Soil Chemical Analysis

Tomorrow’s agriculture, challenged by increasing global demand for food, scarcity of arable lands, and resources alongside multiple environment pressures, needs to be managed smartly through sustainable and eco-efficient approaches. Modern agriculture has to be more productive, sustainable and environmentally friendly. While macronutrients such as nitrogen (N), phosphorus (P), potassium (K) and sulfur (S) supplied by mineral fertilizers are vital to crop production, agriculturally beneficial microorganisms may also contribute directly (i.e. biological N2 fixation, P solubilization, phytohormone production, etc.) or indirectly (i.e. antimicrobial compounds biosynthesis, elicitation of induced systemic resistance, etc.) to crop improvement and fertilizers efficiency. Microbial-based bioformulations that increase plant performance are greatly needed, and in particular bioformulations that exhibit complementary and synergistic effects with mineral fertilization. Such an integrated soil fertility management strategy has been demonstrated through several controlled and non-controlled experiments, but more efforts have to be made in order to thoroughly understand the multiple functions of beneficial microbes’ functions within the soil microbial community itself and in interaction with plants and mineral resources. In fact, the combined usage of microbial (i.e. beneficial microorganisms: N2-fixing (NF), P-solubilizing and P mobilizing, etc.) and mineral resources is an emerging research area that aims to design and develop efficient microbial formulations which are highly compatible with mineral inputs, with positive impacts on both crops and environment. This novel approach is likely to be of a global interest, especially in most N- and P-deficient agro-ecosystems. In this review, we report on the importance of NF bacteria and P solubilizing/mobilizing microbes as well as their interactions with mineral P fertilization in improving crop productivity and fertilizers efficiency. In addition, we shed light on the interactive and synergistic effects that may occur within multi-trophic interactions involving those two microbial groups and positive consequences on plant mineral uptake, crop productivity and resiliency to environmental constraints. Improving use of mineral nutrients is a must to securing higher yield and productivity in a sustainable manner, therefore continuously designing, developing and testing innovative integrated plant nutrient management systems based on relevant biological resources (crops and microorganisms) is highly required.

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Soil Microbial Resources for Improving Fertilizers Efficiency in an Integrated Plant Nutrient Management System

Bottlenecks in commercialisation and future prospects of PGPR

Chitin is an important component of the exteriors of insects and fungi. Upon degradation of chitin by a number of organisms, severe damage and even death may occur in pathogens and pests whose external surfaces contain this polymer. Currently, chemical fungicides and insecticides are the major means of controlling these disease-causing agents. However, due to the potential harm that these chemicals cause to the environment and to human and animal health, new strategies are being developed to replace or reduce the use of fungal- and pest-killing compounds in agriculture. In this context, chitinolytic microorganisms are likely to play an important role as biocontrol agents and pathogen antagonists and may also function in the control of postharvest rot. In this review, we discuss the literature concerning chitin and the basic knowledge of chitin-degrading enzymes, and also describe the biocontrol effects of chitinolytic microorganisms and their potential use as more sustainable pesticides and fungicides in the field.

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Chitinase-producing bacteria and their role in biocontrol

Unlocking the potential of plant growth-promoting rhizobacteria on soil health and the sustainability of agricultural systems.

Characterization and in planta nitrogen fixation of plant growth promoting endophytic diazotrophic Lysinibacillus sphaericus isolated from rice (Oryza sativa)

Two indigenous rhizospheric phosphate solubilizing isolates PSB 12 identified as Gluconacetobacter sp. (MTCC 8368) and PSB 73 identified as Burkholderia sp. (MTCC 8369) were examined for their growth enhancement potential of rice (Jyothi PTB 39) under pot culture assays. The results showed significant impact on microbial count and PSB population, phosphatase and dehydrogenase activity, available phosphorous in the soil, plant nutrient uptake and yield parameters. Gluconacetobacter sp. + RP60 treatment (30.96 µg PNP g−1 soil) retained highest phosphatase activity whereas Gluconacetobacter sp. + Burkholderia sp. + RP60 treatment recorded maximum dehydrogenase activity (38.88 µg TPF g−1 soil) after 60 days of treatment. The treatments Burkholderia sp. + RP60 and Gluconacetobacter sp. + RP60 produced comparable amount of P and these treatments were statistically at par throughout the growth period. Highest nutrient uptake and yield was noted in Gluconacetobacter sp. + Burkholderia sp. + RP60 treatment. A positive synergistic interaction between strains of Gluconacetobacter sp. and Burkholderia sp. has been noticed for their plant growth promotion activity. These strains could be of potential to develop as biofertilizers after testing their performance under field conditions either alone or as components of integrated nutrient management systems.

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Growth enhancement of rice (Oryza sativa) by phosphate solubilizing Gluconacetobacter sp. (MTCC 8368) and Burkholderia sp. (MTCC 8369) under greenhouse conditions

Biocontrol potential of Halotolerant bacterial chitinase from high yielding novel Bacillus Pumilus MCB-7 autochthonous to mangrove ecosystem

Previous studies indicate that high concentration of pesticides and their associated toxic effects are high at their point source of application. Use of pesticide-degrading bacteria at point sources could augment degradation and thereby reduce toxic effects associated with pesticide persistence in soil. Quinalphos, an organophosphorus insecticide, though ranked “moderately hazardous” in the WHO's acute hazard ranking, still continues to be used extensively in developing countries. The presence of a chloride radical usually makes this pesticide sparingly soluble in water and hence difficult to degrade. The present study aimed to isolate autochthonous bacterial strains capable of utilizing quinalphos as a carbon source. Primary screening of pesticide-contaminated soil by enrichment culture and degradation analysis by UV-VIS spectrophotometry led to the isolation of 12 different bacterial isolates, of which three efficient isolates of Pseudomonas sp, Serratia sp, and Pseudomonas aeruginosa with degradation r...

Biosurfactant Facilitated Biodegradation of Quinalphos at High Concentrations by Pseudomonas aeruginosa Q10

Chitinases – the primary chitin lytic enzyme has gained great attention due to its industrial, environmental, agriculture, medicinal and biotechnological applications. However, the industrial production of this enzyme is still at its infancy due to low yielding strains and high cost of production. The current paper targets the cumulative optimisation of chitinase production from low cost substrate chitin using high yielding novel chitinase producing strain. Bacterial chitinase producers were isolated from the potential mangrove ecosystem of Valanthakad, Cochin, Kerala. Among the various isolates, the best chitinase producer MCB-7 identified as Bacillus pumilus exhibited an inherent high chitinase activity of 3.36 U/mL. Using Plackett–Burman design the factors such as chitin concentration, peptone and pH were found to be significant. Further optimisation with a multivariate statistical approach using Box–Behnken design resulted in a 6.9 fold increase of chitinase activity to a final yield of 23.19 U/mL. The use of cheap and consistent nature of the chitin as carbon source along with a high chitinase yielding isolate would be beneficial in providing consistent yields of the enzyme. To the best of our knowledge, this is the first report on high chitinase yielding B. pumilus strains from mangroves. The current isolate of B. pumilus MCB-7 is also unique in its halotolerance, pH tolerance and thermostability – which could widen its spectrum of applications.

K.S. Rishad

Papers

Characterization and in planta nitrogen fixation of plant growth promoting endophytic diazotrophic Lysinibacillus sphaericus isolated from rice (Oryza sativa)

Growth enhancement of rice (Oryza sativa) by phosphate solubilizing Gluconacetobacter sp. (MTCC 8368) and Burkholderia sp. (MTCC 8369) under greenhouse conditions

Biocontrol potential of Halotolerant bacterial chitinase from high yielding novel Bacillus Pumilus MCB-7 autochthonous to mangrove ecosystem

Biosurfactant Facilitated Biodegradation of Quinalphos at High Concentrations by Pseudomonas aeruginosa Q10

Optimised production of chitinase from a novel mangrove isolate, Bacillus pumilus MCB-7 using response surface methodology