected twelve Actinomycetes produced extracellular lytic enzymes. The results revealed that Streptomyces parvulus produced protease (18 ± 2 U/mL), amylase (20 ± 1 U/mL), lipase (13 ± 1 U/mL) and cellulase (8 ± 0 U/mL) at high levels than other Actinomycetes (p < 0.01). In addition, the ability of the screened Actinomycetes to produce plant growth-promoting agents was analyzed. The results showed that S. parvulus and other strains produced Indole acetic acid (1.5 ± 0.3 to 34.1 ± 3.4 μg/mL), phosphate solubilisation ability (1.5–24.3 PO4−3 μg/mL). The thermostable and pH-stable secondary metabolite-producing organism was characterized as S. parvulus VRR3. The in vivo growth-promoting activity of the green gram plant was tested in the greenhouse. The results showed that the selected S. parvulus was able to improve the growth of green gram seedlings, showing enhanced shoot-, and root length (p < 0.01). In addition, the seedlings treated with S. parvulus showed a decreased incidence of Fusarium wilt disease symptoms, whereas the positive control developed >80% disease symptoms (p < 0.01). Hence, S. parvulus VRR3 has the potential to become an important biocontrol agent in modern agricultural practice.

Characterization of a Novel Bacillus glycinifermentans Strain MGMM1 Based on Full Genome Analysis and Phenotypic Properties for Biotechnological Applications.

Bacillus species have gained much attention based on their phenotypic characteristics and their genetic architecture as biological control agents and plant growth-promotor with bioremediation potential. In this study, we analyzed the whole genome of a novel strain, Bacillus glycinifermentans MGMM1, isolated from the rhizosphere of a weed plant (Senna occidentalis) and assayed its phenotypic characteristics, as well as antifungal and biocontrol ability. The whole genome analysis of MGMM1 identified 4259 putative coding sequences, with an encoding density of 95.75% attributed to biological functions, including genes involved in stimulating plant growth, such as acetolactate synthase, alsS, and genes involved in the resistance to heavy metal antimony (arsB and arsC). AntiSMASH revealed the presence of biosynthetic gene clusters plipastatin, fengycin, laterocidine, geobacillin II, lichenysin, butirosin A and schizokinen. Tests in vitro confirmed that MGMM1 exhibited antifungal activity against Fusarium oxysporum f.sp. radicis-lycopersici (Forl) ZUM2407, Alternaria alternata, F. graminearum and F. spp. and produce protease, lipase amylase and cellulase. Bacillus glycinifermentans MGMM1 demonstrated proteolytic (4.82 ± 1.04 U/mL), amylolytic (0.84 ± 0.05 U/mL) and cellulosic (0.35 ± 0.02 U/mL) enzymatic activities, as well as indole-3-acetic acid production (48.96 ± 1.43 μg/mL). Moreover, the probiotic strain MGMM1 demonstrated a high biocontrol potential of inhibiting (up to 51.45 ± 8.08%) the development of tomato disease caused by Forl ZUM2407. These results suggest that B. glycinifermentans MGMM1 has significant potential as a biocontrol, plant growth-promoting agent in agriculture.

Arbuscular mycorrhizal fungi-mediated activation of plant defense responses in direct seeded rice (Oryza sativa L.) against root-knot nematode Meloidogyne graminicola.

Rhizosphere is the battlefield of beneficial and harmful (so called phytopathogens) microorganisms. Moreover, these microbial communities are struggling for their existence in the soil and playing key roles in plant growth, mineralization, nutrient cycling and ecosystem functioning. In the last few decades, some consistent pattern have been detected so far that link soil community composition and functions with plant growth and development; however, it has not been studied in detail. AM fungi are model organisms, besides potential role in nutrient cycling; they modulate biochemical pathways directly or indirectly which lead to better plant growth under biotic and abiotic stress conditions. In the present investigations, we have elucidated the AM fungi-mediated activation of plant defense responses against Meloidogyne graminicola causing root-knot disease in direct seeded rice (Oryza sativa L.). The study describes the multifarious effects of Funneliformis mosseae, Rhizophagus fasciculatus, and Rhizophagus intraradices inoculated individually or in combination under glasshouse conditions in rice plants. It was found that F. mosseae, R. fasciculatus and R. intraradices when applied individually or in combination modulated the biochemical and molecular mechanisms in the susceptible and resistant inbred lines of rice. AM inoculation significantly increased various plant growth attributes in plants with simultaneous decrease in the root-knot intensity. Among these, the combined application of F. mosseae, R. fasciculatus, and R. intraradices was found to enhance the accumulation and activities of biomolecules and enzymes related to defense priming as well as antioxidation in the susceptible and resistant inbred lines of rice pre-challenged with M. graminicola. The application of F. mosseae, R. fasciculatus and R. intraradices, induced the key genes involved in plant defense and signaling and it has been demonstrated for the first time. Results of the present investigation advocated that the application of F. mosseae, R. fasciculatus and R. intraradices, particularly a combination of all three, not only helped in the control of root-knot nematodes but also increased plant growth as well as enhances the gene expression in rice. Thus, it proved to be an excellent biocontrol as well as plant growth-promoting agent in rice even when the crop is under biotic stress of the root-knot nematode, M. graminicola.

Complete genome sequencing ofBacillus subtilis(CWTS 5), a siderophore-producing bacterium triggers antagonistic potential againstRalstonia solanacearum

The aims of this study were to explore the antagonistic potential of siderophore-producing Bacillus subtilis (CWTS 5) for the suppression of Ralstonia solanacearum and to explore the mechanisms of inhibition by FTIR, LC-MS, and whole genome analysis. A siderophore-producing B. subtilis (CWTS 5) possessing several plant growth-promoting properties such as IAA and ACC deaminase production, phosphate solubilization, and nitrogen fixation was assessed for its inhibitory effect against R. solanacearum, and its mechanisms were explored by in vitro and in vivo analyses. The active secondary metabolites in the siderophore extracts were identified as 2-deoxystreptamine, miserotoxin, fumitremorgin C, pipercide, pipernonaline, gingerone A, and deoxyvasicinone by LC-MS analysis. The Arnow's test and antiSMASH analysis confirmed the presence of catecholate siderophores, and the functional groups determined by FTIR spectroscopy confirmed the presence of secondary metabolites in the siderophore extract possessing antagonistic effect. The complete genome sequence of CWTS 5 revealed the gene clusters responsible for siderophore, antibiotics, secondary metabolite production, and antibacterial and antifungal metabolites. Furthermore, the evaluation of CWTS 5 against R. solanacearum in pot studies demonstrated 40.0% reduced disease severity index (DSI) by CWTS 5, methanolic extract (DSI-26.6%), ethyl acetate extract (DSI-20.0%), and increased plant growth such as root and shoot length, wet weight and dry weight of Solanum lycopersicum L. owing to its antagonistic potential. This genomic insight will support future studies on the application of B. subtilis as a plant growth promoter and biocontrol agent against R. solanacearum for bacterial wilt management. The results of this study revealed that B. subtilis (CWTS 5) possesses multiple mechanisms that control R. solanacearum, reduce disease incidence, and improve S. lycopersicum growth.