Demand for agricultural crop continues to escalate in response to increasing population and damage of prime cropland for cultivation. Research interest is diverted to utilize soils with marginal ...plant production. Moisture stress has negative impact on crop growth and productivity. The plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGR) are vital for plant developmental process under moisture stress. The current study was carried out to investigate the effect of PGPR and PGRs (Salicylic acid and Putrescine) on the physiological activities of chickpea grown in sandy soil. The bacterial isolates were characterized based on biochemical characters including Gram-staining, P-solubilisation, antibacterial and antifungal activities and catalases and oxidases activities and were also screened for the production of indole-3-acetic acid (IAA), hydrogen cyanide (HCN) and ammonia (NH3). The bacterial strains were identified as Bacillus subtilis, Bacillus thuringiensis and Bacillus megaterium based on the results of 16S-rRNA gene sequencing. Chickpea seeds of two varieties (Punjab Noor-2009 and 93127) differing in sensitivity to drought were soaked for 3 h before sowing in fresh grown cultures of isolates. Both the PGRs were applied (150 mg/L), as foliar spray on 20 days old seedlings of chickpea. Moisture stress significantly reduced the physiological parameters but the inoculation of PGPR and PGR treatment effectively ameliorated the adverse effects of moisture stress. The result showed that chickpea plants treated with PGPR and PGR significantly enhanced the chlorophyll, protein and sugar contents. Shoot and root fresh (81%) and dry weights (77%) were also enhanced significantly in the treated plants. Leaf proline content, lipid peroxidation and antioxidant enzymes (CAT, APOX, POD and SOD) were increased in reaction to drought stress but decreased due to PGPR. The plant height (61%), grain weight (41%), number of nodules (78%) and pod (88%), plant yield (76%), pod weight (53%) and total biomass (54%) were higher in PGPR and PGR treated chickpea plants grown in sandy soil. It is concluded from the present study that the integrative use of PGPR and PGRs is a promising method and eco-friendly strategy for increasing drought tolerance in crop plants.
The demand for agricultural crops continues to escalate with an increasing population. To meet this demand, marginal land can be used as a sustainable source for increased plant productivity. ...However, moisture stress not only affects crop growth and productivity but also induces plants' susceptibility to various diseases. The positive role of plant growth hormone, salicylic acid (SA), on the defence systems of plants has been well documented. With this in mind, a combination of plant growth promoting rhizobacteria (PGPR) and SA was used to evaluate its performance on wheat grown under rainfed conditions (average moisture 10-14%). The selected bacterial strains were characterized for proline production, indole-3-acetic acid (IAA), hydrogen cyanide (HCN), ammonia (NH3), and exopolysaccharides (EPS). Wheat seeds of two genotypes, Inqilab-91 (drought tolerant) and Shahkar-2013 (drought sensitive), which differed in terms of their sensitivity to drought stress, were soaked for three hours prior to sowing in 24-hour old cultures of the bacterial strains Planomicrobium chinense strain P1 (accession no. MF616408) and Bacillus cereus strain P2 (accession no. MF616406). SA was applied (150 mg/L), as a foliar spray on one-month-old wheat seedlings. A significant reduction in the physiological parameters was noted in the plants grown in rainfed conditions but the PGPR and SA treatment effectively ameliorated the adverse effects of moisture stress. The wheat plants treated with PGPR and SA showed significant increases in leaf protein and sugar contents and maintained higher chlorophyll content, chlorophyll fluorescence (fv/fm) and performance index (PI) under rainfed conditions. Leaf proline content, lipid peroxidation, and antioxidant enzyme activity were higher in the non-inoculated plants grown in rainfed conditions but significantly reduced in the inoculated plants of both genotypes. Integrative use of a combination of PGPR strains and SA appears to be a promising and eco-friendly strategy for reducing moisture stress in plants.
Genetic improvement for drought tolerance in chickpea requires a solid understanding of biochemical processes involved with different physiological mechanisms. The objective of this study is to ...demonstrate genetic variations in altered metabolic levels in chickpea varieties (tolerant and sensitive) grown under contrasting water regimes through ultrahigh‐performance liquid chromatography/high‐resolution mass spectrometry‐based untargeted metabolomic profiling. Chickpea plants were exposed to drought stress at the 3‐leaf stage for 25 days, and the leaves were harvested at 14 and 25 days after the imposition of drought stress. Stress produced significant reduction in chlorophyll content, Fv/Fm, relative water content, and shoot and root dry weight. Twenty known metabolites were identified as most important by 2 different methods including significant analysis of metabolites and partial least squares discriminant analysis. The most pronounced increase in accumulation due to drought stress was demonstrated for allantoin, l‐proline, l‐arginine, l‐histidine, l‐isoleucine, and tryptophan. Metabolites that showed a decreased level of accumulation under drought conditions were choline, phenylalanine, gamma‐aminobutyric acid, alanine, phenylalanine, tyrosine, glucosamine, guanine, and aspartic acid. Aminoacyl‐tRNA and plant secondary metabolite biosynthesis and amino acid metabolism or synthesis pathways were involved in producing genetic variation under drought conditions. Metabolic changes in light of drought conditions highlighted pools of metabolites that affect the metabolic and physiological adjustment in chickpea that reduced drought impacts.
Drought stress is one of the major problems in chickpea‐growing areas. Though drought stress changes biochemical mechanisms in plants, however, little is known about the complex metabolic regulation for genetic improvement in chickpea under drought stress environments. This study was conducted to identify changes at different metabolites in two chickpea varieties contrasting for drought tolerance under drought and control conditions. This study also demonstrates the metabolic pathways potentially involved in drought tolerance mechanisms in chickpea.
The plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGRs) can be applied to improve the growth and productivity of plants, with potential to be used for genetic improvement ...of drought tolerance. However, for genetic improvement to be achieved, a solid understanding of the physiological and biochemical changes in plants induced by PGPR and PGR is required. The present study was carried out to investigate the role of PGPR and PGRs on the physiology and biochemical changes in chickpea grown under drought stress conditions and their association with drought tolerance. The PGPR, isolated from the rhizosphere of chickpea, were characterized on the basis of colony morphology and biochemical characters. They were also screened for the production of indole-3-acetic acid (IAA), hydrogen cyanide (HCN), ammonia (NH
), and exopolysaccharides (EPS) production. The isolated PGPR strains, named P1, P2, and P3, were identified by 16S-rRNA gene sequencing as Bacillus subtilis, Bacillus thuringiensis, and Bacillus megaterium, respectively. The seeds of two chickpea varieties, Punjab Noor-2009 (drought sensitive) and 93127 (drought tolerant) were soaked for 2-3 h prior to sowing in 24 h old cultures of isolates. The salicylic acid (SA) and putrescine (Put) were sprayed (150 mg/L) on 25 day old chickpea seedlings. The results showed that chickpea plants treated with a consortium of PGPR and PGRs significantly enhanced the chlorophyll, protein, and sugar contents compared to irrigated and drought conditions. Leaf proline content, lipid peroxidation, and activities of antioxidant enzymes (CAT, APOX, POD, and SOD) all increased in response to drought stress but decreased due to the PGPR and PGRs treatment. An ultrahigh performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) analysis was carried out for metabolic profiling of chickpea leaves planted under controlled (well-irrigated), drought, and consortium (drought plus PGPR and PGRs) conditions. Proline, L-arginine, L-histidine, L-isoleucine, and tryptophan were accumulated in the leaves of chickpea exposed to drought stress. Consortium of PGPR and PGRs induced significant accumulation of riboflavin, L-asparagine, aspartate, glycerol, nicotinamide, and 3-hydroxy-3-methyglutarate in the leaves of chickpea. The drought sensitive chickpea variety showed significant accumulation of nicotinamide and 4-hydroxy-methylglycine in PGPR and PGR treated plants at both time points (44 and 60 days) as compared to non-inoculated drought plants. Additionally, arginine accumulation was also enhanced in the leaves of the sensitive variety under drought conditions. Metabolic changes as a result of drought and consortium conditions highlighted pools of metabolites that affect the metabolic and physiological adjustments in chickpea that reduce drought impacts.
To feed the ever-increasing population under changing climate scenarios, it is imperative to investigate the role of halophytes, which are equipped with special adaptation mechanisms to cope under ...extreme conditions of salinity. In the current review, we aimed to report newly identified bioactive secondary metabolites that might play a role in establishing rhizosphere microbe associations, elucidate the negative impacts of salt stress, and direct the growth and yield of halophytes. A systematic approach was developed that deciphers those metabolites involved in regulating the physiological, biochemical, and molecular responses of halophytes to salt stress. The mechanism of salinity tolerance, recruitment of beneficial microbes, and signaling role of secondary metabolites were also discussed. The role of halotolerant rhizobacteria’ secondary metabolites in the physiology and growth parameters of halophytes was also discussed.
During the last two decades the world has experienced an abrupt change in climate. Both natural and artificial factors are climate change drivers, although the effect of natural factors are lesser ...than the anthropogenic drivers. These factors have changed the pattern of precipitation resulting in a rise in sea levels, changes in evapotranspiration, occurrence of flood overwintering of pathogens, increased resistance of pests and parasites, and reduced productivity of plants. Although excess CO
2
promotes growth of C
3
plants, high temperatures reduce the yield of important agricultural crops due to high evapotranspiration. These two factors have an impact on soil salinization and agriculture production, leading to the issue of water and food security. Farmers have adopted different strategies to cope with agriculture production in saline and saline sodic soil. Recently the inoculation of halotolerant plant growth promoting rhizobacteria (PGPR) in saline fields is an environmentally friendly and sustainable approach to overcome salinity and promote crop growth and yield in saline and saline sodic soil. These halotolerant bacteria synthesize certain metabolites which help crops in adopting a saline condition and promote their growth without any negative effects. There is a complex interkingdom signaling between host and microbes for mutual interaction, which is also influenced by environmental factors. For mutual survival, nature induces a strong positive relationship between host and microbes in the rhizosphere. Commercialization of such PGPR in the form of biofertilizers, biostimulants, and biopower are needed to build climate resilience in agriculture. The production of phytohormones, particularly auxins, have been demonstrated by PGPR, even the pathogenic bacteria and fungi which also modulate the endogenous level of auxins in plants, subsequently enhancing plant resistance to various stresses. The present review focuses on plant-microbe communication and elaborates on their role in plant tolerance under changing climatic conditions.
The drought ameliorative effects of poly(acrylic acid) hydrogel (HG), biochar (BC) and plant growth-promoting rhizobacteria (PGPR) were evaluated on soybean exposed to drought stress. Prior to ...sowing, soybean seeds were soaked for 3-4 h in the broth culture of Planomicrobium chinense (MF616408) and Pseudomonas putida (KX574857), while BC (5 g/kg soil) and HG (2 g/kg soil) were mixed with autoclaved soil. Plants were well watered and grown under natural conditions for 35 d, followed by 4 d of drought exposure. While drought stress negatively impacted plant growth, effects of individual application of BC, HG and PGPR in combating the drought stress were noteworthy and a predominant increase in plant biomass by BC and plant antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)) and elevated soil nutrients by PGPR were observed. PGPR assisted HG in retaining the soil moisture content (SMC) and further elevated the leaf relative water content (LRWC) and fresh weight (FW) root. The combined application of HG and PGPR consortium was most effective in improving photosynthetic pigments, FW shoot and soil fertility status. Likewise, the combined application of BC and PGPR had stimulatory effects on plant osmoregulants, with BC combined with Pseudomonas putida significantly improving soil nutrient retention. It is inferred that HG and BC in combination with PGPR isolates and PGPR consortium are effective drought mitigating strategies.
This study aimed to assess the role of two Plant growth promoting rhizobacteria (PGPR),
Pseudomonas stutzeri
(KX574858) and
Pseudomonas putida
(KX574857) against charcoal rot instigated by
...Macrophomina phaseolina
in soybean (
Glycine max
L.) varieties; Ajmeri and NARC grown in pots under greenhouse condition.
Macrophomina
inocula were added to the soil at the time of sowing. Disease incidence and severity were recorded on 90th day of sowing. Seeds were inoculated with PGPR prior to sowing. Growth parameters such as germination index, shoot height and shoot fresh weight were measured at flowering stage.
P. stutzeri
significantly (
p
< 0.05) increased germination index (147% and 115%), shoot height (117% and 103%) and shoot fresh weight (120% and 100%) in cv. Ajmeri and cv. NARC, respectively, in infected plants. Both
P. stutzeri
(76% and 60%) and
P. putida
(23% and 22%) significantly decreased the disease severity index of charcoal rot in cv. Ajmeri and cv. NARC, respectively.
P. stutzeri
induced polyphenol oxidase (435% and 386%), phenylalanine ammonia-lyase (257% and 180%), superoxide dismutase (290% and 240%), peroxidase (733% and 666%) and catalase activities (1867% and 1424%) were linearly increased in cv. Ajmeri and cv. NARC, respectively, after 90 days of infection. Significantly higher accumulation of leaf proline and soluble proteins was recorded in both varieties due to
P. stutzeri
under infected condition. PGPR enhanced the availability of macronutrients in the rhizosphere of infested soil. The antioxidant and defense enzymes in plant were significantly correlated with disease suppression. The PGPR can be used as a supplement with fungicides to combat adverse effect of disease.
In the climate change scenario the drought has been diagnosed as major stress affecting crop productivity. This review demonstrates some recent findings on the amelioration of drought stress. ...Nanoparticles, synthetic growth regulators viz. Trinexapac-ethyl, and Biochar addition helps to economize the water budget of plants, enhances the bioavailability of water and nutrients as well as overcomes drought induced osmotic and oxidative stresses. Besides ABA, SA and JA are also involved in inducing tolerance to drought stress through modulation of physiological and biochemical processes in plants. Plant growth promoting rhizobacteria (PGPR) offer new opportunities in agricultural biotechnology. These beneficial microorganisms colonize the rhizosphere/endo-rhizosphere of plants and impart drought tolerance by improving root architechture, enhancing water use efficiency, producing exopolysaccharides, phytohormones viz, ABA, SA and IAA and volatile compounds. Further PGPR also play positive role in combating osmotic and oxidative stresses induced by drought stress through enhancing the accumulation of osmolytes, antioxidants and upregulation or down regulation of stress responsive genes. In transgenic plants stress inducible genes enhanced abiotic stress tolerance by encoding key enzymes regulating biosynthesis of compatible solutes. The role of genes/cDNAs encoding proteins involved in regulating other genes/proteins, signal transduction process and strategies to improve drought stress tolerance have also been discussed.
The current investigation designed to estimate the bioremediation potential of plant growth-promoting rhizobacteria (PGPR) and Ag-nanoparticles. Tube well and HIT water comprising Mn and Fe above ...recommended values were used as treatments while tap water irrigation was treated as control. The HIT water showed 24, 200, and 64.11% higher content of Na, K Ca over control. Seeds were sterilized in 95% ethanol and soaked for 3 h before sowing in 73 h old culture of Pseudomonas stutzeri (Kx574858) @ 10
8
cells/ml. Phytotoxic effect of Fe and Mn reduce plant biomass and suppress photosynthetic activity indicates. The carotenoids, proline, and proline activity were 366, 450, and 678% higher in tube well water with combined PGPR and Ag-nanoparticles treatments. Pseudomonas stutzeri was more effective than Ag-nanoparticles to reduce oxidative stress with higher production of carotenoids, flavonoids, proline content, and enzyme SOD and CAT activities in HIT water. It is contingent that the high Mn and Fe bearing waste water enhance PGPR bioremediation potential to reduce metal stress in plants with synergistic action of PGPR and organic matter to alleviate oxidative stresses under metal stress. The residual effect of P. stutzeri on organic matter content of the rhizosphere soil and germination rate was higher for Momordica charantia L.
This is the first statement indicating that Ag-nanoparticles oxidize Mn and Fe efficiently to reduce COD and organic matter works synergistically with PGPR and Ag-nanoparticles to enhance ROS production that increase proline, carotenoids, flavonoids, phenolics, and enzymes SOD, POD, PAL, and CAT activities to reduce oxidative stress in cucurbits.
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