Jyoti Kumar Thakur

RESPONSE OF WHEAT TO INOCULATION WITH MYCORRHIZAE ALONE AND COMBINED WITH SELECTED RHIZOBACTERIA INCLUDING FLAVOBACTERIUM SP. AS A POTENTIAL BIOINOCULANT

A pot experiment was conducted to evaluate different arbuscular mycorrhiza sps. (AM) for their effect on plant growth, yield and nutrient uptake by wheat. All the AM fungal sps. significantly enhanced all the plant parameters and nutrient uptake by the plant. A positive correlation was observed between percent root colonization by AM fungi and most of the plant parameters studied. Glomus macrocarpum giving best results was selected for studying interactive effect with Azotobacter, Azospirillum (well-known PGPRs), and Flavobacterium and Proteus vulgaris (less studied PGPRs). All the PGPRs significantly increased most of the plant parameters studied and their combination with AMF had a synergistic effect. Amongst PGPRs, Flavobacterium gave best response both singly and in combination with AMF and thus, is a potential new bioinoculant for wheat. Application of 120 kg nitrogen (N) ha−1was the best treatment. Inoculation with most of the PGPRs gave better response than 60 kg N ha−1.

Microbes: A Sustainable Approach for Enhancing Nutrient Availability in Agricultural Soils

The soil scientists along with microbiologists had a big responsibility to come forward with a sustainable solution to enhance soil nutrient supplying capacity, without applying the agrochemical and mineral fertilizers. The only way out to this problem is through the use of efficient microbes which plays a vital role as organic or biological agents in facilitating uptake of many primary and secondary nutrients. Moreover, the fertility of any soil is directly proportional to the microbial biomass and its potential of functional activity and diversity. Billions of microbes which are present in soil are major key players of nutrient cycling and their solubilization and mineralization. This fact has been known and scientifically reported for a number of decades, but still its significance has not yet channelized into the mainstream of intensive agriculture. Thus, in this chapter, exhaustive overview of the different groups of agriculturally important microbes has been given which are responsible for enhancing nutrient availability particularly nitrogen, phosphorus, potassium, sulphur, iron and zinc in agricultural soils.

SOIL MICROBIAL POPULATION AND ENZYME ACTIVITIES UNDER ORGANIC, BIODYNAMIC AND CONVENTIONAL AGRICULTURE IN SEMI-ARID TROPICAL CONDITIONS OF CENTRAL INDIA

Present field experiment was conducted at the Indian Institute of Soil Science, Bhopal, India in a clayey soil (Typic Haplusterts) under soybean (Glycine max, cv. JS 335) wheat (Triticum durum, cv. HI 8498) cropping system in a randomized block design with seven treatments in four replications to study the changes in soil fungal, bacterial and actinomycetes population; and resultant enzymatic activities in soil under organic, biodynamic and conventional agriculture management. The results of study revealed that, the soil microbial population (bacteria, fungi and actinomycetes), soil enzyme activities and soil microbial biomass carbon were found in the order of organic > conventional ≥ biodynamic agriculture. The organic agriculture registered 27-102% and 28-111% higher enzymatic activities than conventional and biodynamic agriculture, respectively. Similarly, soil microbial biomass carbon was found 30-45% and 33-42% higher under organic agriculture management as compared to conventional and biodynamic agriculture management, respectively. No significant effect of biodynamic agriculture management on soil microbial properties was observed. * Corresponding author

Effects of Bt-cotton on biological properties of Vertisols in central India

ABSTRACT Growing areas under transgenic crops have created a concern over their possible adverse impact on the soil ecosystem. This study evaluated the effect of Bt-cotton based cropping systems on soil microbial and biochemical activities and their functional relationships with active soil carbon pools in Vertisols of central India (Nagpur, Maharastra, during 2012–2013). Culturable groups of soil microflora, enzymatic activities and active pools of soil carbon were measured under different Bt-cotton based cropping systems (e.g. cotton-soybean, cotton-redgram, cotton-wheat, cotton-vegetables and cotton-fallow). Significantly higher counts of soil heterotrophs (5.7–7.9 log cfu g−1 soil), aerobic N-fixer (3.9–5.4 log cfu g−1 soil) and P-solubilizer (2.5−3.0 log cfu g−1 soil) were recorded in Bt-cotton soils. Similarly, soil enzymatic activities, viz. dehydrogenase (16.6–22.67 µg TPF g−1 h−1), alkaline phosphatase (240–253 µg PNP g−1 h−1) and fluorescein di-acetate hydrolysis (14.6–18.0 µg fluorescein g−1 h−1), were significantly higher under Bt-cotton-soybean system than other Bt- and non-Bt-cotton based systems in all crop growth stages. The growth stage-wise order of soil microbiological activities were: boll development > harvest > vegetative stage. Significant correlations were observed between microbiological activities and active carbon pools in the rhizosphere soil. The findings indicated no adverse effect of Bt-cotton on soil biological properties.

Phylloplane bacteria of Jatropha curcas: diversity, metabolic characteristics, and growth-promoting attributes towards vigor of maize seedling

The complex role of phylloplane microorganisms is less understood than that of rhizospheric microorganisms in lieu of their pivotal role in plants sustainability. This experiment aims to study the diversity of the culturable phylloplane bacteria of Jatropha curcas and evaluate their growth-promoting activities towards maize seedling vigor. Heterotrophic bacteria were isolated from the phylloplane of J. curcas and their 16S rRNA genes were sequenced. Sequences of the 16S rRNA gene were very similar to those of species belonging to the classes Bacillales (50%), Gammaproteobacteria (21.8%), Betaproteobacteria (15.6%), and Alphaproteobacteria (12.5%). The phylloplane bacteria preferred to utilize alcohol rather than monosaccharides and polysaccharides as a carbon source. Isolates exhibited ACC (1-aminocyclopropane-1-carboxylic acid) deaminase, phosphatase, potassium solubilization, and indole acetic acid (IAA) production activities. The phosphate-solubilizing capacity (mg of PO4 solubilized by 108 cells) varied from 0.04 to 0.21. The IAA production potential (μg IAA produced by 108 cells in 48 h) of the isolates varied from 0.41 to 9.29. Inoculation of the isolates to maize seed significantly increased shoot and root lengths of maize seedlings. A linear regression model of the plant-growth-promoting activities significantly correlated (p < 0.01) with the growth parameters. Similarly, a correspondence analysis categorized ACC deaminase and IAA production as the major factors contributing 41% and 13.8% variation, respectively, to the growth of maize seedlings.

Plant–Microbe Interaction for the Removal of Heavy Metal from Contaminated Site

The diversity of microbes present in the rhizosphere plays a significant role in nutrient cycling and soil sustainability. Plant–microbe-modulated phytoremediation is a viable technology for the cleanup of contaminated environments. Several plants that were identified have various degrees of capacity to eliminate, degrade or detoxify, metabolize, or immobilize a wide range of soil contaminants. Plant-based remediation technologies are not yet commercialized because of its major limitation of slow process and restricted bioavailability of the contaminants, and it is greatly influenced by the climatic factors. The extensive use of plants can overcome most of the limitations by exploring the potential of microbe–plant–metal interaction. The biogeochemical process occurring in the root zone can influence on several rhizobacteria and mycorrhizae directly linked with microbial metabolite synthesis. Thus, a holistic approach of novel remediation technologies and understanding of plant–microbe–contaminant interaction would help for customizing phytoremediation process in relation to site-specific contamination. There is a huge challenge to remediation of contaminated sites by long-term accumulation of heavy metal. Unlike organic contaminants, metals are very much resistant to degradation, and in the long run, continuous accumulation may cause food chain contamination. It is very important to decontaminate the polluted sites in order to reach safe level of metal concentration below the threshold limit of toxicity. Recent studies revealed that phytoextraction, mainly the use of hyperaccumulator plants to extract toxic metals from the contaminated sites, has emerged as a cost-effective, eco-friendly cleanup technology. Novel, efficient microbes and their potential use in the plant rhizosphere could further enhance the phytoremediation for wider range of soil contaminants.