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. 2000 Aug;66(8):3393-8.
doi: 10.1128/AEM.66.8.3393-3398.2000.

Rhizosphere soil aggregation and plant growth promotion of sunflowers by an exopolysaccharide-producing Rhizobium sp. strain isolated from sunflower roots

Y Alami  1 , W Achouak, C Marol, T Heulin
Affiliations

Rhizosphere soil aggregation and plant growth promotion of sunflowers by an exopolysaccharide-producing Rhizobium sp. strain isolated from sunflower roots

Y Alami et al. Appl Environ Microbiol. 2000 Aug.

Abstract

Root-adhering soil (RAS) forms the immediate environment where plants take up water and nutrients for their growth. We report the effect of an exopolysaccharide (EPS)-producing rhizobacterium (strain YAS34) on the physical properties of sunflower (Helianthus annuus L.) RAS, associated with plant growth promotion, under both water stress and normal water supply conditions. Strain YAS34 was isolated as a major EPS-producing bacterium from the rhizoplane of sunflowers grown in a French dystric cambisol. Strain YAS34 was assigned to the Rhizobium genus by 16S ribosomal DNA gene sequencing. Inoculation of sunflower seeds and soil with strain YAS34 caused a significant increase in RAS per root dry mass (dm) (up to 100%) and a significant increase in soil macropore volume (12 to 60 microm in diameter). The effect of inoculation on sunflower shoot dm (up to +50%) and root dm (up to +70%) was significant under both normal and water stress conditions. Inoculation with strain YAS34 modified soil structure around the root system, counteracting the negative effect of water deficit on growth. Using [(15)N]nitrate, we showed that inoculation made the use of fertilizer more effective by increasing nitrogen uptake by sunflower plantlets.

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Figures

FIG. 1
FIG. 1
Effect of inoculation with Rhizobium sp. strain YAS34 and soil hydric treatment on the cumulative mercury pore volume of RAS aggregates. (A) Noninoculated control treatment in drained soil; (B) inoculated treatment in drained soil; (C) noninoculated control treatment in dry soil; (D) inoculated treatment in dry soil.
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References

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