Efficacy of organic-based carrier material for plant beneficial rhizobacteria application in okra under normal and salt-affected soil conditions.

AIMS: Plant beneficial rhizobacteria (PBR) improve salt tolerance and plant yield in vegetable plants by producing 1-aminocyclopropane-1-carboxylate-deaminase, indole-3-acetic acid and phosphate solubilization. Organic-based carrier material is needed to ensure the PBR's uniform application, distribution, survival and functioning in a variety of fields. The PBR also use carbon present in the carrier as food and energy source. The selection of a suitable organic-based carrier material for the application of the PBR in normal and saline soils always has received less attention. The current study compared the PBR suitability of different organic-based carrier materials (biochar, biogas residues [BGRs] and coconut powder) and evaluated their effects on okra productivity under normal and saline soil conditions. METHODS AND RESULTS: In a pot experiment, the PBR strain Bacillus sp. MR-1/2 (accession number, MG548383) was applied with/or without organic-based carrier materials to okra grown in three different soils: S1 (EC 1.0 dS m-1 ), S2 (EC 3.0 dS m-1 ) and S3 (EC 5.0 dS m-1 ). The experiment was set up in a completely randomized design with five replicates in factorial arrangement. Results indicated that in soil S1, PBR + BGR increased the number of pods per plant, plant dry weight and indole compounds by 64%, 68% and 17% while reduced the electrolyte leakage (ELL), malonaldehyde (MDA) contents and stress ethylene level by 17%, 55% and 38%, respectively over the PBR application without any carrier. Similarly, in soil S2, the treatment PBR + BGR increased the number of pods by 81%, plant dry weight by 40% and indole compounds by 13% while reduced the ELL by 17%, MDA contents by 50% and stress ethylene by 30% over the PBR alone treatment. In soil S3, PBR + biochar increased the number of pods by 51%, plant dry weight by 62% and indole compounds by 20%, while reduced the ELL by 21%, MDA by 40% and indole compounds by 54% over the PBR alone treatment. CONCLUSIONS: Results concluded that in soil S1 and S2 (normal soils), BGR as carrier for PBR showed best results, while in soil S3, biochar as carrier for PBR resulted in enhanced potassium (K+ ) and calcium (Ca+2 ) uptake and increased the productivity of okra. SIGNIFICANCE AND IMPACT OF STUDY: Response of different carrier materials in supporting PBR under different soil conditions was variable. This study will help in the selection and use of best suitable carrier material for PBR application under different soil conditions. It is recommended that farmer should use BGR as carrier material for PBR application in normal soils while biochar should be used as carrier for the PBR application in saline soil.

Metal-tolerant Pantoea sp. WP-5 and organic manures enhanced root exudation and phytostabilization of cadmium in the rhizosphere of maize.

This study investigated the phytoremediation potential of maize (Zea mays L.) in Cd-contaminated soil through co-inoculation of metal-tolerant plant beneficial rhizobacteria (MtPBR: Pantoea sp. strain WP-5) with organic manures (PM, poultry manure, and BGR, biogas residues). The objectives of this study were to (i) examine comparative efficiency of MtPBR, PM and BGR alone or in combined form to improve maize biomass and physiology and (ii) understand the role of organic acid production in root exudates of maize for Cd accumulation and translocation. Pantoea sp. WP-5 showed organic acid production and tolerance to high Cd concentration (1000 mg L-1), thereby inoculated to maize seeds sown in soil spiked with 75 mg Cd kg-1 soil and 500 g each of the organic manures per pot. The co-inoculation of MtPBR + BGR significantly (P<0.05) increased chlorophyll contents, root/shoot dry weight, photosynthetic rate, stomatal conductance, and relative water contents and decreased electrolyte leakage, malondialdehyde contents, ascorbate peroxidase, and catalase activity in maize over the control treatment. The co-inoculation of MtPBR + BGR produced significantly (P<0.05) higher concentrations of acetic and citric acid (52.7±0.5 and 22.8±0.08 µg g-1 root fwt, respectively) in root exudates of maize, which immobilized Cd within plant roots inferred by the positive relation (root Cd vs. organic acids; R2 = 0.80-0.92) and reduced Cd translocation to shoots inferred by the negative relation (shoot Cd vs. organic acids; R2 = 0.81-0.90). It is concluded that the application of MtPBR + BGR enhanced organic acid induced phytostabilization and accumulation of Cd in roots and restricted its translocation to shoots.

Regulation of antioxidant production, ion uptake and productivity in potato (Solanum tuberosum L.) plant inoculated with growth promoting salt tolerant Bacillus strains.

The exchangeable sodium (Na+) in salt affected soils is a major constraint in potassium (K+) availability to plants that disturb ion transport and inhibit plant growth, adversely. Salt tolerant plant growth promoting rhizobacteria (PGPR) may regulate the Na+/K+ efflux and increase K+ uptake by the plant from the soil. Therefore, a pot study was performed to examine the effect of salt tolerant PGPR Bacillus sp. alone and in consortium, on antioxidant enzyme activity, ion uptake and potato (Solanum tuberosum L.) tuber yield in normal and salt affected soils. We observed that Bacillus sp. (strains SR-2-1 and SR-2-1/1) solubilized insoluble phosphorous and produced indole-3-acetic acid while only SR-2-1/1 produced ACC deaminase in culture medium supplemented with various concentrations of NaCl (0-6%). In the pot experiment, the consortium treatment of strains was found to increase relative leaf water contents whereas decreased the electrolyte leakage and antioxidant enzyme activity both in normal and salt affected soils. Similarly, consortium treatment decreased Na+ whereas increased K+, Ca+2, K+/Na+ and Ca+2/Na+ in plant dry matter in both soils. It has been investigated that inoculation of PGPR significantly (p < 0.05) increased plant biomass, number of tubers per plant and tuber weight as compared to un-inoculated plants in both soils. In addition, PGPR inoculation enhanced auxin production in root exudates of young potato plants and bacterial population dynamics in both soils. Na+ ion regulation (R2 = 0.95) and tuber weight (R2 = 0.90) in salt affected soil were significantly correlated with auxin production in the rhizosphere. Results of this study conferred that consortium of Bacillus strains (SR-2-1, SR-2-1/1) enhanced auxin production in the rhizosphere of potato plants and that ultimately regulated antioxidant enzyme production and uptake of Na+, K+ and Ca+2 in potato plants resulted into a higher tuber yield in both normal and salt affected soils.

Combined application of bio-organic phosphate and phosphorus solubilizing bacteria (Bacillus strain MWT 14) improve the performance of bread wheat with low fertilizer input under an arid climate.

This study was aimed to investigate the effect of bio-organic phosphate either alone or in combination with phosphorus solubilizing bacteria strain (Bacillus MWT-14) on the growth and productivity of two wheat cultivars (Galaxy-2013 and Punjab-2011) along with recommended (150-100NPkgha-1) and half dose (75-50NPkgha-1) of fertilizers. The combined application of bio-organic phosphate and the phosphorous solubilizing bacteria strain at either fertilizer level significantly improved the growth, yield parameters and productivity of both wheat cultivars compared to non-inoculated control treatments. The cultivar Punjab-2011 produced the higher chlorophyll contents, crop growth rate, and the straw yield at half dose of NP fertilizer; while Galaxy-2013, with the combined application of bio-organic phosphate and phosphorous solubilizing bacteria under recommended NP fertilizer dose. Combined over both NP fertilizer levels, the combined use of bio-organic phosphate and phosphorous solubilizing bacteria enhanced the grain yield of cultivar Galaxy-2013 by 54.3% and that of cultivar Punjab-2011 by 83.3%. The combined application of bio-organic phosphate and phosphorous solubilizing bacteria also increased the population of phosphorous solubilizing bacteria, the soil organic matter and phosphorous contents in the soil. In conclusion, the combined application of bio-organic phosphate and phosphorous solubilizing bacteria offers an eco-friendly option to harvest the better wheat yield with low fertilizer input under arid climate.

Combined application of bio-organic phosphate and phosphorus solubilizing bacteria (Bacillus strain MWT 14) improve the performance of bread wheat with low fertilizer input under an arid climate

Abstract This study was aimed to investigate the effect of bio-organic phosphate either alone or in combination with phosphorus solubilizing bacteria strain (Bacillus MWT-14) on the growth and productivity of two wheat cultivars (Galaxy-2013 and Punjab-2011) along with recommended (150100 NP kg ha1) and half dose (7550 NP kg ha1) of fertilizers. The combined application of bio-organic phosphate and the phosphorous solubilizing bacteria strain at either fertilizer level significantly improved the growth, yield parameters and productivity of both wheat cultivars compared to non-inoculated control treatments. The cultivar Punjab-2011 produced the higher chlorophyll contents, crop growth rate, and the straw yield at half dose of NP fertilizer; while Galaxy-2013, with the combined application of bio-organic phosphate and phosphorous solubilizing bacteria under recommended NP fertilizer dose. Combined over both NP fertilizer levels, the combined use of bio-organic phosphate and phosphorous solubilizing bacteria enhanced the grain yield of cultivar Galaxy-2013 by 54.3% and that of cultivar Punjab-2011 by 83.3%. The combined application of bio-organic phosphate and phosphorous solubilizing bacteria also increased the population of phosphorous solubilizing bacteria, the soil organic matter and phosphorous contents in the soil. In conclusion, the combined application of bio-organic phosphate and phosphorous solubilizing bacteria offers an eco-friendly option to harvest the better wheat yield with low fertilizer input under arid climate.

Combined application of bio-organic phosphate and phosphorus solubilizing bacteria (Bacillus strain MWT 14) improve the performance of bread wheat with low fertilizer input under an arid climate

Abstract This study was aimed to investigate the effect of bio-organic phosphate either alone or in combination with phosphorus solubilizing bacteria strain (Bacillus MWT-14) on the growth and productivity of two wheat cultivars (Galaxy-2013 and Punjab-2011) along with recommended (150-100 NP kg ha−1) and half dose (75-50 NP kg ha−1) of fertilizers. The combined application of bio-organic phosphate and the phosphorous solubilizing bacteria strain at either fertilizer level significantly improved the growth, yield parameters and productivity of both wheat cultivars compared to non-inoculated control treatments. The cultivar Punjab-2011 produced the higher chlorophyll contents, crop growth rate, and the straw yield at half dose of NP fertilizer; while Galaxy-2013, with the combined application of bio-organic phosphate and phosphorous solubilizing bacteria under recommended NP fertilizer dose. Combined over both NP fertilizer levels, the combined use of bio-organic phosphate and phosphorous solubilizing bacteria enhanced the grain yield of cultivar Galaxy-2013 by 54.3% and that of cultivar Punjab-2011 by 83.3%. The combined application of bio-organic phosphate and phosphorous solubilizing bacteria also increased the population of phosphorous solubilizing bacteria, the soil organic matter and phosphorous contents in the soil. In conclusion, the combined application of bio-organic phosphate and phosphorous solubilizing bacteria offers an eco-friendly option to harvest the better wheat yield with low fertilizer input under arid climate.