Cultivation-Based and Molecular Assessment of Bacterial Diversity in the Rhizosheath of Wheat under Different Crop Rotations

Abstract

A field study was conducted to compare the formationand bacterial communities of rhizosheaths of wheat grown under wheat-cotton and wheat-rice rotation and to study the effects of bacterial inoculation on plant growth. Inoculation of Azospirillum sp. WS-1 and Bacillus sp. T-34 to wheat plants increased root length, root and shoot dry weight and dry weight of rhizosheathsoil when compared to non-inoculated control plants, and under both crop rotations. Comparing both crop rotations, root length, root and shoot dry weight and dry weight of soil attached with roots were higher under wheat-cotton rotation. Organic acids (citric acid, malic acid, acetic acid and oxalic acid) were detected in rhizosheaths from both rotations, with malic acid being most abundant with 24.8±2 and 21.3±1.5 μg g-1 dry soil in wheat-cotton and wheat-rice rotation, respectively. Two sugars (sucrose, glucose) were detected in wheat rhizosheath under both rotations, with highest concentrations of sucrose (4.08±0.5 μg g-1and 7.36±1.0 μg g-1) and glucose (3.12±0.5 μg g-1 and 3.01± μg g-1) being detected in rhizosheaths of non-inoculated control plants under both rotations. Diversity of rhizosheath-associated bacteria was evaluated by cultivation, as well as by 454-pyrosequencing of PCR-tagged 16S rRNA gene amplicons. A total of 14 and 12 bacterial isolates predominantly belonging to the genera Arthrobacter, Azospirillum, Bacillus, Enterobacter and Pseudomonaswere obtained from the rhizosheath of wheat grown under wheat-cotton and wheat-rice rotation, respectively. Analysis of pyrosequencing data revealed Proteobacteria, Bacteriodetes and Verrucomicrobia as the most abundant phyla in wheat-rice rotation, whereas Actinobacteria, Firmicutes, Chloroflexi, Acidobacteria, Planctomycetes and Cyanobacteria were predominant in wheat-cotton rotation. From a total of 46,971 sequences, 10.9% showed ≥97% similarity with 16S rRNA genes of 32 genera previously shown to include isolates with plant growth promoting activity (nitrogen fixation, phosphate-solubilization, IAA production). Among these, the most predominant genera were Arthrobacter, Azoarcus, Azospirillum, Bacillus, Cyanobacterium, Paenibacillus, Pseudomonas and Rhizobium.

BACTERIA IN COMBINATION WITH FERTILIZERS IMPROVE GROWTH, PRODUCTIVITY AND NET RETURNS OF WHEAT (Triticum aestivum L.)

“…reduced pH from 7.0 to 4.8±0.2 of the Pikovskaya broth medium supplemented with TCP (Table 3) and solubilised maximum amount of phosphorous (355±14 µg/mL). Association and isolation of phosphate solubilising Bacillus strains from the rhizosphere of various crops like wheat, rice, sugarcane and maize has been frequently reported (Tahir et al, 2015;Tahir et al, 2013). Two bacterial strains Pseudomonas sp.…”

“…The reason for this may be the soil factors like temperature, moisture, aeration, root exudates nature and indigenous bacterial population at that specific plant growth stage was more suitable for the growth, survival and activity of the Pseudomonas strain. Previous studies have reported that the population, diversity, survival and activity of bacteria is affected due to nature of root exudates and indigenous rhizosphere bacteria (Shridhar, 2012;Tahir et al, 2015;Walker et al, 2003). Both the bacterial strains, Pseudomonas sp.…”

“…Rhizosphere bacteria including Azospirillum, Azotobacter, Bacillus, Enterobacter and Pseudomonas produced significant amount of IAA as major property to improve plant productivity (Tahir et al, 2013). Isolation of Bacillus strains from the rhizosphere of various crops, phosphate solubilization, IAA production in vitro and plant growth promoting potential of Bacillus strains under field conditions have been reported (Tahir et al, 2015;Tahir et al, 2013). In addition, Pseudomonas spp.…”

“…In addition, Pseudomonas spp. equipped with plant-beneficial traits like phosphate solubilization, N fixation, IAA production and bio-control of plant pathogens have been isolated from the rhizosphere of various crops (Babana et al, 2012;Kumar et al, 2012;Pastor et al, 2014;Tahir et al, 2015). Keeping in view all these problems, the objective of the present study was to isolate, characterize the rhizosphere bacteria on the basis of plant growth promoting qualities (phosphate solubilization, N fixation and IAA producing ability) and to identify the selected isolates through 16S rRNA sequencing.…”

Comprehensive Account of Inoculation and Coinoculation in Soybean

“…These bacteria also produce the siderophores and synthesize enzymes, antibiotics, or fungicidal compounds that protect the plants against phytopathogenic microorganisms [63,64]. There are several factors such as agricultural practices, plant genotype, bacteria species, and strain that may affect the success of inoculation and plant response to these PGPB [65,66]. Chickpea and Rhizobium leguminosrum subsp.…”