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

Tahir M, Mirza MS, Hameed S, Dimitrov MR, Smidt H - PLoS ONE (2015)

Bottom Line: 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.Diversity of rhizosheath-associated bacteria was evaluated by cultivation, as well as by 454-pyrosequencing of PCR-tagged 16S rRNA gene amplicons.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).

View Article: PubMed Central - PubMed

Affiliation: National Institute for Biotechnology and Genetic Engineering (NIBGE), Jhang Road Faisalabad, Punjab, Pakistan.

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(-1) and 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.

No MeSH data available.


Related in: MedlinePlus

Population of culturable bacteria (cfu.g-1 of soil) on LB medium in rhizosheath of wheat.Wheat-rice rotation (A) and wheat-cotton rotation (B). Plants were inoculated with Azospirillum sp. WS-1, Bacillus sp. T-34 or non-inoculated (control). Bacterial population sizes were measured in rhizosheath soil samples by plating of serial dilutions on LB agar. Log values were calculated for colony forming units (cfu). Given values are the mean of 3 replications. Four different predominant types of colonies (A, B, C, D) could be distinguished as based on 16S rRNA gene sequence analysis.
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pone.0130030.g004: Population of culturable bacteria (cfu.g-1 of soil) on LB medium in rhizosheath of wheat.Wheat-rice rotation (A) and wheat-cotton rotation (B). Plants were inoculated with Azospirillum sp. WS-1, Bacillus sp. T-34 or non-inoculated (control). Bacterial population sizes were measured in rhizosheath soil samples by plating of serial dilutions on LB agar. Log values were calculated for colony forming units (cfu). Given values are the mean of 3 replications. Four different predominant types of colonies (A, B, C, D) could be distinguished as based on 16S rRNA gene sequence analysis.

Mentions: In order to comprehensively assess the diversity and identity of bacteria in wheat rhizosheaths under both rotations, after 35 DAS, we used cultivation on LB medium, as well as pyrosequencing of PCR-amplified 16S rRNA gene fragments. Four morphologically different colony types, A, B, C and D (Fig 4A and 4B), were dominantly present along with other less abundant colony types in all plated samples of rhizosheath soil. The ranges of colony type A(log 2–4 cfu.g-1 of dry soil), colony type B(log 4–7 cfu.g-1 of dry soil), colony type C (log 4–7 cfu.g-1 of dry soil) and colony type D (log 2–7 cfu.g-1 of dry soil) were detected under both the crop rotations (Fig 4A and 4B). cfu of colony types A, C and D were highest in the rhizosheath of wheat grown under wheat-cotton rotation while the number of type B colonies was highest in the rhizosheath of wheat grown under wheat-rice crop rotation. Among the treatments maximum total cfu g-1 dry soil (>108 cfu.g-1 dry soil) was obtained in the rhizosheath of plants inoculated with Bacillus sp. T-34 strain in both rotations (Fig 4A and 4B). The total number of cfu obtained on LB medium for bulk soil suspensions was also significantly (P<0.05) affected by inoculation of bacterial isolates (Fig 5). Bacterial population (cfu.g-1dry soil) was significantly higher (p<0.05) in soil inoculated with Bacillus sp. T-34 as compared to other treatments under both the systems. In this treatment total cfu.g-1 dry soil were higher (>108 cfu.g-1 dry soil) in rhizosheath (Fig 5) compared with bulk soil (≤106cfu.g-1 dry soil). One representative colony from each dominant colony type was identified by 16S rRNA gene sequence analysis. Colony type A was identified as Bacillus sp. (isolate PA), colony type B as Enterobacter sp. (isolate WP-8), colony type C as Arthrobacter sp. (isolate WK2T) and colony type D as Acinetobacter sp. isolate WS-1D (Table 4).


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

Tahir M, Mirza MS, Hameed S, Dimitrov MR, Smidt H - PLoS ONE (2015)

Population of culturable bacteria (cfu.g-1 of soil) on LB medium in rhizosheath of wheat.Wheat-rice rotation (A) and wheat-cotton rotation (B). Plants were inoculated with Azospirillum sp. WS-1, Bacillus sp. T-34 or non-inoculated (control). Bacterial population sizes were measured in rhizosheath soil samples by plating of serial dilutions on LB agar. Log values were calculated for colony forming units (cfu). Given values are the mean of 3 replications. Four different predominant types of colonies (A, B, C, D) could be distinguished as based on 16S rRNA gene sequence analysis.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4487687&req=5

pone.0130030.g004: Population of culturable bacteria (cfu.g-1 of soil) on LB medium in rhizosheath of wheat.Wheat-rice rotation (A) and wheat-cotton rotation (B). Plants were inoculated with Azospirillum sp. WS-1, Bacillus sp. T-34 or non-inoculated (control). Bacterial population sizes were measured in rhizosheath soil samples by plating of serial dilutions on LB agar. Log values were calculated for colony forming units (cfu). Given values are the mean of 3 replications. Four different predominant types of colonies (A, B, C, D) could be distinguished as based on 16S rRNA gene sequence analysis.
Mentions: In order to comprehensively assess the diversity and identity of bacteria in wheat rhizosheaths under both rotations, after 35 DAS, we used cultivation on LB medium, as well as pyrosequencing of PCR-amplified 16S rRNA gene fragments. Four morphologically different colony types, A, B, C and D (Fig 4A and 4B), were dominantly present along with other less abundant colony types in all plated samples of rhizosheath soil. The ranges of colony type A(log 2–4 cfu.g-1 of dry soil), colony type B(log 4–7 cfu.g-1 of dry soil), colony type C (log 4–7 cfu.g-1 of dry soil) and colony type D (log 2–7 cfu.g-1 of dry soil) were detected under both the crop rotations (Fig 4A and 4B). cfu of colony types A, C and D were highest in the rhizosheath of wheat grown under wheat-cotton rotation while the number of type B colonies was highest in the rhizosheath of wheat grown under wheat-rice crop rotation. Among the treatments maximum total cfu g-1 dry soil (>108 cfu.g-1 dry soil) was obtained in the rhizosheath of plants inoculated with Bacillus sp. T-34 strain in both rotations (Fig 4A and 4B). The total number of cfu obtained on LB medium for bulk soil suspensions was also significantly (P<0.05) affected by inoculation of bacterial isolates (Fig 5). Bacterial population (cfu.g-1dry soil) was significantly higher (p<0.05) in soil inoculated with Bacillus sp. T-34 as compared to other treatments under both the systems. In this treatment total cfu.g-1 dry soil were higher (>108 cfu.g-1 dry soil) in rhizosheath (Fig 5) compared with bulk soil (≤106cfu.g-1 dry soil). One representative colony from each dominant colony type was identified by 16S rRNA gene sequence analysis. Colony type A was identified as Bacillus sp. (isolate PA), colony type B as Enterobacter sp. (isolate WP-8), colony type C as Arthrobacter sp. (isolate WK2T) and colony type D as Acinetobacter sp. isolate WS-1D (Table 4).

Bottom Line: 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.Diversity of rhizosheath-associated bacteria was evaluated by cultivation, as well as by 454-pyrosequencing of PCR-tagged 16S rRNA gene amplicons.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).

View Article: PubMed Central - PubMed

Affiliation: National Institute for Biotechnology and Genetic Engineering (NIBGE), Jhang Road Faisalabad, Punjab, Pakistan.

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(-1) and 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.

No MeSH data available.


Related in: MedlinePlus