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

A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Agricultural Engineering".

Deadline for manuscript submissions: 30 September 2020.

Special Issue Editor

Dr. Naeem Khan
Website SciProfiles
Guest Editor
Department of Agronomy, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA
Interests: Plant-Microbe Interactions; Biofertilizer technology; Abiotic stresses; Plant breeding; Plant protection; Soil microbiology; Phytohormones; Phytoremediation and Metabolic responses of Plants to environmental stresses

Special Issue Information

Dear Colleagues,

Plant growth-promoting microorganisms (PGPMs) are groups of rhizosphere microorganisms capable of colonizing the root environment. Some of the microbes that inhabit this zone are bacteria and fungi that are capable of colonizing efficiently roots and rhizosphere soil. These microorganisms can be used as biofertilizers for improving agricultural production even under stressful environmental conditions. In contrast to PGPMs, plant growth regulators (PGRs) are chemical compounds that significantly affect the growth and differentiation of plant cells and tissues. They function as chemical messengers for intercellular communication and play a vital role in plant signaling networks as they are involved in the plant developmental process and a wide range of biotic and abiotic stress responses.

The application of PGPMs and plant growth regulators/hormones or the synthesis of PGRs and signal transduction, perception, and cross-talk create a complex network that plays an essential role in the regulation of plant physiological processes. A better understanding of the mechanism of action of PGPMs and PGRs and their roles in plant growth and development, interaction and independence in their action, and hormonal cross-talk under stresses is essential for agricultural production and research. Therefore, this Special Issue aims to collect research papers and reviews that promote this aspect of plant growth-promoting microorganisms and plant growth regulators.

Dr. Naeem Khan
Guest Editor

Manuscript Submission Information

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Keywords

  • Plant growth-promoting microorganisms
  • Plant growth regulators
  • Crop plants
  • Cross-talk
  • Signaling network
  • Stress environments

Published Papers (10 papers)

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Research

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Open AccessArticle
Co-Inoculation of Rhizobacteria and Biochar Application Improves Growth and Nutrientsin Soybean and Enriches Soil Nutrients and Enzymes
Agronomy 2020, 10(8), 1142; https://doi.org/10.3390/agronomy10081142 - 06 Aug 2020
Abstract
Gradual depletion in soil nutrients has affected soil fertility, soil nutrients, and the activities of soil enzymes. The applications of multifarious rhizobacteria can help to overcome these issues, however, the effect of co-inoculation of plant-growth promoting rhizobacteria (PGPR) and biochar on growth andnutrient [...] Read more.
Gradual depletion in soil nutrients has affected soil fertility, soil nutrients, and the activities of soil enzymes. The applications of multifarious rhizobacteria can help to overcome these issues, however, the effect of co-inoculation of plant-growth promoting rhizobacteria (PGPR) and biochar on growth andnutrient levelsin soybean and on the level of soil nutrients and enzymes needs in-depth study. The present study aimed to evaluate the effect of co-inoculation of multifarious Bradyrhizobium japonicum USDA 110 and Pseudomonas putida TSAU1 and different levels (1 and 3%) of biochar on growth parameters and nutrient levelsin soybean and on the level of soil nutrients and enzymes. Effect of co-inoculation of rhizobacteria and biochar (1 and 3%) on the plant growth parameters and soil biochemicals were studied in pot assay experiments under greenhouse conditions. Both produced good amounts of indole-acetic acid; (22 and 16 µg mL−1), siderophores (79 and 87%SU), and phosphate solubilization (0.89 and 1.02 99 g mL−1). Co-inoculation of B. japonicum with P. putida and 3% biochar significantly improved the growth and nutrient content ofsoybean and the level of nutrients and enzymes in the soil, thus making the soil more fertile to support crop yield. The results of this research provide the basis of sustainable and chemical-free farming for improved yields and nutrients in soybean and improvement in soil biochemical properties. Full article
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Open AccessArticle
Volatile Organic Compounds from Rhizobacteria Increase the Biosynthesis of Secondary Metabolites and Improve the Antioxidant Status in Mentha piperita L. Grown under Salt Stress
Agronomy 2020, 10(8), 1094; https://doi.org/10.3390/agronomy10081094 - 29 Jul 2020
Abstract
Salinity is a major abiotic stress factor that affects crops and has an adverse effect on plant growth. In recent years, there has been increasing evidence that microbial volatile organic compounds (mVOC) play a significant role in microorganism–plant interactions. In the present study, [...] Read more.
Salinity is a major abiotic stress factor that affects crops and has an adverse effect on plant growth. In recent years, there has been increasing evidence that microbial volatile organic compounds (mVOC) play a significant role in microorganism–plant interactions. In the present study, we evaluated the impact of microbial volatile organic compounds (mVOC) emitted by Bacillus amyloliquefaciens GB03 on the biosynthesis of secondary metabolites and the antioxidant status in Mentha piperita L. grown under 0, 75 and 100 mM NaCl. Seedlings were exposed to mVOCs, avoiding physical contact with the bacteria, and an increase in NaCl levels produced a reduction in essential oil (EO) yield. Nevertheless, these undesirable effects were mitigated in seedlings treated with mVOCs, resulting in an approximately a six-fold increase with respect to plants not exposed to mVOCs, regardless of the severity of the salt stress. The main components of the EOs, menthone, menthol, and pulegone, showed the same tendency. Total phenolic compound (TPC) levels increased in salt-stressed plants but were higher in those exposed to mVOCs than in stressed plants without mVOC exposure. To evaluate the effect of mVOCs on the antioxidant status from salt-stressed plants, the membrane lipid peroxidation was analyzed. Peppermint seedlings cultivated under salt stress and treated with mVOC showed a reduction in malondialdehyde (MDA) levels, which is considered to be an indicator of lipid peroxidation and membrane damage, and had an increased antioxidant capacity in terms of DPPH (2,2-diphenyl−1-picrylhydrazyl) radical scavenging activity in relation to plants cultivated under salt stress but not treated with mVOCs. These results are important as they demonstrate the potential of mVOCs to diminish the adverse effects of salt stress. Full article
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Open AccessArticle
Evaluating Biochar-Microbe Synergies for Improved Growth, Yield of Maize, and Post-Harvest Soil Characteristics in a Semi-Arid Climate
Agronomy 2020, 10(7), 1055; https://doi.org/10.3390/agronomy10071055 - 21 Jul 2020
Abstract
Arid and semi-arid regions are characterized by high temperature and low rainfall, leading to degraded agricultural soils of alkaline calcareous nature with low organic matter contents. Less availability of indigenous nutrients and efficacy of applied fertilizers are the major issues of crop production [...] Read more.
Arid and semi-arid regions are characterized by high temperature and low rainfall, leading to degraded agricultural soils of alkaline calcareous nature with low organic matter contents. Less availability of indigenous nutrients and efficacy of applied fertilizers are the major issues of crop production in these soils. Biochar application, in combination with plant growth promoting rhizobacteria with the ability to solubilize nutrients, can be an effective strategy for improving soil health and nutrient availability to crops under these conditions. Experiments were planned to evaluate the impact of biochar obtained from different sources in combination with acid-producing, nutrient-solubilizing Bacillus sp. ZM20 on soil biological properties and growth of maize (Zea mays L.) crops under natural conditions. Various biochar treatments, viz. wheat (Triticum aestivum L.) straw biochar, Egyptian acacia (Vachellia nilotica L.) biochar, and farm-yard manure biochar with and without Bacillus sp. ZM20, were used along with control. Soil used for pot and field trials was sandy loam in texture with poor water holding capacity and deficient in nutrients. Results of the pot trial showed that fresh and dry biomass, 1000 grain weight, and grain yield was significantly improved by application of biochar of different sources with and without Bacillus sp. ZM20. Application of biochar along with Bacillus sp. ZM20 also improved soil biological properties, i.e., soil organic matter, microbial biomass carbon, ammonium, and nitrate nitrogen. It was also observed that a combined application of biochar with Bacillus sp. ZM20 was more effective than a separate application of biochar. The results of wheat straw biochar along with Bacillus sp. ZM20 were better as compared to farm-yard manure biochar and Egyptian acacia biochar. Maximum increase (25.77%) in grain yield was observed in the treatment where wheat straw biochar (0.2%) was applied in combination with Bacillus sp. ZM20. In conclusion, combined application of wheat straw biochar (0.2%) inoculated with Bacillus sp. ZM20 was the most effective treatment in improving the biological soil properties, plant growth, yield, and quality of maize crop as compared to all other treatments. Full article
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Open AccessArticle
Role of Trichoderma aggressivum f. europaeum as Plant-Growth Promoter in Horticulture
Agronomy 2020, 10(7), 1004; https://doi.org/10.3390/agronomy10071004 - 13 Jul 2020
Abstract
The main objective of this study was to determine the capacity of Trichoderma aggressivum f. europaeum to promote pepper and tomato seedling growth compared to that of T. saturnisporum, a species recently characterised as a biostimulant. Consequently, in vitro seed germination and [...] Read more.
The main objective of this study was to determine the capacity of Trichoderma aggressivum f. europaeum to promote pepper and tomato seedling growth compared to that of T. saturnisporum, a species recently characterised as a biostimulant. Consequently, in vitro seed germination and seedling growth tests were performed under commercial plant nursery conditions. Additionally, the effects of different doses and a mixture of both species on seedling growth under plant nursery and subsequently under greenhouse conditions were determined. Furthermore, mass production of spores was determined in different substrates, and their siderophore and indole acetic acid production and phosphate (P) solubilisation capacity were also determined. Direct application of Trichoderma aggressivum f. europaeum to seeds in vitro neither increases the percentage of pepper and tomato seed germination nor improves their vigour index. However, substrate irrigation using different doses under commercial plant nursery conditions increases the quality of tomato and pepper seedlings. Tomato roots increased by 66.66% at doses of 106 spores per plant. Applying T. aggressivum f. europaeum or T. saturnisporum under plant nursery conditions added value to seedlings because their growth-promoting effect is maintained under greenhouse conditions up to three months after transplantation. The combined application of the two species had no beneficial effect in relation to that of the control. The present study demonstrates the biostimulant capacity of T. aggressivum f. europaeum in pepper and tomato plants under commercial plant nursery and greenhouse conditions. Full article
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Open AccessArticle
Rhizobacteria Isolated from Saline Soil Induce Systemic Tolerance in Wheat (Triticum aestivum L.) against Salinity Stress
Agronomy 2020, 10(7), 989; https://doi.org/10.3390/agronomy10070989 - 10 Jul 2020
Abstract
Halo-tolerant plant growth-promoting rhizobacteria (PGPR) have the inherent potential to cope up with salinity. Thus, they can be used as an effective strategy in enhancing the productivity of saline agro-systems. In this study, a total of 50 isolates were screened from the rhizospheric [...] Read more.
Halo-tolerant plant growth-promoting rhizobacteria (PGPR) have the inherent potential to cope up with salinity. Thus, they can be used as an effective strategy in enhancing the productivity of saline agro-systems. In this study, a total of 50 isolates were screened from the rhizospheric soil of plants growing in the salt range of Pakistan. Out of these, four isolates were selected based on their salinity tolerance and plant growth promotion characters. These isolates (SR1. SR2, SR3, and SR4) were identified as Bacillus sp. (KF719179), Azospirillum brasilense (KJ194586), Azospirillum lipoferum (KJ434039), and Pseudomonas stutzeri (KJ685889) by 16S rDNA gene sequence analysis. In vitro, these strains, in alone and in a consortium, showed better production of compatible solute and phytohormones, including indole acetic acid (IAA), gibberellic acid (GA), cytokinin (CK), and abscisic acid (ABA), in culture conditions under salt stress. When tested for inoculation, the consortium of all four strains showed the best results in terms of improved plant biomass and relative water content. Consortium-inoculated wheat plants showed tolerance by reduced electrolyte leakage and increased production of chlorophyll a, b, and total chlorophyll, and osmolytes, including soluble sugar, proline, amino acids, and antioxidant enzymes (superoxide dismutase, catalase, peroxidase), upon exposure to salinity stress (150 mM NaCl). In conclusion, plant growth-promoting bacteria, isolated from salt-affected regions, have strong potential to mitigate the deleterious effects of salt stress in wheat crop, when inoculated. Therefore, this consortium can be used as potent inoculants for wheat crop under prevailing stress conditions. Full article
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Open AccessArticle
Agricultural Utilization of Unused Resources: Liquid Food Waste Material as a New Source of Plant Growth-Promoting Microbes
Agronomy 2020, 10(7), 954; https://doi.org/10.3390/agronomy10070954 - 02 Jul 2020
Abstract
Organic amendment is important for promoting soil quality through increasing soil fertility and soil microbes. This study evaluated the effectiveness of using liquid food waste material (LFM) as a microbial resource, by analyzing the microbial community composition in LFM, and by isolating plant [...] Read more.
Organic amendment is important for promoting soil quality through increasing soil fertility and soil microbes. This study evaluated the effectiveness of using liquid food waste material (LFM) as a microbial resource, by analyzing the microbial community composition in LFM, and by isolating plant growth-promoting bacteria (PGPB) from the material. High-throughput sequencing of LFM, collected every month from May to September 2018, resulted in the detection of >1000 bacterial operational taxonomic units (OTUs) in the LFM. The results showed that Firmicutes was abundant and most frequently detected, followed by Proteobacteria and Actinobacteria. Of the culturable strains isolated from LFM, almost all belonged to the genus Bacillus. Four strains of PGPB were selected from the isolated strains, with traits such as indole acetic acid production and 1-aminocyclopropane-1-carboxylic acid deaminase activity. Lettuce growth was improved via LFM amendment with PGPB, and Brassica rapa showed significant differences in root biomass when LFM amendment was compared with the use chemical fertilizer. Field experiments using LFM showed slight differences in growth for Brassica rapa, lettuce and eggplant, when compared with the use of chemical fertilizer. LFM is a useful microbial resource for the isolation of PGPB, and its use as fertilizer could result in reduced chemical fertilizer usage in sustainable agriculture. Full article
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Open AccessArticle
Identification and Quantification of Plant Growth Regulators and Antioxidant Compounds in Aqueous Extracts of Padina durvillaei and Ulva lactuca
Agronomy 2020, 10(6), 866; https://doi.org/10.3390/agronomy10060866 - 18 Jun 2020
Abstract
Aqueous seaweed extracts have diverse compounds such as Plant-Growth Regulators (PGRs) which have been utilized in agricultural practices for increasing crop productivity. Algal biomass of Padina durvillaei and Ulva lactuca have been suggested for use as biofertilizers because of plant growth-enhancing properties. This [...] Read more.
Aqueous seaweed extracts have diverse compounds such as Plant-Growth Regulators (PGRs) which have been utilized in agricultural practices for increasing crop productivity. Algal biomass of Padina durvillaei and Ulva lactuca have been suggested for use as biofertilizers because of plant growth-enhancing properties. This work aimed to identify the main PGRs and antioxidant properties in P. durvillaei and U. lactuca extracts, such as abscisic acid, auxins, cytokinins, gibberellins, jasmonates, and salicylates, to assess their potential use as biofertilizers that improve plant growth and crop yield. Phytochemical analyses of two seaweed extracts showed a significantly higher content of sulfates, flavonoids, and phenolic compounds in P. durvillaei extract, which could be linked to its higher antioxidant activity (DPPH, ABTS, and FRAP) compared to U. lactuca extract. The identification and quantification of PGRs showed two gibberellins (GA1 and GA4), abscisic acid (ABA), indoleacetic acid (IAA), three cytokinins (tZ, IP, and DHZ), jasmonic acid (JA), and salicylic acid (SA) in two seaweed extracts. However, GA4, tZ, and DHZ contents were significantly higher in P. durvillaei compared to U. lactuca extracts. These findings evidence that P. durvillaei and U. lactuca extracts are suitable candidates for use as biofertilizers. Full article
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Open AccessArticle
PGPR Modulation of Secondary Metabolites in Tomato Infested with Spodoptera litura
Agronomy 2020, 10(6), 778; https://doi.org/10.3390/agronomy10060778 - 30 May 2020
Cited by 2
Abstract
The preceding climate change demonstrates overwintering of pathogens that lead to increased incidence of insects and pest attack. Integration of ecological and physiological/molecular approaches are imperative to encounter pathogen attack in order to enhance crop yield. The present study aimed to evaluate the [...] Read more.
The preceding climate change demonstrates overwintering of pathogens that lead to increased incidence of insects and pest attack. Integration of ecological and physiological/molecular approaches are imperative to encounter pathogen attack in order to enhance crop yield. The present study aimed to evaluate the effects of two plant growth promoting rhizobacteria (Bacillus endophyticus and Pseudomonas aeruginosa) on the plant physiology and production of the secondary metabolites in tomato plants infested with Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). The surface sterilized seeds of tomato were inoculated with plant growth promoting rhizobacteria (PGPR) for 3–4 h prior to sowing. Tomato leaves at 6 to 7 branching stage were infested with S. litura at the larval stage of 2nd instar. Identification of secondary metabolites and phytohormones were made from tomato leaves using thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC) and fourier-transform infrared spectroscopy (FTIR). Infestation with S. litura significantly decreased plant growth and yield. The PGPR inoculations alleviated the adverse effects of insect infestation on plant growth and fruit yield. An increased level of protein, proline and sugar contents and enhanced activity of superoxide dismutase (SOD) was noticed in infected tomato plants associated with PGPR. Moreover, p-kaempferol, rutin, caffeic acid, p-coumaric acid and flavonoid glycoside were also detected in PGPR inoculated infested plants. The FTIR spectra of the infected leaf samples pre-treated with PGPR revealed the presence of aldehyde. Additionally, significant amounts of indole-3-acetic acid (IAA), salicylic acid (SA) and abscisic acid (ABA) were detected in the leaf samples. From the present results, we conclude that PGPR can promote growth and yield of tomatoes under attack and help the host plant to combat infestation via modulation in IAA, SA, ABA and other secondary metabolites. Full article
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Open AccessArticle
Paecilomyces variotii as A Plant-Growth Promoter in Horticulture
Agronomy 2020, 10(4), 597; https://doi.org/10.3390/agronomy10040597 - 22 Apr 2020
Cited by 1
Abstract
In the present study, P. variotii, an endophytic fungus isolated from plant roots from the Cabo de Gata Natural Park (Parque Nacional Cabo de Gata—Spain), was tested to determine the effect on the growth promotion of tomato and pepper seeds and seedlings. [...] Read more.
In the present study, P. variotii, an endophytic fungus isolated from plant roots from the Cabo de Gata Natural Park (Parque Nacional Cabo de Gata—Spain), was tested to determine the effect on the growth promotion of tomato and pepper seeds and seedlings. For these purposes, germination trials in a laboratory and two experiments in a commercial nursery and greenhouse conditions were performed. The P. variotii isolate has shown a high ability to produce siderophores and IAA, but low ability to solubilize P. High values for germination percentage, seedling vigor, root and shoot length were obtained by P. variotii on tomato and pepper against control. P. variotii applications resulted in improved most of the growth parameters evaluated, for both horticultural crops, with the best results in the development of pepper seedlings. The application of a higher dose of P. variotii improved most of the morphological parameters and the Dickson quality index (DQI) value in tomato in seedlings and plants. The establishment of the endophytic fungus at the root enabled its biostimulant effects to persist after transplantation without any additional application. Few studies have analyzed this species as a biostimulant. The positive results from the tests showed its high potential. The application of this isolate can be of enormous benefit to horticultural crops for its high reproductive and establishment capacity. Full article
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Review

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Open AccessReview
Insights into the Physiological and Biochemical Impacts of Salt Stress on Plant Growth and Development
Agronomy 2020, 10(7), 938; https://doi.org/10.3390/agronomy10070938 - 30 Jun 2020
Abstract
Climate change is causing soil salinization, resulting in crop losses throughout the world. The ability of plants to tolerate salt stress is determined by multiple biochemical and molecular pathways. Here we discuss physiological, biochemical, and cellular modulations in plants in response to salt [...] Read more.
Climate change is causing soil salinization, resulting in crop losses throughout the world. The ability of plants to tolerate salt stress is determined by multiple biochemical and molecular pathways. Here we discuss physiological, biochemical, and cellular modulations in plants in response to salt stress. Knowledge of these modulations can assist in assessing salt tolerance potential and the mechanisms underlying salinity tolerance in plants. Salinity-induced cellular damage is highly correlated with generation of reactive oxygen species, ionic imbalance, osmotic damage, and reduced relative water content. Accelerated antioxidant activities and osmotic adjustment by the formation of organic and inorganic osmolytes are significant and effective salinity tolerance mechanisms for crop plants. In addition, polyamines improve salt tolerance by regulating various physiological mechanisms, including rhizogenesis, somatic embryogenesis, maintenance of cell pH, and ionic homeostasis. This research project focuses on three strategies to augment salinity tolerance capacity in agricultural crops: salinity-induced alterations in signaling pathways; signaling of phytohormones, ion channels, and biosensors; and expression of ion transporter genes in crop plants (especially in comparison to halophytes). Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: PGPR Mediated Control of Spodoptera litura Infestation in Tomato (Solanum lycopersicumL.) through Modulation of Secondary Metabolites
Authors: Asghari Bano; Bani Kousar; Naeem Khan
Affiliation: University of Wah
Abstract: Present investigation was aimed to evaluate the effects of two PGPR (Bacillus endophyticus and Pseudomonas aeruginosa) on the growth and yield of tomato and b) the production of secondary metabolites in tomato plants infested with Spodoptera litura. The surface sterilized seeds of tomato were inoculated with PGPR for 3-4 h. Tomato leaves were infested with Spodoptera litura at larval stage of 2nd instar. Identification of secondary metabolites were made from tomato leaves using TLC and analyses for phytohormones were made using HPLC. FTIR analyses were performed for the TLC eluted leaves extract. Infestation with Spodoptera litura significantly decreased plant growth and yield. The PGPR inoculations alleviated the adverse effects of insect infestation on plant growth and tomato fruit yield. The PGPR effect was mediated by increase in protein,proline and sugar contents and enhanced activity of SOD. p-kaempferol, rutin and salicylic acid were detected in addition to the caffeic and p-coumaric acid in PGPR treated plants receiving infestation. The FTIR analyses of the leaf extracts from infested plants demonstrated the lack of aldehyde peak detected in infested plants pre-treated with PGPR The infested plant leaves lack IAA and produced very little amount of Salicylic acid and ABA as compared to PGPR inoculated plants . PGPR can be implicated to promote growth and yield of tomato both under control as well as infested conditions via modulation in IAA and GA and increased production of SA, ABA and secondary metabolites.

Title: Evaluation of Impact of Bioengineered Copper Quantum dots in Chickpea: A Case Study on growth, Morphology and Antioxidant Response
Authors: Humaira Rani; Akhilesh Kumar Singh; Iram Wahid; Rahul Gupta; Saurabh Singh Rathore; M. Iqbal R Khan
Affiliation: Plant Systems Biology Laboratory Department of Botany School of Chemical and Life Science Jamia Hamdard New Delhi 110062, India
Abstract: Present the study highlights the impact of Dark Stress Environment of Cicer arietinum Linn. (Chickpea) seed after treatment of Bioengineered copper quantum dots (Cu-QDs) performances in terms of antioxidant defense and Enzymatic activity This study has a significance of nanotechnology in contributing to the field of scientific research and enhancing the scientific libraries of effective agricultural techniques. We treated Chickpea seed with control (untreated) and with different concentration of Bioengineered Cu-QDs to examine the biochemical and physiological changes. Results indicate that Bioengineered Cu-QDs significantly enhance the root length and shoot length, and the antioxidant ability of plants depending upon the concentrations of Cu-QDs. Lower concentrations of Cu-QDs significantly increased the plant length and antioxidant activity Whereas the increase in Cu-QDs concentration adversely affects plant growth and its antioxidant profile. The activity % of inhibition of DPPH, Malondialdehyde (MDA) and Catalase (CAT) content reduced the Superoxide dismutase (SOD), Glutathione reductase (GR), Peroxidase (POD), Glutathione (GSH), Ascorbate Peroxidase (APX), activity as compared with control under dark stress conditions. These parameters were negatively affected by the high concentration of Cu-QDs. As per the results of this study, we conclude that Cu-QDs can be used to boost chickpea seed efficiency for crop production.

Title: PGPR Modulation of Secondary Metabolites in tomato infested with Spodoptera litura
Authors: Bani Kousar; Asghari Bano; Naeem Khan
Affiliation: Department of Biosciences, University of Wah
Abstract: The preceding climate change demonstrates overwintering of pathogens leading to increased incidence of insects and pest attack. Integration of ecological and physiological/molecular approaches are imperative to encounter pathogen attack in order to enhance crop yield. Present study was aimed to evaluate the effects of two PGPR (Bacillus endophyticus and Pseudomonas aeruginosa) isolated from rhizosphere of maize grown in arid and semiarid regions on the physiology of tomato plants and the production of secondary metabolites in tomato plants infested with Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). The surface sterilized seeds of tomato were inoculated with PGPR for 3-4 h prior to sowing. Tomato leaves were infested with S. litura at the larval stage of 2nd instar. Identification of secondary metabolites and phytohormones were made from tomato leaves using TLC and HPLC and FTIR. Infestation with S. litura significantly decreased plant growth and yield. The PGPR inoculations alleviated the adverse effects of insect infestation on plant growth and fruit yield. The PGPR effect was mediated by increase in protein, proline and sugar contents and enhanced activity of superoxide dismutase (SOD). Plant metabolites; p-kaempferol, rutin and flavonoid glycoside were detected in addition to the caffeic and p-coumaric acid in infested plants treated with PGPR. The FTIR of the leaves extracted from infested plants pretreated with PGPR revealed the presence of additional peaks of aldehyde. The infested leaves of plants pretreated with PGPR produced significant amounts of indole-3-acetic acid (IAA), salicylic acid (SA) and abscisic acid (ABA) over that of infested plants. PGPR can be implicated to promote growth and yield of tomatoes and can combat infestation via modulation in IAA, SA, ABA and other secondary metabolites.

Title: Growth regulators in agricultural: Innovation for sustainable plant nutrition
Authors: El Chami Daniel; Galli Fabio
Affiliation: Timac Agro Italia S.p.A., S.P.13 – Località Ca' Nova I-26010 – Ripalta Arpina (CR), Italy.
Abstract: Agricultural Production today has to deal with different challenges. It has to increment production for a continuously increasing population, reducing the environmental burdens on the natural systems. In conventional agriculture, this is possible through the increase of inputs, especially nutrients, which, however, are responsible for the biggest part of emissions. It becomes more complicated though, adopting sustainable agricultural practices, to improve the quality and the quantity of agricultural production reducing the inputs use. Plant growth regulators are described in the literature for the significant role in securing crop management of modern agriculture. Therefore, this joint field experiment has been carried out on a pear orchard (Pyrus communis L. cv. Abate Fètel) in Emilia Romagna (Italy) by Fondazione Navarra and TIMAC AGRO Italia S.p.A., to test the “less for more” theory which consists in getting more and better agricultural produce using fewer inputs. Preliminary results of two consecutive years have confirmed our assumption as it was possible to substantially reduce the total fertilization units applied, improving significantly quantitative and qualitative production indicators (i.e. the yield (t/ha), the average yield by tree (kg), the average weight of fruits (g)).

Title: Insights into the Physiological and Biochemical Impacts of Salt Stress on Plant Growth and Development
Authors: Muhammad Adnan Shahid; Ali Sarkhosh; Naeem Khan; Rashad Mukhtar Balal; Shahid Ali; Lorenzo Rossi; Celina Gómez; Neil S. Mattson; Francisco García-Sánchez
Affiliation: Department of Agriculture, Nutrition and Food Systems, University of New Hampshire, Durham, NH, 03824, USA
Abstract: Plants exposed to salt stress undergo changes in their physiology and metabolism. Environmental stress physiology is a major area of scientific concern because of its constraints to normal growth of plant, as well as, crop productivity. Among the various abiotic stresses salinity and drought stress are the most destructive to crop plants. The ability of plants to tolerate salt is determined by multiple biochemical pathways that facilitate retention and water acquisition, protect chloroplast functions and maintain ion homeostasis. Climate change is considered one of the major contributors to increment in saline soil conditions, leading to degradation and desertification. Poor quality irrigation water is another important factor contributing to land salinization thus limiting agricultural production. Halophytes regulate their biochemical and physiological processes through ionic compartmentalization, production of osmolytes and compatible solutes, enzymatic changes and absorption of selective ions. Cell membrane stability (CMS) technique is widely utilized to judge the behavior of various plant genotypes in response to salt stress. Thus, it can distinctly contribute in assessing the salt tolerance of plant genotypes. CMS is also reported to correlate with potassium ions, osmotic potential, osmotic adjustment, and relative water contents. Saline conditions induced smaller sized nodules, reduced nodule volume per plant, less nodulation, and inferior plant growth. The osmotic adjustment has appeared to be a significant and effective salinity resistant mechanism in crop plants. It can be exploited efficiently in selection and breeding programs to induce salinity tolerance in different plant species. Polyamines are reported to execute their involvement in various physiological mechanisms including rhizogenesis, somatic embryogenesis, maintenance of cell pH and ionic balance, pollen and flower formation, abscission, senescence and dormancy.

Title: Harnessing Recent Approaches In Pre-Storage Application Of Novel Phytohormones For Quality Fruit Production: A Review
Authors: Nirmal Kumar Meena; Ram Asrey
Affiliation: Department of Fruit Science, College of Horticulture and Forestry, Jhalawar Agriculture University, Kota (Rajasthan)-326023, India; ICAR-Indian Agricultural Research Institute, New Delhi-110012, India
Abstract: World’s population is increasing tremendously. Rising temperature, atmospheric CO2 and improper uses of resources negatively hampered the quality fruit production. Despite, production has increased in last few years but quality remains inattentive. Improper postharvest handling especially in developing countries varies from 5 to 35 per cent. There is lack of sound post harvest management system in supply chain management. Abiotic and biotic stress also affects crop quality in cumulative mode. In changing scenario, people are more concerning about quality. In plants regulatory processes are synchronized by an array of phytohormones which differentially regulate physiological and cellular processes in an integrated manner. Novel phytohormones are ecofriendly approaches which regulate physiological and metabolic processes in fruits. Since past couple of years, novel hormones like Brassinosteroids, Salicylic acid, Methyl jasmonate, Polyamines and oxalic acid got attention of researchers. Pre-storage application of these hormones extends shelf life and maintains firmness, colour, flavour and organoleptic properties in various fruit crops. Moreover, these hormone based signalling pathway in fresh fruits are well understood but mechanism remains unclear. Therefore, alteration in fruit physiology by potential novel phytohormones may provide potentiality of enhancing yield and quality by changing metabolism and tolerance against abiotic stresses. This review emphasizes a comprehensive investigation about pre-storage application of these novel hormones and their possible mechanism.

Title: Volatile organic compounds from rhizobacteria increase the biosynthesis of secondary metabolites and improve the antioxidant status in Mentha piperita L. grown under salt stress
Authors: Lorena del Rosario Cappellari; Julieta Chiappero; Tamara Belén Palermo; Walter Giordano; Erika Banchio
Affiliation: INBIAS Instituto de Biotecnología Ambiental y Salud (CONICET- Universidad Nacional de Río Cuarto), Campus Universitario, 5800 Río Cuarto, Argentina.
Abstract: Salinity is a major abiotic stress factor that limits crop production due to ionic, osmotic and oxidative stresses, and has a negative impact on plant growth. Bacteria interact with plants in many different ways. In recent years, there is an increasing evidence that microbial volatile organic compounds (mVOC) play an important role in the microorganism-plant interaction. In the present study, we evaluated the impact of microbial volatile organic compounds (mVOC) emitted by Bacillus amyloliquefaciens GB03 on the biosynthesis of secondary metabolites and the antioxidant status in Mentha piperita L. grown under different levels of NaCl stress (0, 75, 100 mM NaCl). Plants were exposed to mVOCs without having any physical contact with the rhizobacteria. An increase in the level of salt stress produced a reduction in essential oil (EO) yield. However, these negative effects were mitigated in plants exposed to mVOCs, resulting in an approximately 6-fold increase respect to plants not exposed to mVOCs, regardless of the severity of the salt stress. The main components of EOs, menthone, menthol and pulegone, showed the same tendency. TPC levels increased in salt-stressed plants but were higher in those exposed to mVOCs than in stressed plants without mVOC exposure. To evaluate the effect of mVOCs on the antioxidant status, the membrane lipid peroxidation was analyzed to determine the effect of mVOCs on salt- stressed plants. Peppermint plants grown under salt stress and exposed to mVOC showed a better performance and had reduced levels of malondialdehyde (MDA), which is considered to be an indicator of lipid peroxidation and membrane damage, and had an increased antioxidant capacity in terms of DPPH radical scavenging activity compared to controls (plants grown under salt stress, but not exposed to VOCs). These results are important as they illustrate the potential of mVOCs to mitigate the adverse consequences of salt stress.

Title: Rhizobacteria isolated from saline soil induce systemic tolerance in wheat (Triticum aestivum L.) against salinity stress
Authors: Noshin Ilyas; Roomina Mazhar; Humaira Yasmin; Wajiha Khan; Sumera Iqbal
Affiliation: Department of Botany, PMAS-Arid Agriculture University, Rawalpindi, Pakistan.
Abstract: Halotolerant Plant Growth Promoting Rhizobacteria (PGPR) have inherent potential to cope up with salinity. Thus, they can be used an effective strategy in enhancing the productivity of saline agro-systems. In this study, a total of 50 isolates were screened from the rhizospheric soil of plants growing in salt range of Pakistan. Out of these, four isolates were selected based upon the basis of salinity tolerance and plant growth promotion characters. These isolates (SR1. SR2, SR3, and SR4) were identified as Bacillus sp. (KF719179), Azospirillum brasilense (KJ194586), Azospirillum lipoferum (KJ434039) and Pseudomonas stutzeri (KJ685889) by 16S rDNA gene sequence analysis. In vitro, these strains, in alone and in consortium, showed better production of compatible solute (12.1 μg mg-1 proline and 222 μg mg-1 sugar), phytohormones including IAA (2.1 μg ml−1), gibberellic acid (7.5 μg ml−1), cytokinin (3.4 μg ml−1) and abscisic Acid (0.64 μg ml−1) in cultures conditions under salt stress. When tested for inoculation, consortium of all four strains showed the best results in terms of improved plant biomass and relative water content (21.05%). Consortium inoculated wheat plants showed tolerance by reduced electrolyte leakage (19%) and increased production of chlorophyll a, b and total chlorophyll (13.23%, 12.49% and 12 9%,) osmolytes including soluble sugar (28.57%), proline (46.6%), amino acids (19.29%), antioxidant enzymes (superoxide dismutase by 21.33%, catalase by 16%, peroxidase by 34.4%) upon exposure to salinity stress (150 mM NaCl). In conclusion, plant growth promoting bacteria, isolated from salt affected region have strong potential to mitigate the deleterious effects of salt stress in wheat crop, when inoculated. Therefore, this consortium can be used as potent inoculants for wheat crop under prevailing stress conditions.

Title: Chlorophyll fluorescence parameters and antioxidant defense system can display salt tolerance of salt acclimated sweet pepper plants with chitosan and Plant Growth Promoting Rhizobacteria
Authors: Muneera ALKahtani; Kotb Attia; Yaser Hafez; Naeem Khan; Ahmed Eid; Mohamed Ali; Khaled Abdelaal
Affiliation: Excellence Center (EPCRS), Plant Pathology and Biotechnology Lab., Faculty of Agriculture, Kafrelsheikh University, Egypt
Abstract: Salinity stress deleteriously affects the growth and yield of many plants. So, two pot experiments were conducted during two seasons 2019 and 2020 to evaluate the role of plant growth promoting rhizobacteria (Bacillus thuringiensis MH161336 106–8 CFU mL-1) as seed treatment and foliar application of chitosan 30 mg L-1 on sweet pepper plants cv. Yolo Wonder under two salinity concentrations (2000 and 4000 ppm). Our findings revealed that, the chlorophyll fluorescence parameters (Fm and Fv/Fm ratio), chlorophyll a and b concentrations, relative water content (RWC) and fruit yield characters were negatively affected and significantly reduced under salinity conditions mostly, the high salinity concentration. Nevertheless, electrolyte leakage, lipid peroxidation, hydrogen peroxide (H2O2) and superoxide (O2−) significantly increased in stressed plants. Nevertheless, Bacillus seed treatment and foliar application of chitosan led to improve sweet pepper growth and significant increase in RWC, concentrations of chlorophyll, chlorophyll fluorescence parameters (Fm and Fv/Fm ratio) and fruit yield, conversely Fo, lipid peroxidation, electrolyte leakage, O2− and H2O2 significantly reduced in stressed plants. Also, chitosan and Bacillus led to regulate proline accumulation and enzyme activity as well as increased the number of fruit plant-1, fruit fresh weight plant-1 and total fruit yield of sweet pepper under salt conditions.

Title: Evaluating biochar-microbe synergies for improved growth, yield of maize and post-harvest soil characteristics in a semi-arid climate
Authors: Maqshoof Ahmad; Xiukang Wang2; Thomas H. Hilger; Muhammad Luqman; Farheen Nazli; Azhar Hussain; Zahir Ahmad Zahir; Muhammad Latif; Qudsia Saeed; Adnan Mustafa
Affiliation: qaa
Abstract: Arid and semi-arid regions are characterized by high temperature and low rainfall leading to degraded agricultural soils of alkaline calcareous nature with low organic matter contents. Less availability of indigenous nutrients and efficacy of applied fertilizers are the major issues of crop production in these soils. Biochar application in combination with plant growth promoting rhizobacteria having ability to solubilize nutrients can be an effective strategy for improving soil health and nutrient availability to crops under these conditions. Experiments were planned to evaluate the impact of biochar obtained from different sources in combination with acid producing, nutrient solubilizing Bacillus sp. ZM20 on soil biological properties and growth of maize crop under natural conditions. Various biochar treatments viz. wheat straw biochar, keekar biochar and farm-yard manure biochar with and without Bacillus sp. ZM20 were used along with control. Soil used for pot and field trials was sandy loam in texture with poor water holding capacity and deficient in nutrients. Results of the pot trial showed that number of leaves plant-1, number of seeds plant-1, fresh and dry biomass, grain weight and grain yield was significantly improved by application of biochar of different sources with and without Bacillus sp. ZM20. Application of biochar along with Bacillus sp. ZM20 also improved rhizosphere soil biological properties i.e. soil organic matter, microbial biomass carbon, ammonium and nitrate nitrogen. It was also observed that combined application of biochar with Bacillus sp. ZM20 was more effective than separate application of biochar. Moreover, biochar source and rate also influenced the rhizosphere soil properties and plant growth with different degrees of efficacy. The results of wheat straw biochar along with Bacillus sp. ZM20 were better as compared to farm-yard manure biochar and keekar biochar. Combined application of wheat straw biochar (0.2%) inoculated with Bacillus sp. ZM20 was the most effective treatment in improving the rhizosphere soil properties, plant growth, yield and quality of maize crop as compared to all other treatments.

Title: Volatile organic compounds from rhizobacteria increase the biosynthesis of secondary metabolites and improve the antioxidant status in Mentha piperita L. grown under salt stress
Authors: Lorena del Rosario Cappellari; Julieta Chiappero; Tamara Belén Palermo; Walter Giordano; Erika Banchio*
Affiliation: a
Abstract: Salinity is a major abiotic stress factor that limits crop production due to ionic, osmotic and oxidative stresses, and has a negative impact on plant growth. Bacteria interact with plants in many different ways. In recent years, there is an increasing evidence that microbial volatile organic compounds (mVOC) play an important role in the microorganism-plant interaction. In the present study, we evaluated the impact of microbial volatile organic compounds (mVOC) emitted by Bacillus amyloliquefaciens GB03 on the biosynthesis of secondary metabolites and the antioxidant status in Mentha piperita L. grown under different levels of NaCl stress (0, 75, 100 mM NaCl). Plants were exposed to mVOCs without having any physical contact with the rhizobacteria. An increase in the level of salt stress produced a reduction in essential oil (EO) yield. However, these negative effects were mitigated in plants exposed to mVOCs, resulting in an approximately 6-fold increase respect to plants not exposed to mVOCs, regardless of the severity of the salt stress. The main components of EOs, menthone, menthol and pulegone, showed the same tendency. TPC levels increased in salt-stressed plants but were higher in exposed to mVOCs than stressed plants without mVOC exposure. To evaluate the effect of mVOCs on the antioxidant status, the membrane lipid peroxidation was analyzed to determine the effect of mVOCs on salt- stressed plants. Peppermint plants grown under salt stress and exposed to mVOC showed a better performance and had reduced levels of malondialdehyde (MDA), which is considered to be an indicator of lipid peroxidation and membrane damage, and had an increased antioxidant capacity in terms of DPPH radical scavenging activity compared to controls (plants grown under salt stress, but not exposed to VOCs). These results are important as they illustrate the potential of mVOCs to mitigate the adverse consequences of salt stress.

Title: Agricultural utilization of unused resources: liquid food waste materials as a new source of plant growth promoting microbes
Authors: Waleed Asghar; Shiho Kondo; Riho Iguchi; Ahmad Mahmood; Ryota Kataoka
Affiliation: a
Abstract: This study evaluated the effectiveness of liquid food waste material (LFM) as a microbial resource by analyzing the microbial community composition in LFM and by isolating plant growth promoting bacteria (PGPB) from the material. High throughput sequencing of LFM collected every month from May to September resulted in the detection of >1,000 observed species in the LFM. The results showed that Firmicutes was abundant and most frequently detected, followed by Proteobacteria and Actinobacteria. Of the culturable strains isolated from LFM, almost all belonged to the genus Bacillus. Four strains of PGPB were selected from the isolated strains with traits such as indole acetic acid production and 1-aminocyclopropane-1-carboxylic acid deaminase activity. Lettuce growth was improved with LFM amendment including PGPB, and Brassica rapa showed significant differences in the root biomass with LFM amendment when compared with chemical fertilizer. Field experiments using LFM showed slight better growth for Brassica rapa, lettuce and eggplant when compared with chemical fertilizer. LFM is a useful microbial resource for the isolation of PGPB, and its use as fertilizer could result in reduced chemical fertilizer usage in sustainable agriculture.

Title: Implications of Abscisic acid in Drought Stress Tolerance of Plants
Authors: Shahid Ali; Wang Li; Linan Xie
Affiliation: a
Abstract: Drought is a severe environmental constraint, which significantly affects plant growth, productivity, and quality. Plants have developed specific mechanisms that perceive the stress signals and respond to mitigation strategies to address environmental changes. Phytohormone, abscisic acid (ABA) serves as an important signalling mediator for plant adaptive response to different environmental stress conditions. ABA triggers many variations in the physiological process including, bud dormancy, seed germination, stomatal closure, transcriptional and post-transcriptional regulation of stress-responsive gene expression The site of their biosynthesis and action must be clarified to understand the signalling network of ABA. Various studies have documented multiple sites for ABA biosynthesis, their transporter proteins in plasma membrane, and several components of ABA-dependent signalling pathways, suggesting that ABA responds to stresses is a complex networking mechanism. Knowing about stress signals and responses will increase our ability to enhance crop stress tolerance through the use of various advanced techniques. This review will elaborate, ABA biosynthesis, transportation, and signalling network at the molecular level in response to drought stress by changing root growth, stomatal regulation, seed dormancy, and provide new directions for future studies.

Title: Effect of Trichoderma harzianum T – 22 and biostimulators on the healthiness and antagonistic activity of rhizosphere microorganisms of carrot
Authors: Elżbieta Patkowska
Affiliation: Department of Plant Protection, Faculty of Horticulture and Landscape Architecture, University of Life Sciences in Lublin, 20-069 Lublin, Poland
Abstract: The principles of good agricultural and horticultural practice, which considers both environmental protection and high yielding of plants, require modern methods of cultivation. The modern cultivation of horticultural plants uses, for example, cover crops, living mulches, PGPMs and biostimulators protecting the soil from degradation and the plants from phytopathogens and stress. The purpose of field and laboratory studies was to determine the effect of Trianum P (containing Trichoderma harzianum T - 22), Beta-Chikol (a.s. chitosan), Timorex Gold 24 EC (based on the essential tea tree oil), fungicide Zaprawa Nasienna T DS/WS (a.s. tiuram 75%) on the healthiness of carrot (Daucus carota L.) and on the microorganisms population in the rhizosphere of this plant. Moreover, the antagonistic effect of rhizosphere fungi towards selected fungi pathogenic to carrot was determined. A laboratory mycological analysis made it possible to determine the qualitative and quantitative composition of fungi colonizing the underground parts of carrot. Besides, basing on the microbiological analysis of the rhizosphere soil the total population of fungi and bacteria was established (including Bacillus sp. and Pseudomonas sp.). The application of Plant Growth Promoting Fungus (Trichoderma harzianum T - 22) and biostimulators for seed dressing or carrot spraying positively influenced the growth, development and healthiness of this plant. T. harzianum T – 22, chitosan and fungicide most effectively protected carrot from infection by soil-borne fungi from the genus Alternaria, Fusarium, Haematonectria, Sclerotinia and Rhizoctonia. The population of rhizosphere Bacillus sp. and Pseudomonas sp. in the treatments with Trianum P or Zaprawa Nasienna T DS/WS was bigger than in the other experimental treatments. A reverse relation was observed in the population of rhizosphere fungi. T. harzianum T – 22, chitosan and tea tree oil promoted the growth of antagonistic fungi (Clonostachys spp., Myrothecium spp., Penicillium spp. and Trichoderma spp.) in the rhizosphere of carrot. The antagonistic activity of these fungi towards Alternaria dauci, Alternaria radicina, Sclerotinia sclerotiorum and Rhizoctonia solani was higher after the application of T. harzianum T – 22 and biostimulators compared to the control. Consequently, Trianum P, Beta-Chikol, Timorex Gold 24 EC can be recommended as plant growth-promoting microorganisms or natural compounds (biostimulators) in the ecological agricultural production, also including the cultivation of Daucus carota.

Title: Rhizobacteria isolated from saline soil induce systemic tolerance in wheat (Triticum aestivum L.) against salinity stress.
Authors: Noshin Ilyas; Roomina Mazhar; Humaira Yasmin; Wajiha Khan; Sumera Iqbal; Hesham El Enshasy; Daniel Joe Dailin
Affiliation: PMAS Arid Agriculture University Rawalpindi, Pakistan
Abstract: Halotolerant Plant Growth Promoting Rhizobacteria (PGPR) have inherent potential to cope up with salinity. Thus, they can be used an effective strategy in enhancing the productivity of saline agro-systems. In this study, a total of 50 isolates were screened from the rhizospheric soil of plants growing in salt range of Pakistan. Out of these, four isolates were selected based upon the basis of salinity tolerance and plant growth promotion characters. These isolates (SR1. SR2, SR3, and SR4) were identified as Bacillus sp. (KF719179), Azospirillum brasilense (KJ194586), Azospirillum lipoferum (KJ434039) and Pseudomonas stutzeri (KJ685889) by 16S rDNA gene sequence analysis. In vitro, these strains, in alone and in consortium, showed better production of compatible solute (12 µg mg-1 proline and 222 µg mg-1 sugar), phytohormones including IAA (2 μg ml−1), gibberellic acid (7.5 μg ml−1), cytokinin (3.4 μg ml−1) and abscisic Acid (0.64 μg ml−1) in cultures conditions under salt stress. When tested for inoculation, consortium of all four strains showed the best results in terms of improved plant biomass and relative water content (21%). Consortium inoculated wheat plants showed tolerance by reduced electrolyte leakage (19%) and increased production of chlorophyll a, b and total chlorophyll (13.23%, 12.49% and 12.9%,) osmolytes including soluble sugar (28.57%), proline (46.6%), amino acids (19.29%), antioxidant enzymes (superoxide dismutase by 21.33%, catalase by 16%, peroxidase by 34.4%) upon exposure to salinity stress (150 mM NaCl). In conclusion, plant growth promoting bacteria, isolated from salt affected region have strong potential to mitigate the deleterious effects of salt stress in wheat crop, when inoculated. Therefore, this consortium can be used as potent inoculants for wheat crop under prevailing stress conditions.

Title: Co-inoculation of rhizobacteria and biochar application improves growth and nutrient in soybean and enriches soil nutrients and enzymes
Authors: Dilfuza Jabborova; Stephan Wirth; Annapurna Kannepalli; Abdujalil Narimanov; Said Desouky; Kakhramon Davranov; Riyaz Sayyed; Hesham El Enshasy; Roslinda A. Malek; Asad Syed; Prof. Dr. Ali H. Bahkali
Affiliation: Laboratory of Medicinal Plants Genetics and Biotechnology, Institute of Genetics and Plant Experimental Biology, Uzbekistan Academy of Sciences, Tashkent, Uzbekistan
Abstract: Gradual depletion in the soil nutrients has deteriorated the soil fertility, reduced soil nutrients, and has affected the activities of soil enzymes. The applications of multifarious plant growth-promoting rhizobacteria (PGPR) along with biochar has been recommended as the best remedy to overcome these issues, however, the influence of PGPR and biochar on growth of soybean, enrichment of nutrients in soybean and soil and improvement in soil enzymes as well as the potential of biochar to enhance the symbiotic performance of soybean under natural field conditions needs in-depth study. Therefore, this study was aimed to evaluate the effect of coinoculation of multiple plant growth-promoting (PGP) traits producing Bradyrhizobium japonicum USDA 110 and Pseudomonas putida TSAU1 and different levels (1-3%) of biochar on growth parameters of soybean, increase in the level of plant and soil nutrients and increase in the level of soil enzymes. We hypothesized that growth and vigor of soybean and increase in plant nutrients, soil nutrients, and the soil enzymes are enhanced by PGPR and biochar application. The effect of PGP producing rhizobacteria and biochar (1 and 3%) on the growth of soybean, plant and soil nutrients, and soil enzymes (before planting and after harvesting) were studied in pot experiments under greenhouse conditions at 24 °C (day) and 16 °C (night) for 30 days. Both PGPR cultures produced good amounts of PGP traits viz. indole-acetic acid; (22 and 16 µg mL-1), siderophores (79 and 87 %SU), and phosphate solubilization (0.89 and 1.02 99 g mL-1). Application of 3% biochar produced more nodules, improved root and shoot length, and root and shoot dry weight of soybean as compared to the control and 1% biochar treatment. Inoculation with B. japonicum USDA 110 has substantially improved the plant growth parameters, plant nutrients, and soil nutrients and soil enzymes, however, the application of B. japonicum with P. putida and 3% biochar significantly improved the overall growth and nutrient contents in soybean plant and improved nutrients and enzymes in the soil thus making the soil more fertile that supports more growth of the plant. The results of this research provide the basis of sustainable and chemical-free farming of soybean and for improving the yields and nutrient content in soybean besides improvement in soil fertility.

Title: Physiological Disruption, Structural Deformation and Low Grain Yield induced by Neonicotinoid Insecticides in Chickpea: A Long Term Phytotoxicity Investigation
Authors: Mohammad Shahid
Affiliation: Department of Agricultural Microbiology, Faculty of Agricultural Sciences, Aligarh Muslim University, India
Abstract: Toxicological potential of two neonicotinoid insecticides, imidacloprid and thiamethoxam was evaluated using chickpea as a test crop. Application of insecticides at three varying doses revealed a gradual decrease in biological performance of chickpea plants which however, varied noticeably among insecticides and their doses. Significant (P≤0.05) decline in germination efficiency, length of plant organs under in vitro condition was observed in a dose related manner. Among insecticides, 3X dose of imidacloprid (300 μgkg-1) maximally and significantly (P≤0.05) inhibited germination efficiency, vigor index, length, dry matter accumulation, photosynthetic pigment formation, nodule volume and mass, nutrient uptake, grain yield and protein over untreated control. In contrast, 75 μg thiamethoxam kg-1 (3X dose) considerably declined the leghaemoglobin content, shoot phosphorus and root nitrogen. Enhanced expression of stress biomarkers including proline, malondialdehyde (MDA), and antioxidant defence enzymes was noticed in the presence of insecticides. For instance, at 3X of imidacloprid, shoot proline, MDA, ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and peroxidase (POD) were increased significantly by 66%, 81%, 36% and 35%, respectively. Additionally, electrolyte leakage was maximally (77%) increased at 3X dose of imidacloprid, whereas, H2O2 in foliage was maximally accumulated (0.0156 μ moles min-1 g-1 fw) at 3X thiamethoxam which was 58% greater than untreated foliage. A clear distortion/damage in tip and surface of roots as and ultrastructural deformation in xylem and phloem of plant tissues an indication of insecticidal phytotoxicity was observed under scanning electron microscope (SEM). For oxidative stress and cytotoxicity assessment, root tips were stained with combination of acridine orange and propidium iodide, and Evan blue dyes and examined. Confocal laser scanning microscopic (CLSM) images of roots revealed a 10-fold and 13.5-fold increase in red and blue fluorescence when 3X IMID treated roots were assessed quantitatively. Conclusively, the present investigation recommends that a careful and protected approach should be adopted before the application of insecticides in agricultural ecosystems.

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