Abstract
Abstract 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 3 ), 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.
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Claims 10
Claim · model-written summary
The three chickpea rhizosphere isolates were identified as Bacillus subtilis, B. thuringiensis and B. megaterium.
- Taxon
- chickpea
Cicer arietinume1 - Interactor
- Bacillus subtilis
Bacillus subtilise0symbiont - Outcome
- identified by 16S-rRNA gene sequencinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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.”
e1“rhizosphere of chickpea”
Claim · model-written summary
Combined PGPR and PGR treatment significantly increased chickpea chlorophyll, protein and sugar contents versus irrigated and drought conditions.
- Taxon
- chickpeaCicer arietinume0
- Treatment
- a consortium of PGPR and PGRse0
- Outcome
- chlorophyll, protein, and sugar contentse0
- Direction
- enhancede0
- Comparator
- irrigated and drought conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chickpea plants treated with a consortium of PGPR and PGRs significantly enhanced the chlorophyll, protein, and sugar contents compared to irrigated and drought conditions”
Claim · model-written summary
Drought increased leaf proline content, lipid peroxidation and antioxidant enzyme activities.
- Taxon
- ChickpeaCicer arietinumt0
- Treatment
- drought stresse0
- Outcome
- Leaf proline content, lipid peroxidation, and activities of antioxidant enzymese0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Chickpea”
e0“Leaf proline content, lipid peroxidation, and activities of antioxidant enzymes (CAT, APOX, POD, and SOD) all increased in response to drought stress”
Claim · model-written summary
PGPR and PGR treatment decreased leaf proline, lipid peroxidation and antioxidant enzyme activities.
- Taxon
- ChickpeaCicer arietinumt0
- Treatment
- PGPR and PGRs treatmente0
- Outcome
- Leaf proline content, lipid peroxidation, and activities of antioxidant enzymese0
- Direction
- decreasede0
- Comparator
- drought stresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Chickpea”
e0“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”
Claim · model-written summary
Drought caused accumulation of proline, L-arginine and L-histidine in chickpea leaves.
- Taxon
- chickpeaCicer arietinume0
- Organ / stage
- leavese0
- Treatment
- drought stresse0
- Outcome
- Proline, L-arginine, L-histidinee0
- Direction
- accumulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Proline, L-arginine, L-histidine, L-isoleucine, and tryptophan were accumulated in the leaves of chickpea exposed to drought stress”
Claim · model-written summary
Drought caused accumulation of L-isoleucine and tryptophan in chickpea leaves.
- Taxon
- chickpeaCicer arietinume0
- Organ / stage
- leavese0
- Treatment
- drought stresse0
- Outcome
- L-isoleucine, and tryptophane0
- Direction
- accumulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Proline, L-arginine, L-histidine, L-isoleucine, and tryptophan were accumulated in the leaves of chickpea exposed to drought stress”
Claim · model-written summary
PGPR and PGR consortium significantly accumulated riboflavin, L-asparagine and aspartate.
- Taxon
- chickpeaCicer arietinume0
- Treatment
- Consortium of PGPR and PGRse0
- Outcome
- riboflavin, L-asparagine, aspartatee0
- Direction
- accumulatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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”
Claim · model-written summary
PGPR and PGR consortium significantly accumulated glycerol, nicotinamide and 3-hydroxy-3-methyglutarate.
- Taxon
- chickpeaCicer arietinume0
- Treatment
- Consortium of PGPR and PGRse0
- Outcome
- glycerol, nicotinamide, and 3-hydroxy-3-methyglutaratee0
- Direction
- accumulatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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”
Claim · model-written summary
In drought sensitive chickpea, PGPR and PGR treatment increased nicotinamide and 4-hydroxy-methylglycine at 44 and 60 days versus noninoculated drought plants.
- Taxon
- chickpeaCicer arietinume0
- Treatment
- PGPR and PGRe0
- Outcome
- nicotinamide and 4-hydroxy-methylglycinee0
- Direction
- accumulatione0
- Qualifier
- 44 and 60 dayse0
- Comparator
- non-inoculated drought plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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”
Claim · model-written summary
Drought enhanced arginine accumulation in the sensitive chickpea variety.
- Taxon
- ChickpeaCicer arietinumt0
- Material
- sensitive varietye0
- Treatment
- drought conditionse0
- Outcome
- arginine accumulatione0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“arginine accumulation was also enhanced in the leaves of the sensitive variety under drought conditions”
t0“Chickpea”
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