Recent crop production studies have aimed at an increase in the biotic and abiotic tolerance of plant communities, along with increased nutrient availability and crop yields. This can be achieved in various ways, but one of the emerging approaches is to understand the phytomicrobiome structure and associated chemical communications. The phytomicrobiome was characterized with the advent of high-throughput techniques. Its composition and chemical signaling phenomena have been revealed, leading the way for “rhizosphere engineering”. In addition to the above, phytomicrobiome studies have paved the way to best tackling soil contamination with various anthropogenic activities. Agricultural lands have been found to be unbalanced for crop production. Due to the intense application of agricultural chemicals such as herbicides, fungicides, insecticides, fertilizers, etc., which can only be rejuvenated efficiently through detailed studies on the phytomicrobiome component, the phytomicrobiome has recently emerged as a primary plant trait that affects crop production. The phytomicrobiome also acts as an essential modifying factor in plant root exudation and vice versa, resulting in better plant health and crop yield both in terms of quantity and quality. Not only supporting better plant growth, phytomicrobiome members are involved in the degradation of toxic materials, alleviating the stress conditions that adversely affect plant development. Thus, the present review compiles the progress in understanding phytomicrobiome relationships and their application in achieving the goal of sustainable agriculture.

Plant growth promoting rhizobacteria (PGPR) is beneficial bacteria that colonize plant roots and enhance plant growth by wide variety of mechanism like phosphate solubilisation, etc. Use of PGPR has steadily increased in agriculture and offers an attractive way to replace chemical fertilizers, pesticides and supplements. The present research work was designed to isolate and characterize the PGP activity of Burkholderia sp. For this purpose rhizospheric soil from Rhododendron arboreum of Kumaun Himalaya was collected and efficient bacterial strain was screened on the basis of phosphate solubilization. Further, assessment of various parameters of plant growth promotion activity was done and enhanced production of IAA (16.4 µgml ) was observed in the presence of 250µgml -1 and 500 µg ml -1 of tryptophan, respectively. Correspondingly, in respect of 7.8 µg ml -1 IAA without tryptophan, and their confirmation was executed by TLC. A remarkable change in color from green to reddish-brown zone on CAS plates, suggests the positive result for siderophore production, and finally the seed germination and pot trial experiment depicted the growth index of wheat plant. Therefore, the present study suggests that Burkholderia sp. is beneficial for plant growth promotion.

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Polycyclic Aromatic Hydrocarbons (PAH) are ubiquitous contaminants in environments, are generated as a by-product of incomplete combustion of organic substances. PAH continuously increases and accumulate in surrounding finally affect the environment as well as crop production. Thus, appropriate treatment is required to reduce the concentration and toxicity of these substances. Bioremediation, an effective method, uses the ability of an organism to reduce the concentration of PAH to an acceptable level. This study investigated the ability of PAHs (fluorene) degrading as well plant growth promoting activity by three bacterial strains (MHR 4 , MHR 2 and MB 2) isolated from crude oil polluted soil near fuel filling stations from Haldwani and Bhowali in Uttarakhand region. These strains showed considerable growth over fluorene, as the sole carbon source with 100-500 ppm concentration in Mineral Salt Medium (MSM) agar plates after 24 h. Although, all the strains have potential towards plant growth promoting activity. Comparative study of fluorene degradation was found prominent, 81.2% in strain MHR 4 followed by strain MB 2 , 55% and strain MHR 2 , 37.5%, likewise, the efficiencies of various PGP activities in strain MHR 4 were detected quite high. This was convincing enough to investigate the strain MHR 4 for their molecular identification and to check their efficiency in pot trail experiment. Therefore, the efficient strain MHR 4 was identified on the basis of 16S rDNA sequencing and confirmed as Enterobacter sp. The multi traits strain effectively to remove fluorene both from the oil contaminated environment as well as to eliminate the chemical fertilizer by providing diverse PGP activity, is a novel achievement and suggests that Enterobacter sp. MHR 4 have extremely useful for a biotechnological process involving fluorene degradation and plant growth promotion. The unique nature of fluorene degradation as well as plant growth promotion activity has not yet been studied in the same bacterial strain to our knowledge.

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