Current soil management strategies are mainly dependent on inorganic chemical-based fertilizers, which caused a serious threat to human health and environment. The exploitation of beneficial microbes as a biofertilizer has become paramount importance in agriculture sector for their potential role in food safety and sustainable crop production. The eco-friendly approaches inspire a wide range of application of plant growth promoting rhizobacteria (PGPRs), endo- and ectomycorrhizal fungi, cyanobacteria and many other useful microscopic organisms led to improved nutrient uptake, plant growth and plant tolerance to abiotic and biotic stress. The present review highlighted biofertilizers mediated crops functional traits such as plant growth and productivity, nutrient profile, plant defense and protection with special emphasis to its function to trigger various growth- and defense-related genes in signaling network of cellular pathways to cause cellular response and thereby crop improvement. The knowledge gained from the literature appraised herein will help us to understand the physiological bases of biofertlizers towards sustainable agriculture in reducing problems associated with the use of chemicals fertilizers.

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Biofertilizers function as key player in sustainable agriculture by improving soil fertility, plant tolerance and crop productivity

Plants are sessile beings, so the need of mechanisms to flee from unfavorable circumstances has provided the development of unique and sophisticated responses to environmental stresses. Depending on the degree of plasticity, many morphological, cellular, anatomical, and physiological changes occur in plants in response to abiotic stress. Phytohormones are small molecules that play critical roles in regulating plant growth and development, as well as stress tolerance to promote survival and acclimatize to varying environments. To congregate the challenges of salinity, temperature extremes, and osmotic stress, plants use their genetic mechanism and different adaptive and biological approaches for survival and high production. In the present attempt, we review the potential role of different phytohormones and plant growth-promoting rhizobacteria in abiotic stresses and summarize the research progress in plant responses to abiotic stresses at physiological and molecular levels. We emphasized the regulatory circuits of abscisic acid, indole acetic acid, cytokinins, gibberellic acid, salicylic acid, brassinosteroids, jasmonates, ethylene, and triazole on exposure to abiotic stresses. Current progress is exemplified by the identification and validation of several significant genes that enhanced crop tolerance to stress in the field. These findings will make the modification of hormone biosynthetic pathways for the transgenic plant generation with augmented abiotic stress tolerance and boosting crop productivity in the coming decades possible.

Potential role of phytohormones and plant growth-promoting rhizobacteria in abiotic stresses: consequences for changing environment.

Drought stress not only effect the population and activities of microorganisms inhabiting the rhizosphere but also various physiological and biochemical process in plants that is, photosynthesis, respiration, translocation, uptake of ions, carbohydrates, and nutrient metabolism. Plant growth promoting rhizobacteria (PGPR) and their exopolysaccharides (EPS) showed profound effects on plant growth and drought tolerance. Reactions of bacteria to drought stress at various organizational levels are different which depends on intensity of stress, duration, species, and growth stage. PGPR could be effectively utilized in developing strategies to facilitate water conservation strategies of plants. They have the ability to improve plant growth directly by enhancing level of phytohormones, siderophore, biofilm, and exopolysaccharides production and by increasing the nutrient availability in the rhizosphere or indirectly by protecting plants from pathogen attack. EPS producing bacteria are capable to maintain higher soil moisture content and growth of plants even under severe dried sandy soils. The evidence of survival of rhizobacteria under low moisture content obtained from the fact of rhizobacterial occurrence in the soil of desert and effective nodule formation in desert soil. Beside this, EPS produced by PGPR form rhizosheath around the roots and thus protect the plant roots from desiccation for a longer period of time. Important role exhibited by exopolysaccharides includes, protection from desiccation, microbial aggregation, plant-microbe interaction, surface attachment, bioremediation and its use by many industries for stabilizing, thickening, coagulating, gelling, suspending and for film forming. Plants inoculated with EPS-producing bacteria showed higher accumulation of proline, sugars, and free amino acids under water deficit stress. Biofilms formed by the PGPR around the roots are made up of bacterial populations or bacterial communities that encased inside the polymeric extracellular matrix formed by bacteria itself, they adhered to the external surfaces that contain sufficient moisture. It is concluded that the application of PGPR in combination with their EPS is a promising measure to combat drought stress thus, increasing global food security.

Exopolysaccharides producing rhizobacteria and their role in plant growth and drought tolerance.

The molecular approach

Jatropha curcas L. (hereinafter Jatropha) is often considered as a magical biodiesel plant with multitude of environmental benefits and therefore, the plantation of Jatropha has been done on a global scale without crop improvement, proper field validation, standardization of agronomic practices and high quality certified planting materials. Importantly, the seed yield and oil content of the species were not validated before the field introduction. Moreover, farmers are not aware of the biology and ecology of Jatropha and even not aware of the pest incidence and common diseases in Jatropha. As a result, there was a total mismatch between the expectations as well as the real performance of this species under field condition. Therefore, the present article is aimed to critically analyze the actual reasons behind the failure of Jatropha in field conditions and recommend suitable strategies for the future utilization of this plant for sustainable biofuel program.

Jatropha curcas L.: A crucified plant waiting for resurgence

Jatropha curcas has been widely planted without knowing its standard package of practice for optimizing the yield. Therefore, a standardized agro-technology of Jatropha is required. With this purpose, in this study an elite accession of Jatropha was planted at seven sites in India, covering a range of edapho-climatic conditions. Three experimental trials (spacing, pruning and irrigation and fertilizer) were carried out wherein its growth and yield performance were assessed for five years (2007-2012) at all the sites. The growth characters like plant height and number of branches showed significant variations among the sites and the effects of treatments were not uniform across the sites, indicating that site-specific package of practices should be followed instead of adopting the general recommendations. The seed yield was disappointing to recommend it randomly for large scale plantations on degraded lands in India. But results from the multi-location trials have shown good prospects at semi-arid (Bhavnagar) and drylands (Hyderabad); where plants in close spacing (2 x 2 m) produced significantly higher seed yield per unit area upto 1.4 t ha(-1) (Bhavnagar) in comparison to wide spacing. Pruning showed a negative effect on seed yield during initial five years. We found that the following prescription was sufficient to optimize the yield on India's degraded soils: irrigation at a 30 day interval, and for each planting hole 2 kg of Farm Yard Manure (organic manure) and nitrogen, phosphorous and potassium at 10 g, 20 g, and 10 g, respectively. (C) 2012 Elsevier Ltd. All rights reserved.

Agro-technology of Jatropha curcas for diverse environmental conditions in India

Bamboos are versatile, arborescent, perennial and non-wood forest trees with tremendous eco-sociological and commercial importance. Different propagation techniques are available for bamboo, such as seed propagation, clump division, rhizome and culm cuttings, but these classical techniques suffer from serious drawbacks for large or mass scale propagation. For mass scale propagation, these are largely insufficient and inefficient and micropropagation is the only viable method. Indeed, the order of magnitude of the demand for bamboo planting material indicates that micropropagation will inevitably be necessary for mass scale propagation. The potential of micropropagation for mass scale propagation of bamboo has raised high hopes and a lot of research has been focused on the development of protocols for large and rapid scale propagation. These encompass optimization and establishment of in vitro culture techniques including micropropagation, somatic embryogenesis, in vitro flowering, macro proliferation, field performance and clonal fidelity. This review briefly provides the state-of-the-art information on tissue culture mediated biotechnological interventions made in bamboo for large scale micropropagation, that being the need of the hour. Keywords : Bamboo, micropropagation, somatic embryogenesis, in vitro flowering, macroproliferation, field performance, clonal fidelity African Journal of Biotechnology Vol. 12(20), pp. 2770-2785

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Micropropagation of important bamboos: A review

Rise in human population always demands a rapid and sustainable increase in cereal production. As a result nitrogenous fertilizers were used constantly in excess, which resulted in a number of problems such as green house emissions (particularly N2O) and leaching to ground-water. Moreover they are expensive. So long term sustainability in agriculture can only be obtained with the use of low cost fertilizer which should also be ecologically safe. In this regard biological nitrogen fixation by microbes, that is, biofertilizer, plays an active role helping in better maintenance of crop nutrient as well as soil health.Azospirillum, an associative symbiotic nitrogen fixing bacterium has a higher nitrogen fixing potential in non-legumes in comparison to other nitrogen fixing bacterium, by the formation of para nodules. However further investigation is needed to find possible avenues for the exploitation of this bacterium. The current review emphasizes the central issues of Azospirillum and its application either alone or in combination with other plant growth promoting rhizobacteria for the benefit of the non leguminous crops.

	Key words: Azospirillum, non legumes, BNF, para-nodules, inoculation, rhizosphere.

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A review on the role of Azospirillum in the yield improvement of non leguminous crops

An efficient protocol for in vitro micropropagation of Bambusa nutans Wall. ex. Munro has been described. Nodal explants obtained from 1½-year-old field-grown culms of B. nutans produced up to 7.0 multiple shoots per explant on Murashige and Skoog (MS) basal medium supplemented with 6- benzylaminopurine (BAP, 1.0 mg/L). Continuous shoot proliferation up to 11.33 shoots was achieved by sub-culturing shoot clumps (4 shoots/cluster) in BAP (0.5 mg/L) and 0.1 mg/l α-naphthalene acetic acid (NAA) fortified medium every 4 weeks. 85% rooting was recorded on 2.0 mg/L NAA supplemented medium after 30 to 35 days of culture period. Micropropagated plantlets of B. nutans showed 70% survivability during the hardening stage. After hardening, rooted plantlets were successfully transferred to the soil and exhibited 80% survivability and normal growth. Plantlets cultivated in field condition achieved 95% survivability. Seed explants were also used for in vitro culture establishment of B. nutans on different combination of MS medium. Keywords: Bambusa nutans , micropropagation, nodal explants, seed explants. African Journal of Biotechnology , Vol 13(19), 1961-1972

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Effect of nodal positions, seasonal variations, shoot clump and growth regulators on micropropagation of commercially important bamboo, Bambusa nutans Wall. ex. Munro

Jatropha (Jatropha curcas Linn) is a non-edible oilseed plant with adaptability to marginal semi-arid lands and wastelands The Indian Government is promoting jatropha to reduce dependence on the crude oil and to achieve energy independence by the year 2012, under the National Biodiesel Mission Adaptive trials on J curcas were undertaken at the North East Institute of Science and Technology, Jorhat, Assam The aim of the study was to determine source variation in J curcas accessions collected from 17 states (34 locations) of India and to identify the best sources to be utilized for reforestation and future genetic improvement work The evaluation of 34 cultivars revealed a good degree of variation for plant height, stem girth, branches per plant and 100 seed weight The accessions have shown measurable growth responses, which were sufficient for a conclusive remark Hence the present study was carried out with the respective first and second year growth performances Variation in the physiological parameters of different sources was also studied The pattern of variation exhibited for different characters was found to be different and varied with age Such variation among different populations may be due to different intensities of natural selection acting upon the traits in their natural habitat High 100 seed weight (142 g) was observed in one cultivar The performance of Naharlagun (Arunachal Pradesh), Lamphelpat (Manipur), Dergaon (Assam) and Namsa (Nagaland) sources was satisfactory The results indicate that genetic differences exist among accessions of J curcas The relative performance of these sources was fairly consistent throughout the observation period

http://www.indiaenvironmentportal.org.in/files/Jatropha%20curcas%20Linn.pdf

Siddhartha Proteem Saikia

Papers

Agro-technology of Jatropha curcas for diverse environmental conditions in India

Micropropagation of important bamboos: A review

A review on the role of Azospirillum in the yield improvement of non leguminous crops

Effect of nodal positions, seasonal variations, shoot clump and growth regulators on micropropagation of commercially important bamboo, Bambusa nutans Wall. ex. Munro

Study of accession source variation in morpho-physiological parameters and growth performance of Jatropha curcas Linn.