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During the present study, Pseudomonas moraviensis and Bacillus cereus, were isolated from rhizosphere soil of halophytic weed (cenchrus ciliaris L.) of Khewra salt range, and used as bioinoculants. The plant growth promoting rhizobacteria (PGPR) were applied to wheat (Triticum aestivum) by seeds soaking, and aqueous solution of tryptophan was added to the rhizosphere soil at 1ug/L, after seed germination. Experiment was conducted at Quaid-e-Azam University Islamabad both in pots (filled with sterilized soil) under axenic condition and in field under natural condition, for two consecutive years. The inoculation of Pseudomonas moraviensis and Bacillus cereus, significantly increased the organic matter, P, K, Ca, and NO 3 -N availability of soil. The inoculation of these PGPR positively enhanced growth and physiology of treated plants, and this affect was further augmented in the presence of tryptophan. Addition of tryptophan with Pseudomonas moraviensis and Bacillus cereus increased the fresh weight, proline contents and activities of antioxidant enzymes significantly over control. Added tryptophan with both PGPR, improved the number of plants at yield and seeds establishment by improving number of seeds/spike and spike length. Effects of PGPR inoculation alone and with tryptophan were more pronounced in pots grown plants. It is inferred from the results, that tryptophan addition is a competent source for increasing potential of PGPR, thereby improving wheat growth, and physiology.

The aim of the study was to determine tolerance of plant growth promoting rhizobacteria (PGPR) in different concentrations of Cu, Cr, Co, Cd, Ni, Mn, and Pb and to evaluate the PGPR-modulated bioavailability of different heavy metals in the rhizosphere soil and wheat tissues, grown in saline sodic soil. Bacillus cereus and Pseudomonas moraviensis were isolated from Cenchrus ciliaris L. growing in the Khewra salt range. Seven-day-old cultures of PGPR were applied on wheat as single inoculum, co-inoculation and carrier-based biofertilizer (using maize straw and sugarcane husk as carrier). At 100 ppm of Cr and Cu, the survival rates of rhizobacteria were decreased by 40%. Single inoculation of PGPR decreased 50% of Co, Ni, Cr and Mn concentrations in the rhizosphere soil. Co-inoculation of PGPR and biofertilizer treatment further augmented the decreases by 15% in Co, Ni, Cr and Mn over single inoculation except Pb and Co where decreases were 40% and 77%, respectively. The maximum decrease in biological concentration factor (BCF) was observed for Cd, Co, Cr, and Mn. P. moraviensis inoculation decreases the biological accumulation coefficient (BAC) as well as translocation factor (TF) for Cd, Cr, Cu Mn, and Ni. The PGPR inoculation minimized the deleterious effects of heavy metals, and the addition of carriers further assisted the PGPR.

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