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The date palm tree rhizosphere is a niche for plant growth promoting bacteria in the oasis ecosystem.

Ferjani R, Marasco R, Rolli E, Cherif H, Cherif A, Gtari M, Boudabous A, Daffonchio D, Ouzari HI - Biomed Res Int (2015)

Bottom Line: Assessing the influence of such factors is a key to understand (i) the driving forces determining the shape of root-associated bacterial communities and (ii) the plant growth promoting (PGP) services they provide.The bacterial communities in the soil fractions associated with the root system of date palms cultivated in seven oases in Tunisia were assessed by culture-independent and dependent approaches.The comparable numbers and types of PGP traits indicate their importance in maintaining the plant functional homeostasis despite the different environmental selection pressures.

View Article: PubMed Central - PubMed

Affiliation: LR03ES03 Laboratoire Microorganismes et Biomolécules Actives, Faculté des Sciences de Tunis, Université de Tunis El Manar, Campus Universitaire, 2092 Tunis, Tunisia.

ABSTRACT
In arid ecosystems environmental factors such as geoclimatic conditions and agricultural practices are of major importance in shaping the diversity and functionality of plant-associated bacterial communities. Assessing the influence of such factors is a key to understand (i) the driving forces determining the shape of root-associated bacterial communities and (ii) the plant growth promoting (PGP) services they provide. Desert oasis environment was chosen as model ecosystem where agriculture is possible by the microclimate determined by the date palm cultivation. The bacterial communities in the soil fractions associated with the root system of date palms cultivated in seven oases in Tunisia were assessed by culture-independent and dependent approaches. According to 16S rRNA gene PCR-DGGE fingerprinting, the shapes of the date palm rhizosphere bacterial communities correlate with geoclimatic features along a north-south aridity transect. Despite the fact that the date palm root bacterial community structure was strongly influenced by macroecological factors, the potential rhizosphere services reflected in the PGP traits of isolates screened in vitro were conserved among the different oases. Such services were exerted by the 83% of the screened isolates. The comparable numbers and types of PGP traits indicate their importance in maintaining the plant functional homeostasis despite the different environmental selection pressures.

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Station location and analysis of bacterial community structure associated with soil fraction of date root system. (a) The location of the studied oases is indicated on the map of Tunisia. (b) A principal coordinate analysis (PCO), deduced from the 16S rRNA gene-based PCR-DGGE profiles, resumes the diversity of the bacterial communities associated with the date palm root soil fractions. 84.8% of total variation is explained in the presented PCO. The soil fractions analysed are R: rhizosphere; S: root surrounding soil; and B: bulk soil. (c) Dist LM analysis to evaluate which are the main geoclimatic variables influencing the structure of the bacterial communities associated with date palm root soil fractions. Lat. N: latitude north; Long. E: longitude east; Alt.: altitude; Tmin⁡: minimum temperature; Tmax⁡: maximum temperature; Rainfall min: minimum rainfall; Rainfall max: maximum rainfall. (d) Box-plot graph represents the quantification of 16S rRNA gene by qPCR. The number of copies is expressed in Log10. Statistical analysis (pairwise test) of bacterial assemblage across locations was indicated by the letter.
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fig1: Station location and analysis of bacterial community structure associated with soil fraction of date root system. (a) The location of the studied oases is indicated on the map of Tunisia. (b) A principal coordinate analysis (PCO), deduced from the 16S rRNA gene-based PCR-DGGE profiles, resumes the diversity of the bacterial communities associated with the date palm root soil fractions. 84.8% of total variation is explained in the presented PCO. The soil fractions analysed are R: rhizosphere; S: root surrounding soil; and B: bulk soil. (c) Dist LM analysis to evaluate which are the main geoclimatic variables influencing the structure of the bacterial communities associated with date palm root soil fractions. Lat. N: latitude north; Long. E: longitude east; Alt.: altitude; Tmin⁡: minimum temperature; Tmax⁡: maximum temperature; Rainfall min: minimum rainfall; Rainfall max: maximum rainfall. (d) Box-plot graph represents the quantification of 16S rRNA gene by qPCR. The number of copies is expressed in Log10. Statistical analysis (pairwise test) of bacterial assemblage across locations was indicated by the letter.

Mentions: The sampling was carried out from seven oases in different geographic locations in Tunisia, along a latitude/longitude gradient, respectively from 32° to 34°N and from 7° to 9°E (Figure 1(a) and Supplementary Table 1 in the Supplementary Material available online at http://dx.doi.org/10.1155/2015/153851). A traditional crop management was used in all the oases, including groundwater-based flooding irrigation and fertilization with organic fertilizers. In each oasis, the roots of three date palm trees of similar age, lying in the distance of less than 15 meters and growing in the same soil were separately collected at 20–30 cm depth in order to obtain the adhering rhizosphere soil (R) tightly attached to roots. After removing the roots, the root surrounding soil (S) was collected. Bulk soil samples (B) not influenced by date palm root system were also sampled as control. All soil samples were collected under sterile conditions using sterile tools. Recovered samples were stored at −20°C for molecular analysis or at 4°C for isolation.


The date palm tree rhizosphere is a niche for plant growth promoting bacteria in the oasis ecosystem.

Ferjani R, Marasco R, Rolli E, Cherif H, Cherif A, Gtari M, Boudabous A, Daffonchio D, Ouzari HI - Biomed Res Int (2015)

Station location and analysis of bacterial community structure associated with soil fraction of date root system. (a) The location of the studied oases is indicated on the map of Tunisia. (b) A principal coordinate analysis (PCO), deduced from the 16S rRNA gene-based PCR-DGGE profiles, resumes the diversity of the bacterial communities associated with the date palm root soil fractions. 84.8% of total variation is explained in the presented PCO. The soil fractions analysed are R: rhizosphere; S: root surrounding soil; and B: bulk soil. (c) Dist LM analysis to evaluate which are the main geoclimatic variables influencing the structure of the bacterial communities associated with date palm root soil fractions. Lat. N: latitude north; Long. E: longitude east; Alt.: altitude; Tmin⁡: minimum temperature; Tmax⁡: maximum temperature; Rainfall min: minimum rainfall; Rainfall max: maximum rainfall. (d) Box-plot graph represents the quantification of 16S rRNA gene by qPCR. The number of copies is expressed in Log10. Statistical analysis (pairwise test) of bacterial assemblage across locations was indicated by the letter.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383278&req=5

fig1: Station location and analysis of bacterial community structure associated with soil fraction of date root system. (a) The location of the studied oases is indicated on the map of Tunisia. (b) A principal coordinate analysis (PCO), deduced from the 16S rRNA gene-based PCR-DGGE profiles, resumes the diversity of the bacterial communities associated with the date palm root soil fractions. 84.8% of total variation is explained in the presented PCO. The soil fractions analysed are R: rhizosphere; S: root surrounding soil; and B: bulk soil. (c) Dist LM analysis to evaluate which are the main geoclimatic variables influencing the structure of the bacterial communities associated with date palm root soil fractions. Lat. N: latitude north; Long. E: longitude east; Alt.: altitude; Tmin⁡: minimum temperature; Tmax⁡: maximum temperature; Rainfall min: minimum rainfall; Rainfall max: maximum rainfall. (d) Box-plot graph represents the quantification of 16S rRNA gene by qPCR. The number of copies is expressed in Log10. Statistical analysis (pairwise test) of bacterial assemblage across locations was indicated by the letter.
Mentions: The sampling was carried out from seven oases in different geographic locations in Tunisia, along a latitude/longitude gradient, respectively from 32° to 34°N and from 7° to 9°E (Figure 1(a) and Supplementary Table 1 in the Supplementary Material available online at http://dx.doi.org/10.1155/2015/153851). A traditional crop management was used in all the oases, including groundwater-based flooding irrigation and fertilization with organic fertilizers. In each oasis, the roots of three date palm trees of similar age, lying in the distance of less than 15 meters and growing in the same soil were separately collected at 20–30 cm depth in order to obtain the adhering rhizosphere soil (R) tightly attached to roots. After removing the roots, the root surrounding soil (S) was collected. Bulk soil samples (B) not influenced by date palm root system were also sampled as control. All soil samples were collected under sterile conditions using sterile tools. Recovered samples were stored at −20°C for molecular analysis or at 4°C for isolation.

Bottom Line: Assessing the influence of such factors is a key to understand (i) the driving forces determining the shape of root-associated bacterial communities and (ii) the plant growth promoting (PGP) services they provide.The bacterial communities in the soil fractions associated with the root system of date palms cultivated in seven oases in Tunisia were assessed by culture-independent and dependent approaches.The comparable numbers and types of PGP traits indicate their importance in maintaining the plant functional homeostasis despite the different environmental selection pressures.

View Article: PubMed Central - PubMed

Affiliation: LR03ES03 Laboratoire Microorganismes et Biomolécules Actives, Faculté des Sciences de Tunis, Université de Tunis El Manar, Campus Universitaire, 2092 Tunis, Tunisia.

ABSTRACT
In arid ecosystems environmental factors such as geoclimatic conditions and agricultural practices are of major importance in shaping the diversity and functionality of plant-associated bacterial communities. Assessing the influence of such factors is a key to understand (i) the driving forces determining the shape of root-associated bacterial communities and (ii) the plant growth promoting (PGP) services they provide. Desert oasis environment was chosen as model ecosystem where agriculture is possible by the microclimate determined by the date palm cultivation. The bacterial communities in the soil fractions associated with the root system of date palms cultivated in seven oases in Tunisia were assessed by culture-independent and dependent approaches. According to 16S rRNA gene PCR-DGGE fingerprinting, the shapes of the date palm rhizosphere bacterial communities correlate with geoclimatic features along a north-south aridity transect. Despite the fact that the date palm root bacterial community structure was strongly influenced by macroecological factors, the potential rhizosphere services reflected in the PGP traits of isolates screened in vitro were conserved among the different oases. Such services were exerted by the 83% of the screened isolates. The comparable numbers and types of PGP traits indicate their importance in maintaining the plant functional homeostasis despite the different environmental selection pressures.

Show MeSH
Related in: MedlinePlus