Use Of Plant Growth-promoting Rhizobacteria Research Articles

Deciphering the Structural and Functional Diversity of Rhizobacteria from Stone Pine Inoculated with Plant Growth Promoting Rhizobacteria (PGPR) before and after Transplanted into Degraded Agricultural Soil

The use of plant growth-promoting rhizobacteria (PGPR) inoculated on plants has shown that it can increase the success of reforestation and accelerate soil recovery by improving soil microbial diversity. Three PGPR isolated from natural pine populations were selected for their metabolic capabilities and taxonomic affiliation (Z4.3; Bacillus sp., Z5.4; Arthobacter sp., and Z7.15; and Pseudomonas sp.) when inoculated alone or in combination (consortium) on stone pine seedlings before transplanting to the field. Before transplanting and after nine months, rhizospheric soil samples were collected for structural and functional metagenomic studies. First, the data were analyzed using EasyMAP. Neither alpha nor beta diversity showed significant differences between the samples, although unique taxa representative of each sample were detected. The predominant phylum in all cases was Proteobacteria, followed by Bacteroidetes and Acidobacteria. The linear discriminant analysis (LDA) effect size (LEfSe) found significantly over-represented taxa in some samples, highlighting different representatives of the order Sphingomonadales in several of them. Functional inference performed with PICRUSt also showed significantly over-represented functions in some samples. The study demonstrates that PGPR have a positive effect on plants and cause detectable changes in microbial communities in terms of both structure and function.

167 Use of plant growth-promoting rhizobacteria in bermudagrass systems of the Southeast US

Abstract Since the discovery of plant growth-promoting rhizobacteria (PGPR) in the mid-20th century, efforts have focused on utilizing them to reduce synthetic fertilizer usage and to improve the sustainability of agricultural systems. However, research in forage systems is lacking. The objective of the current study was to determine the use of PGPR in bermudagrass (Cynodon dactylon) forage systems in Central Alabama. The study was designed as a split plot and conducted at the E.V. Smith Research and Extension Center (Shorter, AL) and compared four levels of PGPR and five levels of nitrogen fertility rates. The PGPR included a negative control, Paenibacillus riograndensis DH44, Bacillus subtilis DH267, and UrtrishaN (Corteva Agriscience, Indianapolis, IN) were allocated to main plots. The strains of DH44 and DH267 were sprayed during each application at a population of 1-5 × 108 cfu/mL while UtrishaN (Corteva) was sprayed at a population of 3×107 cfu/mL with an activator at the rate of 0.25% vol/vol according to the manufacturer’s recommendations. The nitrogen fertilizer treatments were the subplot and were 25 and 50% of the recommended nitrogen for bermudagrass. The N treatments were as follows: negative control, 25% urea, 25% ammonium sulfate, 50% urea (F4), and 50% ammonium sulfate. Plots were treated with PGPR and N fertilizer starting on 11 May 2023. The forage harvest operation was conducted with at least 4 wk intervals depending on precipitation. After one year of the study, PGPR did not have any significant effect on forage biomass (1,209 kg /ha; P = 0.58). There was also no effect of N fertilizer (1,596 kg/ha; P = 0.35) or PGPR × N fertilizer interaction on forage biomass (1,408 kg/ha; P = 0.56). The lack of differences between positive and negative control plots indicates that growing conditions (i.e., lack of timely rainfall) during the first year of the study limited forage production for all treatments. The results from future years of this study will provide a more accurate conclusion on the use of PGPR with and without N fertilizer for bermudagrass systems.

Effect of Different Strains of Bacillus Species on Lipid Peroxidation and Antioxidant Enzymes in Rice Exposed to Drought Stress

The impact of climate change-induced droughts in various regions worldwide has led to a range of stresses in plants, resulting in a decline in overall yield. Numerous strategies have been employed to alleviate stress on plants, but the use of plant growth-promoting rhizobacteria has emerged as a cost-effective and efficient approach. This study explores the influence of three distinct isolates of Bacillus species on lipid peroxidation and selected antioxidant enzymes in drought-stressed rice. Standard procedures were employed to assess antioxidant enzymes. Catalase, Ascorbate peroxidase, and Superoxide dismutase—while Malondialdehyde levels were utilized to gauge lipid peroxidation over 0, 3, 6, and 9 days of drought stress exposure. Among the three isolates, Bacillus subtilis SA1 (accession number OM184294) exhibited superior properties in inducing antioxidant enzymes, effectively countering the impact of generated free radicals. Additionally, this same organism demonstrated exceptional efficacy in reducing lipid peroxidation levels in the plant's leaves, thereby mitigating the adverse effects of free radicals. Consequently, this particular organism proves promising for minimizing the impact of drought stress in rice, complementing its role as a plant growth-promoting rhizobacteria.

Plant growth-promoting bacteria in sorghum development in coppercontaminated soil

Copper (Cu) is a metal that can become toxic to sorghum when present in high concentrations in the soil. The use of plant growth-promoting rhizobacteria can be an alternative for the development of sorghum [Sorghum bicolor (L.) Moench] in soil contaminated with copper. The objective of this study was to determine the effect of Azospirillum brasilense inoculation on the development and copper levels of sorghum cultivated in soil contaminated with Cu, enabling the reuse of these areas. The experimental design was randomized blocks in a factorial arrangement (9 × 2), with nine doses of copper [(0: natural content of the soil), 30, 60, 90, 120, 150, 180, 240, and 300 mg of copper kg-1 of soil] with and without A. brasilense inoculation, with six replicates. In the treatment without inoculation, a dose of 200 kg-1ha was applied. Plant height (PH), stem diameter, dry mass of the air part (DMAP), volume, length, and root dry mass (RDM), relative index of chlorophyll a and b, and copper contents in DMAP and RDM were evaluated. The inoculation with A. brasilense allows a higher index of chlorophyll a and b and the development of the aerial part of the sorghum, reducing copper content in the aerial part, enabling the reuse of soil containing 52.5% clay, contaminated with up to 300 mg of copper kg-1 of soil. Inoculation with A. brasilense increases the specific surface area (SSA) of sorghum roots compared with non-inoculated plants grown only with nitrogen fertilization in soil contaminated with copper.

Enhancing agricultural sustainability through plant growth-promoting rhizobacteria and nanotechnology

The challenges facing the global agricultural system in the twenty-first century, such as declining productivity and ecosystem sustainability, are worsened by predictions of a growing population, which is expected to reach 9.7 billion by 2050. Factors related to climate change, such as rising temperatures and abiotic stresses, such as salinity and drought, put agricultural production at risk. Sustainable agriculture has become crucial, as it offers long-term environmental and social benefits by reducing the use of synthetic pesticides and fertilizers. One promising solution for sustainable agriculture is the use of plant growth-promoting rhizobacteria (PGPR). These bacteria, which are abundant in the rhizosphere, enhance plant growth both directly and indirectly by promoting root growth, biofertilization, and controlling phytopathogens. However, despite their potential, challenges still exist in terms of the inconsistent performance and mechanisms of PGPR, which limits their widespread adoption. Biofertilizers containing PGPR provide a sustainable alternative to conventional fertilizers by enhancing nutrient availability and soil fertility. Additionally, the integration of nanotechnology holds promise in improving agricultural sustainability by facilitating efficient nutrient uptake and the controlled release of fertilizers, thus reducing environmental impacts. PGPR have been shown to be effective in various crops such as maize and sugarcane, offering solutions for soil nutrient deficiencies and pathogen control. Nevertheless, the beneficial effects of PGPR may be influenced by certain bacterial traits, underscoring the importance of selecting appropriate strains for optimal outcomes. In conclusion, the integration of PGPR and nanotechnology offers a comprehensive approach to sustainable agriculture, addressing the complex challenges.

Viruses and viroids in tomato (Solanum lycopersicum) and plant growth promoting rhizobacteria as a management alternative

Viruses and viroids cause several diseases in tomato (Solanum lycopersicum) worldwide, generating important economic losses. About 312 viruses and seven viroids have been associated, of which more than 28 are present in Mexico. Therefore, the use of Plant Growth-Promoting Rhizobacteria (PGPR) can be an effective alternative for the management of viruses and viroids. The genera Pseudomonas, Bacillus, Azospirillum, Anabena and Stenotrophomonas have been implemented against main viruses reported in tomato: Cucumber mosaic virus (CMV), Tobacco mosaic virus (TMV), Tomato chlorotic spot virus (TCSV), Tomato mottle virus (ToMoV), Tomato spotted wilt virus (TSWV), Tomato yellow leaf curl virus (TYLCV), Potato virus Y (PVY), Groundnut bud necrosis virus (GBNV), with benefits in decreased incidence and severity up to 80 % and yield increase over 40 %. In Mexico, only Bacillus has been used. The use of PGPR is a strategy that could mitigate the impact of viral and viroid diseases and can be integrated into integrated management.

IMPACT OF PGPR ON THE SUSTAINABLE DEVELOPMENT OF AGRICULTURE: CURRENT AND FUTURE PROSPECTS

The quest for boosting agricultural yields due to increased stress on food production has inevitably brought about the indiscriminate use of chemical fertilizers and different agrochemicals. Biofertilizers facilitate the overall growth and yield of crops in an eco-friendly manner. They comprise residing or dormant microbes implemented in the soil or used for treating crop seeds. One of the most applicants in this respect is rhizobacteria. Plant growth-promoting rhizobacteria (PGPR) are an important group of beneficial, root-colonizing bacteria. They exhibit harmonious and divergent interactions with the soil microbiota and interact in an array of activities of ecological meaning. They encourage plant growth by facilitating biotic and abiotic stress tolerance and aid the nutrition of host plants. Due to their lively growth endorsing activities, PGPRs are considered an eco-friendly alternative to dangerous chemical fertilizers. Chemical fertilizers used in agriculture to improve yields and eradicate pathogens, however, negatively influence the ecosystem. The doubts over pesticide side effects, there is a growing interest in better thoughtfulhelpful interactions between plants and rhizosphere microbial populations. As a result, biological agents are in high demand around the world. The use of plant growth-promoting Rhizobacteria (PGPR). They have a crucial function in increasing soil fertility, promoting plant growth, and suppressing phytopathogens for the development of environmentally friendly sustainable agriculture.In this section, we try to devise a strategy for increasing crop output and health, developing sustainable agriculture, and commercialization through the use of plant growth-promoting rhizobacteria.

O14 Use of plant growth-promoting rhizobacteria in forage systems

O14 Use of plant growth-promoting rhizobacteria in forage systems

Growth Increase in the Herbaceous Plant Centella asiatica by the Plant Growth-Promoting Rhizobacteria Priestia megaterium HyangYak-01.

Centella asiatica is a traditional herbaceous plant with numerous beneficial effects, widely known for its medicinal and cosmetic applications. Maximizing its growth can lead to beneficial effects, by focusing on the use of its active compounds. The use of plant growth-promoting rhizobacteria (PGPR) is known to be an alternative to chemical fertilizers. In this study, we used the PGPR Priestia megaterium HY-01 to increase the yield of C. asiatica. In vitro assays showed that HY-01 exhibited plant growth-promoting activities (IAA production, denitrification, phosphate solubilization, and urease activity). Genomic analyses also showed that the strain has plant growth-promoting-related genes that corroborate with the different PGP activities found in the assays. This strain was subsequently used in field experiments to test its effectiveness on the growth of C. asiatica. After four months of application, leaf and root samples were collected to measure the plant growth rate. Moreover, we checked the rhizosphere microbiome between the treated and non-treated plots. Our results suggest that treatment with Hyang-yak-01 not only improved the growth of C. asiatica (leaf length, leaf weight, leaf width, root length, root width, and chlorophyll content) but also influenced the rhizosphere microbiome. Biodiversity was higher in the treated group, and the bacterial composition was also different from the control group.

Biological Management of Lentil (Lens culinaris Medik) Fusarium wilt by Using the Potential Pseudomonas Isolates

Lentil (Lens culinaris Medik) is also known as "massoor". A member of the Leguminaceae family is known for their high protein and nutrient content. Wilt incited by Fusarium oxysporum f.sp. lentis can result in significant yield losses upto 50% for lentil farmers. Chemical management through fungicides reduces crop losses significantly but has some environmental drawbacks and conflicts on the human health instead other methods of control such as the use of plant growth-promoting rhizobacteria (PGPR) as a bio-inoculant which gaining attention as a sustainable approach to manage plant diseases. PGPR are soil bacteria that live in the rhizosphere of plants and promote growth. The use of PGPR-based agents has increased in agriculture in recent years. In this study, isolation and evaluation of novel pseudomonad isolates were performed from various soil sources and exploited for controlling lentil wilt caused by F. oxysporum f.sp. lentis and assess their in-vitro ability to inhibit the pathogen.

Rhizospheric actinobacteria of Opuntia sp. “prickly pear” with deaminase activity as growth promoting in Solanum lycopersicum L. under salinity stress

The growing of Solanum lycopersicum L. "tomato" is affected by salinity, reducing its water consumption, and affecting negatively plant growth and development. Therefore, it is necessary to seek sustainable cultivation and fertilization options, such as the use of plant growth-promoting rhizobacteria. This research aimed to determine the potential of rhizospheric Actinobacteria isolated from Opuntia sp. "prickly pear" as tomato growth promoting under salinity. The genera of isolated Actinobacteria were identified, the synthesis of 1-aminocyclopropane-1-carboxylic acid deaminase (ACC) was characterized and its effect on the germination of tomato cultivar Río Grande seeds was evaluated. Two tests on non-saline and saline soils were carried out to compare the effect of Streptomyces spp. and Nocardia sp. in plant development in the greenhouse. Several Actinobacteria genera were isolated from 87.03% of samples, highlighting Streptomyces (46.67%) and Nocardia (34.0%). 9.33% of the Actinobacteria presented ACC deaminase activity, which increased seed germination, and the growth and yield of seedlings with increases of 88.98% (height); 96.30% (number of sheets); 201.35% (aerial biomass); 173.77% (root length); 100.0% (root weight); 150.0% (number of fruits) and 173.14% (weight of fruits), as well as 1.37 mg/g in the chlorophyll content in the saline soil. Also, Streptomyces sp. strain 21 decreased sodium content and increased potassium and K+/Na+ rate in the leaves and roots of the plants with the highest yield (1.068 kg/plant) in the saline soil. In conclusion, the positive effect of Actinobacteria as promoters of tomato growth and yield, increasing chlorophyll content, and decreasing salinity stress was demonstrated.

Microbacterium oxydans Regulates Physio-Hormonal and Molecular Attributes of Solanum lycopersicum under Drought Stress

Among the types of abiotic stresses, drought is one of the most serious growth limiting factors for crop plants. In recent years, various strategies have been employed to alleviate the adverse effects of drought stress in crops, but the use of plant growth-promoting rhizobacteria (PGPR) is among the standout techniques. Currently, we have isolated 55 strains of bacteria from the rhizosphere of Achyranthes aspera L. and Calotropis procera (Aiton). However, AGH3, AGH5, and AGH9 produced significant (p = 0.05) amounts of plant hormones and exhibited siderophore and phosphate solubilization activities. Bioassay experiments on Waito-C rice demonstrated an enhanced growth in the presence of the isolate AGH3. Moreover, the isolate AGH3 promoted the growth of Solynum lycopersicum L. under drought stress. The results revealed that AGH3-associated S. lycopersicum plants showed significantly (p = 0.05) reduced production of abscisic acid (ABA) and jasmonic acid (JA) as compared with the AGH3-free plants under polyethylene glycol (PEG) stress. In addition, high expressions of SlmiR 159 (from 6- to 10-fold), SlHsfA1a (from 1- to 4-fold), and SlHAKT1 (from 0.26- to 1-fold) genes were noticed in AGH3-associated S. lycopersicum plants under drought stress. From the results, it is concluded that rhizobacteria (AGH3) can be used as a pragmatic biofertilizer to ensure organic farming under normal as well as drought conditions.

Qualidade de hastes florais de lisianthus (Eustoma grandiflorum Raf.) inoculadas com Bacillus subtilis e Glomus intraradices

Abstract Lisianthus (Eustoma grandiflorum) is an ornamental species used as a potted plant or cut flower, its popularity is due to the diversity of colors, number of flower buds, and shelf life. Nevertheless, during the first phases of development, problems such as foliar chlorosis and root diseases affects most cultivars, causing poor growth, thin stems, and few flowers. The use of plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) improved plant growth as these microbes colonize the plant system root. Therefore, in order to provide better conditions for the stem development, the aim of this work was to evaluate the individual and combined effect of Bacillus subtilis (PGPR) and Glomus intraradices (AMF) on the growth and postharvest quality of the stems of lisianthus cv. Mariachi. Then commercial product Alubión-X (Bacillus subtilis (PGPR) and mycorrhizal fungus (Glomus intraradices) were used. The variables evaluated were stem height and diameter, foliar area, leaves number and in postharvest, buds number, open and diameter of flowers and stem dry weight. The results showed a significant effect of the inoculation of G. intraradices on the size (66.92 cm) of the stem, as well as the combination of B. subtilis + G. intraradices (65.51 cm) compared to the control (36.9 cm). The number of buds and open flowers of the stems treated with G. intraradices were 33.35 and 23.9 respectively significantly higher than the control. G. intraradices alone is the best option for applying to lisianthus, when compared to applying with B. Subtilis.

Plant Growth Promotion and Heat Stress Amelioration in Arabidopsis Inoculated with Paraburkholderia phytofirmans PsJN Rhizobacteria Quantified with the GrowScreen-Agar II Phenotyping Platform.

High temperatures inhibit plant growth. A proposed strategy for improving plant productivity under elevated temperatures is the use of plant growth-promoting rhizobacteria (PGPR). While the effects of PGPR on plant shoots have been extensively explored, roots-particularly their spatial and temporal dynamics-have been hard to study, due to their below-ground nature. Here, we characterized the time- and tissue-specific morphological changes in bacterized plants using a novel non-invasive high-resolution plant phenotyping and imaging platform-GrowScreen-Agar II. The platform uses custom-made agar plates, which allow air exchange to occur with the agar medium and enable the shoot to grow outside the compartment. The platform provides light protection to the roots, the exposure of it to the shoots, and the non-invasive phenotyping of both organs. Arabidopsis thaliana, co-cultivated with Paraburkholderia phytofirmans PsJN at elevated and ambient temperatures, showed increased lengths, growth rates, and numbers of roots. However, the magnitude and direction of the growth promotion varied depending on root type, timing, and temperature. The root length and distribution per depth and according to time was also influenced by bacterization and the temperature. The shoot biomass increased at the later stages under ambient temperature in the bacterized plants. The study offers insights into the timing of the tissue-specific, PsJN-induced morphological changes and should facilitate future molecular and biochemical studies on plant-microbe-environment interactions.

Plant Growth-Promoting Rhizobacteria : Biotechnological Tools to Improve Cereal Yields

Ensuring food security for the world’s growing population is a significant challenge for scientists. Efforts are constantly being made to solve this problem, including the use of expensive molecular engineering techniques, which are not always successful. A cost-effective and environmentally friendly biotechnological alternative would be the use of plant growthpromoting rhizobacteria, demonstrated by numerous studies to play many beneficial roles in improving plant traits, e.g. enhanced yields.

Effect of Plant Growth Promoting Rhizobacteria on the Growth and Yield of Foxtail Millet (Setaria italica L. Beauv)

The use of plant growth-promoting rhizobacteria (PGPR) is a sustainable way for efficient absorption and utilization of nutrients by crop species to enhance growth and yield and persistence against biotic and abiotic stresses. However, the use of PGPRs in drought tolerant crops such as foxtail millet is limited because of the low adaptability of PGPRs to the low moisture conditions. In this study, PGPRs acclimatised to low moisture conditions, were isolated from the rhizosphere of sorghum and their growth and yield promoting effect on foxtail millet was studied. Four isolates, Pseudomonas putida, Bacillus subtilis, Bacillus cereus, and Pantoea Stewart were isolated from the rhizosphere of sorghum cultivated on black soils. Further their identity was confirmed by sequencing 16S rDNA.
 Foxtail millet seeds were inoculated with the newly isolated PGPR strains and evaluated for their effect on shoot and root growth under greenhouse conditions. Effect of PGPRs on yield related traits such as ear-head weight, grain weight, fodder weight, and ear-head length were assessed under field conditions. Newly isolated PGPRs boosted average root and shoot length when seeds were inoculated with Bacillus cereus (19.33 cm) and Pseudomonas putida (28.66 cm), respectively. On the other hand, among the four bacterial cultures, Bacillus subtilis enhanced grain weight (40.42%), ear-head weight (30.19%), fodder weight (49.72%) and ear-head length (42.56%) compared to the control group under field conditions. When considered collectively, the empirical evidence suggests that PGPR can improve crop growth and yield under greenhouse and field conditions.

Growth and Photosynthetic Characteristics of Sesame Seedlings with Gibberellin-Producing Rhodobacter sphaeroides SIR03 and Biochar

The use of plant growth-promoting rhizobacteria (PGPR) with biochar is apprised to be a promising bio-fertilizer for improving the soil fertility and plant growth and development. The current study aimed to identify a potential plant growth-promoting rhizobacterium alongside biochar to improve sesame seedling productivity. Our results revealed that among the nine isolates, SIR01, SIR03, and SIR07 significantly improved the growth and biomass of sesame and Waito-C rice seedlings. The increase in growth of Waito-C rice seedlings through isolate SIR01, SIR03, and SIR07, suggests their ability to produce phytohormones such as GA4, GA9, GA24, and GA34. Furthermore, the application of isolate SIR03 and biochar together revealed a synergistic increase in sesame seedling growth and biomass (fresh and dry weight) compared with their individual applications. This may be explained by enhancement of photosynthetic rate, chlorophyll fluorescence, stomatal conductance, and transpiration rate by the combined SIR03 and biochar treatment. This suggests that co-inoculation with SIR03 alongside the application of biochar can be considered an eco-friendly, low-cost bio-fertilizer to potentially improve sesame seedling growth and development.

Inhibitory Effects of Phenazine Compounds and Volatile Organic Compounds Produced by Pseudomonas aurantiaca ST-TJ4 Against Phytophthora cinnamomi

Phytophthora cinnamomi is an important plant pathogen that is widely distributed worldwide and has caused serious ecological damage and significant economic losses in forests and plantations in many countries. The use of plant growth-promoting rhizobacteria is an effective and environmentally friendly strategy for controlling diseases caused by P. cinnamomi. In this study, we investigated the antagonistic mechanism of Pseudomonas aurantiaca ST-TJ4 against P. cinnamomi through different antagonistic approaches, observations of mycelial morphology, study of mycelial metabolism, and identification of antagonistic substances. The results showed that Pseudomonas aurantiaca ST-TJ4 was able to significantly inhibit mycelial growth, causing mycelial deformation and disrupting internal cell structures. Additionally, pathogen cell membranes were damaged by ST-TJ4, and mycelial cell content synthesis was disrupted. Ultraperformance liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry analyses showed that phenazine compounds and 2-undecanone were the main antagonistic components. The ammonia produced by the ST-TJ4 strain also contributed to the inhibition of the growth of P. cinnamomi. In conclusion, our results confirm that Pseudomonas aurantiaca ST-TJ4 can inhibit P. cinnamomi through multiple mechanisms and can be used as a biological control agent for various plant diseases caused by P. cinnamomi.

Effects of Volatile Organic Compounds Produced by Pseudomonas aurantiaca ST-TJ4 against Verticillium dahliae.

Verticillium dahliae is one of the most destructive fungal pathogens, causing substantial economic losses in agriculture and forestry. The use of plant growth-promoting rhizobacteria (PGPR) is an effective and environmentally friendly strategy for controlling diseases caused by V. dahliae. In this study, 90 mm in diameter Petri plates were used to test the effect of volatile organic compounds (VOCs) produced by different concentrations of Pseudomonas aurantiaca ST-TJ4 cells suspension on V. dahliae mycelia radial growth and biomass. The mycelial morphology was observed by using scanning electron microscopy. The conidia germination and microsclerotia formation of V. dahliae were evaluated. The VOCs with antifungal activity were collected by headspace solid-phase microextraction (SPME), and their components were analyzed by gas chromatography-mass spectrometry (GC-MS). The VOCs produced by strain ST-TJ4 significantly inhibited the growth of mycelium of V. dahliae. The morphology of the hyphae was rough and wrinkled when exposed to VOCs. The VOCs of strain ST-TJ4 have a significant inhibitory effect on V. dahliae conidia germination and microsclerotia formation. At the same time, the VOCs also reduce the expression of genes related to melanin synthesis in V. dahliae. In particular, the expression of the hydrophobin gene (VDAG-02273) was down-regulated the most, about 67-fold. The VOCs effectively alleviate the severity of cotton root disease. In the volatile profile of strain ST-TJ4, 2-undecanone and 1-nonanol assayed in the range 10–200 µL per plate revealed a significant inhibitory effect on V. dahliae mycelial radial growth. These compounds may be useful to devise new control strategies for control of Verticillium wilt disease caused by V. dahliae.

Advances in Biochar and PGPR engineering system for hydrocarbon degradation: A promising strategy for environmental remediation

In soil, polycyclic aromatic hydrocarbons (PAHs) have resulted in severe environmental deterioration, compromised soil characteristics, and negatively affect all life forms, including humans. Developing appropriate and effective clean-up technology is crucial in solving the contamination issues. The traditional methods to treat PHAs contaminated soil are less effective and not ecofriendly. Bioremediation, based on bioaugmentation and biostimulation approaches, is a promising strategy for remediating contaminated soil. The use of plant growth-promoting rhizobacteria (PGPR) as a bioaugmentation tool is an effective technique for treating hydrocarbon contaminated soil. Plant growth-promoting rhizobacteria (PGPR) are group of rhizospheric bacteria that colonize the roots of plants. Biochar is a carbon-rich residue, which acts as a source of nutrients, and is also a bio-stimulating candidate to enhance the activities of oil-degrading bacteria. The application of biochar as a nutrient source to bioremediate oil-contaminated soil is a promising approach for reducing PHA contamination. Biochar induces polyaromatic hydrocarbons (PAHs) immobilization and removes the contaminants by various methods such as ion exchange electrostatic attractions and volatilization. In comparison, PGPR produce multiple types of biosurfactants to enhance the adsorption of hydrocarbons and mineralize the hydrocarbons with the conversion to less toxic substances. During the last few decades, the use of PGPR and biochar in the bioremediation of hydrocarbons-contaminated soil has gained greater importance. Therefore, developing and applying a PGPR-biochar-based remediating system can help manage hazardous PAH contaminated soil. The goal of this review paper is to (i) provide an overview of the PGPR mechanism for degradation of hydrocarbons and (ii) discuss the contaminants absorbent by biochar and its characteristics (iii) critically discuss the combined effect of PGPR and biochar for degradation of hydrocarbons by decreasing their mobility and bioavailability. The present review focuses on techniques of bioaugmentation and biostimulation based on use of PGPR and biochar in remediating the oil-contaminated soil.