Abstract
Rhizosphere microbial communities are dynamic and play a crucial role in diverse biochemical processes and nutrient cycling. Soil type and cultivar modulate the composition of rhizosphere microbial communities. Changes in the community composition significantly alter microbial function and ecological process. We examined the influence of soil type on eubacterial and diazotrophic community abundance and microbial metabolic potential in chickpea (cv. BG 372 and cv. BG 256) rhizosphere. The total eubacterial and diazotrophic community as estimated through 16S rDNA and nifH gene copy numbers using qPCR showed the soil type influence with clear rhizosphere effect on gene abundance. PLFA study has shown the variation in microbial community structure with different soil types. Differential influence of soil types and cultivar on the ratio of Gram positive to Gram negative bacteria was observed with most rhizosphere soils corresponding to higher ratios than bulk soil. The rhizosphere microbial activities (urease, dehydrogenase, alkaline phosphatase and beta-glucosidase) were also assessed as an indicator of microbial metabolic diversity. Principal component analysis and K-means non-hierarchical cluster mapping grouped soils into three categories, each having different soil enzyme activity or edaphic drivers. Soil type and cultivar influence on average substrate utilization pattern analyzed through community level physiological profiling (CLPP) was higher for rhizosphere soils than bulk soils. The soil nutrient studies revealed that both soil type and cultivar influenced the available N, P, K and organic carbon content of rhizosphere soil. Our study signifies that soil type and cultivar jointly influenced soil microbial community abundance and their metabolic potential in chickpea rhizosphere.
Highlights
Soil is the home for prodigious number of living organisms and as far as the plant growth and soil properties are concerned, microbial communities inhabiting rhizosphere region play a crucial role in diverse biochemical processes and nutrient cycling
We examined the influence of soil type on eubacterial and diazotrophic community abundance and microbial metabolic potential in chickpea
Though the chickpea was grown under controlled conditions at New Delhi, our results showed different soil type had varied chemical and biological properties
Summary
Soil is the home for prodigious number of living organisms and as far as the plant growth and soil properties are concerned, microbial communities inhabiting rhizosphere region play a crucial role in diverse biochemical processes and nutrient cycling. Many studies have focused on traditional culturable techniques to study the rhizosphere microbial diversity and function, ‘great plate count anomaly’ states that a greater fraction (95–99%) of microbial community involved in rhizosphere process is unculturable (Nichols 2007) Advanced analytical techniques such as Amplified Ribosomal DNA Restriction Analysis (ARDRA, Gich et al 2000), BOX PCR (Satyaprakash and Annapurna 2006), Denaturing Gradient Gel Electrophoresis (DGGE, Miller et al 1999), Quantitative PCR (Fierer et al 2005), phospholipid fatty acid (PLFA, Guckert and White 1986), and community level physiological profiling (CLPP, Preston-Mafham et al 2002) are used to examine the diversity of fingerprints allowing for more detailed analyses of abundance and activities of soil microbial communities (Mittal and Virdi 2002)
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