Plant Growth-promoting Substances Research Articles

Germination characteristics of Sorghum bicolor (L.) Moench. under different pH regimes after chemo-priming

AbstractSoil pH not only plays a regulatory role in seed germination but also influences seedling development, flowering, and crop yield. The study investigated the germination characteristics of sorghum [Sorghum bicolor (L.) Moench.] under varying pH to understand the potential ameliorative effects of seed priming using plant growth-promoting substances. Seeds were sown in Petri dishes with pH moistened solutions at 1, 3, 5, 7, 9, 11, and 13 respectively. These were replicated five times in the second stage, viable seeds were first primed in 150 ppm indole-3-acetic acid, gibberellic acid, and vitamin C before sowing in pH solutions. The experiment showed no significant changes in morphology or physiology of primed and unprimed seeds and no germination at extreme pH. However, there was a significant difference in the activity of enzymes, germination time, and speed as well as germination percentages of both primed and unprimed seeds. Although chemo-priming did not reverse the effect of pH, it was observed however that vitamin C had a significant effect on germination percentage at higher pH. Germination was observed to be impaired at extreme pH. Seeds did not respond to germination capacity suggesting an optimal pH range of 3 and 11 for germination without priming. However, priming did not show any improved germinability index. Seeds primed in the presence of light showed enhanced germination at pH 7. Generally, the germination index without priming showed better germination characteristics than primed seeds, which suggests pH interactions with primers may be a limiting factor.

Application of Panchagavya, a Cow-based Liquid Formulation, as a Lever for Sustainable and Enhanced Vegetable Crop Production: A Review

Panchagavya, a fermented liquid bio-formulation derived from cow-based products such as dung, urine, milk, curd and ghee, has recently gained importance in agricultural practices due to its reported effectiveness in enhancing vegetable crop production. Its formulation involves a fermentation process that harnesses the diverse microbial communities present in cow-derived substances, resulting in a potent nutrient-rich solution that is believed to possess plant growth-promoting properties. One of the primary mechanisms underlying its efficacy lies in the diverse array of microorganisms present in the formulation. These microorganisms, including beneficial bacteria, fungi and actinomycetes, play crucial roles in nutrient cycling, disease suppression and soil conditioning. Additionally, Panchagavya contains plant growth-promoting substances such as hormones, enzymes, vitamins and amino acids, which contribute to enhanced nutrient uptake, root development and overall plant vigour. Furthermore, application of Panchagavya has been shown to improve soil health by enhancing microbial activity, increasing organic matter content and improving soil properties. These soil improvements not only benefit the current crop but also have long-term positive implications for soil fertility and sustainability. This multifaceted approach to crop management offers a holistic solution to enhance crop productivity while reducing reliance on synthetic inputs. This review aims to comprehensively analyse the literature on the effects of Panchagavya on vegetable crops, highlighting its mechanisms of action and potential benefits for increased vegetable crop production.

Plant Growth Promoting Activity of Colletotrichum sp., an Endophyte of Helicteres isora L. and its Growth Optimization using Response Surface Methodology

Endophytes are the beneficial group of plant symbionts and are potent sources for producing novel metabolites with biotechnological applications. They are efficient sources for the synthesis of plant growth-promoting substances- Indole acetic acid, ammonia, solubilizing phosphates and thus open up sustainable agricultural opportunities. In the present investigation, twenty-two fungal endophytes were isolated from an ethnomedicinal plant-Helicteres isora L., collected from forests of Singbhum, Jhargram, India, and the isolate-Colletotrichum sp. HelS1, exhibited the most potent in vitro plant growth-promoting activities among all. HelS1 synthesized auxin (111.13 µg ml-1), ammonia, and solubilized phosphate (47.22 µg ml-1) in specific culture conditions. A treatment with fungal extract effectively increases the growth of the experimental plant (tomato seedlings) in terms of improvement in relative water contents, dry weight, nodal length, and pigment profiles compared to the untreated ones. There was an increase in root length by 27% compared to the control group. The isolate produced the maximum IAA after 7 days of incubation on Czepak Dox Broth supplemented with tryptophan (5 mg mL-1), sucrose (30 g L-1), and NaNO3 (2.2 g L-1) at pH 6.2. Fourier Transform Infrared Spectroscopic analysis of the crude fungal extract further confirmed the production of indole-like compounds. This investigation suggested that secondary metabolites of endophytes act as a potent plant growth inducer and can be utilized in bio-based crop management techniques.

Bioactivity and genome analysis of Bacillus amyloliquefaciens GL18 isolated from the rhizosphere of Kobresia myosuroides in an alpine meadow.

The unique eco-environment of the Qinghai-Tibet Plateau breeds abundant microbial resources. In this research, Bacillus amyloliquefaciens GL18, isolated from the rhizosphere of Kobresia myosuroides from an alpine meadow, and the antagonistic activity, bacteriostatic hydrolase activity, and low temperature, salt, and drought resistance of it were determined and analysed. The seedlings of Avena sativa were root-irrigated using bacteria suspensions (cell concentration 1 × 107cfu/mL) of GL18, and the growth-promoting effect of GL18 on it was determined under cold, salt and drought stress, respectively. The whole genome of GL18 was sequenced, and its functional genes were analysed. GL18 presented significant antagonistic activity to Fusarium graminearum, Fusarium acuminatum, Fusarium oxysporum and Aspergillus niger (inhibition zone diameter > 17mm). Transparent zones formed on four hydrolase detection media, indicating that GL18 secreted cellulase, protease, pectinase and β-1,3-glucanase. GL18 tolerated conditions of 10°C, 11% NaCl and 15% PEG-6000, presenting cold, salt and drought resistance. GL18 improved the cold, salt and drought tolerance of A. sativa and it showed significant growth effects under different stress. The total length of the GL18 genome was 3,915,550bp, and the number of coding DNA sequence was 3726. Compared with the clusters of orthologous groups of proteins, gene ontology and kyoto encyclopedia of genes and genomes databases, 3088, 2869 and 2357 functional genes were annotated, respectively. GL18 contained gene clusters related to antibacterial substances, functional genes related to the synthesis of plant growth-promoting substances, and encoding genes related to stress resistance. This study identified an excellent Bacillus strain and provided a theoretical basis for improving stress resistance and promoting the growth of herbages under abiotic stress.

Isolation and characterization of Indole Acetic Acid-producing bacteria isolated from rhizospheric soil of paddy rice

Plant growth-promoting rhizobacteria have immense potential to be used as an environmentally friendly replacement for chemical fertilizers and pesticides, through the production of various plant growth-promoting substances. The objectives of this study were the isolation, characterization, and identification of indole acetic acid-producing bacteria from the rhizospheric soil of paddy rice. Out of all screened isolates, isolate 1.4 was the highest IAA producer with 29.76 µg/mL. The culture medium conditions to obtain the highest IAA production were optimized as follows: the culture temperature was 30°C, the incubation time was three days, and the pH was 7.0. The 16S rRNA gene sequence showed that isolate 1.4 has been genetically identified as Bacillus altitudinis, and it can potentially be used as an efficient biofertilizer.

Revealing the phosphate-solubilizing characteristics and mechanisms of the plant growth-promoting bacterium Agrobacterium deltaense C1.

This study explores the phosphate (Pi)-solubilizing characteristics and mechanisms of a novel phosphate-solubilizing bacterium, Agrobacterium deltaense C1 (C1 hereafter). The growth-promoting effects of C1 were investigated by gnotobiotic experiments, and the Pi-solubilizing mechanism was revealed by extracellular metabolomics, liquid chromatography analysis, and reverse transcription quantitative polymerase chain reaction. Results showed that C1 significantly increased Arabidopsis biomass and total phosphorus (P) content under P deficiency. Under Ca3(PO4)2 condition, the presence of C1 resulted in a significant and negative correlation between available P content and medium pH changes, implying that Pi dissolution occurs through acid release. Metabolomics revealed C1's ability to release 99 organic acids, with gluconic acid (GA), citric acid, and α-ketoglutaric acid contributing 64.86%, 9.58%, and 0.94%, respectively, to Pi solubilization. These acids were significantly induced by P deficiency. Moreover, C1's Pi solubilization may remain significant even in the presence of available P, as evidenced by substantial pH reduction and high gcd gene expression. Additionally, C1 produced over 10 plant growth-promoting substances. C1 dissolves Pi primarily by releasing GA, which enhances plant growth under P deficiency. Notably, its Pi solubilization effect is not significantly limited by available Pi.

Potential of psychrotolerant rhizobacteria for the growth promotion of wheat (Triticum aestivum L.).

Wheat is the second most important staple crop grown and consumed worldwide. Temperature fluctuations especially the cold stress during the winter season reduces wheat growth and grain yield. Psychrotolerant plant growth-promoting rhizobacteria (PGPR) may improve plant stress-tolerance in addition to serve as biofertilizer. The present study aimed to isolate and identify PGPR, with the potential to tolerate cold stress for subsequent use in supporting wheat growth under cold stress. Ten psychrotolerant bacteria were isolated from the wheat rhizosphere at 4°C and tested for their ability to grow at wide range of temperature ranging from -8°C to 36°C and multiple plant beneficial traits. All bacteria were able to grow at 4°C to 32°C temperature range and solubilized phosphorus except WR23 at 4°C, whereas all the bacteria solubilized phosphorus at 28°C. Seven bacteria produced indole-3-acetic acid at 4°C, whereas all produced indole-3-acetic acid at 28°C. Seven bacteria showed the ability to fix nitrogen at 4°C, while all the bacteria fixed nitrogen at 28°C. Only one bacterium showed the potential to produce cellulase at 4°C, whereas four bacteria showed the potential to produce cellulase at 28°C. Seven bacteria produced pectinase at 4°C, while one bacterium produced pectinase at 28°C. Only one bacterium solubilized the zinc at 4°C, whereas six bacteria solubilized the zinc at 28°C using ZnO as the primary zinc source. Five bacteria solubilized the zinc at 4°C, while seven bacteria solubilized the zinc at 28°C using ZnCO3 as the primary zinc source. All the bacteria produced biofilm at 4°C and 28°C. In general, we noticed behavior of higher production of plant growth-promoting substances at 28°C, except pectinase assay. Overall, in vitro testing confirms that microbes perform their inherent properties efficiently at optimum temperatures rather than the low temperatures due to high metabolic rate. Five potential rhizobacteria were selected based on the in vitro testing and evaluated for plant growth-promoting potential on wheat under controlled conditions. WR22 and WR24 significantly improved wheat growth, specifically increasing plant dry weight by 42% and 58%, respectively. 16S rRNA sequence analysis of WR22 showed 99.78% similarity with Cupriavidus campinensis and WR24 showed 99.9% similarity with Enterobacter ludwigii. This is the first report highlighting the association of C. campinensis and E. ludwigii with wheat rhizosphere. These bacteria can serve as potential candidates for biofertilizer to mitigate the chilling effect and improve wheat production after field-testing.

Unveiling the Diversity of Periphytic Cyanobacteria (Cyanophyceae) from Tropical Mangroves in Penang, Malaysia.

Cyanobacteria are one of the most important groups of photoautotrophic organisms, contributing to carbon and nitrogen fixation in mangroves worldwide. They also play an important role in soil retention and stabilisation and contribute to high plant productivity through their secretion of plant growth-promoting substances. However, their diversity and distribution in Malaysian mangrove ecosystems have yet to be studied in detail, despite Malaysia hosting a significant element of remaining mangroves globally. In a floristic survey conducted in Penang, peninsular Malaysia, 33 morphospecies of periphytic cyanobacteria were identified and described for the first time from a mangrove ecosystem in Malaysia. Sixteen genera, comprising Aphanocapsa, Chroococcus, Chroococcidiopsis, Cyanobacterium, Desmonostoc, Geitlerinema, Leptolyngbya, Lyngbya, Microcystis, Myxosarcina, Oscillatoria, Phormidium, Pseudanabaena, Spirulina, Trichocoleus and Xenococcus, were obtained from field material growing on diverse natural and artificial substrata. Oscillatoriales was the dominant order with Phormidium the dominant genus at nine of the 15 sampling sites examined. Three of the morphospecies, Aphanocapsa cf. concharum, Xenococcus cf. pallidus and Oscillatoria pseudocurviceps, are rare and poorly known morphospecies worldwide. Chroococcus minutus, Phormidium uncinatum, P. amphigranulata, and some species of Oscillatoriales are considered as pollution indicator species. This study provides important baseline information for further investigation of the cyanobacterial microflora present in other mangrove areas around Malaysia. A complete checklist will enhance understanding of their ecological role and the potential for benefits arising from useful secondary metabolites or threats via toxin production to the ecosystem.

Isolation and characterization of novel potassium-solubilizing purple nonsulfur bacteria from acidic paddy soils using culture-dependent and culture-independent techniques.

The current research as aimed (i) to isolate and select the purple nonsulfur bacteria (PNSB) possessing the potassium-solubilizing ability from acid paddy fields and (ii) to evaluate the ability to release the plant growth-promoting substances (PGPS) of selected PNSB. A total of 35 acid sulfate (AS) soil samples were collected in An Giang province, Vietnam. Then, 70 PNSB strains were isolated from the AS soil samples. In the current study, the isolated strains were screened and selected according to their tolerability to acidic conditions, ability to solubilize potassium, and characteristics of a plant growth promoter on basic isolation media with various incubation conditions. Therein, three strains, TT07.4, AN05.1, and AC04.1, presented the highest potassium solubilization under the microaerobic light (11.8-17.7 mg L-1) and aerobic dark (16.4-24.7 mg L-1) conditions and stresses from Al3+, Fe2+, and Mn2+ toxicity. The selected strains were identified as Rhodopseudomonas pentothenatexigens by the 16S rDNA sequence, with 99% similarity. The selected acidic-resistant strains possessed the traits of biofertilizers under both microaerobic light and aerobic dark conditions, with abilities to fix nitrogen (0.17-6.24; 7.93-11.2 mg L-1); solubilize phosphorus from insoluble compounds with 3.22-49.9 and 9.49-11.2 mg L-1 for Al-P, 21.9-25.8 and 20.2-25.1 mg L-1 for Ca-P, and 10.1-29.8 and 18.9-23.2 mg L-1 for Fe-P; produce 5-aminolevulinic acid (0.63-3.01; 1.19-6.39 mg L-1), exopolymeric substances (0.14-0.76; 0.21-0.86 mg L-1), indole-3-acetic acid (12.9-32.6; 13.6-17.8 mg L-1), and siderophores (28.4-30.3; 6.15-10.3%). The selected potassium-solubilizing strains have a great potential to apply in liquid form into rice seed and solid form in AS soils to supply nutrients and PGPS for enhancing rice growth and grain yield.

Screening of salt tolerant endophytic bacteria with plant growth promoting characters isolated from Acanthus ilicifolius L., a species of mangrove ecosystem located at Corangi wildlife sanctuary, Andhra Pradesh

Mangroves harbour many beneficial microorganisms in their rhizosphere, phyllosphere and endophytically, which forms an ideal ecological habitation for isolating halotolerant endophytic bacteria with unique characteristics. Endophytes can produce numerous bioactive secondary metabolites and phytohormones, which may be directly or in some way beneficial to the host plant. The present study aimed to identify novel endophytes capable of producing plant growth-promoting substances. The mangrove plants Acanthus ilicifolius L. at Corangi Wildlife Sanctuary were selected, and their leaves and roots were collected for endophyte isolation. Eight isolates from the leaves and roots were collected, purified and preserved. All these isolates were subjected to morphological, phenotypical and biochemical studies. Isolates were grown best at 3% NaCl nutrient agar and could tolerate salinity upto 8%NaCl. Most of them could grow upto 42°C. The majority were gram’s positive, motile, aerobic, rod-shaped and some were gram’s negative, rod-shaped organisms. Many of the endophytic organisms had the ability to synthesize Indole-3-acetic acid(IAA) varied from 0.7 µg/ml (AIL1) to 51.0 µg/ml (AIL2) and the highest phosphate solubilizing ability was recorded with AIR3 (3.71 ppm) followed by AIR4 (3.00 ppm) and lowest was recorded by AIL4 (1.80 ppm). Among total isolates, AIL2 (51µg/ml) showed promising potential in producing IAA and had phosphate solubilization ability. Based on 16S ribosomal RNA molecular method the isolate AIL2 was identified as Bacillus altitudinis. This is the first to report that B.altitudinis strain AIL2 isolated from A.ilicifolius L. could produce IAA, which can be used as a bioinoculant in agriculture and allied sector.

Potential of Bacillus pumilus to directly promote plant growth.

Plant Growth-Promoting Bacteria (PGPB) are a promising alternative to conventional fertilization. One of the most interesting PGPB strains, among the spore-forming bacteria of the phylum Firmicutes, is Bacillus pumilus. It is a bacterial species that inhabits a wide range of environments and shows resistance to abiotic stresses. So far, several PGPB strains of B. pumilus have been described, including B. pumilus LZP02, B. pumilus JPVS11, B. pumilus TUAT-1, B. pumilus TRS-3, and B. pumilus EU927414. These strains have been shown to produce a wide range of phytohormones and other plant growth-promoting substances. Therefore, they can affect various plant properties, including biometric traits, substance content (amino acids, proteins, fatty acids), and oxidative enzymes. Importantly, based on a study with B. pumilus WP8, it can be concluded that this bacterial species stimulates plant growth when the native microbiota of the inoculated soil is altered. However, there is still a lack of research with deeper insights into the structure of the native microbial community (after B. pumilus application), which would provide a better understanding of the functioning of this bacterial species in the soil and thus increase its effectiveness in promoting plant growth.

Plant Growth-Promoting Activities of Bacteria Isolated from an Anthropogenic Soil Located in Agrigento Province.

Bacteria producers of plant growth-promoting (PGP) substances are responsible for the enhancement of plant development through several mechanisms. The purpose of the present work was to evaluate the PGP traits of 63 bacterial strains that were isolated from an anthropogenic soil, and obtained by modification of vertisols in the Sicily region (Italy) seven years after creation. The microorganisms were tested for the following PGP characteristics: indole acetic acid (IAA), NH3, HCN and siderophore production, 1-aminocyclopropane-1-carboxylate deaminase activity (ACC) and phosphate solubilization. The results of principal component analysis (PCA) showed that Bacillus tequilensis SI 319, Brevibacterium frigoritolerans SI 433, Pseudomonas lini SI 287 and Pseudomonas frederiksbergensis SI 307 expressed high levels of IAA and production of ACC deaminase enzyme, while for the rest of traits analyzed the best performances were registered with Pseudomonas genus, in particular for the strains Pseudomonas atacamensis SI 443, Pseudomonas reinekei SI 441 and Pseudomonas granadensis SI 422 and SI 450. The in vitro screening provided enough evidence for future in vivo growth promotion tests of these eight strains.

Microbiome as a Key Player in Sustainable Agriculture and Human Health

The aggregate of microorganisms in the soil environment is a microbiome that emerged as a vital component of sustainable agriculture in the recent past. These beneficial microorganisms perform multiple plant growth-promoting activities including fixation, mineralization, solubilization, and mobilization of nutrients, production of siderophores, antagonistic substances, antibiotics, and release of plant growth-promoting substances, such as auxin and gibberellin hormones, mediated by interactions between host plant roots and microbes in the rhizosphere. Numerous plant species forms symbiotic association with microbes and draw the benefit of mineral nutrient supply with the expense of minimal energy, and their distribution is governed by nature and the number of root exudates, crop species, and cultivars. On the other hand, microorganisms with critical roles in the microbiome can be isolated, formulated, and developed as a new biological product called biofertilizers. Agriculturally, important microbes with Fe- and Zn-solubilizing attributes can be used for the biofortification of micronutrients in different cereal crops. Regardless of the approach to be used, innovations with the use of microbiomes represent the future of sustainable agriculture. Probiotic microbes, such as Lactobacillus, etc., are increasingly being used as dietary supplements in functional food products. Effective utilization of microbiome aids in promoting sustainable agriculture that accomplishes a safe environment, which in turn manifests positively on human health.

Does a hormonal plant growth promoter (KIN, GA3, and IBA) affect grain yield and N, P, K, Ca, and Mg uptake in wheat crop in Southern Brazil?

Plant growth-promoting substances have been commercialized in agriculture, especially synthetic hormones such as kinetin (KIN), gibberellic acid (GA3), and indole-3-butyric acid (IBA). However, few studies proved the agronomic effect of these substances on the main crops. The objective of this work was to evaluate rates and methods of application of a hormonal plant growth promoter (HPGP −0.09 g L−1 KIN, 0.05 g L−1 GA3, and 0.05 g L−1 IBA) and their effects on wheat grain yield and nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) uptake. The research was carried out in Londrina, Brazil. A randomized block design was implemented, considering a 2 × 3 × 4 factorial arrangement. It was composed of two genotypes (BRS Gralha–Azul and BRS Sanhaço), three HPGP rates (0, 5, and 10 mL kg−1) applied on the seeds, and four HPGP rates (0, 0.25, 0.5, and 1 L ha−1) sprayed on the leaves. Applications of HPGP did not change grain yield, density of fertile plants, lodging, plant height, aboveground dry matter (AGDM); P, Ca, and Mg concentration in the AGDM; and P, K, Ca, and Mg utilization efficiency (UE). In 2016, the application of 5 mL kg−1 HPGP on the seeds (without HPGP on the leaves) increased by 20.9% the N concentration in the AGDM. In 2017, NUE increased up to 21.2% in response to HPGP sprayed on the leaves. The diversity of interactions among genotypes, HPGP application techniques, and weather conditions hinders the assertive use of the product by farmers.

Beneficial traits of root endophytes and rhizobacteria associated with plants growing in phytomanaged soils with mixed trace metal-polycyclic aromatic hydrocarbon contamination

The diversity of cultivable bacteria associated with plants from phytomanaged soils with mixed trace metal (TM) and polycyclic aromatic hydrocarbon (PAH) contamination in Pierrelaye (France) was evaluated. The emphasis was on the cultivable bacterial community since the overall objective is to obtain inoculants to improve the remediation of this type of contaminated site. Root endophytic and rhizosphere soil bacterial counts were determined, and isolates were pooled by amplified rDNA restriction analysis and identified by 16S rDNA sequencing. Isolates were further characterized for the production of plant growth-promoting (PGP) substances, and resistance to TM. The selected strains were evaluated for their ability to degrade PAHs. The potential of cell-free microbial supernatant to increase the mobilisation of PAHs from the polluted soil of Pierrelaye was also evaluated. Proteobacteria and Actinobacteria dominated the collection of isolates, and differences in taxonomic diversity were observed between plant species (Populus or Zea mays) and depending on the remediation treatment (Populus inoculation with mycorrhizae or Populus intercropping with Alnus). The majority of isolates exhibited at least one of the tested PGP traits, as well as resistance to more than one TM. Several rhizosphere, endophyte and even one bulk soil isolate showed high rates of fluoranthene and pyrene reduction. The endophyte Rhizobium strain MR28 isolated from maize and degrading pyrene produced bioemulsifying molecules capable of improving the availability of PAHs from the soil of Pierrelaye. A selection of the most interesting strains was made for further re-inoculation experiments in order to assess their potential in rhizoremediation processes.

Will Phosphate Bio-Solubilization Stimulate Biological Nitrogen Fixation in Grain Legumes?

Biological nitrogen fixation (BNF) refers to a bacterially mediated process by which atmospheric N2is reduced, either symbiotically or non-symbiotically, into ammonia (NH3) in the presence of the enzyme complex nitrogenase. In N2-fixing grain legumes, BNF is often hampered under low phosphorus (P) availability. The P status of legumes, particularly nodules, as well as P availability in the rhizosphere, play a vital role in regulating BNF. Aside from increasing P availability via fertilization, other plant traits (i.e., extensive rooting system and their spatial distribution, hyper-nodulation, root exudates, rhizosphere acidification, and heterogeneity) contribute to greater P uptake and hence more effective BNF. The positive interaction between P availability and BNF can be exploited through beneficial soil P solubilizing microorganisms (PSM). These microorganisms can increase plant-available P by modifying either rhizosphere soil processes or promoting plant traits, which lead to increased P uptake by the production of plant growth-promoting substances, both of which could indirectly influence the efficiency of BNF in legumes. In this review, we report on the importance of microbial P bio-solubilization as a pathway for improving BNF in grain legumes via PSM and P solubilizing bacteria (PSB). Because BNF in legumes is a P-requiring agro-ecological process, the ability of soil PSB to synergize with the rhizobial strains is likely a key belowground process worth investigating for advanced research aiming to improve rhizosphere biological functions necessary for sustainable legume-based cropping systems.

Characterization of Pseudomonas bacteria of Piper tuberculatum regarding the production of potentially bio-stimulating compounds for plant growth

ABSTRACT Despite advances in the identification and characterization of endophytic bacteria in various plant species worldwide, little is known about such microorganisms in plants from the Amazon region. Previous studies reported that Piper tuberculatum endophytic Pseudomonas (isolates Pt12 and Pt13, identified as Pseudomonas putida and Pseudomonas sp., respectively) were able to inhibit the in vitro growth of Fusarium solani f. sp. piperis, which causes root rot in black pepper (Piper nigrum), and that Pt13 promoted the growth of P. nigrum. Therefore, the aim here was to characterize these bacteria regarding their ability to produce plant growth-promoting substances [siderophores, indol acetic acid (IAA) and soluble phosphate]. Chrome azurol S assays were performed for the detection of siderophores. For qualitative and quantitative assays of IAA production and phosphate solubilization, Salkowski´s reagent and NBRIP medium with molybdenum blue reagent, respectively, were used. Results revealed that Pt12 and Pt13 were able to synthesize IAA, mainly under a high concentration of L-tryptophan, indicating that they are IAA-producing bacteria, probably through a tryptophan-dependent biosynthesis pathway. The presence of P. nigrum extract positively influenced the IAA production by Pt12 and Pt13, with highest values of 125 and 90 µg mL-1, respectively. In addition, Pt12 was positive for the production of siderophores and produced 56.56 µg mL-1 of soluble phosphate. In contrast, Pt13 showed no ability to produce siderophores or to solubilize phosphate. Besides their potential in controlling plant diseases, Pt12 and Pt13 have potential as biofertilizers, favoring sustainable agriculture.

Utilization of organic fertilisers a potential approaches for agronomic crops: A review

Organic fertilisers are of biological origin and the amount of nutrients they produce varies greatly. Besides providing the essential macro and micro nutrients, they also provide an array of plant growth-promoting substances. Organic agronomy is a relatively recent technique of farming in developed countries. While several studies were conducted on the impact of organic fertilisers on soil properties and crop production, further research is needed to determine comparative results between organic fertilisers. This paper aims to review some of the influences and impacts of poultry manure, cow dung, goat manure, vermicomposter and seaweed extracts. Much-needed characteristics of numerous crops were enhanced with the appropriate application of these organic fertilisers. Organic fertilizer applications influences the increase of plant heights, vegetative growth, yields and yield attributes. The application of adequate fertilisers also influences the qualitative parameters and post-harvest traits of most crops. Selecting the best organic fertilisers at an optimal application rate that could be the best source of nutrient supplement in cultivating qualitative crops, is a gap that needs to bridge. Therefore, different application rates of the above organic fertilisers were also studied.

Complete genome sequence of plant growth-promoting and heavy metal-tolerant Enterobacter tabaci 4M9 (CCB-MBL 5004).

Enterobacter tabaci 4M9 (CCB-MBL 5004) was reported to have plant growth-promoting and heavy metal tolerance traits. It was able to tolerate more than 300 mg/L Cd, 600 mg/L As, and 500 mg/L Pb and still maintained the ability to produce plant growth-promoting substances under metal stress conditions. To explore the genetic basis of these beneficial traits, the complete genome sequencing of 4M9 was carried out using Pacific Bioscience (PacBio) sequencing technology. The complete genome consisted of one chromosome of 4,654,430 bp with a GC content of 54.6% and one plasmid of 51,135 bp with a GC content of 49.4%. Genome annotation revealed several genes involved in plant growth-promoting traits, including the production of siderophore, indole acetic acid, and 1-aminocyclopropane-1-carboxylate deaminase; solubilization of phosphate and potassium; and nitrogen metabolism. Similarly, genes involved in heavy metals (As, Co, Zn, Cu, Mn, Se, Cd, and Fe) tolerance were detected. These support its potential as a heavy metal-tolerant plant growth-promoting bacterium and a good genetic resource that can be employed to improve phytoremediation efficiency of heavy metal-contaminated soil via biotechnological techniques. This, to the best of our knowledge, is the first report on the complete genome sequence of heavy metal-tolerant plant growth-promoting E. tabaci.

Effect of Seed Priming with Potassium Nitrate on the Performance of Tomato

The seed industry and farmers have challenges, which include the production of poor quality and non-certified tomato seed, which ultimately results in decreased crop production. The issue carefully demands pre-sowing treatments using exogenous chemical plant growth-promoting substances. Therefore, to mitigate the above-stated problem, a series of experiments were conducted to improve the quality of tomato seeds (two cultivars, i.e., “Sundar” and “Ahmar”) and to enhance the stand establishment, vigor, physiological, and biochemical attributes under growth chamber and greenhouse conditions by using potassium nitrate (KNO3) as a seed priming agent. Seeds were imbibed in 0.25, 0.50, 0.75, 1.0, and 1.25 KNO3 (weight/volume) for 24 h and then dried before experiments. The results of growth chamber and greenhouse screening show that experimental units receiving tomato seeds primed with 0.75% KNO3 in both cultivars performed better as compared to other concentrations and nonprimed control. Significant increase in final emergence (%), mean emergence time, and physiological attributes were observed with 0.75% KNO3. Collectively, the improved performance of tomato due to seed priming with 0.75% KNO3 was linked with higher activities of total soluble sugars and phenolics under growth chamber and greenhouse screening.