Physiological and genetic analysis of root responsiveness to auxin-producing plant growth-promoting bacteria in common bean (Phaseolus vulgaris L.). Plant Soil 302:149-161 DOI 10.1007/s11104-007-9462-7

Plant and Soil (Impact Factor: 2.95). 01/2007; 302(1):149-161. DOI: 10.1007/s11104-007-9462-7


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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    • "Similarly, Fagaria et al. reported higher N use efficiency in 50 mgN treated with Rhizobium inoculation as compared to that obtained from 200 mgN treatment). On top of fixing N from atmosphere, many species of rhizobia can secrete growth hormone and thereby improving root growth (Antoun et al. 1998; Canbolat et al. 2006; Remans et al. 2008; Ahemad and Khan 2012) and nutrients uptake. This could also be due to increases the plant access to soil nutrients and, improving P availability through solubilizing unavailable P (Zaidi et al. 2009) and thus enhancing the N use efficiency of common bean. "
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    ABSTRACT: Due to common bean derives lower nitrogen (N) from symbiotic N 2 -fixation, it requires N either from inorganic fertilizer or soil N. Field experiments were conducted at four locations to evaluate the effect of Rhizobium leguminosarum bv. phaseoli inoculation on agronomic efficiency of N of common bean var. Dursitu major growing areas of eastern Ethiopia. Six levels of inorganic N (0, 20, 40, 60, 80 and 100 kg N ha −1 ) and two inoculation treatments (uninoculated and inoculated) were factorially combined and laid out in randomized completely block design, replicated three times. AE-N, nodule number per plant (NN) and nodule dry weight per plant (NDW) decreased with N rates of application beyond 20 kg N ha −1 . The highest AE-Ns at Babillae, Fedis and Haramaya sites were obtained from 20 kg N ha −1 applied with Rhizobium inoculation while 40 kg N ha −1 supplied with Rhizobium inoculation at Hirna site. Regardless of experimental sites, inoculation improved AE-N. A positive relationship between AE-N and NDW was also observed in all experimental sites. Significant increase in grain yield with increasing rates of N application was also observed. Hence, it can be concluded that inoculation is recommendable to increases the efficient utilization of applied Mineral N.
    12/2015; 4(1). DOI:10.1186/s40068-015-0036-z
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    • "All rights reserved. characterized auxin produced by many plant-associated bacteria [36], can stimulate primary root elongation, whereas high IAA levels stimulate the formation of lateral roots, thereby decreasing the primary root length [37] [38] [39]. These results suggest that P. polymixa E681 may produce phytohormones and secondary metabolites to boost Arabidopsis growth [40] "
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    ABSTRACT: Plant growth-promoting rhizobacteria (PGPR) facilitate the plant growth and enhance their induced systemic resistance (ISR) against a variety of environmental stresses. In this study, we carried out integrative analyses on the proteome, transcriptome, and metabolome to investigate Arabidopsis root and shoot responses to the well-known PGPR strain Paenibacillus polymyxa (P. polymyxa) E681. Shoot fresh and root dry weights were increased, whereas root length was decreased by treatment with P. polymyxa E681. 2-DE approach in conjunction with MALDI-TOF/TOF analysis revealed a total of 41 (17 spots in root, 24 spots in shoot) that were differentially expressed in response to P. polymyxa E681. Biological process- and molecular function-based bioinformatics analysis resulted in their classification into seven different protein groups. Of these, 36 proteins including amino acid metabolism, antioxidant, defense and stress response, photosynthesis, and plant hormone-related proteins were up-regulated, whereas five proteins including three carbohydrate metabolism- and one amino acid metabolism-related, and one unknown protein were down-regulated, respectively. A good correlation was observed between protein and transcript abundances for the 12 differentially expressed proteins during interactions as determined by qPCR analysis. Metabolite analysis using LC-MS/MS revealed highly increased levels of tryptophan, indole-3-acetonitrile (IAN), indole-3-acetic acid (IAA), and camalexin in the treated plants. Arabidopsis plant inoculated P. polymyxa E681 also showed resistance to Botrytis cinerea infection. Taken together these results suggest that P. polymyxa E681 may promote plant growth by induced metabolism and activation of defense-related proteins against fungal pathogen.
    Proteomics 10/2015; DOI:10.1002/pmic.201500196 · 3.81 Impact Factor
    • "For BAT477, on the contrary, a negative effect of Azospirillum–Rhizobium co-inoculation on yield and nitrogen fixation was observed on most of the sites as compared to single Rhizobium inoculation. The contrasting response to Azospirillum– Rhizobium co-inoculation of BAT477 and DOR364 observed for yield and N 2 fixation is consistent with the difference in nodulation response observed previously in controlled greenhouse experiments (Remans et al. 2008a). The field results indicate that the difference in host responsiveness to Azospirillum between bean genotypes can have an important impact on agronomic outputs. "
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    ABSTRACT: Azospirilla are generally regarded as rhizosphere bacteria and colonize the root surface and only a few strains are able to infect plants. The stimulatory effect exerted by Azospirillum has been attributed to several mechanisms but under certain environmental and soil conditions, Azospirillum can positively influence plant growth, crop yields, and N-content of the legume. Most Azospirillum—rhizobacteria co-inoculation studies have focused on the final effects on plant growth and nodulation parameters; in contrast, few data are available on the simultaneous effect of double inoculation and stressful conditions on the early signalling exchange between the symbiotic partners. Co-inoculation of legume with rhizobia plus Azospirillum exerted changes on the concentration, content, and/or distribution of several mineral nutrients in roots and/or shoots of plants, change in flavonoids, and can help to tolerate stress. This chapter summarized some effects that occur when legumes are co-inoculated with Azospirillum
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