Physiological and genetic analysis of root responsiveness to auxin-producing plant growth-promoting bacteria in common bean (Phaseolus vulgaris L.)

Plant and Soil (Impact Factor: 3.24). 01/2007; 302(1):149-161. DOI: 10.1007/s11104-007-9462-7

ABSTRACT Plant root development can be largely affected through the association of roots with plant growth-promoting rhizobacteria
(PGPR). However, little is known about the identity of plant genes enabling such PGPR-plant root associations. Differences
in the responsiveness to PGPR among cultivars suggest genetic variation for this trait within germplasm. In this study, two
genotypes of common bean (Phaseolus vulgaris L.), BAT477 and DOR364, were identified showing contrasting responsiveness in root development to inoculation with the PGPR
Azospirillum brasilense Sp245. Inoculation with an A. brasilense Sp245 mutant strain strongly reduced in auxin biosynthesis or addition of increasing concentrations of exogenous auxin to
the plant growth medium, indicated that the differential response to A. brasilense Sp245 among the bean genotypes is related to a differential response to the bacterial produced auxin. To further assess the
role of the plant host in root responsiveness, a population of Recombinant Inbred Lines (RILs) of the DOR364×BAT477 cross
was used to evaluate the efficacy of exogenous auxin on root development. We detected significant phenotypic variation among
the RILs for basal root formation during germination upon addition of auxin to the growth medium. Genetic analysis revealed
two quantitative trait loci (QTLs) associated with basal root responsiveness to auxin of which one explained 36% of the phenotypic
variation among the RILs. This latter QTL mapped to the same location as a QTL for root tip formation at low P, suggesting
that the host effect on root responsiveness to IAA interacts with specific root development. Also, significant correlations
between basal root responsiveness to auxin and growth, root tips and root dry weight at low P were identified. To our knowledge,
this is the first report on QTL detection for root responsiveness to auxin.

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Available from: Roseline Remans, Aug 23, 2014
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    ABSTRACT: Background and Aims Salt stress is an increasing problem in agricultural soils in many parts of the world, and salt tolerant cropping systems are in great demand. We investigated the effect of co-inoculation of G. officinalis with Rhizobium galegae and two plant growth promoting Pseudomonas species on plant growth, nodulation and N content under salt stress. Methods The effect of inoculation with R. galegae HAMBI 1141 alone and in combination with the root colonizing P. trivialis TSAU20 or P. extremorientalis 3Re27 on the growth of G. officinalis exposed to salt stress (50 and 75 mM NaCl) was studied under gnotobiotic and greenhouse conditions. Results The growth of goat’s rue was reduced at 50 and 75 mM, NaCl both in gnotobiotic sand system and in potting soil in greenhouse. Co-inoculation of unstressed and salt-stressed goat’s rue either with R. galegae HAMBI 1141 and P. trivialis 3Re27 or P. extremorientalis TSAU20 significantly improved root, shoot growth and nodulation of plant roots grown in gnotobiotic sand system and low-fertilized potting soils compared to that of plants inoculated with R. galegae alone. The nitrogen content of co-inoculated plant roots was significantly increased at 75 NaCl in potting soil Co-inoculation of G. officinalis with either of the two PGPR Pseudomonas strains also improved root tip-colonization by R. galegae cells. Conclusion Thus, the co-inoculation of goat’s rue with Rhizobium and PGPR Pseudomonas strains was able to alleviate salt stress of plants grown in salt-affected gnotobiotic sand system and in potting soil in the greenhouse. Key words: goat's rue, Galega officinalis, Galega orientalis, Rhizobium galegae, Pseudomonas, plant growth promotion, salt stress, bacterial colonization
    Plant and Soil 08/2013; 369(1-2). DOI:10.1007/s11104-013-1586-3 · 3.24 Impact Factor
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    ABSTRACT: Plant growth promoting rhizobacteria are the soil bacteria inhabiting around/on the root surface and are directly or indirectly involved in promoting plant growth and development via production and secretion of various regulatory chemicals in the vicinity of rhizosphere. Generally, plant growth promoting rhizobacteria facilitate the plant growth directly by either assisting in resource acquisition (nitrogen, phosphorus and essential minerals) or modulating plant hormone levels, or indirectly by decreasing the inhibitory effects of various pathogens on plant growth and development in the forms of biocontrol agents. Various studies have documented the increased health and productivity of different plant species by the application of plant growth promoting rhizobacteria under both normal and stressed conditions. The plant-beneficial rhizobacteria may decrease the global dependence on hazardous agricultural chemicals which destabilize the agro-ecosystems. This review accentuates the perception of the rhizosphere and plant growth promoting rhizobacteria under the current perspectives. Further, explicit outlooks on the different mechanisms of rhizobacteria mediated plant growth promotion have been described in detail with the recent development and research. Finally, the latest paradigms of applicability of these beneficial rhizobacteria in different agro-ecosystems have been presented comprehensively under both normal and stress conditions to highlight the recent trends with the aim to develop future insights.
    Journal of King Saud University - Science 01/2013; 26(1). DOI:10.1016/j.jksus.2013.05.001
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    Plant Pathology, 04/2012; , ISBN: 978-953-51-0489-6