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Salt stress can affect survival, multiplication and ability of plant growth promoting microorganisms to enhance plant growth. Changes in a microbe’s proteome profile is one of the mechanisms employed by PGPM to enhance tolerance of salt stress. This study was focused on understanding changes in the exoproteome profile of Bacillus amyloliquefaciens EB2003A and Lactobacillus helveticus EL2006H when exposed to salt stress. The strains were cultured in 100  mL  M13 (B. amyloliquefaciens) and 100  mL De man, Rogosa and Sharpe (MRS) (L. helveticus) media, supplemented with 200 and 0  mM NaCl (control), at pH 7.0. The strains were then incubated for 48  h (late exponential growth phase), at 120  rpm and 30 (B. amyloliquefaciens) and 37 (L. helveticus) °C. The microbial cultures were then centrifuged and filtered sterilized, to obtain cell free supernatants whose proteome profiles were studied using LC–MS/MS analysis and quantified using scaffold. Results of the study revealed that treatment with 200  mM NaCl negatively affected the quantity of identified proteins in comparison to the control, for both strains. There was upregulation and downregulation of some proteins, even up to 100%, which resulted in identification of proteins significantly unique between the control or 200  mM NaCl (p≤  0.05), for both microbial species. Proteins unique to 200  mM NaCl were mostly those involved in cell wall metabolism, substrate transport, oxidative stress tolerance, gene expression and DNA replication and repair. Some of the identified unique proteins have also been reported to enhance plant growth. In conclusion, based on the results of the work described here, PGPM alter their exoproteome profile when exposed to salt stress, potentially upregulating proteins that enhance their tolerance to this stress. [ABSTRACT FROM AUTHOR]

Lipo-chito-oligosaccharide (LCO–from Bradyrhizobium japonicum) and thuricin 17 (Th17–from Bacillus thuringiensis) are bacterial signal compounds from the rhizosphere of soybean that have been shown to enhance plant growth in a range of legumes and non-legumes. In this study, an attempt to quantify phytohormones involved in the initial hours after exposure of Arabidopsis thaliana to these compounds was conducted using UPLC-ESI-MS/MS. A petri-plate assay was conducted to screen for drought stress tolerance to PEG 8000 infusion and plant growth was studied 21-days post-stress. Arabidopsis thaliana plants grown in trays with drought stress imposed by water withhold were used for free proline determination, elemental analysis, and untargeted proteomics using LCMS/MS studies. At 24 h post-exposure to the signal compounds under optimal growth conditions, Arabidopsis thaliana rosettes varied in their responses to the two signals. While LCO-treated rosettes showed a decrease in total IAA, cytokinins, gibberellins, and jasmonic acid, increases in ABA and SA was very clear. Th17-treated rosettes, on the other hand, showed an increase in IAA and SA. Both treatments resulted in decreased JA levels. Under severe drought stress imposed by PEG 8000 infusion, LCO and Th17 treatments were found to significantly increase fresh and dry weight over drought-stressed control plates, indicating that the presence of the signaling compounds decreased the negative effects experienced by the plants. Free proline content increased in LCOand Th17-treated plants after water-withhold drought stress. Elemental analysis showed a significant increase in carbon percentage at the lower concentration of Th17. Untargeted proteomics revealed changes in the levels of drought-specific ribosomal proteins, glutathione S-transferase, late embryogenesis proteins, vegetative storage proteins 1 and 2, thaumatin-like proteins, and those related to chloroplast and carbon metabolism. The roles of some of these significantly affected proteins detected under drought stress are discussed. [ABSTRACT FROM AUTHOR]

Bacillus species and their metabolites have potential alternative uses as chemical pesticides that can limit the growth of potential plant pathogens and enhance crop productivity. The aim of this study was to investigate the potential of Bacillus subtilis FJ3 for promoting plant growth and controlling fungal plant pathogens. The study evaluated the ability of the strain to promote plant growth in vitro by characterizing its growth-promoting traits, which included the production of hydrolytic enzymes, indole acetic acid, siderophores, biofilm formation, and phosphate solubilization. Polymerase Chain Reaction (PCR) testing revealed that strain FJ3 has the potential to produce lipopeptides such as fengycin, surfactin, mycosubtilin, and pilpastatin. Through in vitro antagonism testing it was demonstrated that strain FJ3 is able to inhibit Fusarium oxysporum by 52% compared to the untreated control and was antagonistic against Aspergillus flavus, Aspergillus niger, and Rhizopus oryzae using a dual method. The minimum inhibitory concentration of Bacillus crude extract resulted in a 92%, 90%, 81.5%, and 56% growth inhibition of Fusarium oxysporum, A. niger, A. flavus, and Rhizopus oryzae, respectively. In FT-IR and GC-MS analysis of crude LPs extract, the transmission and mass spectrum confirmed the existence of aforesaid lipopeptides containing b-fatty acids with chain lengths ranging from C14 to C21 in which the majority were saturated fatty acids. Greenhouse experimentation revealed that Bacillus strain FJ3 and its metabolites significantly diminished the disease incidence with an average reduction of 31.56%. In sterilized soil, FJ3 and its metabolites caused 24.01% and 10.46% growth promotion, respectively, in chickpea. The results demonstrated that Bacillus strain FJ3 has broad-spectrum antifungal and plant growth-promoting applications and could be a promising candidate for development into a commercialized biobased product for use in sustainable agriculture practice. [ABSTRACT FROM AUTHOR]

Introduction: The endosphere of a plant is an interface containing a thriving community of endobacteria that can affect plant growth and potential for bioremediation. Eichhornia crassipes is an aquatic macrophyte, adapted to estuarine and freshwater ecosystems, which harbors a diverse bacterial community. Despite this, we currently lack a predictive understanding of how E. crassipes taxonomically structure the endobacterial community assemblies across distinct habitats (root, stem, and leaf). Methods: In the present study, we assessed the endophytic bacteriome from different compartments using 16S rRNA gene sequencing analysis and verified the in vitro plant beneficial potential of isolated bacterial endophytes of E. crassipes. Results and discussion: Plant compartments displayed a significant impact on the endobacterial community structures. Stem and leaf tissues were more selective, and the community exhibited a lower richness and diversity than root tissue. The taxonomic analysis of operational taxonomic units (OTUs) showed that the major phyla belonged to Proteobacteria and Actinobacteriota (> 80% in total). The most abundant genera in the sampled endosphere was Delftia in both stem and leaf samples. Members of the family Rhizobiaceae, such as in both stem and leaf samples. Members of the family Rhizobiaceae, such as Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium were mainly associated with leaf tissue, whereas the genera Nannocystis and Nitrospira from the families Nannocystaceae and Nitrospiraceae, respectively, were statistically significantly associated with root tissue. Piscinibacter and Steroidobacter were putative keystone taxa of stem tissue. Most of the endophytic bacteria isolated from E. crassipes showed in vitro plant beneficial effects known to stimulate plant growth and induce plant resistance to stresses. This study provides new insights into the distribution and interaction of endobacteria across different compartments of E. crassipes Future study of endobacterial communities, using both culture-dependent and -independent techniques, will explore the mechanisms underlying the wide-spread adaptability of E. crassipesto various ecosystems and contribute to the development of efficient bacterial consortia for bioremediation and plant growth promotion. [ABSTRACT FROM AUTHOR]

Agriculture involving industrial fertilizers is another major human made contributing factor to soil pH variation after natural factors such as soil parent rock, weathering time span, climate, and vegetation. The current study assessed the potential effect of cell-free supernatant (CFS) obtained from Bacillus subtilis EB2004S and Lactobacillus helveticus EL2006H cultured at three pH levels (5, 7, and 8) on potato (var Goldrush) growth enhancement in a greenhouse pot experiment. The results showed that CFSs obtained from B. subtilis EB2004S and L. helveticus EL2006H cultured at pH 5 significantly improved photosynthetic rates, stomatal conductance, root fresh weight, and whole plant fresh weight. interactive effects of pot pH and that of CFSs obtained from pH 5 influenced chlorophyll, plant height, and shoot and whole plant fresh weight. Moreover, treatment 52EB2004S~0.4% initiated early tuberization for potato grown at pH 7 and 8. Potato grown at pH 5, which received a 72EB2004S~0.4% CFS treatment, had greater whole plant fresh and dry weight than that treated with L. helveticus EL2006H CFS and a positive control. Taken together, the findings of this study are unique in that it probed the effect of CFS produced under differing pH conditions which revealed a new possibility to mitigate stresses in plants. [ABSTRACT FROM AUTHOR]

Plant growth promoting microorganisms and their derived compounds, such as cell-free supernatant (CFS), enhance plant growth under stressed and non stressed conditions. Such technology is sustainable and environmentally friendly, which is desirable amidst the climate change threat. The current study evaluated the effect of CFS obtained from Lactobacillus helveticus EL2006H on its ability to enhance mean percentage germination and mean radicle length of corn and soybean, as well as growth parameters of potato, using treatment formulations that consisted of 0.2 and 1.0% [v/v] L. helveticus EL2006H CFS concentrations and 100 mM NaCl and 150 mM NaCl levels. Results show that treatment with 100 mM NaCl lowered percentage germination of corn by 52.63%, at 72 h, and soybean by 50%, at 48 h. Treatment with 100 NaCl +0.2% EL2006H enhanced percentage germination of soybean by 44.37%, at 48 h, in comparison to that of the 100 mM NaCl control. One hundred mM NaCl lowered radicle length of corn and soybean by 38.58 and 36.43%, respectively. Treatment with 100 Mm NaCl +1.0% EL2006H significantly increased radicle length of corn by 23.04%. Treatment with 100 mM NaCl +0.2% EL2006H significantly increased photosynthetic rate, leaf greenness and fresh weight of potato. Increasing NaCl concentration to 150 NaCl lowered the effectiveness of the 0.2% EL2006H CFS on the same growth variables of potato. In general, the lower CFS concentration of 0.2% was more efficient at enhancing germination in soybean while the higher concentration of 1.0% was more efficient at enhancing radicle length of corn. There was an observed variation in the effectiveness of L. helveticus EL2006H CFS across the different CFS concentrations, NaCl levels and crop species studied. In conclusion, based on findings of this study, CFS obtained from L. helveticus can be used as a bio stimulant to enhance growth of corn, soybean and potato. However, further studies need to be conducted, for validation, especially under field conditions, for commercial application. [ABSTRACT FROM AUTHOR]

Endophytic microbes promote plant growth through various biochemical mechanisms and assist plants in resuming their morpho-physiological traits under abiotic stresses. The current study was conducted to investigate the plant growth promotion properties and biochemical characterization of Bacillus safensis (SCAL1) under various heat stress regimes. Further investigations aimed to understand the potential of heat-tolerant B. safensis (SCAL1) in amelioration of heat stress in two varieties of tomato (Solanum lycopersicum cv. Riogrande and Sweetie). Properties characterized include 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) (0.84–0.96 μM/mg protein/h) and exopolysaccharide (EPS) (0.73–0.92 mg ml−1) under normal and heat stressed conditions. An increased level of ACC deaminase (12.5%) and EPS (20.65%) was observed under heat stress as compared to normal conditions. B. safensis also produced plant growth regulators such as indole acetic acid (IAA) (0.71, 0.57, and 0.49 μg ml−1), gibberellic acid (GA3) (19.4, 18.2, and 19.2 μg ml−1), and kinetin (32.07, 27.3, and 26.8 μg ml−1) under heat stress and control conditions. IAA and kinetin production were slightly reduced under heat stress conditions compared to control conditions. A greenhouse experiment was carried out to analyze the bacterial potential to promote plant growth under heat stress conditions. Inoculation of both tomato varieties with B. safensis significantly improved plant growth parameters, antioxidant enzyme activities, and chlorophyll content under heat stress. The results suggest that inoculating tomato with thermo-tolerant plant growth-promoting endophytic bacterium may provide an eco-friendly management strategy to mitigate heat stress. [ABSTRACT FROM AUTHOR]

Exposure to unfavorable conditions is becoming more frequent for plants due to climate change, posing a threat to global food security. Stressful temperature, as a major environmental factor, adversely affects plant growth and development, and consequently agricultural production. Hence, development of sustainable approaches to assist plants in dealing with environmental challenges is of great importance. Compatible plant-microbe interactions and signal molecules produced within these interactions, such as bacteriocins, could be promising approaches to managing the impacts of abiotic stresses on crops. Although the use of bacteriocins in food preservation is widespread, only a small number of studies have examined their potential in agriculture. Therefore, we studied the effect of three concentrations of Thuricin17 (Th17), a plant growth-promoting rhizobacterial signal molecule produced by Bacillus thuringiensis, on germination and vegetative growth of canola (Brassica napus L.) under stressful temperatures. Canola responded positively to treatment with the bacterial signal molecule under stressful temperatures. Treatment with 10 -9 M Th17 (Thu2) was found to significantly enhance germination rate, seed vigor index, radical and shoot length and seedling fresh weight under low temperature, and this treatment reduced germination time which would be an asset for higher latitude, short growing season climates. Likewise, Thu2 was able to alleviate the adverse effects of high temperature on germination and seed vigor. Regarding vegetative growth, interestingly, moderate high temperature with the assistance of the compound caused more growth and development than the control conditions. Conversely, low temperature negatively affected plant growth, and Th17 did not help overcome this effect. Specifically, the application of 10 -9 (Thu2) and 10 -11 M (Thu3) Th17 had a stimulatory effect on height, leaf area and biomass accumulation under above-optimal conditions, which could be attributed to modifications of below-ground structures, including root length, root surface, root volume and root diameter, as well as photosynthetic rate. However, no significant effects were observed under optimal conditions for almost all measured variables. Therefore, the signal compound tends to have a stimulatory impact at stressful temperatures but not under optimal conditions. Hence, supplementation with Th17 would have the potential as a plant growth promoter under stressed circumstances. [ABSTRACT FROM AUTHOR]

Root exudates play a key role in mediating plant-plant and plant-rhizomicrobiome interactions, including regulating biochemical/physiological aspects of plant-associated microorganisms, to enhance host plant growth and resilience. Root exudates can act as signals to reduce the competition from neighboring plants and recruiting/choreographing a wide range of diverse rhizomicrobiome members to make the host plant a good fit with its immediate environment. Root exudate production is a dynamic and key process, but there is a limited understanding of the metabolites or metabolic pathways involved in the inter-organismal communications facilitated by them. Given the well-known symbiotic relationships between plants and associated rhizomicrobiome members, adding root exudates to microbial isolation media may allow some of the large segments of rhizomicrobiome members that are not currently culturable to be grown in vitro. This will provide new insights into how root signals orchestrate associated microbes, will benefit agricultural production in the face of challenges posed by climate change, and will help to sustainably provide food for a growing global human population. [ABSTRACT FROM AUTHOR]

Salt stress is a major threat to modern agriculture, significantly affecting plant growth and yield, and causing substantial economic losses. At this crucial time of increasing climate change conditions, soil salinity will continue to develop and become an even more serious challenge to crop agriculture. Hence, there is a pressing need for sustainable techniques in agricultural production that could meet the dual challenges of crop productivity and environmental instability. The use of biostimulants in agricultural production has greatly influenced plant health and global food production. In particular, the application of bioactive materials produced by beneficial microbes is becoming a common practice in agriculture and provides numerous benefits to plant growth and resistance to stressful conditions. In this research two biostimulants; a type of plant secondary metabolite (flavonoids) and a microbebased material (CFS: Cell-Free Supernatant) containing active compounds secreted by a novel bacterial strain isolated from Amphecarpaea bracteata root nodules (Devosia sp - SL43), have been utilized to improve the growth and stress resistance of two major oil seed crops; canola and soybean, under optimal and salt stress conditions. Our findings suggested significant improvements in crop growth of canola and soybean following the application of both biostimulants. Under optimal growth conditions, soybean growth was significantly affected by foliar spray of flavonoids with increases in shoot fresh and dry weight, and leaf area, by 91, 99.5, and 73%, respectively. However, soybean growth was unaffected by flavonoids under salt stress. In contrast, CFS with a meaningful capacity to mitigate the negative effects of salinity stress improved soybean shoot fresh biomass, dry biomass, and leaf area by 128, 163 and 194%, respectively, under salt stress conditions. Canola was less responsive to both biostimulants, except for canola root variables which were substantially improved by flavonoid spray. Since this was the first assessment of these materials as foliar sprays, we strongly encourage further experimentation to confirm the findings reported here and to determine the full range of applicability of each of these potential technologies. [ABSTRACT FROM AUTHOR]

Potato (Solanum tuberosum L.) is one of the most important crops in maintaining global food security. Plant stand and yield are affected by production technology, climate, soil type, and biotic factors such as insects and diseases. Numerous fungal diseases including Neocosmospora rubicola, causing stem rot, are known to have negative effects on potato growth and yield quality. The pathogen is known to stunt growth and cause leaf yellowing with grayish-black stems. The infectivity of N. rubicola across a number of crops indicates the need to search for appropriate management approaches. Synthetic pesticides application is a major method to mitigate almost all potato diseases at this time. However, these pesticides significantly contribute to environmental damage and continuous use leads to pesticide resistance by pathogens. Consumers interest in organic products have influenced agronomists to shift toward the use of biologicals in controlling most pathogens, including N. rubicola. This review is an initial effort to carefully examine current and alternative approaches to control N. rubicola that are both environmentally safe and ecologically sound. Therefore, this review aims to draw attention to the N. rubicola distribution and symptomatology, and sustainable management strategies for potato stem rot disease. Applications of plant growth promoting bacteria (PGPB) as bioformulations with synthetic fertilizers have the potential to increase the tuber yield in both healthy and N. rubicola infested soils. Phosphorus and nitrogen applications along with the PGPB can improve plants uptake efficiency and reduce infestation of pathogen leading to increased yield. Therefore, to control N. rubicola infestation, with maximum tuber yield benefits, a pre-application of the biofertilizer is shown as a better option, based on the most recent studies. With the current limited information on the disease, precise screening of the available resistant potato cultivars, developing molecular markers for resistance genes against N. rubicola will assist to reduce spread and virulence of the pathogen. [ABSTRACT FROM AUTHOR]

Soil salinity negatively modulates plant growth and development, contributing to severe decreases in the growth and production of crops. Mucilaginibacter sp. K is a root endophytic bacterium that was previously reported by our laboratory to stimulate growth and confer salt tolerance in Arabidopsis (Arabidopsis thaliana). The main purpose of the present study is to elucidate the physiological and molecular machinery responsible for the prospective salt tolerance as imparted by Mucilaginibacter sp. K. We first report that auxin, gibberellin, and MPK6 signalings were required for strain K-induced growth promotion and salt tolerance in Arabidopsis. Then, this strain was assessed as a remediation strategy to improve maize performance under salinity stress. Under normal growth conditions, the seed vigor index, nitrogen content, and plant growth were significantly improved in maize. After NaCl exposure, strain K significantly promoted the growth of maize seedlings, ameliorated decline in chlorophyll content and reduced accretion of MDA and ROS compared with the control. The possible mechanisms involved in salt resistance in maize could be the improved activities of SOD and POD (antioxidative system) and SPS (sucrose biosynthesis), upregulated content of total soluble sugar and ABA, and reduced Na+ accumulation. These physiological changes were then confirmed by induced gene expression for ion transportation, photosynthesis, ABA biosynthesis, and carbon metabolism. In summary, these results suggest that strain K promotes plant growth through increases in photosynthesis and auxin- and MPK6-dependent pathways; it also bestows salt resistance on plants through protection against oxidative toxicity, Na+ imbalance, and osmotic stress, along with the activation of auxin-, gibberellin-, and MPK6-dependent signaling pathways. This is the first detailed report of maize growth promotion by a Mucilaginibacter sp. strain from wild plant. This strain could be used as a favorable biofertilizer and a salinity stress alleviator for maize, with further ascertainment as to its reliability of performance under field conditions and in the presence of salt stress. [ABSTRACT FROM AUTHOR]

Soil salinity is a major abiotic stressor inhibiting plant growth and development by affecting a range of physiological processes. Plant growth promoting rhizobacteria (PGPR) are considered a sustainable option for alleviation of stress and enhancement of plant growth, yet their mode of action is complex and largely unexplored. In this study, an untargeted proteomic approach provided insights into growth and stress response mechanisms elicited in soybean plants by Rhizobium sp. SL42 and Hydrogenophaga sp. SL48 and co-inoculated with Bradyrhizobium japonicum 532C. The plants were grown under optimal and salt-stressed conditions up to their mid-vegetative stage; shoot growth variables were increased in the bacteria-treated plants. Shotgun proteomics of soybean leaf tissue revealed that a number of proteins related to plant growth and stress tolerance were modulated in the bacterial inoculation treatments. Several key proteins involved in major metabolic pathways of photosynthesis, respiration, and photorespiration were upregulated. These include photosystem I psaK, Rubisco subunits, glyceraldehyde-3-phosphate dehydrogenase, succinate dehydrogenase, and glycine decarboxylase. Similarly, stress response proteins such as catalase and glutathione S-transferase (antioxidants), proline-rich precursor protein (osmolyte), and NADP-dependent malic enzyme (linked to ABA signaling) were increased under salt stress. The functions of proteins related to plant growth and stress adaptation led to an expanded understanding of plant-microbe interactions. These findings suggest that the PGPR strains regulated proteome expression in soybean leaves through multiple signaling pathways, thereby inducing salinity tolerance, and improving plant growth in the presence of this abiotic stress challenge. Data are available via ProteomeXchange with identifier PXD025596. [ABSTRACT FROM AUTHOR]

The use of microbial derived compounds is a technological approach currently gaining popularity among researchers, with hopes of complementing, supplementing and addressing key issues associated with use of microbial cells for enhancing plant growth. The new technology is a promising approach to mitigating effects of salinity stress in agricultural crops, given that these compounds could be less prone to effects of salt stress, are required in small quantities and are easier to store and handle than microbial cells. Microorganism derived compounds such as thuricin17, lipochitooligosaccharides, phytohormones and volatile organic compounds have been reported to mitigate the effects of salt stress in agricultural crops such as soybean and wheat. This mini-review compiles current knowledge regarding the use of microbe derived compounds in mitigating salinity stress in crops, the mechanisms they employ as well as future prospects. [ABSTRACT FROM AUTHOR]

Due to their interesting properties for human health, medicinal plants are of worldwide interest, including Iran. More has yet to be investigated and analyzed on the use of methods affecting medicinal plant growth and biochemical properties under stress. The important question about medicinal plants is the purpose of their plantation, determining their growth conditions. The present review article is about the effects of salinity stress on the growth and production of secondary metabolites (SM) in medicinal plants. In stressful conditions including salinity, while the growth of medicinal plants decreases, the production of secondary metabolites (SM) may increase significantly affecting plant medicinal properties. SMs are self-protective substances that medicinal plants quickly accumulate to resist changes in the external environment. Although previous research has indicated the effects of salt stress on the growth and yield of medicinal plants, more has yet to be indicated on how the use of biological methods including plant growth regulators (PGR) and soil microbes (mycorrhizal fungi and plant growth-promoting rhizobacteria, PGPR) may affect the physiology of medicinal plants and the subsequent production of SM in salt stress conditions. The use of modern omics has become significantly important for the identification and characterization of new SM, transcriptomics, genomics, and proteomics of medicinal plants, as well as for the high production of plant-derived medicines. Accordingly, the possible biological mechanisms, which may affect such properties, have been presented. Future research perspectives for the production of medicinal plants in saline fields, using biological methods, have been suggested. Key points: • The important question about medicinal plants is the purpose of their plantation. • Secondary metabolites (SM) may significantly increase under salinity stress. • Biological methods, affecting the production of SM by stressed medicinal plants. [ABSTRACT FROM AUTHOR]

Crop disease remains a major problem to global food production. Excess use of pesticides through chemical disease control measures is a serious problem for sustainable agriculture as we struggle for higher crop productivity. The use of plant growth promoting rhizobacteria (PGPR) is a proven environment friendly way of controlling plant disease and increasing crop yield. PGPR suppress diseases by directly synthesizing pathogen-antagonizing compounds, as well as by triggering plant immune responses. It is possible to identify and develop PGPR that both suppress plant disease and more directly stimulate plant growth, bringing dual benefit. A number of PGPR have been registered for commercial use under greenhouse and field conditions and a large number of strains have been identified and proved as effective biocontrol agents (BCAs) under environmentally controlled conditions. However, there are still a number of challenges before registration, large-scale application, and adoption of PGPR for the pest and disease management. Successful BCAs provide strong theoretical and practical support for application of PGPR in greenhouse production, which ensures the feasibility and efficacy of PGPR for commercial horticulture production. This could be pave the way for widespread use of BCAs in agriculture, including under field conditions, to assist with both disease management and climate change conditions. [ABSTRACT FROM AUTHOR]

Sustainable agriculture remains a focus for many researchers, in an effort to minimize environmental degradation and climate change. The use of plant growth promoting microorganisms (PGPM) is a hopeful approach for enhancing plant growth and yield. However, the technology faces a number of challenges, especially inconsistencies in the field. The discovery, that microbial derived compounds can independently enhance plant growth, could be a step toward minimizing shortfalls related to PGPM technology. This has led many researchers to engage in research activities involving such compounds. So far, the findings are promising as compounds have been reported to enhance plant growth under stressed and non-stressed conditions in a wide range of plant species. This review compiles current knowledge on microbial derived compounds, taking a reader through a summarized protocol of their isolation and identification, their relevance in present agricultural trends, current use and limitations, with a view to giving the reader a picture of where the technology has come from, and an insight into where it could head, with some suggestions regarding the probable best ways forward. [ABSTRACT FROM AUTHOR]

Plant growth promoting rhizobacteria (PGPR) are a functionally diverse group of microbes having immense potential as biostimulants and stress alleviators. Their exploitation in agro-ecosystems as an eco-friendly and cost-effective alternative to traditional chemical inputs may positively affect agricultural productivity and environmental sustainability. The present study describes selected rhizobacteria, from a range of origins, having plant growth promoting potential under controlled conditions. A total of 98 isolates (ectophytic or endophytic) from various crop and uncultivated plants were screened, out of which four endophytes (n, L, K and Y) from Phalaris arundinacea, Solanum dulcamara, Scorzoneroides autumnalis, and Glycine max, respectively, were selected in vitro for their vegetative growth stimulating effects on Arabidopsis thaliana Col-0 seedlings with regard to leaf surface area and shoot fresh weight. A 16S rRNA gene sequencing analysis of the strains indicated that these isolates belong to the genera Pseudomonas, Bacillus, Mucilaginibacter and Rhizobium. Strains were then further tested for their effects on abiotic stress alleviation under both Petri-plate and pot conditions. Results from Petri-dish assay indicated strains L, K and Y alleviated salt stress in Arabidopsis seedlings, while strains K and Y conferred increases in fresh weight and leaf area under osmotic stress. Results from subsequent in vivo trials indicated all the isolates, especially strains L, K and Y, distinctly increased A. thaliana growth under both normal and high salinity conditions, as compared to control plants. The activity of antioxidant enzymes (ascorbate peroxidase, catalase and peroxidase), proline content and total antioxidative capacity also differed in the inoculated A. thaliana plants. Furthermore, a study on spatial distribution of the four strains, using either conventional Petri-plate counts or GFP-tagged bacteria, indicated that all four strains were able to colonize the endosphere of A. thaliana root tissue. Thus, the study revealed that the four selected rhizobacteria are good candidates to be explored as plant growth stimulators, which also possess salt stress mitigating property, partially by regulating osmolytes and antioxidant enzymes. Moreover, the study is the first report of Scorzoneroides autumnalis (fall dandelion) and Solanum dulcamara (bittersweet) associated endophytes with PGP effects. [ABSTRACT FROM AUTHOR]

A wide range of prokaryotes produce and excrete bacteriocins (proteins with antimicrobial activity) to reduce competition from closely related strains. Application of bacteriocins is of great importance in food industries, while little research has been focused on the agricultural potential of bacteriocins. A number of bacteriocin producing bacteria are members of the phytomicrobiome, and some strains are plant growth promoting rhizobacteria (PGPR). Thuricin 17 is a single small peptide with a molecular weight of 3.162 kDa, a subclass IId bacteriocin produced by Bacillus thuringiensis NEB17, isolated from soybean nodules. It is either cidal or static to a wide range of prokaryotes. In this way, it removes key competition from the niche space of the producer organism. B. thuringiensis NEB17 was isolated from soybean root nodules, and thus is a member of the phytomicrobiome. Interestingly, thuricin 17 is not active against a wide range of rhizobial strains involved in symbiotic nitrogen fixation with legumes or against other PGPR. In addition, it stimulates plant growth, particularly in the presence of abiotic stresses. The stresses it assists with include key ones associated with climate change (drought, high temperature, and soil salinity). Hence, in the presence of stress, it increases the size of the overall niche space, within plant roots, for B. thuringiensis NEB17. Through its anti-microbial activity, it could also enhance plant growth via control of specific plant pathogens. None of the isolated bacteriocins have been examined as broadly as thuricin 17 on plant growth promotion. Thus, this review focuses on the effect of thuricin 17 as a microbe to plant signal that assists crop plants in managing stress and making agricultural systems more climate change resilient. [ABSTRACT FROM AUTHOR]

Plants, being sessile organisms, are exposed to widely varying environmental conditions throughout their life cycle. Compatible plant-microbe interactions favor plant growth and development, and help plants deal with these environmental challenges. Microorganisms produce a diverse range of elicitor molecules to establish symbiotic relationships with the plants they associate with, in a given ecological niche. Lipo-chitooligosaccharide (LCO) and Thuricin 17 (Th17) are two such compounds shown to positively influence plant growth of both legumes and non-legumes. Arabidopsis thaliana responded positively to treatment with the bacterial signal compounds LCO and Th17 in the presence of salt stress (up to 250 mM NaCl). Shotgun proteomics of unstressed and 250 mM NaCl stressed A. thaliana rosettes (7 days post stress) in combination with the LCO and Th17 revealed many known, putative, hypothetical, and unknown proteins. Overall, carbon and energy metabolic pathways were affected under both unstressed and salt stressed conditions when treated with these signals. PEP carboxylase, Rubisco-oxygenase large subunit, pyruvate kinase, and proteins of photosystems I and II were some of the noteworthy proteins enhanced by the signals, along with other stress related proteins. These findings suggest that the proteome of A. thaliana rosettes is altered by the bacterial signals tested, and more so under salt stress, thereby imparting a positive effect on plant growth under high salt stress. The roles of the identified proteins are discussed here in relation to salt stress adaptation, which, when translated to field grown crops can be a crucial component and of significant importance in agriculture and global food production. The mass spectrometry proteomics data have been deposited to the ProteomeXchange with identifier PXD004742. [ABSTRACT FROM AUTHOR]

Developing efficient nutrient management regimes is a prerequisite for promoting canola ( Brassica napus L.) as a viable cash crop in eastern Canada. Field experiments were conducted to investigate the growth, yield, and yield components of canola in response to various combinations of preplant and sidedress nitrogen (N) with soil-applied sulfur (S) and soil and foliar-applied boron (B). Canola yield and all its yield components were strongly correlated ( r2 = 0.99) with the amount of N applied, as was the above-ground biomass at 20% flowering and the leaf area index. Sidedress N was more efficiently utilized by the crop, leading to greater yields than preplant N application. On average, canola yields increased by 9.7 kg ha−1 for preplant N application and by 13.7 kg ha−1 for sidedress N application, for every kg N ha−1 applied, in 6 of the 10 site-years. Soil-applied S also increased canola yields by 3-31% in 7 of the 10 site-years, but had no effect on yield components. While there was no change in yield from soil-applied B, the foliar B application at early flowering increased yields up to 10%, indicating that canola plants absorb B efficiently through their leaves. In summary, canola yields were improved by fertilization with N (8 of 10 site-years), S (7 of 10 site-years) and B (4 of 10 site-years). Yield gains were also noted with split N-fertilizer application that involved sidedressing N between the rosette and early flowering stage. Following these fertilizer practices could improve the yield and quality of canola crop grown in rainfed humid regions similar to those in eastern Canada. [ABSTRACT FROM AUTHOR]

The effects of the seaweedAscophyllum nodosumextracts (ANE) on nitrogen (N)–fixing nodules and growth of alfalfa plants were studied under greenhouse conditions. The treatment of alfalfa roots increased the number of total nodules per plant with ANE (69%) and organic sub-fractions methanol (20%) and chloroform (35%) at 1 g L−1concentration. The number of functional nodules was greater per plant in ANE (36%) and its organic sub-fraction chloroform (105%). Maximum increase in shoot length was observed in ANE-treated plants (42%) and chloroform-treated plants (42%). Root length was longer in the chloroform fraction (15%), whereas the shoot dry-weight accumulation was greater in plants treated with ANE (118%), methanol (85%), and chloroform (85%) than the control. Root dry-weight accumulation increased in plants treated with ANE (118%) and chloroform (69%) compared to the control. Further studies are under way to identify the chemical components in ANE and organic fractions. [ABSTRACT FROM AUTHOR]

Suboptimal root zone temperatures (RZTs) (below 25°C) in Canada until July may adversely affect the secretion of interorganismal signal molecules such as genistein by soybean and hence, the soybean-Bradyrhizobium symbiosis. We also proposed for the first time that soil texture might play a role in these biochemical communications. Soybean plants, planted in undisturbed soil samples (with sandy, loamy and clay textures), collected from the field, were subjected to three different soil temperatures (14, 19 and 24°C). Bradyrhizobium japonicum (strain 532C) inocula, preincubated with four levels of genistein (0, 5, 10 and 20 µM), were used to inoculate the plants. The experiment was conducted at the research greenhouse of Macdonald Campus, McGill University, Canada. The effects of genistein 5 and 20 µM on soybean nodulation and growth were significant at 14°C. As genistein was more effective in loamy and clay soils, soil texture may also be a determining factor in the biochemical communications between B. japonicum and soybean. [ABSTRACT FROM AUTHOR]

The mechanisms by which many plant growth promoting rhizobacteria (PGPR) affect plants are unknown. We recently isolated a rhizosphere bacterium ( Bacillus thuringiensis NEB17), that promotes soybean growth and screened the liquid growth medium in which it grew for plant growth stimulating materials. We have also shown that it produces a bacteriocin (named by us as thuricin-17 and a member of the recently described class IId bacteriocins). Here we show that application of this bacteriocin to leaves (spray) or roots (drench) directly stimulates the growth of both a C3 dicot (soybean) and a C4 monocot (corn). This growth stimulation is similar in nature to that previously seen when plants are treated with Nod factors. Strain NEB17 contains three copies of the gene for thuricin 17 that code for identical amino acid sequences. These two lines of evidence suggest that the dual functions of these proteins may have constrained their evolution. This is the first report of direct plant growth enhancement by a bacteriocin. [ABSTRACT FROM AUTHOR]

Methyl jasmonate (MeJA) has recently been shown to act as a plant-to-bacteria signal. We tested the hypothesis that pre-induction of Rhizobium leguminosarum bv. phaseoli cells with genistein and/or MeJA would at least partially overcome the negative effects of low root zone temperature (RZT) on bean nodulation, nitrogen fixation and plant growth. Otebo bean plants were grown at constant air temperature (25 o C) and two RZT regimes (25 and 17 o C) and inoculated with R. leguminosarum bv. phaseoli pre-induced with MeJA and/or genistein. Our results indicate that low RZT inhibited nodulation, nitrogen fixation and plant growth. The plants growing at low RZT began fixing nitrogen seven days later compared to those at higher RZT. The low RZT plants had fewer nodules, lower nodule weight, less N fixation, slower plant growth, fewer leaves, smaller leaf area, and less dry matter accumulation comared to plants at a higher RZT. Rhzobium leguminosarum bv. phaseoli cells induced with genistein and/or MeJA enhanced bean nodulation, nitrogen fixation and growth at both optimum and suboptimum RZTs. The results of this study indicate that MeJA improves bean nitrogen fixation and growth at both optimum and suboptimum RZTs, and can be used alone or in combination with genistein to partially overcome the low RZT induced inhibitory effects on nodulation and nitrogen fixation. [ABSTRACT FROM AUTHOR]

Nodulation and subsequent nitrogen fixation by soybean [Glycine max (L.) Merr.] plants are inhibited by low root zone temperatures (RZTs). Plant growth promoting bacteria can help overcome these deleterious effects. Three Bacillus strains, B. subtilis NEB4 and NEB5 and B. thuringiensis NEB17, were isolated from inside the nodules of vigorous field-grown soybean plants in 1998, and were shown to have plant growth promoting activity on pouch-grown soybean plants under greenhouse conditions. To test their ability to improve soybean nodulation and growth under low RZTs, these strains were coinoculated onto soybean plants, with Bradyrhizobium japonicum, under greenhouse conditions at RZTs of 25, 17, and 15°C, and under field conditions in a short growing season area. In all cases, the experiments were conducted with soybean cultivar OAC Bayfield. All the three Bacillus strains enhanced soybean nodulafion and growth in greenhouse and field experiments. Coinoculatiun with NEB17 provided the largest and most consistent increases in nodule number, nodule weight, shoot weight, root weight, total biomass, total nitrogen, and grain yield. The other two strains provided positive responses in only 1 of the 2 yr of field-testing. Thus, B. thuringiensis NEB17 would be suitable for use as a plant growth promoting bacterial strain in soybean production systems in short growing season regions. [ABSTRACT FROM AUTHOR]

Serratia proteamaculans 1‐102 (1‐102) promotes soybean–bradyrhizobia nodulation and growth, but the mechanism is unknown. After adding isoflavonoid inducers to 1‐102 culture, an active peak with a retention time of about 105 min in the HPLC fractionation was isolated using a bioassay based on the stimulation of soybean seed germination. The plant growth‐promoting activity of this material was compared with 1‐102 culture (cells) and supernatant under greenhouse conditions. The activator was applied to roots in 83, 830 and 8300 HPLC microvolts (μV) per seedling when plants were inoculated with bradyrhizobia or sprayed onto the leaves in same concentrations at 20 d after inoculation. The root‐applied activator, especially at 1 ml of 830 μV per seedling, enhanced soybean nodulation and growth at the same level as 1‐102 culture under both optimal and sub‐optimal root zone temperatures. Thus, this activator stimulating soybean seed germination is also responsible for the plant growth‐promoting activity of 1‐102 culture. However, when sprayed onto the leaves, the activator did not increase growth and in higher concentrations decreased average single leaf area. The results suggest that this inducible activator might be a lipo‐chitooligosaccharide (LCO) analogue. LCOs act as rhizobia‐to‐legume signals stimulating root nodule formation. The activator could provide additional ‘signal’, increasing in the signal quality (the signal‐to‐noise ratio, SNR) of the plant–rhizobia signal exchange process. [ABSTRACT FROM PUBLISHER]

Endophytic bacteria reside within plant tissues and have often been found to promote plant growth. Fourteen strains of putative endophytic bacteria, not including endosymbiotic Bradyrhizobium strains, were isolated from surface-sterilized soybean (Glycine max. (L.) Merr.) root nodules. These isolates were designated as non-Bradyrhizobium endophytic bacteria (NEB). Three isolates (NEB4, NEB5, and NEB17) were found to increase soybean weight when plants were co-inoculated with one of the isolates and Bradyrhizobium japonicum under nitrogen-free conditions, compared with plants inoculated with B. japonicum alone. In the absence of B. japonicum, these isolates neither nodulated soybean, nor did they affect soybean growth. All three isolates were Gram-positive spore-forming rods. While Biolog tests indicated that the three isolates belonged to the genus Bacillus, it was not possible to determine the species. Phylogenetic analysis of 16S rRNA gene hypervariant region sequences demonstrated that both NEB4 and NEB5 are Bacillus subtilis strains, and that NEB17 is a Bacillus thuringiensis strain.Key words: root nodule, endophytic bacteria, plant-growth-promoting bacteria, Bacillus subtilis, Bacillus thuringiensis.Les bactéries endophytes sont des bactéries qui résident à l'intérior des tissus végétaux. Plusieurs études ont démontré la capacité de ces bactéries à favoriser la croissance des plantes. Quatorze souches de bactéries endophytes ont été isolées à partir de nodules de soya (Glycinemax (L.) Merr.) stérilisés en surface. Ces isolats ont été désignées comme étant des bactéries endophytes n'appartenant pas au genre Bradyrhizobium (NEB). Lorsque co-inoculés avec Bradyrhizobium japonicum, trois isolats (NEB4, NEB5 et NEB17) se sont avérées capable d'augmenter le poids de plantes soya. En absence de la souche de B. japonicum, ces même isolats ont été incapable d'affecter la croissance des plants ou de noduler. NEB4, NEB5 et NEB17 sont des bactéries Gram positives formant des spores. Des essais Biolog n'ont pas permis l'obtention d'une identification au niveau de l'espèce, mais ont quand même indiqué que les trois souches appartiennent au genre Bacillus. L'analyse phylogénétique des séquences d'une région très variable du gène 16S rARN a démontré que NEB4 et NEB5 sont des souches appartenant à l'espèce Bacillus subtilis, et que NEB17 est une souche appartnenant à l'espèce Bacillus thuringiensis.Mots clés : nodosités racinaires, bactérie endophyte, bactérie favorisant la croissance des plantes, Bacillus subtilis, Bacillus thuringiensis.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Drought, as an important challenge in Iran, affects all growth indicators for plants. Application of plant growth promoting microorganisms (PGPM) can reduce the detrimental effects of water deficit on plants. Two separate field experiments were conducted at the Tehran and Hashtrood sites, Iran in 2019 to study the influences of Azotobacter chroococcum (Az) and Piriformospora indica (Pi) or Az + Pi on growth, physio-biochemical properties and oil content of soybean (Glycine max L.) under water deficit conditions. Although water deficit dramatically reduced the plant height, percent vegetation cover and relative water content (RWC), plots treated with Az and Pi exhibited higher performance mentioned traits at both sites. Besides, co-inoculation of Az and Pi increased proline in Tehran (48.85 and 29.24% in leaf and root, respectively) and Hashtrood (46.91 and 48.91% in leaf and root, respectively) under severe water deficit. Accumulation of glycine betaine, soluble sugars and proteins increased for plots which received Az and Pi. Under severe water deficit conditions, the co-inoculation with Az and Pi enhanced the oil content of soybean by 12.87 and 9.37% at Tehran and Hashtrood sites respectively. Application of Az and Pi resulted in reducing the adverse effects of water deficit on oil quality of soybean by increasing the linoleic and linolenic acid in oil. Moreover, inoculation of soybean with Az and Pi can provide drought tolerance by improving ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD) and peroxidase (POX) activity. However, co-inoculation with Az and Pi was generally more effective in the alleviation of water deficit detrimental effects than sole inoculation with Az and Pi. Consequently, it can be a good approach for improving tolerance, growth and oil production of soybean under water deficit conditions. • Combined microbial inoculation exhibited a synergistic impact on osmolytes. • Water deficit and microbial inoculation incited antioxidant enzyme activation. • Combined microbial inoculation improved the oil quality and content in soybean. • Microbial inoculation reduced the negative effects of water deficit in soybean. [ABSTRACT FROM AUTHOR]

Terrestrial plants evolution occurred in the presence of microbes, the phytomicrobiome. The rhizosphere microbial community is the most abundant and diverse subset of the phytomicrobiome and can include both beneficial and parasitic/pathogenic microbes. Prokaryotes of the phytomicrobiome have evolved relationships with plants that range from non-dependent interactions to dependent endosymbionts. The most extreme endosymbiotic examples are the chloroplasts and mitochondria, which have become organelles and integral parts of the plant, leading to some similarity in DNA sequence between plant tissues and cyanobacteria, the prokaryotic symbiont of ancestral plants. Microbes were associated with the precursors of land plants, green algae, and helped algae transition from aquatic to terrestrial environments. In the terrestrial setting the phytomicrobiome contributes to plant growth and development by (1) establishing symbiotic relationships between plant growth-promoting microbes, including rhizobacteria and mycorrhizal fungi, (2) conferring biotic stress resistance by producing antibiotic compounds, and (3) secreting microbe-to-plant signal compounds, such as phytohormones or their analogues, that regulate aspects of plant physiology, including stress resistance. As plants have evolved, they recruited microbes to assist in the adaptation to available growing environments. Microbes serve themselves by promoting plant growth, which in turn provides microbes with nutrition (root exudates, a source of reduced carbon) and a desirable habitat (the rhizosphere or within plant tissues). The outcome of this coevolution is the diverse and metabolically rich microbial community that now exists in the rhizosphere of terrestrial plants. The holobiont, the unit made up of the phytomicrobiome and the plant host, results from this wide range of coevolved relationships. We are just beginning to appreciate the many ways in which this complex and subtle coevolution acts in agricultural systems. [ABSTRACT FROM AUTHOR]

Climate change has already affected food security in many parts of the world, and this situation will worsen if nothing is done to combat it. Unfortunately, agriculture is a meaningful driver of climate change, through greenhouse gas emissions from nitrogen-based fertilizer, methane from animals and animal manure, as well as deforestation to obtain more land for agriculture. Therefore, the global agricultural sector should minimize greenhouse gas emissions in order to slow climate change. The objective of this review is to point out the various ways plant growth promoting microorganisms (PGPM) can be used to enhance crop production amidst climate change challenges, and effects of climate change on more conventional challenges, such as: weeds, pests, pathogens, salinity, drought, etc. Current knowledge regarding microbial inoculant technology is discussed. Pros and cons of single inoculants, microbial consortia and microbial compounds are discussed. A range of microbes and microbe derived compounds that have been reported to enhance plant growth amidst a range of biotic and abiotic stresses, and microbe-based products that are already on the market as agroinputs, are a focus. This review will provide the reader with a clearer understanding of current trends in microbial inoculants and how they can be used to enhance crop production amidst climate change challenges. [ABSTRACT FROM AUTHOR]

The beneficial phytomicrobiome is a sustainable approach with the potential to enhance plant growth; it has been evaluated for a number of crop species, but not for Cannabis sativa. The legalization of cannabis and awareness of its end-use applications has resulted in the renewed consumer demand. An important challenge is achievement of high yield with minimum input for indoor production. This study evaluated three individual plant growth-promoting rhizobacteria (Bacillus sp., Mucilaginibacter sp. and Pseudomonas sp.) on the root development and subsequent plant growth of cannabis (cv. CBD Kush) cuttings. The hypothesis tested was that the application of plant growth-promoting rhizobacteria would improve rooting speed of cuttings, yield attributes, and physiological variables. When compared with control plants (mock inoculation with MgSO 4), plants inoculated with plant growth-promoting rhizobacteria increased root length at the vegetative stage. At harvest, flower fresh weight was increased by 5.13%, 6.94% and 11.45%, compared to the control, for plants inoculated with Bacillus sp., Mucilaginibacter sp. and Pseudomonas sp. respectively. However, the plant height, node number, branch number and leaf area of plants treated with plant growth-promoting rhizobacteria were rarely different from the control group. Inoculation with Pseudomonas sp. resulted in the greatest increase in photosynthetic rate during the vegetative and reproductive growth stages, and harvest index, while Bacillus sp., and Mucilaginibacter sp. increased flower number and axillary bud outgrowth rate. Because cannabinoids composition is the one of most important attributes of cannabis flowers, future research should investigate the effects of plant growth-promoting rhizobacteria on flower secondary metabolite profile at harvest. • Inoculation with selected PGPR increased cannabis growth and development. • A Pseudomonas sp. showed the best performance on yield enhancement. • Morphological, physiological and flower yield were significantly enhanced by Mucilaginibacter sp. and Pseudomonas sp. • PGPR utilization is a new sustainable technology for cannabis production. [ABSTRACT FROM AUTHOR]

Summary: The foliar application of Nod factor [Nod Bj V (C18:1, MeFuc)] enhanced (P<0.05) the photosynthetic rate of corn; the increases were 36%, 23% and 12% for 10−6, 10−8 and 10−10 M treated plants, respectively. Similarly, lumichrome at 10−5 and 10−6 M stimulated the photosynthetic rate of corn plants 1 and 2 days after application. Lumichrome (10−5 and 10−6 M) also increased the photosynthetic rates of soybean plants 3 days after treatment. Foliar applications of LCO (10−6 M) to corn and soybean and of lumichrome (10−5 M) to soybean increased leaf area, shoot dry mass and total dry mass relative to control plants. However, lumichrome treatments did not affect any growth variable of corn. Results of this study indicate that this signal compound can enhance the photosynthetic rate and growth of plants. [Copyright &y& Elsevier]

• Hard red spring wheat growth & treatment variables from 6 site-years were analyzed. • Versatile flows of causation varied depending on environmental conditions. • Positive total effect of vegetative dry weight on height at maturity in Québec. • Based on Québec 2016 data the optimal rate of biofertilization was 356 mL ha−1. The experimental hard red spring wheat (Triticum aestivum [L.]) cultivars AC Barrie, Cardale, Superb, and Vesper are adapted to the wheat-growing regions of the Canadian Prairies. They were bred to resist diseases, but their response to a biofertilizer that is a consortium of bacteria (Bacillus subtilis , Candida utilis , Lactobacillus casei , L. helveticus , L. plantarum , L. rhamnosus , Lactococcus lactis , Rhodopseudomonas palustris -1, and R. palustris -2), filamentous fungi (Aspergillus oryzae and Candida utilis), and yeast (Saccharomyces cerevisiae) was not known. The objectives of this research were to model the structures of causal relationships between plant variables using a member of the family of structural-equation modelling tools, called path analysis; to calculate the rate of "biofertilization" that would optimize wheat grain yield; and to model the effect of the experimental treatments on wheat yield over sites in Québec, Manitoba, Saskatchewan, and Alberta (Canada). The path models, presented in diagrams depicting heterogeneous structures, indicated that the variability of the wheat harvest index in Ste-Anne-de-Bellevue, Québec, depended on the experimental biofertilizer and dry weight at maturity in 2015; and biofertilizer and dry weight at the vegetative stage in 2016. The variability of plant height at maturity in Ste-Anne-de-Bellevue, Québec, depended on the biofertilizer, dry weight at the vegetative stage and dry weight at maturity in 2015, and dry weight at the vegetative stage and yield in 2016. The covariance between seedling emergence and the height of the primary stem at the vegetative stage of plant development was consistently zero, meaning structural independence for these variables. The ultimate effect of the biofertilizer on yield was positive in Manitoba and Saskatchewan, and positive and statistically significant in 2015 on Chateauguay clay loam at the Québec site. Results also indicated that a biofertilizer formulation free of cellular material inhibited yield from T. aestivum cv. Superb in Alberta. A quadratic model indicated that at the 2016 Québec site, the optimal application rate of the experimental biofertilizer was 356 mL ha−1, in addition to 2 L of commercially available nutrient fertilizer ha−1. These rates of biofertilization and nutrient fertilization are based on results with AC Barrie that was grown under cool spring conditions. [ABSTRACT FROM AUTHOR]

Ferments containing lactic acid bacteria (LAB) have been used for decades in agricultural systems to improve soils, control disease and promote plant growth, however, the functional roles of LAB in the phytomicrobiome have yet to be discovered. An understanding of the symbiotic relationship between plants and LAB could be exploited to improve agricultural plant production. Scientific investigations to validate plant growth promoting properties of LAB are increasing in number and scope. LAB isolated from diverse sources have been shown to be effective biofertilizers, biocontrol agents, biostimulants. As biofertilizers, LAB can improve nutrient availability from compost and other organic material. In fermented food, LAB has served as an effective biocontrol agent; recently LAB have been shown to be effective in the control of a wide variety of fungal and bacterial phytopathogens. As biostimulants, LAB can directly promote plant growth or seed germination, as well as alleviating various abiotic stresses. In this review, we discuss the history and ecology of plants and LAB, appraise the available information on the use of LAB in improving plant production, and consider the limitations and potential new directions for the use of LAB in plant agriculture. [ABSTRACT FROM AUTHOR]

Salinity is one of the major abiotic streöes affecting plant growth and development as salinization of cultivated land is increasing globally. There is considerable variation in salinity tolerance of wheat genotypes and selection of salt tolerant genotypes is of great interest in salt affected regions. An experiment was conducted to evaluate the salt tolerance of 13 newly developed synthetic hexaploid wheats (2n=6x=42; AABBDD) along with two check varieties Kharchia-65 and Shorawaki. Thirteen-day-old seedlings, grown in a hydroponics system, were subjected to 0, 75 and 150 mM NaCl in Hoagland's nutrient solution for five days. Increasing salt streö generally affected all physiological aspects of the plants; however, various enzyme activities, proline content, soluble sugars and protein content increased with increased salt concentration. Exposure to salt streö affected plant dry biomaö of all the genotypes; however, there was a difference in response of wheat genotypes to salinity streö. Among the tested genotypes, Kharchia-65, Shorawaki, N-7, N-9 and N-13 showed better performance in terms of plant biomaö, K+: Na+ ratio, chlorophyll content, net aöimilation rate (A), transpiration rate (E) and stomatal conductance ( gs). There was a strong correlation between K+:Na+ ratio, chlorophyll, proline, SOD, CAT and gs against shoot dry biomaö. Based on overall performance, the tested wheat genotypes were grouped as tolerant, moderately tolerant and sensitive. Wheat genotypes N-7, N-9 and N-13 were grouped as tolerant, N-33 and N-12 as moderately tolerant and the remaining genotypes were found sensitive to salt streö. In this regard K+Na+ ratio, chlorophyll, proline, SOD, CAT and gs may be used as potential biochemical and physiological selection criteria for screening of salt tolerance in wheat genotypes. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to investigate combined effects of Cd and elevated CO2 on growth, physiological and physiochemical characteristics, elemental compositions in Lolium mutiforum and Lolium perenne grown in soils amended with three Cd concentrations (0, 25, 100mgkg−1) under two CO2 levels (375, 810μLL−1). Elevated CO2 increased net assimilation rate and internal CO2 concentration, and consequently increased total plant biomass by 51 to 31%. At same spiked Cd level, malondialdehyde content in leaves was lower under elevated than under ambient CO2, whereas superoxide dismutase activity was higher. Elevated CO2 decreased Cd, S, and phytochelatin concentrations in roots and shoots to a various degree, depending on plant species and element, but the PC–Cd ratio was not affected. It was concluded that elevated CO2 ameliorated Cd toxicity in both Lolium species under Cd stress, and that the increase of plant biomass and the alleviation of Cd toxicity with elevated CO2 for the Lolium species may be more dependent on increased photosynthesis and enhanced antioxidant capacity. Results of the study may provide insights into the interaction between soil Cd contamination and atmospheric CO2 concentration with regard to plant ability to grow and remove the Cd from soils. [Copyright &y& Elsevier]

Abstract: Production of N-acetyl-d-glucosamine (GlcNAc) and N-acetyl chitooligosaccharides is important to the food, agriculture and biotechnology sectors, where they can be employed as both plant growth promoters and agents of biocontrol for plant pathogens. N-Acetyl-d-glucosamine (GlcNAc) and N-acetyl chitooligosaccharides were produced from colloidal chitin by use of crude enzyme obtained from Paenibacillus illinoisensis KJA-424. The production rate of GlcNAc increased continuously during incubation, while that of GlcNAc oligomers declined. The maximum production of GlcNAc was 1.71mg mL−1 (yield of 62.2%) after 24h of incubation. At the same time chitobiose [(GlcNAc)2], chitotriose [(GlcNAc)3], chitoheptose [(GlcNAc)7] and chitooctose [(GlcNAc)8] were 0.13 (yield of 4.9%), 0.03 (yield of 1.2%), 0.01 (yield of 4.1%) and 0.24mgmL−1 (yield of 9.6%), respectively. The rate of total N-acetyl chitooligosaccharide production decreased by over 44% and 87% after 2 and 24h of incubation, respectively. The multi-chitinolytic enzyme complex produced by Paenibacillus illinoisensis KJA-424 is effective in the production of GlcNAc and N-acetyl chitooligosaccharides, facilitating its potential use in industrial applications. [Copyright &y& Elsevier]

Abstract: Jasmonic acid (JA) is a plant hormone produced via the octadecanoid pathway from its precursor, linolenic acid. Jasmonates are involved in plant wound responses and defense against insects and fungal elicitors. They can also act as signal molecules in the Bradyrhizobium-soybean symbiosis. Pre-incubation of Bradyrhizobium japonicum inocula with gensitein (Ge), an effective inducer of nodulation genes in this species enhances soybean nodulation, nitrogen fixation and yield under low spring soil temperature field conditions. Since jasmonates are also able to induce nodulation genes and cause the production of lipo-chitooligosaccharides (LCOs) by B. japonicum, we conducted two field experiments, in southwestern Quebec, Canada, to determine whether pre-incubation of B. japonicum with methyl jasmonate (MeJA) alone or in combination with genistein (Ge), prior to inoculation, increased soybean plant dry matter production and grain yield. Experiments at each site used a two factor randomized complete block design (RCBD) with four replicates. Two B. japonicum strains (USDA3 and 532C) and four inducer molecule treatments [control, Ge (20μM), MeJA (50μM), and Ge+MeJA (20μM+50μM)] were used in the study. The bacterial cultures were induced for 24h with the inducer molecules and then applied into the furrows at the time of planting. Both Ge and MeJA, alone or in combination, increased plant growth, dry matter accumulation, and grain yield. This study showed that MeJA, alone or in combination with Ge, can be used to promote soybean plant growth and grain yield under short season field conditions. [Copyright &y& Elsevier]

Inoculation dose affects the efficacy of bacterial inoculants applied in agriculture. Effects of the co-inoculation dose of two plant growth promoting rhizobacteria (PGPR) strains, Serratia proteamaculans 1-102 and S. liquefaciens 2-68, with Bradyrhizobium japonicum on soybean [Glycine max (L.) Merr.] growth, nodulation and nitrogen fixation were investigated under controlled root zone temperatures (RZTs; 25, 20 and 15 °C) in soil-less media. The results showed that the effective dose range for both PGPR strains is 107–109 and their optimal co-inoculation dose was 1×108 cells per seedling. This was not affected by RZT. The co-inoculation of PGPR at their optimal dose increased nodule number, plant dry weight and fixed nitrogen. Nitrogen fixation efficiency was also improved by the co-inoculations. Use of nodulation dynamic linear models made the quantitative description of the nodulation process possible. The calculated dynamic parameters revealed that PGPR co-inoculation shortened the nodule initiation time and increased the nodulation rate. [Copyright &y& Elsevier]

Summary: The effect of Nod factors on gas exchange characteristics and growth of soybean plants was studied. Soybean responded positively to some concentrations of Nod factors. Photosynthesis was increased up to 13% over the control, and this was accompanied by increases in stomatal conductance; plant dry weight was also increased. Near-fully expanded leaves responded more strongly to Nod factors than fully expanded leaves. Only Nod factor NodBj-V (C18:1, MeFuc) had significant effects on soybean. The finding suggests that Nod factors can affect photosynthesis, possibly indirectly, by stimulating sink strength. [Copyright &y& Elsevier]