Plant Growth-promoting Microorganisms Research Articles

Analysis of microbial populations in plastic\u2013soil systems after exposure to high poly(butylene succinate-co-adipate) load using high-resolution molecular technique

BackgroundBio-based and biodegradable plastics are considered as plastics of the future owing to their ability to decompose under various environmental conditions. However, their effects on the soil microbiome are poorly characterised. In this study, we aimed to investigate the effects of an important bio-based and biodegradable plastic, polybutylene succinate-co-adipate (PBSA), on soil microbial diversity and community composition using high-resolution molecular technique (Illumina sequencing) targeting all three microbial domains: archaea, bacteria, and fungi.ResultsAdding high load of PBSA to soil (6% (w/w)) caused a significant decline in archaeal (13%) and fungal (45%) richness and substantial changes in both bacterial (Proteobacteria, Actinobacteria, and Acidobacteria) and fungal (Eurotiomycetes, Sordariomycetes, Leotiomycetes, and Dothideomycetes) community composition compared with no PBSA addition to soil. The combined effects of PBSA and (NH4)2SO4 fertilisation on the soil microbiome were much greater than the effects of PBSA alone. We only detected opportunistic human pathogens in low abundance on PBSA and in the surrounding soil. However, some plant pathogenic fungi were detected and/or enriched on the PBSA films and in surrounding soil. Apart from plant pathogens, many potential microbial control agents and plant growth-promoting microorganisms were also detected/enriched owing to PBSA addition. Adding high load of PBSA together with (NH4)2SO4 fertilisation can either eliminate some plant pathogens or enrich specific pathogens, especially Fusarium solani, which is economically important.ConclusionsWe conclude that high load of bio-based and biodegradable PBSA plastic may negatively affect soil microbiome.

Soil physical disturbance reduces maize growth, nutrition, and mycorrhiza formation in a green manure rotation with vetch

Green manure crops such as vetch (Vicia sativa L.) and their association with plant growth-promoting microorganisms like arbuscular mycorrhizal fungi (AMF) and diazotrophic bacteria are known to improve soil fertility and crop nutrition in agroecosystems. In a greenhouse pot experiment with a fully factorial design, we investigated the effects of green manure with vetch (incorporated or cut leaving the soil undisturbed), soil disturbance simulating a tillage event (without and with) and mineral fertilization (without and with NPK) on the abundance of available soil nutrients (NO3−, NH4+ and HPO42−), maize growth and nutrient content (N and P), and maize mycorrhiza formation by native AMF. First vetch was grown for 10 weeks and then left to mineralize for 12 weeks incorporated or not into the soil. Then before maize sowing, another soil-disturbance event was performed (with and without) and finally maize was grown for 18 weeks without and with NPK fertilization. Main results showed that the amount of soil NO3− and HPO42− increased substantially after the green manure mineralization before maize sowing, though with lower values after green manure soil incorporation, compared to that of the treatment without soil incorporation. Green manure soil incorporation reduced the final total maize dry weight biomass without NPK fertilization, but when combined with NPK green manure soil incorporation resulted in the highest final total maize dry weight biomass. However, type of green manure management had no effects on the other maize plant variables measured nor AMF root colonization. On the contrary, soil disturbance before maize sowing resulted in decreased AMF root colonization, cob dry weight, and cob N and P content. In conclusion, our results show that soil physical disturbance caused alterations in the plant-microbe-soil dynamics in the present vetch-maize rotation resulting in reduced maize growth, nutrition, and mycorrhiza formation.

Plant Growth-Promoting Microorganisms in Coffee Production: From Isolation to Field Application

Coffee is an important, high-value crop because its roasted beans are used to produce popular beverages that are consumed worldwide. Coffee plantations exist in over 70 countries and constitute the main economic activity of approximately 125 million people. Currently, there is global concern regarding the excessive use of agrochemicals and pesticides in agriculture, including coffee crops. This situation has motivated researchers, administrators, and farmers to seek ecologically friendly alternatives to decrease the use of synthetic fertilizers and pesticides. In the last decades, multiple studies of the rhizosphere, at the chemical, physical and biological levels, have improved our understanding of the importance of beneficial microorganisms to plant health and growth. This review aims to summarize the state of the use of plant growth-promoting microorganisms (PGPM) in coffee production, where the most extensively studied microorganisms are beneficial plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF). This review also contains information on PGPM, in regard to plantations at different latitudes, isolation techniques, mass multiplication, formulation methods, and the application of PGPM in nurseries, monoculture, and coffee agroforestry systems. Finally, this review focuses on relevant research performed during the last decade that can help us improve sustainable coffee production.

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

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

Manipulating the soil microbiomes during a community recovery process with plant beneficial species for the suppression of Fusarium wilt of watermelon

Fusarium wilt is a devastating disease which impacts watermelon production. Soil fumigation using dazomet followed by biological organic fertilizer was applied to suppress the Fusarium wilt disease. We propose that fumigation suppresses the soil indigenous community, especially the soil-borne pathogens, while the utilization of bio-organic fertilizer facilitates the recovery of the soil microbiome to a beneficial, suppressive state through the introduction of plant growth-promoting microorganisms. Greenhouse experiment showed that applied biological organic fertilizer after dazomet fumigation effective restrain the disease incidence with a 93.6% disease control. Fumigation strongly decreased soil microbial diversity and altered relative taxa abundances, suggesting the possibility of niche release by the resident soil microbial community. Fumigation followed by bio-fertilizer transformed the soil microbial community composition and resulted in higher relative abundances of beneficial microbial groups such as Bacillus (8.5%) and Trichoderma (13.5%), coupled with lower Fusarium abundance compared to other treatments. Network analysis illustrated that soil fumigation decreased interactions within the soil microbial community with less nodes and links while bio-fertilizer addition promoted node interactions. In addition, bio-fertilizer addition after fumigation resulted in the beneficial species becoming the key network connectors. Collectively, fumigation appears to release the resident soil niche resulting in lower diversity while the beneficial microbes introduced by bio-fertilizer addition colonize these niches, leading to a more complex community with fewer pathogens that suppresses Fusarium wilt disease incidence.

Climate Change and Salinity Effects on Crops and Chemical Communication Between Plants and Plant Growth-Promoting Microorganisms Under Stress

During the last two decades the world has experienced an abrupt change in climate. Both natural and artificial factors are climate change drivers, although the effect of natural factors are lesser than the anthropogenic drivers. These factors have changed the pattern of precipitation resulting in a rise in sea levels, changes in evapotranspiration, occurrence of flood overwintering of pathogens, increased resistance of pests and parasites, and reduced productivity of plants. Although excess CO2promotes growth of C3plants, high temperatures reduce the yield of important agricultural crops due to high evapotranspiration. These two factors have an impact on soil salinization and agriculture production, leading to the issue of water and food security. Farmers have adopted different strategies to cope with agriculture production in saline and saline sodic soil. Recently the inoculation of halotolerant plant growth promoting rhizobacteria (PGPR) in saline fields is an environmentally friendly and sustainable approach to overcome salinity and promote crop growth and yield in saline and saline sodic soil. These halotolerant bacteria synthesize certain metabolites which help crops in adopting a saline condition and promote their growth without any negative effects. There is a complex interkingdom signaling between host and microbes for mutual interaction, which is also influenced by environmental factors. For mutual survival, nature induces a strong positive relationship between host and microbes in the rhizosphere. Commercialization of such PGPR in the form of biofertilizers, biostimulants, and biopower are needed to build climate resilience in agriculture. The production of phytohormones, particularly auxins, have been demonstrated by PGPR, even the pathogenic bacteria and fungi which also modulate the endogenous level of auxins in plants, subsequently enhancing plant resistance to various stresses. The present review focuses on plant-microbe communication and elaborates on their role in plant tolerance under changing climatic conditions.

Use of Microbial Biostimulants to Increase the Salinity Tolerance of Vegetable Transplants

Vegetable plants are more sensitive to salt stress during the early growth stages; hence, the availability of poor-quality brackish water can be a big issue for the nursery vegetable industry. Microbial biostimulants promote growth and vigor and counterbalance salt stress in mature plants. This study aimed to evaluate the application of plant growth-promoting microorganisms for improving salt tolerance of lettuce and tomato seedlings irrigated with different water salinity levels (0, 25, and 50 mM NaCl) during nursery growth. Two commercial microbial biostimulants were applied to the substrate before seeding: 1.5 g L−1 of TNC BactorrS13 containing 1.3 × 108 CFU g−1 of Bacillus spp.; 0.75 g L−1 of Flortis Micorrize containing 30% of Glomus spp., 1.24 × 108 CFU g−1 of Agrobacterium radiobacter, Bacillus subtilis, Streptomyces spp. and 3 × 105 CFU g−1 of Thricoderma spp. Many morpho-physiological parameters of lettuce and tomato seedlings suffered the negative effect of salinity. The use of the microbial biostimulants modified seedling growth and its response to salt stress. They had a growth-promoting effect on the unstressed seedlings increasing fresh and dry biomass accumulation, leaf number, and leaf area and were successful in increasing salinity tolerance of seedlings especially when using Flortis Micorizze that enhanced salinity tolerance up to 50 mM NaCl. The inoculation of the substrate with microbial biostimulants could represent a sustainable way to improve lettuce and tomato transplant quality and to use brackish water in vegetable nurseries limiting its negative effect on seedling growth.

Plant Growth-promoting Microorganisms Isolated from Plants as Potential Antimicrobial Producers: A Review

The agricultural industry worldwide faces challenges in the struggle against plant diseases. In efforts to increase agricultural intensities, the dependency on agrochemicals for crop protection has become significantly high. Moreover, the increasing use of agrochemical-based products has resulted in multidrug-resistant pathogens and environmental pollution. This paper reviews the biocontrol capacity of plant growth-promoting microorganisms (PGPMs) originating from plants towards plant pathogens. The current trend in discovering new compounds has shown antimicrobial activity gaining immense interest due to its vast potential. On a related note, PGPMs are an aspect of that research interest that can be further explored as antimicrobial producers. In this work, we also covered the types of biocontrol mechanisms pertaining to PGPMs as well as their roles in biocontrol activity. A biocontrol approach exploits disease-suppressive microorganisms to improve plant health by controlling related pathogens. The understanding of these microorganisms and mechanisms of pathogen antagonismare primary factors in ensuring improvement for future applications. Inevitably, there is indeed room for rigorous expansion with respect to PGPMs in the future of agriculture.

Suppression of Pseudomonas syringae pv. tomato infection by rhizosphere fungi.

Induced resistance against several plant pathogens was reported using different beneficial plant growth-promoting microorganisms. The potential of five fungal isolates, Trichoderma harzianum GT 3-2, Fusarium equiseti GF 18-3, F.equiseti GF 19-1, Phoma sp. GS 10-1 and Phoma sp. GS 14-1, to stimulate tomato growth and resistance against bacterial speck disease caused by Pseudomonas syringae pathovar (pv.) tomato DC3000 was evaluated. Based on the results of disease severity and growth promotion experiments, GF 18-3 exhibited the best results among all fungal isolates. Treatment with barley grain inocula (BGI) and culture filtrate (CF) of the isolates promoted tomato growth and suppressed the pathogen in pot trials. Furthermore, expressions of the pathogenesis-related genes (PR-1, β-1,3-glucanase A, β-1,3-glucanase B and LOX) were relatively higher than the control in the leaves of tomato plants treated with both BGI and CF. The transcription levels remained consistently higher than the control plants for 6 days post-inoculation with pathogen. Taken together, the results indicate that the tested fungal isolates have the potential to promote tomato growth and induce systemic resistance against the bacterial speck disease. Analysis of certain PR gene expression revealed significant activation in both BGI and CF treatments, leading to stimulated resistance against the pathogen. © 2021 Society of Chemical Industry.

Potential Use of Beneficial Microorganisms for Soil Amelioration, Phytopathogen Biocontrol, and Sustainable Crop Production in Smallholder Agroecosystems

Smallholder agroecosystems play a key role in the world's food security providing more than 50% of the food produced globally. These unique agroecosystems face a myriad of challenges and remain largely unsupported, yet they are thought to be a critical resource for feeding the projected increasing human population in the coming years. The new challenge to increase food production through agricultural intensification in shrinking per capita arable lands, dwindling world economies, and unpredictable climate change, has led to over-dependence on agrochemical inputs that are often costly and hazardous to both human and animal health and the environment. To ensure healthy crop production approaches, the search for alternative ecofriendly strategies that best fit to the smallholder systems have been proposed. The most common and widely accepted solution that has gained a lot of interest among researchers and smallholder farmers is the use of biological agents; mainly plant growth promoting microorganisms (PGPMs) that provide essential agroecosystem services within a holistic vision of enhancing farm productivity and environmental protection. PGPMs play critical roles in agroecological cycles fundamental for soil nutrient amelioration, crop nutrient improvement, plant tolerance to biotic and abiotic stresses, biocontrol of pests and diseases, and water uptake. This review explores different research strategies involving the use of beneficial microorganisms, within the unique context of smallholder agroecosystems, to promote sustainable maintenance of plant and soil health and enhance agroecosystem resilience against unpredictable climatic perturbations.

Plant Microbiota Beyond Farming Practices: A Review

Plants have always grown and evolved surrounded by numerous microorganisms that inhabit their environment, later termed microbiota. To enhance food production, humankind has relied on various farming practices such as irrigation, tilling, fertilization, and pest and disease management. Over the past few years, studies have highlighted the impacts of such practices, not only in terms of plant health or yields but also on the microbial communities associated with plants, which have been investigated through microbiome studies. Because some microorganisms exert beneficial traits that improve plant growth and health, understanding how to modulate microbial communities will help in developing smart farming and favor plant growth-promoting (PGP) microorganisms. With tremendous cost cuts in NGS technologies, metagenomic approaches are now affordable and have been widely used to investigate crop-associated microbiomes. Being able to engineer microbial communities in ways that benefit crop health and growth will help decrease the number of chemical inputs required. Against this background, this review explores the impacts of agricultural practices on soil- and plant-associated microbiomes, focusing on plant growth-promoting microorganisms from a metagenomic perspective.

Application of Plant Growth Promoting Microorganism and Plant Growth Regulators in Agricultural Production and Research

Plant growth-promoting microorganisms (PGPM) are rhizosphere microorganisms that colonize the root environment [...]

Pre-evaluation response of rhizosphere hybridization in acid lime

Rhizosphere hybridization is a new concept to secure the plant growth-promoting microorganisms to produce better nursery plants. Taking into the objective of rhizosphere hybridization, the present investigation was conducted in the secondary nursery block of ICAR-Central Citrus Research Institute, Nagpur. As many ten treatments consisting of rhizosphere microbes in form of water extract of the rhizosphere of acid lime, neem, bamboo, banyan and microbial consortium were tested in acid lime seedlings (cv NRCC Acid lime-7) raised on a solarized but containerized soil completely randomized design with three replications during 2018-20. Results showed a significant response to different treatments on plant growth parameters. In our study, the effect of the combined rhizosphere of banyan (Ficus benghalensis), neem (Azadirachta indica) and bamboo (Dendrocalamus strictus) was significantly superior to the rest of the treatments in increasing the biometric (seedling height, seedling diameter and number of branches per seedling), number of leaves per seedling, root architecture (tap root length, tap root diameter and number of secondary roots per seedling) and microbial biomass (fungal count and bacterial count) response of acid lime seedling compared to control treatment. Rhizosphere soil treatment was found to be superior over rhizosphere water extract treatment. Among various rhizosphere water extract treatments, acid lime rhizosphere water extract performed better in biometric response of acid lime seedling. Microbial consortium was observed to be better in increasing the microbial biomass of the rhizosphere, which could probably translate its response at later stages but added an additional resilience to rhizosphere, thereby, potentially effective in reducing the mortality once planted in main field.

Identification of Beneficial Microbial Consortia and Bioactive Compounds with Potential as Plant Biostimulants for a Sustainable Agriculture.

A growing body of evidence demonstrates the potential of various microbes to enhance plant productivity in cropping systems although their successful field application may be impaired by several biotic and abiotic constraints. In the present work, we aimed at developing multifunctional synthetic microbial consortia to be used in combination with suitable bioactive compounds for improving crop yield and quality. Plant growth-promoting microorganisms (PGPMs) with different functional attributes were identified by a bottom-up approach. A comprehensive literature survey on PGPMs associated with maize, wheat, potato and tomato, and on commercial formulations, was conducted by examining peer-reviewed scientific publications and results from relevant European projects. Metagenome fragment recruitments on genomes of potential PGPMs represented in databases were also performed to help identify plant growth-promoting (PGP) strains. Following evidence of their ability to coexist, isolated PGPMs were synthetically assembled into three different microbial consortia. Additionally, the effects of bioactive compounds on the growth of individually PGPMs were tested in starvation conditions. The different combination products based on microbial and non-microbial biostimulants (BS) appear worth considering for greenhouse and open field trials to select those potentially adoptable in sustainable agriculture.

Microbial Derived Compounds, a Step Toward Enhancing Microbial Inoculants Technology for Sustainable Agriculture

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.

Rhizosphere Engineering With Plant Growth-Promoting Microorganisms for Agriculture and Ecological Sustainability

The rhizosphere is undoubtedly the most complex microhabitat, comprised of an integrated network of plant roots, soil, and a diverse consortium of bacteria, fungi, eukaryotes, and archaea. The rhizosphere conditions have a direct impact on crop growth and yield. Nutrient-rich rhizosphere environments stimulate plant growth and yield and vice versa. Extensive cultivation exhaust most of the soils which need to be nurtured before or during the next crop. Chemical fertilizers are the major source of crop nutrients but their uncontrolled and widespread usage has posed a serious threat to the sustainability of agriculture and stability of an ecosystem. These chemicals are accumulated in the soil, drained in water, and emitted to the air where they persist for decades causing a serious threat to the overall ecosystem. Plant growth-promoting rhizobacteria (PGPR) present in the rhizosphere convert many plant-unavailable essential nutrients e.g., nitrogen, phosphorous, zinc, etc. into available forms. PGPR produces certain plant growth hormones (such as auxin, cytokinin, and gibberellin), cell lytic enzymes (chitinase, protease, hydrolases, etc.), secondary metabolites, and antibiotics, and stress alleviating compounds (e.g., 1-Aminocyclopropane-1- carboxylate deaminase), chelating agents (siderophores), and some signaling compounds (e.g., N-Acyl homoserine lactones) to interact with the beneficial or pathogenic counterparts in the rhizosphere. These multifarious activities of PGPR improve the soil structure, health, fertility, and functioning which directly or indirectly support plant growth under normal and stressed environments. Rhizosphere engineering with these PGPR has a wide-ranging application not only for crop fertilization but developing eco-friendly sustainable agriculture. Due to severe climate change effects on plants and rhizosphere biology, there is growing interest in stress-resilient PGPM and their subsequent application to induce stress (drought, salinity, and heat) tolerance mechanism in plants. This review describes the three components of rhizosphere engineering with an explicit focus on the broader perspective of PGPM that could facilitate rhizosphere engineering in selected hosts to serve as an efficient component for sustainable agriculture.

Evaluation of two microcosm systems for co-treatment of LDPEoxo and lignocellulosic biomass for biochar production

BackgroundThe co-transformation of solid waste of natural and anthropogenic origin can be carried out through solid-state-fermentation systems to obtain bio-products with higher added value and lower environmental impact.MethodsTo evaluate the effect of Pleurotus ostreatus on co-transformation of oxo-degradable low-density polyethylene (LDPEoxo) sheets and lignocellulosic biomass (LCB), were assembled two 0.75 L microcosm systems in vertical (VMS) and horizontal (HMS) position. The pre-treated sheets with luminescent O2 plasma discharges were mixed with pine bark, hydrolyzed brewer’s yeast and paper napkin fragments and incubated for 135 days at 20 ± 1.0 °C in the presence of the fungus. With the co-transformation residues, biochar (BC) was produced at 300 ± 1.0 °C (BC300) for 1 h, then used to carry out adsorption studies, using the malachite green dye (MG) at pH 4.0, 7.0 and 9.0 ± 0.2. Finally, the biochar was the substrate for the germination of carnation seeds (Dianthus caryophyllus) and Ray-grass (Lolium sp.) in vitro.ResultsFor HMS, the decrease in static contact angle (SCA) was 63.63% (p = 0.00824) and for VMS 74.45% (p = 0.00219), concerning the pristine. Plastic roughness in VMS was higher (26%) concerning the control. Throughout the 135 days, there were fungal growth and consequently laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP) activities. During the first 75 days, CO2 production increased to 4.78 ± 0.01 and 4.98 ± 0.01 mg g-1 for HMS and VMS, respectively. In MG adsorption studies, the highest amount of the colourant adsorbed at both pH 4.0 and 7.0 ± 0.2.ConclusionsFinally, the biochar or the biochar enriched with low concentrations of plant growth-promoting microorganisms and inorganic fertilizer favours the germination of Dianthus caryophyllus and Lolium sp., seeds.

Choosing source of microorganisms and processing technology for next generation beet bioinoculant

The increase of human population and associated increasing demand for agricultural products lead to soil over-exploitation. Biofertilizers based on lyophilized plant material containing living plant growth-promoting microorganisms (PGPM) could be an alternative to conventional fertilizers that fits into sustainable agricultural technologies ideas. We aimed to: (1) assess the diversity of endophytic bacteria in sugar and sea beet roots and (2) determine the influence of osmoprotectants (trehalose and ectoine) addition during lyophilization on bacterial density, viability and salt tolerance. Microbiome diversity was assessed based on 16S rRNA amplicons sequencing, bacterial density and salt tolerance was evaluated in cultures, while bacterial viability was calculated by using fluorescence microscopy and flow cytometry. Here we show that plant genotype shapes its endophytic microbiome diversity and determines rhizosphere soil properties. Sea beet endophytic microbiome, consisting of genera characteristic for extreme environments, is more diverse and salt resistant than its crop relative. Supplementing osmoprotectants during root tissue lyophilization exerts a positive effect on bacterial community salt stress tolerance, viability and density. Trehalose improves the above-mentioned parameters more effectively than ectoine, moreover its use is economically advantageous, thus it may be used to formulate improved biofertilizers.

Alleviation of zinc deficiency in wheat inoculated with root endophytic fungus Piriformospora indica and rhizobacterium Pseudomonas putida

Plant growth, grain yield, and the nutritional grain quality reduce in Zinc (Zn)-deficient soils. As a practical approach, the utilization of plant growth-promoting microorganisms offers a promising approach to cope with Zinc deficiency. This study was carried out to determine the effects of endophytic fungus Piriformospora indica and rhizobacterium Pseudomonas putida on growth, nutrient status, and antioxidant enzyme activities of two wheat (Triticum aestivum L.) genotypes under Zn deficiency. The experiment was conducted using a completely randomized factorial design with three replications and three treatments: wheat genotypes [Zn-efficient (H-Zn) genotype, Azadi and Zn-inefficient (L-Zn) genotype, Niknejad]), Zn concentrations (0 and 2 μmol Zn L−1) and microbial inoculations (P. indica and P. putida). Under Zn deficiency, P. indica, P. putida, and dual inoculation of P. indica with P. putida significantly increased the shoot dry weight of L-Zn genotype up to 10.3%, 25.6% and, 15.4% compared to control plants, respectively. Inoculation of P. indica led to an increase in thinner and highly-branched roots and subsequently increased Zn uptake in the shoot of L-Zn genotype under Zn deficiency. Under such condition, individual inoculation of L-Zn genotype with P. putida and P. indica increased peroxidase activity by 85.7% and 40% compared with non-inoculated plants. Malondialdehyde content of both wheat genotypes inoculated with P. indica was significantly decreased compared to the non-inoculated plants. Generally, depending on the wheat genotype, P. indica and P. putida can increase plant tolerance by affecting only part of the tolerance mechanisms (including antioxidant and non-antioxidant mechanisms) under Zn deficiency stress. In summary, P. indica and P. putida could improve the fitness of the L-Zn genotype under Zn-deficiency stress.

Field trial evidence of silicon and phosphorus application to improve rice growth and nutrients uptake in Northern Iran

One of the major problems in the paddy fields in northern Iran is the low solubility and availability of phosphorus. To solve this problem, the plant growth-promoting microorganisms and the application of silicon fertilizer can be appropriate way and assessed for rice crop as split plots based on a randomized complete block design (RCBD) with three replications in Amol region during 2017 and 2018. The spray of nano-silicon, the soil application of potassium silicate and calcium silicate and control condition were used as main plots. Phosphorus treatment including control, 100 kg triple superphosphate ha−1, 50 kg triple superphosphate ha−1 + Herbaspirillum seropodicae bacteria inoculation and 50 kg triple superphosphate ha−1 + mycorrhiza fungi (Gholusmosseae) inoculation were used as subplots. The results demonstrated that with the application of silicon resources, grain filling period and internodes lodging index (I3LI and L4LI) were statistically decreased compared to the control, but paddy yields (PY) were significantly enhanced. The maximum amounts of I3LI (49.44%) and I4LI (52.36%) were calculated with the application of phosphorus + bacteria. The maximum PY (4542 kg ha−1) was produced with the spray of nano-Si and the application of chemical phosphorus (4670 kg ha−1). The spray of nano-silicon and the combined application of phosphorus + bacterial lead to higher uptake of nutrient (Si, N, P and K). It can be concluded that the spray of nano-silicon and the application of chemical fertilizer + bacterial can increase the yields and control the blast disease in the rice fields.