Identification, Characterization and Evaluation of Multifaceted Traits of Plant Growth Promoting Rhizobacteria from Soil for Sustainable Approach to Agriculture.

This study assessed potential of plant growth promoting rhizobacteria (PGPR) found in 34 soil samples collected from Sirmaur, Himachal Pradesh. Out of 238 rhizobacterial isolates, 48 rhizobacterial isolates exhibited multiple PGP (plant growth promoting) traits. Out of the 48 isolates, nine isolates exhibiting most promising PGP traits were evaluated. CSRS12 isolate showed maximum solubilization of phosphate and potassium up to 530.71 and 30.44 mg l-1, respectively. Maximum zinc solubilizing efficiency (ZSE) was also observed in case of isolate CSRS12. The maximum IAA production was observed by isolate PPRS17 with 37.34 mg l-1 followed by PCRS24 with 34.44 mg l-1 after 120 h. Maximum siderophore unit production was observed upto 92.29% by isolate CSRS12 followed by 65.54% with isolate TA1PS. The selected PGPR isolates were identified through 16S rDNA sequencing. The identified PGPRs were Burkholderia arboris (isolate CSRS12), Pseudomonas aeruginosa (isolate PPRS17) and Acinetobacter baumannii (isolate TA1PS). B. arboris CSRS12 isolate showed multiple PGP traits as mineral solubilization of phosphate, potassium and zinc, production of siderophore and ammonia. Among all three PGPR treatment, B. arboris CSRS12 isolate showed significant increment in lateral root number, root and shoot length, fresh and dry weight of root and shoot of mung bean (Vigna radiata) in pot experiments. The results showed that CSRS12 isolate could be used for exploitation as bio-inoculant, which can facilitate better productivity and ecological dynamics for both domesticated crops as well as wild varieties.

Iron Availability Affects Phosphate Deficiency-Mediated Responses, and Evidence of Cross-Talk with Auxin and Zinc in Arabidopsis.

Phosphate (Pi) is pivotal for plant growth and development. Pi deficiency triggers local and systemically regulated adaptive responses in Arabidopsis thaliana. Inhibition of primary root growth (PRG) and retarded development of lateral roots (LRs) are typical local Pi deficiency-mediated responses of the root system. Expression of Pi starvation-responsive (PSR) genes is regulated systemically. Here, we report the differential influence of iron (Fe) availability on local and systemic sensing of Pi by Arabidopsis. P-Fe- condition disrupted local Pi sensing, resulting in an elongated primary root (PR). Altered Fe homeostasis in the lpsi mutant with aberration in local Pi sensing provided circumstantial evidence towards the role of Fe in the maintenance of Pi homeostasis. Reporter gene assays, expression analysis of auxin-responsive genes (ARGs) and root phenotyping of the arf7arf19 mutant demonstrated the role of Fe availability on local Pi deficiency-mediated LR development. In addition, Fe availability also exerted a significant influence on PSR genes belonging to different functional categories. Together, these results demonstrated a substantial influence of Fe availability on Pi deficiency-mediated responses of ontogenetically distinct traits of the root system and PSR genes. The study also provided evidence of cross-talk between Pi, Fe and Zn, highlighting a complex tripartite interaction amongst them for maintaining Pi homeostasis.