Root Colonization by Pseudomonas sp. DSMZ 13134 and Impact on the Indigenous Rhizosphere Bacterial Community of Barley

Abstract

Over the last few decades, the ability of rhizosphere bacteria to promote plant growth has been considered to be of scientific, ecological, and economic interest. The properties and mechanisms of interaction of these root-colonizing bacteria have been extensively investigated, and plant protection agents that are based on these bacterial strains have been developed for agricultural applications. In the present study, the root colonization of barley by Pseudomonas sp. DSMZ 13134, that is contained in the commercially available plant protection agent Proradix, was examined using the fluorescence in situ hybridization method with oligonucleotide probes and specific gfp-tagging of the inoculant strain in combination with confocal laser scanning microscopy. In the first phase of root colonization, the inoculant strain competed successfully with seed and soil-borne bacteria (including Pseudomonads) for the colonization of the rhizoplane. Pseudomonas sp. DSMZ 13134 could be detected in all parts of the roots, although it did not belong to the dominant members of the root-associated bacterial community. Gfp-tagged cells were localized particularly in the root hair zone, and high cell densities were apparent on the root hair surface. To investigate the impact of the application of Proradix on the structure of the dominant root-associated bacterial community of barley, T-RFLP analyses were performed. Only a transient community effect was found until 3 weeks post-application.

Potential of three microbial bio-effectors to promote maize growth and nutrient acquisition from alternative phosphorous fertilizers in contrasting soils

“…The absence of response after BE application was observed in many other experiments [45,48,49] and in particular in soils characterized by extraordinary low levels of available P (20 mg kg −1 or lower) or that were limiting in other soil nutrients [10,50,51]. In contrast, other studies have shown that for maize and other crops, the application of BEs was more efficient in the absence of added P fertilizers [36][37][38]. However, in these cases, soil P availability was distinctly higher and P CAL ranged between 35 and 45 mg/kg.…”

“…The strain Trichoderma harzianum Rifai 1295-22 (T22) has demonstrated abilities to increase the solubilization of sparingly soluble calcium phosphates [34] and to promote plant growth in various plant species [35,36] including maize [37]. The strain Pseudomonas DSMZ 13134 is an efficient root colonizer [38] and has been shown to solubilize inorganic phosphate under in vitro conditions [39]. Moreover, it has recently shown the potential to improve plant growth and phosphorus acquisition when inoculated to maize [10,25].…”

“…Moreover, the amount of total and plant available P seems to be a decisive factor for the performance of bacterial BEs [26,27]. Also, competition with naturally occurring rhizosphere microorganisms can limit the survival of introduced BEs [28]. This indicates that more work is needed to unravel the conditions under which BEs can exert plant growth-promoting effects, in order to achieve more homogenous and predictable effects.…”

Effect of bioeffectors and recycled P-fertiliser products on the growth of spring wheat

“…However, an investigation across a number of field studies involving wheat showed that P. bilaii does not significantly affect P uptake and yield [35]. Gram-negative gammaproteobacteria of the genus Pseudomonas are ubiquitous bacteria in soil, are known to proliferate greatly in the rhizosphere [36] and have been studied for their plant growth-promoting activities for many years [37]. Bacteria from this genus have been observed to increase plant productivity under P-limiting conditions [38,39].…”

Response of barley to root colonization byPseudomonassp. DSMZ 13134 under laboratory, greenhouse, and field conditions

“…DSMZ 13134 and its transient impact on the dominant root-associated bacterial community has been shown (Buddrus-Schiemann et al 2010). However, there have been no investigations into the effect of root colonization of Pseudomonas sp.…”