Beneficial Microbial Inoculants Research Articles

Integrated Nutrient management for optimal plant health and crop yield

In the pursuit of sustainable agriculture and optimal crop yields, Integrated Nutrient Management (INM) has emerged as a comprehensive strategy that integrates organic and inorganic sources of nutrients. This article explores the principles and components of INM, emphasizing its role in fostering plant health, enhancing nutrient use efficiency, and ensuring the long-term sustainability of soil and ecosystems. The key components of INM include the judicious use of organic fertilizers, precision application of inorganic fertilizers, crop rotation, and the integration of beneficial microbial inoculants. The benefits of INM encompass improved nutrient use efficiency, sustainable soil health, environmental sustainability, and enhanced resilience to climate variability. As global agriculture faces the challenges of feeding a growing population while minimizing environmental impact, the adoption of Integrated Nutrient Management stands out as a pivotal strategy for achieving a harmonious balance between productivity and sustainability in modern farming.

Microbial communities along the soil-root continuum are determined by root anatomical boundaries, soil properties, and root exudation

The microbiome in plant-soil systems has a significant influence in promoting plant growth. Despite this, the extent of selectivity that the plant exerts on the microbiome in the continuum between the soil and internal plant tissues is not well understood. This study analysed the root microbiome of a legume, Melilotus officinalis (L.) Pall., sweet clover, and focused on dynamic shifts in the microbial community structure through the niches of bulk soil, rhizosphere, periderm, phloem and xylem, and further examined the effects of soil factors, root exudate metabolism, and root cell wall development on microbiome assemblages in different root compartments. Young and mature plants were sampled at 24 field sites and the microbial communities in different niches from bulk soil and rhizosphere through to root compartments were analysed by 16S rRNA gene sequencing. The microbiome composition changed from periderm to phloem to a greater extent than across other boundaries. Variation in microbiome composition was associated with geographic distance and soil properties for the bulk soil, rhizosphere and periderm niches. Root exudation influenced the rhizosphere microbiome assemblages in young and mature plants. The endophyte communities that occupied the phloem and xylem were most conserved and were independent of growing environments and root exudation. Symbiotic rhizobia able to nodulate M. officinalis were prominent colonisers of the periderm (∼15%) and xylem (∼6.2%), but were only a minor component in other soil-related niches (0.1%–2.5%). In xylem tissues, endophyte diversity was correlated with the total cell wall and lignin content across the sampled sites (r = 0.29–0.62). Our results demonstrate that selection of microbiome constituents occurs at different boundaries through bulk soil, rhizosphere, periderm, phloem and xylem, and is especially strong across the periderm boundary. The conserved endophyte community in the innermost tissues (phloem and xylem) was identified, and will be potentially advantageous to the development of specific beneficial microbial inoculants.

Leaf mold compost reduces waste, improves soil and microbial properties, and increases tomato productivity

AbstractSoils in urban settings are often degraded, which can prevent growers from optimizing the health and productivity of their crops. In this study, we investigated whether amending soil with a locally made leaf‐mold compost could (a) improve soil chemical and biological properties, (b) increase survival of a microbial inoculant with plant growth promoting and disease suppressive capabilities, and (c) enhance the yield and quality of a tomato crop. Results were promising, with dramatically greater concentrations of active soil organic matter (SOM) and marketable fruit in plots receiving the amendment in both years of the study. Foliar disease severity was also lower in compost‐amended plots in the second year of the trial. Inoculating tomato (Solanum lycopersicum L.) transplants with Trichoderma harzianum T‐22 reduced deaths that are due to transplant stress in one of the cultivars evaluated, and the compost supported greater populations of this microbe in soil demonstrating that it is possible to enhance the efficacy of beneficial microbial inoculants in field settings using targeted practices. These results indicate that urban farmers can improve the productivity of their farms by amending soils with leaf mold compost, which will help ensure the long‐term sustainability of urban farming initiatives. However, all composts should be tested to ensure they do not contain toxic levels of heavy metals or pathogens, and farmers should avoid overapplication since this can reduce crop health and lead to environmental challenges.

The Impact of Biofertilizers and NPK Fertilizers Application on Soil Phosphorus Availability and Yield of Upland Rice in Tropic Dry Land

Dry land in Indonesia is dominated by marginal soil which have low macro nutrient content, low organic matter content and low soil microbial activity. Improving soil quality it is necessary to increase nutrients availability such as biofertilizers application. Biofertilizers contains beneficial microbial inoculants to increase soil nutrient availability. The use of biofertilizers combined with NPK fertilizer will increase macro nutrients availability and optimize plant growth, thus will increase fertilizers efficiency. This experiment was carried out to study the impact of biofertilizers on available-P, plant P-uptake and yield of upland rice at Land Research of Agriculture Faculty, Universitas Padjadjaran. This experiment used a randomized block design consisting of ten treatments and three replications The treatments consisted with two doses of biofertilizers (50 kg ha-1 and 75 kg ha-1) and three doses of N,P,K fertilizers (100%, 75%, and 50% from recommended doses). Biofertilizers contains N-fixing bacteria and phosphate solubilizing microbes. The result of experiment showed that application of biofertilizers 75 kg ha-1 and biofertilizers 50 kg ha-1 + N, P, K 50% increased soil phosphorus availability. The application of biofertilizers increased P-uptake up to 81%. Futhermore, biofertilizers 75 kg ha-1 + N, P, K 75% increased the yield of upland rice by 164%.

Trichoderma Applications on Strawberry Plants Modulate the Physiological Processes Positively Affecting Fruit Production and Quality.

Many Trichoderma spp. are successful plant beneficial microbial inoculants due to their ability to act as biocontrol agents with direct antagonistic activities to phytopathogens, and as biostimulants capable of promoting plant growth. This work investigated the effects of treatments with three selected Trichoderma strains (T22, TH1, and GV41) to strawberry plants on the productivity, metabolites and proteome of the formed fruits. Trichoderma applications stimulated plant growth, increased strawberry fruit yield, and favored selective accumulation of anthocyanins and other antioxidants in red ripened fruits. Proteomic analysis of fruits harvested from the plants previously treated with Trichoderma demonstrated that the microbial inoculants highly affected the representation of proteins associated with responses to stress/external stimuli, nutrient uptake, protein metabolism, carbon/energy metabolism and secondary metabolism, also providing a possible explanation to the presence of specific metabolites in fruits. Bioinformatic analysis of these differential proteins revealed a central network of interacting molecular species, providing a rationale to the concomitant modulation of different plant physiological processes following the microbial inoculation. These findings indicated that the application of Trichoderma-based products exerts a positive impact on strawberry, integrating well with previous observations on the molecular mechanisms activated in roots and leaves of other tested plant species, demonstrating that the efficacy of using a biological approach with beneficial microbes on the maturing plant is also able to transfer advantages to the developing fruits.

Respon Pertumbuhan dan Hasil Padi Gogo yang dipengaruhi oleh Pemberian Biochar dan Pupuk Hayati

One of the efforts to increase crop yield based in sustainable agriculture is through the utilization of microbial inoculants (biofertilizers) and soil conditioners. Biofertilizer is an ingredient that contains beneficial microbial inoculants to increase soil nutrient availability for plants. Biochar has been recognized as a soil conditioner by improving soil physical, chemical, and biological properties as well as in retaining nutrients, thereby enhancing plant growth. However, the research regarding the effect of the combination between biofertilizers and biochar on growth and yield of upland rice are still at scarce. The field experiment was conducted to determine the impact of biofertilizers and biochar on growth and yield of upland rice in Andisols at Pasir Talang village in Rancakalong district, Sumedang, West Java. This experiment used a Randomized Block Design (RBD) consisted of six treatments and four replicates. Biofertilizers consisted of N-fixer bacteria (Azotobacter chroococum, Azospirillum sp.) and phosphate-solubilizer microbes (Pseudomonas mallei, P. cepaceae, Aspergillus niger and Penicillium sp.). The treatments were combination of biochar (2,4, and 6 t ha-1) and biofertlizers (0 and 50 kg ha-1). The result of experiment revealed that combination of biochar and biofertilizers increased the growth and yield of upland rice significantly. The application 4 t ha-1of biochar and 50 kg ha-1 of biofertilizers gave the best yield of 5,81 t ha-1.

Improved nutrient status and Fusarium root rot mitigation with an inoculant of two biocontrol fungi in the common bean (Phaseolus vulgaris L.)

Among beneficial microbial inoculants, consortia have been advocated for application in modern agriculture as they may easily overcome the rhizospheric constraints, in addition to enhancing biocontrol efficacy through partners' reinforcement in an additive or synergistic manner. Unfortunately, the historical antagonistic potential of Trichoderma spp. has compromised its co-operation with Arbuscular mycorrhizal Fungi (AMF), misleading several attempts in building up artificial consortium between these undefeated biocontrol agents (BCA's). The present study unveils a strategy of exploiting the beneficial traits of a Common bean endophytic Trichoderma (Trichoderma harzianum T8) and a recently described AMF formulation (AMF2) with individual biocontrol traits for better nutrients uptake and resistance induction against Fusarium root rot (FRR) in common bean. Standard plate-based approaches, as well as sequential inoculation of BCA's followed by colorimetric, Flame Photometry (FP) and Atomic Absorption Spectrometry (AAS) analyses revealed that co-inoculation of the BCA's mobilised more zinc (Zn) and phosphorus (P) from the soil substrate to the plant than the BCA's tested alone. Moreover, enhanced shoot growth (123% increase) and chlorophyll pigment synthesis (137% increase) were recorded compared to Trichoderma-treated plants. Most importantly, a substantial suppression of both disease incidence (92% protection) and severity (42.2% protection) was achieved upon combining the BCA's, leading to 140% protective effect relative to Dithane M-45 (Mancozeb) fungicide. The Pearson correlation test depicted a negative correlation between protection rate and total phenols, total soluble flavonoids, total tannins and Phenylalanine Ammonia Lyase activity (r > −0.5; P = 0.05). Meanwhile, a positive correlation was recorded with Polyphenol Oxydase activity (r > 0.5; P = 0.05). The results achieved unveil a substantial enhancement in bean plant growth and resistance against FRR mediated by a consortium of AMF2 and T. harzianum T8. This consortium might represent a cheaper and environmental friendly alternative to agrochemicals if further developed.

Growth and nutrition of cowpea (Vigna unguiculata) under water deficit as influenced by microbial inoculation via seed coating

AbstractDrought can drastically reduce cowpea [Vigna unguiculata (L.) Walp.] biomass and grain yield. The application of plant growth‐promoting rhizobacteria and arbuscular mycorrhizal fungi can confer resistance to plants and reduce the effects of environmental stresses, including drought. Seed coating is a technique which allows the application of minor amounts of microbial inocula. Main effects of the factors inoculation and water regime showed that: severe or moderate water deficit had a general negative impact on cowpea plants; total biomass production, seed weight and seed yield were enhanced in plants inoculated with P. putida; inoculation of R. irregularis significantly increased nitrogen (N) and phosphorus (P) shoot concentrations; and R. irregularis enhanced both chlorophyll b and carotenoids contents, particularly under severe water deficit. Plants inoculated with P. putida + R. irregularis had an increase in shoot P concentration of 85% and 57%, under moderate and severe water deficit, respectively. Singly inoculated P. putida improved potassium shoot concentration by 25% under moderate water deficit. Overall, in terms of agricultural productivity the inoculation of P. putida under water deficit might be promising. Seed coating has the potential to be used as a large‐scale delivery system of beneficial microbial inoculants.

Gene expression profiling of tomato roots interacting with Pseudomonas fluorescens unravels the molecular reprogramming that occurs during the early phases of colonization

The concerns of people over the wide use of chemicals are determining an increasing attention to more eco-friendly management practices in agriculture. Plant growth promoting rhizobacteria (PGPR) are emerging as important beneficial microbial inoculants because of their capability to promote plant growth and improve plant protection. We performed RNASeq to analyze gene expression profiling at 24, 48 and 72 h post inoculation (hpi) by Pseudomonas fluorescens strain CREA 16 (Pf-16), a PGPR previously isolated from Pisum sativum rhizosphere and with proven growth promotion activity on tomato plants, to unravel the extent of transcriptome reprogramming of tomato roots during the colonization. Pf-16 induces transcriptional reprogramming mainly at 24 and 72 hpi particularly affecting the down-regulation of genes. During the investigated time span, two phases can be clearly distinguished. In the first phase, within the first 48 h, Pf-16 strongly represses R-genes, calcium/calmodulin-mediated signaling and various transcription factors involved in the salicylic and jasmonic acid metabolism. Even more, Pf-16 blocks ethylene biosynthesis/signaling and protease-dependent mechanisms. At a later stage, from 48/72 h onwards, an intimate relationship between tomato roots and Pf-16 is established as a result of cell wall modifications. Finally, Pf-16 triggers the up-regulation of genes associated with plant growth promotion. Based on the main findings derived from this research, a model that gathers and describes the molecular events of outmost importance during tomato roots-Pf-16 interaction is proposed.

An endophytic strain of genus Paenibacillus isolated from the fruits of Noni (Morinda citrifolia L.) has antagonistic activity against a Noni's pathogenic strain of genus Aspergillus

Endophytes are microbes capable of colonizing the tissues of healthy plants and subsequently establishing a harmonious relationship with their hosts. In this research, the endophytic strain Paenibacillus sp. NEB was isolated from fruits of healthy Noni (Morinda citrifolia L.). Strain NEB was identified as Paenibacillus polymyxa using MALDI-TOF Mass Spectrometry. Pathogenic fungal strain NP-1 was isolated from Noni fruits infected by smut, and was identified as Aspergillus aculeatus by polyphasic taxonomy basing on morphological identification, and ITS-5.8S rDNA and β-tubulin gene phylogenetic analyses. Through the antagonistic test against the pathogenic strain Aspergillus aculeatus NP-1, the results showed that strain NEB had a good antagonistic activity against smut pathogen of Noni. By sequencing with Illumina HiSeq 2000, the draft genome of Paenibacillus sp. NEB was acquired, and 3 CDSs for glucanases were annotated and potentially correlated to the antagonistic activity of this strain. Using realtime-PCR method with specific primers to amplify the biocontrol gene, β-1,3-1,4- glucanase gene (gluB), it was found in Paenibacillus polymyxa NEB. This study would provide a theoretical and microbial basis for the rationally developing and using Noni beneficial microbial inoculants against its pathogenic strain in the future.

Improvement of copper stress tolerance in pepper plants (Capsicum annuum L.) by inoculation with arbuscular mycorrhizal fungi

The effect of arbuscular mycorrhizal fungi (AMF) inoculation, on pepper plant growth and physiological parameters in response to increasing soil Cu concentrations was studied. Treatments consisted of inoculation or not with Funneliformis mosseae or Rhizophagus intraradices and the addition of Cu to soil at concentrations of 0, 2, 4 and 8 mM CuSO4. The increase in copper concentration diminished the inoculation in all treatments. The highest experimental concentration of Cu (8 mM) reduced significantly the hyphae viability and ALP activity, regardless of the inocula used. The total dry weight and the leaf area were higher for mycorrhizal plants. The mycorrhizal dependence was 30 and 50% for plants inoculated with F. mosseae and R. intraradices, respectively at 8 mM CuSO4. The electrolyte leakage was higher at higher Cu concentrations, in roots and leaves. Net photosynthetic rates and transpiration were lower in plants treated with Cu, regardless of the inocula. At low Cu concentration in soil no differences were observed in Cu content in the shoots and roots. At 4 mM Cu, Cu content in roots was significantly higher than in shoots. At 8 mM Cu, in non-inoculated plants accumulate more Cu than inoculated plants in the roots, leaves and fruits regardless of the inocula. Beneficial microbial inoculants such as AMF, is an attractive strategy to farmers in the context of sustainable agriculture. Pre-inoculation in transplants could be an adequate practice to alleviate the deleterious effects in stress of pepper plants. However different AMF species can differ in their ability to minimize stress effects and promote plant growth.

Exploring the use of recombinant inbred lines in combination with beneficial microbial inoculants (AM fungus and PGPR) to improve drought stress tolerance in tomato

At a world scale, tomato is an important horticultural crop, but its productivity is highly reduced by drought stress. Combining the application of beneficial microbial inoculants with breeding and grafting techniques may be key to cope with reduced tomato yield under drought. This study aimed to investigate the growth responses and physiological mechanisms involved in the performance under drought stress of four tomato recombinant inbred lines (RIL) after inoculation with the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis and the plant growth promoting rhizobacteria (PGPR) Variovorax paradoxus 5C-2. Results showed a variation in the efficiency of the different tomato RILs under drought stress and a differential effect of the microbial inoculants, depending on the RIL involved. The inoculants affected plant parameters such as net photosynthetic capacity, oxidative damage to lipids, osmolyte accumulation, root hydraulic conductivity or aquaporin abundance and phosphorylation status. RIL66 was the one obtaining maximum benefit from the microbial inoculants under drought stress conditions, due likely to improved CO2-fixation capacity and root hydraulic conductivity. We propose that RIL66 could be selected as a good plant material to be used as rootstock to improve tomato growth and productivity under water limiting conditions. Since RIL66 is highly responsive to microbial inoculants, this grafting strategy should be combined with inoculation of R. irregularis and V. paradoxus in order to improve plant yield under conditions of drought stress.

Effect of Beneficial Microorganisms on Cowpea Productivity and Soil Health

Soil microorganisms are the most abundant biota in soil, responsible for a number of abilities such as nutrient cycling and organic matter decomposition, maintenance of soil fertility and restoration and plant health and sustainability in ecosystem functioning. Beneficial microbial inoculants such as actinomycetes, diazotrophic bacteria, mycorrhizal helper bacteria (MHB), mycorrhizal fungi, rhizobia etc. are known to promote plant growth. Microorganisms are also antagonistic to plant pests, parasites or diseases. Many of the beneficial microbials are naturally present in soil, although in certain cases, it may be advised to increase their populations and activity either through direct inoculation or by applying agricultural management techniques. In cognizance with the above, an experiment was conducted to evaluate the effect of microbial inoculants on overall productivity of cowpea and soil health. Results revealed that the application of Rhizobium sp. as seed treatment increased the productivity of cowpea (up to 15%) at various stages of plant growth parameters like plant dry weight, no. of fresh leaves and branches, pods, overall leaf moisture and root length as compared to control. Total microbial population numbers, available K and phosphorus (P) in soil were also increased significantly after the soil was treated with this microbial inoculant indicating the role of beneficial microbial in improving the plant nutrient status and soil health.

Recent Trends in Microbial Inoculants in Agriculture

Recent Trends in Microbial Inoculants in Agriculture

Nursery practice on seed germination and seedling growth of Dalbergia sissoo using beneficial microbial inoculants

Nursery practice using microbial inoculants was performed to find out the efficacy of the inoculants on seed germination and seedling growth of sissoo (Dalbergia sissoo Roxb.). Microbial inoculants or effective microorganisms (EM) are a mixture of many different beneficial microorganisms in a solution. The seedlings were grown in a mixture of sandy soil and cowdung (3:1) kept in polybags with pouring EM solution at different concentrations (0.1%, 0.5%, 1%, 2%, 5% and 10%) before and after a week of sowing the seeds. Seed germination rate and growth parameters of seedlings were measured, such as, shoot and root length, vigor index, fresh and dry weight of shoot and root and total biomass increment. The nodulation status influenced by EM was also observed along with the measurement of pigment contents in leaves. The highest germination rate (69%) was observed in 2% EM treatment, followed by 67% and 65% in 1% and 5% EM. The highest shoot length (33.2 cm) was in 2% EM, whereas highest root length (26.3 cm) was in 1% EM. Both fresh and dry weights from shoot and root, were maximum (4.16 g and 1.57 g; 2.12 g and 0.83 g respectively) in 2% EM and were significantly (p ≤ 0.05) different from control. Vigor index was highest (4071) in 2% EM, which was significantly (p ≤ 0.05) different from control. Total dry weight increment was highest in 2% EM treatment, followed by 1% and 5% concentrations of EM. Nodulation number was higher at very low (0.1%) concentration of EM solution but it normally decreased with the increase of EM concentrations. The contents of chlorophyll a, chlorophyll b and carotenoid were highest (60.11, 17.05 and 42.48 mg·L−1 respectively) in 2% EM treatment and lowest (39.35, 13.55 and 27.29 mg·L−1 respectively) in control treatment. Therefore, low concentration of EM (up to 2%) can be used for getting maximum seed germination rate and seedling development of Dalbergia sissoo Roxb.

REFORESTATION IN BAUXITE MINE SPOILS WITH CASUARINA EQUISETIFOLIA FROST. AND BENEFICIAL MICROBES

ABSTRACT Reforestation in mine spoils difficult because the mine spoils are low or lack in beneficial microbial populations. To overcome this problem a field experiment was conducted on bauxite mine spoils with Casuarina equisetifolia Frost and beneficial microbial inoculants (arbuscular mycorrhizal fungi, Frankia and phosphobacterium) for reforestation. Under nursery experiments the cultured arbuscular mycorrhizal (AM) fungi Glomus aggregatum Schenck & Smith emend. Koske, Phosphobacterium (PSB) and root nodule extract of Frankia have inoculated to C. equisetifolia individually and combinations at nursery level. The mine wastes of bauxite called bauxite mine spoils were collected and used as potting media to grow C. equisetifolia seedlings along with these microbial inoculants. From the nursery experiments it was found that the AM fungi and other beneficial microbial inoculants improved the seedlings in terms of bio mass and growth. The seedlings thereafter were transplanted at bauxite mine spoils and the growth and survival of seedlings were monitored for two years. In field conditions, AM fungi, PSB and Frankia inoculated seedlings of C. equisetifolia showed 90 to 100% survival over the control seedlings. Their growth was also significantly higher than the control seedlings. The nutrient uptake (N, P, K) was also increased in the trees inoculated with AM fungi, Frankia and PSB. From this study it was understood that C. equisetifolia inoculated with beneficial microbes is a suitable tree species for reforestation in bauxite mine spoils

Microbial Inoculants for Sustainable Forests

Fungal root pathogens are widespread and may cause substantial seedling losses in conifer nurseries. Furthermore, poor seedling survival and growth on reforestation sites results in reduced forest regeneration. Use of microbial inoculants for disease control and plant growth promotion has become an important endeavour. A microbial culture collection of 500 strains was assessed for biological control of fungal root pathogens and/or plant growth promotion of conifer seedlings. Seven of these strains showed significant suppres-sive effects on various soil-bome fungal pathogens. On Douglas fir, two strains, RAL3 and 64-3, reduced disease caused by Fusariumby. 7-42% in repeated growth room assays. The same strains significantly increased healthy stand of white spruce seedlings inoculated with Fusariumand Pythiumin a conifer nursery, and increased the survival of bare-root white spruce seedlings planted on a reforestation site by 19-23%. Both strains also significantly increased new root and total plant dry weights. Strain RAL3 in commercial formulation maintained a viable population of about log 8-9 cfu/ml for over a year when stored at 5°C. Strain survival on seed varied with conifer species. No decreases in bacterial populations were observed on seeds of jack pine or Douglas fir after 37 to 44 days storage at 5°C, but decreases were observed on seeds of white spruce and Scots pine. This study has provided candidate beneficial microbial inocu-lants which offer promise for development of commercial inoculants for the forestry industry.