Plant Probiotics Research Articles

Current perspectives and applications in plant probiotics

As agriculture and food security face unprecedented challenges, emerging agricultural innovations and existing practices require ongoing examination in the context of sustainability. In this review, we focus on the use of probiotic microorganisms for improved plant production. As plants are enormously diverse, emphasis is placed on the fundamental sites of plant-microbe interactions regarding benefits and challenges encountered when altering the microbiome of these locations. The soil, the external plant epidermis, and internal plant tissue are considered in discussion regarding the type of plant probiotic application. Plant probiotics range from broader soil beneficial microorganisms (such as Trichoderma spp.) through to specialised epiphytes and endophytes (such as root nodule bacteria). As each site of interaction affects plant growth differently, potential outcomes from the introduction of these exogenous microorganisms are discussed with regard to plant productivity. Finally, recommendations regarding regulation and future use of plant probiotics are points of consideration throughout this review.

Development of low-cost plant probiotic formulations of functional endophytes for sustainable cultivation of Coleus forskohlii

Deployment of plant endophytes at field level is reported to make an impact on agricultural crop productivity; development and deployment of suitable crop specific plant probiotics in a suitable delivery matrix is a value-added task. In our study, we attempted to develop bioformulations of native, fungal endophytes of Coleus forskohlii to improve plant yield using two different carrier-based materials (talc and wheat bran). Initially, fungal endophytes (RF1, SF1, and SF2) were grown on sterilized wheat bran under solid state condition and their growth kinetics and pattern were analyzed by ergosterol content and scanning electron microscope, respectively. 10-day-grown fungal endophytic cultures were used for the development of two types of formulations (wheat bran and talc-based formulations) and tested for their efficacy on host plant, C. forskohlii under field conditions. Interestingly, application of wheat bran-based endophytic formulations significantly (p < 0.01) enhanced plant height (12–29%), number of branches (51–63%), root biomass (26–33%), photosynthetic pigments (32–101%), and forskolin content (35–56%) compared to talc-based formulations under field conditions. Shelf life of endophytes (RF1, SF1, and SF2) in both formulations revealed spore viability in wheat bran-based formulations for 6 months storage period as compared to talc-based formulations. Overall, the present investigation envisages developing plant probiotic bioformulations of functional endophytes of C. forskohlii to enhance root biomass and in planta forskolin content.

Multistrain versus single-strain plant growth promoting microbial inoculants - The compatibility issue

Summary Plant Growth Promoting Microorganisms or Plant Probiotics (PGPMs) constitute a promising solution for agricultural sustainability. The concept that inoculation of PGPM mixtures may perform better in enhancing agricultural production than single strain application dates back to the discovery of plant growth rhizobacteria (PGPR) and is gaining ground in our days. This shift is highlighted by the increasing number of research publications dealing with the positive impact of microbial mixtures in promoting plant growth, controlling plant pathogens, as well as providing abiotic stress tolerance. The continuous deposition of patents as well as commercially available formulations concerning bioprotective and/or biostimulant multistrain mixtures also underlines this shift. A major issue in engineering an effective and consistent synthetic multistrain mixture appears to be the compatibility of its components. The present review provides a thorough literature survey supporting the view that treatment of plants with compatible multistrain mixtures generally exerts a better effect in plant growth and health than single-strain inoculation. Our study focuses on multistrain mixtures based on Pseudomonas, Bacillus and beneficial fungal strains, while commercial products are also being referred.

Isolation of phytase-producing yeasts from rice seedlings for prospective probiotic applications.

The yeasts transmitted from seeds to sprouts might be used as probiotics for host plants. To investigate the inheritable yeasts of rice plants for probiotics, the fungal internal transcribed spacer (ITS) regions (ITS1 and ITS2) in rice sprouts were analyzed by Illumina-based sequencing. The fungal genera Candida, Mortierella, Alternaria, Penicillium, and Tomentella were revealed by both ITS1 and ITS2 sequence analysis. The endophytic yeasts were isolated from rice sprouts by yeast selective medium. Compared with the negative controls, inoculation of isolate Y3 released 2.2 folds higher concentration of free phosphate in soybean meal broth. Most of the phytase activities were located in the yeast cell interiors. The shoot lengths, shoot fresh weights, and root fresh weights of inoculated seedlings increased by 35%, 80%, and 60% compared with the control seedlings, respectively. The results suggested that the rice sprouts contained diverse phytase-producing yeasts transmitted from seeds. These yeasts might be adopted as prospective probiotics to improve rice growth by increasing phosphate utilization efficacy.

Probiotic bacteria promote the growth of associating host(red seaweed, Gracilaria edulis) also synthesize antibacterial protein

Abstract Those plant associated bacteria supporting the growth, reproduction and yield by synthesizing phytohormones, antibiotics and lytic enzymes are called plant probiotics. In this study, isolates of Gram positive Lysinibacillus xylanilyticus associated with red seaweed species were evaluated for antibacterial activity against plant pathogenic bacterium X. oryzae pv. oryzae which cause bacterial blight in rice using disc and well diffusion assays. The isolate HVT234 among the isolates of L. xylanilyticus associated with red seaweed species exhibit high antibacterial activity. The optimum level of extracellular antibacterial protein synthesize in HVT234 was recorded when cultured in 1.5% inoculum in seawater medium with lactose carbon and ammonium chloride nitrogen at pH 7.0 at 35 °C for 48 h. The antibacterial substance extracted in ethyl acetate from the culture supernatant of L. xylanilyticus HVT234 was isolated and separated as 66 kDs protein. The L. xylanilyticus synthesizing antibacterial substance elicited by some non-active co-associating bacteria promote the host Gracilaria edulis growth is considered as probiotic because another associated Bacillus cereus produce antibacterial protein did not support the host growth. This chemical elicitor protein most probably a quorum signal N-acyl homoserine lactone of probiotic L. xylanilyticus which support the host G. edulis growth reported for the first time from this study has immense value in the seaweed mariculture because this species is one of the major biomass feedstocks for agar production.

Plant microbiome: A reservoir of novel genes and metabolites

Decreasing fertility of soil and farm profitability is a noteworthy worldwide concern keeping in mind the end goal to accomplish food security for a prospering total population. The modification of soil microbiomes to enhance crop production is an antiquated practice. The rhizosphere is the region of the soil being persistently impacted by plant roots through the rhizodeposition of exudates, adhesives, and sloughed cells. Mutually, the organisms present in rhizosphere can impact the plant by secreting regulatory compounds. It's very important to understand what genes and functions microbes use to colonize plants because only then have a chance to rationally devise useful ‘plant probiotics’ to help us raise more food and energy crops. Both recently implemented genomic approaches and classical microbiology techniques continue to develop the science of plant-microbe interactions. These investigations of plant microbiome have profited from all-encompassing biological on one-hand and reductionist robotic disclosures on the other. The generation of vast isolate collections what's more, the investigation of engineered microbial groups in blend with plant genetic assets, will permit us to fill this gap and to direct reductionist, speculation driven examinations in progressively complex biological settings up to field tests. These advances can possibly change our comprehension of plant-organism collaborations in nature and in farming and will contribute fundamentally to the following green revolution.

Biogenic Gold Nanoparticle Supplementation to Plant Beneficial Pseudomonas monteilii was Found to Enhance its Plant Probiotic Effect.

Rhizosphere provides unique space for intensive chemical conversation between plant and microorganisms. The common rhizobacterial mechanisms which have been demonstrated to promote plant growth include production of phytohormones, nitrogen fixation, synthesis of 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) and phosphate solubilization. The microbially produced phytohormone indole-3-acetic acid (IAA) is considered to have significant role in interaction between plant and bacteria. Hence any substance with modulatory effect on rhizobacterial IAA production can expect to have its impact on plant-microbe interaction. With the advent of nanotechnology, nanoparticles are being used for diverse applications. However, applications of nanotechnology in agriculture have not been studied in detail. In the study, rhizospheric Pseudomonas monteilii was selected to investigate the concentration-dependent effect of biogenic gold nanoparticles (AuNPs) on its IAA production. For this, AuNPs synthesized by Bacillus subtilis SJ15 were characterized by UV-Vis spectroscopy, FT-IR, TEM and EDS. The results showed AuNPs to have spherical, hexagonal and triangular shapes with a size range of 12-32nm and absorption peak at 545nm. Further, various concentrations of AuNPs were used to identify its impact on IAA production by P. monteilii. From this, enhanced production of IAA by P. monteilii was found to take place in the presence of 50µg/mL AuNPs. When Vigna unguiculata seedlings were grown in presence of50µg/mL of AuNPs, increased growth was observed. The results of the study thus showed the ability of AuNPs to augment the IAA-producing potential of P. monteilii.

Integrated Approach for Development of Environmental Biotechnologies for Treatment of Solid Organic Waste and Obtaining of Biohydrogen and Lignocellulosic Substrate

Solid food waste is a significant threat to the environment. Thermodynamic calculations allow determining theoretically possible metabolic pathways for degradation of organic compounds by microorganisms, and also to select the optimal one to increase efficiency of food waste recycling. The purpose of our work was application of thermodynamic calculations to find out suitable fermentation parameters for regulation of microbial metabolism to ensure high rate of waste decomposition and formation of valuable products. The following methods were used: for pH and oxidation-reduction potential (ORP) measuring – colorimetric and potentiometric, for volume and composition of synthesized gas study – volumetric and chromatographic, for fermentation parameters calculation – mathematical. Fermentation of multicomponent kitchen food waste under theoretically calculated optimal parameters pH = 7.0 and Eh = –250...–350 mV provided extremely high metabolic activity of hydrogen-producing microbial community which resulted in decrease in duration of batch fermentation from to 3 days, increase in hydrogen yield from 16 to 80-115 L/kg of dry waste. The coefficient of waste destruction (Kd) that is ratio of initial and final weight of waste reached 91. Obtained after fermentation unfermented lignocellulosic substrate was shown to be applied as plant probiotics and supply mineral nitrogen for plant nutrition in arid condition. Thus, high efficiency of application of thermodynamic prognosis method of microbial interaction with organic compounds was shown to become the base for biotechnology of destruction of environmentally hazardous solid food waste with simultaneous obtaining of valuable products: environmentally friendly energy carrier – molecular hydrogen, as well as lignocellulosic substrate to increase crop yields. DOI: http://dx.doi.org/10.5755/j01.erem.74.4.20723

The soil-borne legacy in the age of the holobiont.

Future efforts to increase agricultural productivity will focus on crops as functional units comprised of plants and their associated microflora in the context of the various environments in which they are grown. It is suggested that future efforts to increase agricultural productivity will focus on crops as functional units comprised of plants and their associated beneficial microorganisms in the context in which they are grown. Scientists, industry, and farmers must work closely together to develop, adapt, and apply new technologies to a wide range of cropping systems. Consumer education is needed help grow public awareness that 'plant probiotics' offer a safe and environmentally friendly alternative to dependence on the use of chemical pesticides.

Nutrient- and Dose-Dependent Microbiome-Mediated Protection against a Plant Pathogen

Plant-associated microbial communities can promote plant nutrient uptake, growth, and resistance to pathogens [1-3]. Host resistance to infection can increase directly through commensal-pathogen interactions orindirectly through modulation of host defenses [4-6], the mechanisms of which are best described for rhizosphere-associated bacteria. For example, Arabidopsis plants infected with the foliar pathogen, Pseudomonas syringae pathovar tomato (Pst), increase their root secretion of malate, which attracts Bacillus subtillis to the roots and leads to a stronger host response against Pst [7]. Although there are numerous examples of individual defensive symbionts (e.g., [8]), it is less clear whether this type of protection is an emergent property of whole microbial communities. In particular, relatively little is known about whether and how the presence of phyllosphere (above-ground) microbial communities can increase host resistance against pathogens. In this study, we examined the ability of augmented tomato phyllosphere microbiomes to confer resistance against the causal agent of bacterial speck, Pst. Across five independent experiments, the augmented phyllosphere microbiome was found to decrease pathogen colonization. Furthermore, the dose of commensal bacteria applied affected the degree of protection conferred, and although the effect is dependent on microbial composition, it is not clearly related to overall bacterial diversity. Finally, our results suggest that resources available to the phyllosphere microbial community may play an important role in protection, as the addition of fertilizer abolished the observed microbiome-mediated protection. Together, these results have clear relevance to microbiome-mediated protection within agricultural settings and the use of plant probiotics to increase disease resistance.

Rhizosphere pseudomonads as probiotics improving plant health.

Many root-colonizing microbes are multifaceted in traits that improve plant health. Although isolates designated as biological control agents directly reduce pathogen growth, many exert additional beneficial features that parallel changes induced in animal and other hosts by health-promoting microbes termed probiotics. Both animal and plant probiotics cause direct antagonism of pathogens and induce systemic immunity in the host to pathogens and other stresses. They also alter host development and improve host nutrition. The probiotic root-colonizing pseudomonads are generalists in terms of plant hosts, soil habitats and the array of stress responses that are ameliorated in the plant. This article illustrates how the probiotic pseudomonads, nurtured by the carbon (C) and nitrogen (N) sources released by the plant in root exudates, form protective biofilms on the root surface and produce the metabolites or enzymes to boost plant health. The findings reveal the multifunctional nature of many of the microbial metabolites in the plant-probiotic interplay. The beneficial effects of probiotics on plant function can contribute to sustainable yield and quality in agricultural production.

Probiotics for Plants? Growth Promotion by the Entomopathogenic Fungus Beauveria bassiana Depends on Nutrient Availability.

Cultivation of crops requires nutrient supplements which are costly and impact the environment. Furthermore, global demands for increased crop production call for sustainable solutions to increase yield and utilize resources such as nutrients more effectively. Some entomopathogenic fungi are able to promote plant growth, but studies over such effects have been conducted under optimal conditions where nutrients are abundantly available. We studied the effects of Beauveria bassiana (strain GHA) seed treatment on the growth of maize (Zea mays) at high and low nutrient conditions during 6weeks in greenhouse. As expected, B. bassiana seed treatment increased plant growth, but only at high nutrient conditions. In contrast, the seed treatment did not benefit plant growth at low nutrient conditions where the fungus potentially constituted a sink and tended to reduce plant growth. The occurrence of endophytic B. bassiana in experimental plant tissues was evaluated by PCR after 6weeks, but B. bassiana was not documented in any of the above-ground plant tissues indicating that the fungus-plant interaction was independent of endophytic establishment. Our results suggest that B. bassiana seed treatment could be used as a growth promoter of maize when nutrients are abundantly available, while the fungus does not provide any growth benefits when nutrients are scarce.

Unraveling the multilevel aspects of least explored plant beneficial Trichoderma saturnisporum isolate GITX-Panog (C)

Species of Trichoderma offer an eco-friendly and economical solution to the management of plant pathogens in agricultural crops. The secretion and spectrum of different bioactive molecules by Trichoderma spp. is known to follow adaptive and species/strain behavior, depending upon the edaphic conditions. In present study, GITX-Panog (C), an antagonistic isolate of Trichoderma saturnisporum against Fusarium oxysporum was screened for the production of different glycosyl hydrolases and secondary metabolites. The evaluation of antagonistic isolates for lytic enzymes and secondary metabolites revealed their significance as plant probiotics. Profiling of lytic enzymes such as chitinases and β-glucanases secreted by T. saturnisporum GITX-Panog (C) in the presence of autoclaved mycelium of F. oxysporum and colloidal chitin or laminarin showed increased enzyme activities. Production of bioactive secondary metabolites such as siderophore, peptaibols, 6-pentyl-α-pyrone, and the known potential of these compounds in mineral acquisition and suppression of plant F. oxysporum, revealed the potential significance of Trichoderma saturnisporum isolate GITX-Panog C in agricultural application against biotic and abiotic stresses. The antagonistic isolate also showed significant increases in fresh biomass and seed production in Arabidopsis thaliana in the greenhouse compared to controls. Thus, the current study highlights the multiple attributes of an antagonistic isolate of T. saturnisporum for future agricultural applications as a plant probiotic agent.

Chitosan and plant probiotics application enhance growth and yield of strawberry

Abstract Strawberry is a newly introduced fruit crop in Bangladesh, which gained considerable interests from both growers and consumers. Resource poor growers of the country will need alternate production technology to keep the cost under control as well as minimize health hazard by reducing use of synthetic pesticides. This study evaluated and compared the performance of plant probiotic bacteria, chitosan and fungicides on growth and fruit yield of strawberry. Application of two plant probiotic bacteria, Bph-4 and BTLK6a to strawberry plants significantly increased vegetative growth and fruit yield compared to non-treated control. Further investigation on these bacteria revealed that they possessed indole acetic acid production and/or antagonistic properties to phytopathogenic microbes. The Bph-4 and BTLK6a were identified as Stenotrophomonas sp. and Ochrobacterum sp., respectively through 16S rRNA gene sequencing. Chitosan @ 250–500 ppm and BTLK6a application on tissue-cultured plants of cv. Strawberry Festival produced 56% and 43% higher fruit yield, respectively, compared to non-treated control. Out of two different plant types tested, tissue-cultured plants responded to chitosan and probiotics better than runner grown plants for percentage of yield increase. Fungicide treatment did not provide any yield advantage likely due to the absence of targeted diseases. These results suggest that chitosan and plant probiotic bacteria could be used as natural bioregulators for safe production of strawberry fruits in Bangladesh.

Taxonomy and systematics of plant probiotic bacteria in the genomic era.

Recent decades have predicted significant changes within our concept of plant endophytes, from only a small number specific microorganisms being able to colonize plant tissues, to whole communities that live and interact with their hosts and each other. Many of these microorganisms are responsible for health status of the plant, and have become known in recent years as plant probiotics. Contrary to human probiotics, they belong to many different phyla and have usually had each genus analysed independently, which has resulted in lack of a complete taxonomic analysis as a group. This review scrutinizes the plant probiotic concept, and the taxonomic status of plant probiotic bacteria, based on both traditional and more recent approaches. Phylogenomic studies and genes with implications in plant-beneficial effects are discussed. This report covers some representative probiotic bacteria of the phylum Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes, but also includes minor representatives and less studied groups within these phyla which have been identified as plant probiotics.

Plant probiotic bacteria enhance the quality of fruit and horticultural crops.

The negative effects on the environment and human health caused by the current farming systems based on the overuse of chemical fertilizers have been reported in many studies. By contrast, bacterial inoculations produce positive effects on yields without causing this type of harm. Hence, during recent years, the commercialization of biofertilizers has been on the increase, and the number of companies and products available are expanding worldwide every year. In addition to the notable enhancement of crop production, many studies have shown how the application of bacteria has positive effects on food quality such as improved vitamin, flavonoid and antioxidant content, among other benefits. This advantage is interesting with respect to food that is consumed raw, such as fruits and many vegetables, as these bioactive molecules are maintained up until the moment the food is consumed. As regards this review focuses on the collection of studies that demonstrate that microorganisms can act as plant probiotics of fruit and horticultural crops, essential types of food that form part of a healthy diet.

Potential applications of plant probiotic microorganisms in agriculture and forestry.

Agriculture producers, pushed by the need for high productivity, have stimulated the intensive use of pesticides and fertilizers. Unfortunately, negative effects on water, soil, and human and animal health have appeared as a consequence of this indiscriminate practice. Plant probiotic microorganisms (PPM), also known as bioprotectants, biocontrollers, biofertilizers, or biostimulants, are beneficial microorganisms that offer a promising alternative and reduce health and environmental problems. These microorganisms are involved in either a symbiotic or free-living association with plants and act in different ways, sometimes with specific functions, to achieve satisfactory plant development. This review deals with PPM presentation and their description and function in different applications. PPM includes the plant growth promoters (PGP) group, which contain bacteria and fungi that stimulate plant growth through different mechanisms. Soil microflora mediate many biogeochemical processes. The use of plant probiotics as an alternative soil fertilization source has been the focus of several studies; their use in agriculture improves nutrient supply and conserves field management and causes no adverse effects. The species related to organic matter and pollutant biodegradation in soil and abiotic stress tolerance are then presented. As an important way to understand not only the ecological role of PPM and their interaction with plants but also the biotechnological application of these cultures to crop management, two main approaches are elucidated: the culture-dependent approach where the microorganisms contained in the plant material are isolated by culturing and are identified by a combination of phenotypic and molecular methods; and the culture-independent approach where microorganisms are detected without cultivating them, based on extraction and analyses of DNA. These methods combine to give a thorough knowledge of the microbiology of the studied environment.

Assessment of bacterial populations associated with banana tree roots and development of successful plant probiotics for banana crop

Two hundred and sixty-one bacterial isolates associated with banana tree roots in organic systems were isolated from 19 farms located in four different provinces of the Dominican Republic. The isolates were analysed by means of ARDRA plus RAPD, and as a consequence 114 of them were selected for identification by means of complete 16S rRNA sequencing and phylogenetic reconstruction. The 114 isolates belonged to 20 different genera, with Bacillus, Pseudomonas, Enterobacter and Stenotrophomonas the prevailing genera. Of these, 65 isolates showed more than 99.5% similarity with a type strain, and they were assigned to 34 different species from 16 genera; 29 isolates could constitute new species and the remaining 20 isolates belonged to groups containing more than one species with identical 16S rRNA genes, and therefore they could not be assigned to any species. This result showed a higher number of bacterial taxa associated with banana tree roots than previously described. Additionally, we found seven bacterial species with significant in vitro plant growth promoting (PGP) activity, which had not been previously described as PGP bacteria in any crop. Field trials with isolates pre-selected based on their in vitro PGP activity showed that one strain of the species Pseudomonas plecoglossicida improved fruit yield and controlled the incidence of the disease black sigatoka caused by Mycosphaerella fijiensis. This activity was tentatively attributed to induced systemic resistance mechanisms. Bacterial diversity was analysed among the 261 isolates based on the Shannon index of diversity (H), calculated from the ARDRA profiles. Interestingly, the majority of the bacterial diversity was found within farms (86% of the total), being higher than the bacterial diversity between farms (14%). Moreover, the differences in the average H Index between provinces were very low. Consequently the biodiversity of the bacterial communities was little influenced by the soil characteristics. These results could work in favour of the efficient adaptation of the bacterial strains selected for use as plant probiotics in a range of soils in the region analysed.

Plant probiotics to the rescue

Soil Biology![Figure][1] Soil-dwelling bacteria can protect strawberry plants from fungal wilt PHOTO: © OLEKSANDR SHEVCHENKO/ALAMY STOCK PHOTO Some soils protect crops against their microbial attackers without any pesticides or fungicides. Cha et al. investigated the microbial and biochemical basis of this effect in a patch of soil that excluded fungal wilt on strawberry plants, despite 15 years of monoculture. Mixing in the protective soil transferred this suppressive effect into neighboring disease-ridden soils, which gained increasingly better disease-control capacity with successive growing cycles. A strain of Streptomyces bacteria, a group renowned for producing antibiotics, emerged as the chief agent that suppressed the pathogenic fungi. The Streptomyces produced an interesting large heat-stable thiopeptide antibiotic with antifungal properties. Thus, much like the development of probiotics to combat gut diseases, probiotics for soil should be feasible. ISME J. 10 , 119 (2016) [1]: pending:yes

Plants probiotics as a tool to produce highly functional fruits: the case of phyllobacterium and vitamin C in strawberries.

The increasing interest in the preservation of the environment and the health of consumers is changing production methods and food consumption habits. Functional foods are increasingly demanded by consumers because they contain bioactive compounds involved in health protection. In this sense biofertilization using plant probiotics is a reliable alternative to the use of chemical fertilizers, but there are few studies about the effects of plant probiotics on the yield of functional fruits and, especially, on the content of bioactive compounds. In the present work we reported that a strain of genus Phyllobacterium able to produce biofilms and to colonize strawberry roots is able to increase the yield and quality of strawberry plants. In addition, the fruits from plants inoculated with this strain have significantly higher content in vitamin C, one of the most interesting bioactive compounds in strawberries. Therefore the use of selected plant probiotics benefits the environment and human health without agronomical losses, allowing the production of highly functional foods.