15 research outputs found
Impact of two Erwinia sp. on the response of diverse Pisum sativum genotypes under salt stress
The current study reveals that two non-pathogenic strains
of Erwinia sp. are diferent in their PGP traits. By using an
integrated approach, a picture of the pea plant status in three
genotypes subjected to a salt stress condition was obtained
and the role of the two bacterial considered Erwinia sp.
strains has been highlighted. Results showed the relevance
of plant genotype in determining the response to bacterial
inoculants as well as the diferences in the plant mechanisms
activated to cope with the stress in the diferent plant/strain
combination. Overall, this study emphasizes the importance
of understanding the molecular and biochemical processes
occurring in plantâmicrobe interactions at genotype level,
and the influence on plant responses to environmental
stresses. Further analyses are needed to clarify the behaviour of the three genotypes, such as the leaf water potential,
and to verify the efects of the bacterial inoculation in feld
conditions, subjectd by an increased environmental unpredictability due to the climate change scenarioCurrently, salinization is impacting more than 50% of arable land, posing a significant challenge to agriculture globally. Salt causes osmotic and ionic stress, determining cell dehydration, ion homeostasis, and metabolic process alteration, thus negatively influencing plant development. A promising sustainable approach to improve plant tolerance to salinity is the use of plant growth-promoting bacteria (PGPB). This work aimed to characterize two bacterial strains, that have been isolated from pea root nodules, initially called PG1 and PG2, and assess their impact on growth, physiological, biochemical, and molecular parameters in three pea genotypes (Merveille de Kelvedon, Lincoln, Meraviglia d'Italia) under salinity. Bacterial strains were molecularly identified, and characterized by in vitro assays to evaluate the plant growth promoting abilities. Both strains were identified as Erwinia sp., demonstrating in vitro biosynthesis of IAA, ACC deaminase activity, as well as the capacity to grow in presence of NaCl and PEG. Considering the inoculation of plants, pea biometric parameters were unaffected by the presence of the bacteria, independently by the considered genotype. Conversely, the three pea genotypes differed in the regulation of antioxidant genes coding for catalase (PsCAT) and superoxide dismutase (PsSOD). The highest proline levels (212.88 Όmol g-1) were detected in salt-stressed Lincoln plants inoculated with PG1, along with the up-regulation of PsSOD and PsCAT. Conversely, PG2 inoculation resulted in the lowest proline levels that were observed in Lincoln and Meraviglia d'Italia (35.39 and 23.67 Όmol g-1, respectively). Overall, this study highlights the potential of these two strains as beneficial plant growth-promoting bacteria in saline environments, showing that their inoculation modulates responses in pea plants, affecting antioxidant gene expression and proline accumulation
Rhizobium gallicum as an efficient symbiont for bean cultivation
Rhizobia are soil bacteria that fix atmospheric nitrogen in symbiosis with
legumes in specialized organs called nodules. The legumes thus acquire the
autonomy to grow in nitrogen-deficient soils. When nitrogen fixation by
indigenous rhizobia is limited, field inoculation with efficient and
competitive strains is an economically feasible way to increase production.
When the inoculant is made from native strains of rhizobia the success of
inoculation should be increased, since local strains are better adapted than
commercial inoculants. Here, a Rhizobium gallicum strain, 8a3, previously
selected for its competitiveness and symbiotic effectiveness with common
bean under laboratory conditions, was tested in field trials in Tunisia. The
experiments were conducted in six fields using three common bean cultivars.
The majority of the fields showed a low density of the native rhizobia and
inefficient nodulation by Sinorhizobium meliloti, a known symbiont of
Medicago. Our results show that inoculation with R. gallicum strain 8a3
induced an increase in nodule numbers accompanied by a more than twofold
increase in shoot dry yield. Monitoring of the nodulation occupancy through
the fingerprinting of the repetitive extragenic palindromic sequences
(REP-PCR) showed that strain 8a3 was competitive even in the soil showing a
high population density of indigenous R. gallicum, and occupied more than
40% of the nodules. Moreover, in vitro antibiosis assays indicated that strain 8a3
produces antimicrobial activity on agar medium against indigenous common
bean rhizobia, including the inefficient strains of S. meliloti. These
results point out the benefits that could be achieved by selecting efficient
and competitive strains among natural populations of rhizobia
Salt-tolerant rhizobia isolated from a Tunisian oasis that are highly effective for symbiotic N-2-fixation with Phaseolus vulgaris constitute a novel biovar (bv. mediterranense) of Sinorhizobium meliloti
Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceNodulation of common bean was explored in six oases in the south of Tunisia. Nineteen isolates were characterized by PCR-RFLP of 16S rDNA. Three species of rhizobia were identified, Rhizobium etli, Rhizobium gallicum and Sinorhizobium meliloti. The diversity of the symbiotic genes was then assessed by PCR-RFLP of nodC and nifH genes. The majority of the symbiotic genotypes were conserved between oases and other soils of the north of the country. Sinorhizobia isolated from bean were then compared with isolates from Medicago truncatula plants grown in the oases soils. All the nodC types except for nodC type p that was specific to common bean isolates were shared by both hosts. The four isolates with nodC type p induced N-2-fixing effective nodules on common bean but did not nodulate M. truncatula and Medicago sativa. The phylogenetic analysis of nifH and nodC genes showed that these isolates carry symbiotic genes different from those previously characterized among Medicago and bean symbionts, but closely related to those of S. fredii Spanish and Tunisian isolates effective in symbiosis with common bean but unable to nodulate soybean. The creation of a novel biovar shared by S. meliloti and S. fredii, bv. mediterranense, was propose
Agrobacterium strains isolated from root nodules of common bean specifically reduce nodulation by Rhizobium gallicum
Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceIn a previous work, we showed that non-nodulating agrobacteria strains were able to colonize root nodules of common bean. Both rhizobia and agrobacteria co-existed in the infected nodules. No impact on symbiosis was found in laboratory conditions when using sterile gravel as a support for growth. In this study, soil samples originating from different geographic and agronomic regions in Tunisia were inoculated with a mixture of agrobacteria strains isolated previously from root nodules of common bean. A significant effect on nodulation and vegetal growth of common bean was observed. Characterization of nodulating rhizobia and comparison with non-inoculated controls showed a biased genetic structure. It seemed that Rhizobium gallicum was highly inhibited, whereas nodulation by Sinorhizobium medicae was favored. Co-inoculation of non-sterile soils with R. gallicum and agrobacteria confirmed these findings. In vitro antibiosis assays indicated that agrobacteria exercised a significant antagonism against R. gallicum
Chemical Composition and Antimicrobial Activity of Essential Oils from Three Mediterranean Plants against Eighteen Pathogenic Bacteria and Fungi
The chemical composition and antimicrobial activity of essential oils (EOs) obtained from three medicinal plants of the Moroccan flora were evaluated. The chemical composition of EOs of Thymus leptobotrys, Laurus nobilis and Syzygium aromaticum was determined using a gas chromatograph coupled with mass spectrometry. Carvacrol (75.05%) was the main constituent of T. leptobotrys EOs, while 1,8-cineole (31.48%) and eugenol (82.16%) were the predominant components of L. nobilis and S. aromaticum EOs, respectively. The antimicrobial activity of the EOs was evaluated qualitatively and quantitatively against 18 microbial strains pathogenic to humans by using the disc diffusion method, and by measuring the minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC). The EOs of T. leptobotrys were the most active against the strains tested, with inhibitory zone values ranging from 7.00 to 45.00 mm, and MIC and MMC values ranging from 0.312 to 80.00 mg/mL. In many cases, these EOs exhibited higher antibacterial and antifungal activities than the chemical compounds ciprofloxacin and fluconazole, respectively. This high antimicrobial activity can be ascribed to their richness in carvacrol. The EOs of T. leptobotrys, L. nobilis, and S. aromaticum could be considered a promising alternative to replace chemical antimicrobials, and a readily available natural source of bioactive compounds
Isolation of a Chitinolytic Bacillus licheniformis S213 Strain Exerting a Biological Control Against Phoma medicaginis Infection
Among nine chitinase-producing strains isolated from Tunisian soil, one isolate called S213 exhibited a potent chitinolytic activity. S213 strain was identified as Bacillus licheniformis by API 50CH system and sequence analysis of its partial 16S ribosomal DNA. Chitinolytic activity was induced either by colloidal chitin or fungal cell walls, and the highest chitinase activity reached at the late stationary phase exhibiting optimal temperature and pH of 50-60°C and pH6.0, respectively. SDS-PAGE analysis of the secreted colloidal chitin-induced proteins showed a major protein of about 65kDa. This protein was identified as chitinase on the basis of its peptide sequences which displayed high homology with chitinase sequence of B. licheniformis ATCC 14580. Moreover, chitinolytic activity containing supernatant inhibited the growth of several phytopathogenic fungi including Phoma medicaginis. Interestingly, S213 strain reduced efficiently the damping-off disease caused by P. medicaginis in Medicago truncatula and should be envisaged in enzyme-based biopesticides against phytopathogen application
Diversité des champignons mycorhiziens à arbuscules en association avec Acacia saligna dans différentes régions de la Tunisie
National audienceAcacia saligna, appelĂ©e Ă©galement Acacia cyanophylla, est une fabacĂ©e arbustive originaire de l'Australie. Cette plante a une grande rĂ©silience et sâadapte facilement Ă de nombreux Ă©cosystĂšmes diffĂ©rents, ce qui lui confĂšre une importance Ă©conomique forte. De plus, elle forme plusieurs symbioses racinaires avec des microorganismes qui favorisent son dĂ©veloppement et amĂ©liorent sa rĂ©sistance vis Ă vis de diffĂ©rents stress biotiques et abiotiques :(i) les rhizobiums qui fixent lâazote atmosphĂ©rique et (ii) les champignons mycorhiziens Ă arbuscules (CMA) En Tunisie, aucune Ă©tude ciblant des microorganismes formant des symbioses racinaires associĂ©es Ă A. saligna nâa Ă©tĂ© effectuĂ©e. Ce travail sâintĂ©resse Ă Ă©valuer une partie de la diversitĂ© de ces microorganismes, les CMA. Des Ă©chantillons de racines et de sols rhizosphĂ©riques ont Ă©tĂ© prĂ©levĂ©s dans six rĂ©gions de Tunisie, couvrant ainsi diffĂ©rents Ă©tages bioclimatiques. Suite Ă lâextraction dâADN et au sĂ©quençage du marqueur LSU par la technologie MiSeq Illumina, 18 espĂšces de CMA ont Ă©tĂ© identifiĂ©es appartenant aux genres Scutellospora, Septoglomus, Diversispora, Rhizophagus, Funneliformis, Sclerocystis, Claroideoglomus, Ambispora, Kamienskia, Dominikia et Nanoglomus. Cette Ă©tude rĂ©vĂšle lâexistence dâune riche diversitĂ© de CMA et la comparaison des diversitĂ©s microbiennes racinaires et telluriques est en cours. Dâun point de vue appliquĂ©, cette communautĂ© de CMA pourrait servir dâinoculum afin dâamĂ©liorer la croissance des plantes et dâamĂ©liorer la tolĂ©rance des plantes vis Ă vis de diffĂ©rents stress biotiques et abiotiques
Rhizobium azibense sp. nov., a nitrogen fixing bacterium isolated from root-nodules of Phaseolus vulgaris
Application of Native or Exotic Arbuscular Mycorrhizal Fungi Complexes and Monospecific Isolates from Saline Semi-Arid Mediterranean Ecosystems Improved <i>Phoenix dactylifera</i>âs Growth and Mitigated Salt Stress Negative Effects
The date, the palm tree (Phoenix dactylifera L.) is an important component of arid and semi-arid Mediterranean ecosystems, particularly in Morocco where it plays a considerable socio-economic and ecological role. This species is largely affected by desertification, global warming, and anthropic pressure. Salinity is a very worrying problem that negatively affects the growth and the physiological and biochemical activities of the date palm. In these arid zones, the main challenge is to develop new environmentally friendly technologies that improve crop tolerance to abiotic restraints including salinity. In this sense, Arbuscular mycorrhizal fungi (AMF) have received much attention due to their capability in promoting plant growth and tolerance to abiotic and biotic stresses. It is thus fitting that the current research work was undertaken to evaluate and compare the effects of native AMF on the development of the growth and tolerance of date palm to salt stress along with testing their role as biofertilizers. To achieve this goal, two complexes and two monospecific isolates of native and non-native AMF were used to inoculate date palm seedlings under saline stress (0 g·Lâ1 Na Cl, 10 g·Lâ1, and 20 g·Lâ1 Na Cl). The obtained results showed that salinity drastically affected the physiological parameters and growth of date palm seedlings, whilst the application of selected AMF significantly improved growth parameters and promoted the activities of antioxidant enzymes as a protective strategy. Inoculation with non-native AMF complex and monospecific isolates showed higher responses for all analyzed parameters when compared with the native complex and isolate. It therefore becomes necessary to glamorize the fungal communities associated with date palm for their use in the inoculation of Phoenix dactylifera L. seedlings