Search Results
Data evaluating the growth promoting effects of Azospirillum on wheat seedlings according to the inoculum level/root colonization effectiveness (number of bacterial cells), is scarce. Uniform 1-cm size, 72-h old wheat seedlings grown in the dark at 22 °C were inoculated with: i) 10 3 , 10 5 , 10 7 and 10 8 A. brasilense cells per T. aestivum cv. ProINTA Federal seedling; ii) 10 2 , 10 5 and 10 8 A. brasilense cells per T. durum cv. Buck Topacio seedling; iii) 10 6 heat killed bacteria (HKB) cells per cultivar seedling; iv) phosphate buffer pH 6.8 (NI) as control seedlings for both cultivars. Afterwards, seedling growth proceeded in water in the dark at 22 °C for another 48 h. Alive or dead Azospirillum cells were suspended in phosphate buffer pH 6.8. Root and shoot growth were determined measuring the length and projected area of their digitalized images. When treated with inocula concentrations ranging from 10 2 to 10 5 cells per seedling, both Triticum species reached a maximum level of colonization harboring 10 6 to 10 7 cells per seedling. No differences could be detected between NI and HKB treated seedlings for both Triticum species. Triticum aestivum cv. ProINTA Federal seedlings reached the maximum growth promotion when roots were colonized with a number of bacterial cells ranging from 5 · 10 6 to 1.5 · 10 8 per seedling. Triticum durum cv. Buck Topacio seedlings showed maximum growth promotion when 3.3 · 10 7 cells were present in their roots. Higher values of colonization showed no growth promoting effects with respect to the controls. It may be concluded that in these experimental conditions the optimum inoculum concentration is 5 · 10 5 cells per seedling for both T. aestivum cv. ProINTA Federal and T. durum cv. Buck Topacio.
Most agronomic soils contain large reserves of total phosphorus [P], but the fixation and precipitation of P cause P deficiency, and in turn, restrict the growth of crops severely. Phosphorus replenishment, especially in sustainable production systems, remains a major challenge as it is mainly fertilizer-dependent. Though the use of chemical P fertilizers is obviously the best means to circumvent P deficiency in different agro-ecosystems, their use is always limited due to its spiralling cost. A greater interest has, therefore, been generated to find an alternative yet inexpensive technology that could provide sufficient P to plants while reducing the dependence on expensive chemical P fertilizers. Among the heterogeneous and naturally abundant microbes inhabiting the rhizosphere, the phosphate solubilizing microorganisms (PSM) including bacteria have provided an alternative biotechnological solution in sustainable agriculture to meet the P demands of plants. These organisms in addition to providing P to plants also facilitate plant growth by other mechanisms. Despite their different ecological niches and multiple functional properties, P-solubilizing bacteria have yet to fulfil their promise as commercial bio-inoculants. Current developments in our understanding of the functional diversity, rhizosphere colonizing ability, mode of actions and judicious application are likely to facilitate their use as reliable components in the management of sustainable agricultural systems.
plant growth promotion and biological control of seedling disease of rice . Can. J. Microbiol. 47 , 916 – 924 . 2. Andrews , J. H. ( 1992 ) Biological control
Fusarium wilt of tomato is one of the most prevalent and economically important diseases of tomato worldwide especially in tropical regions. The aims of the present study were to isolate and characterize Bacillus bacteria from tomato rhizospheric soil of various regions in Iran and determine the isolates that exhibit high levels of antagonistic efficiency against tomato Fusarium wilt pathogen, Fusarium oxysporum f. sp. lycopersici (Fol) and growth promotion activity. In this study, 303 Bacillus isolates were obtained from tomato rhizospheric soil. Dual culture and volatile metabolite tests were used to screen for antagonism of Bacillus isolates against Fol. Among them, 20 isolates were found to inhibit pathogen growth by 67.77% and 33.33% in dual culture and volatile metabolite tests, respectively. Based on the results of physiological tests and 16S rRNA and gyrA gene sequence analysis of 20 effective isolates, 11, seven and two isolates were identified as B. subtilis, B. velezensis and B. cereus, respectively. The results of greenhouse assessment showed that KR1-2, KR2-7 and A2-9 isolates which were characterized as Bacillus subtilis, reduced the disease index to 16.67% and promoted the plant growth by 80%. These isolates may serve as potential promising biocontrol agents against Fusarium wilt of tomato.
This investigation was carried out based on the hypothesis that there may be some pseudomonad strains, which could exist in rhizosphere of plant species contributing multifaceted beneficial activities. For this purpose, 21 pseudomonad isolates from the rhizosphere of rice, cultivated in western parts of Tamil Nadu were screened. All the 21 isolates were authenticated as pseudomonads by a genus-specific PCR screening. The molecular diversity of these isolates was investigated by Amplified Ribosomal DNA Restriction Analysis (ARDRA) and the dendrogram obtained from the analysis revealed that all the 21 isolates clustered into seven groups. Further, these isolates were screened for plant growth promoting activities such as diazotrophy (PCR amplification of nifH gene and acetylene reduction assay), Indole acetic acid (IAA) and siderophore production (spectrometrically), 1-Aminocyclopropane-1-carboxylic acid (ACC) deaminase for ethylene regulation (PCR screening), mineral solubilization (biochemically) and antagonistic potential against soil pathogenic fungi (dual culture assay). Based on the results, two elite Pseudomonas isolates (S9 and O3) were chosen as multi-functional plant growth-promoting rhizobacteria, paving way for potential use as bioinoculants in rice.
Twenty strains of Pseudomonas fluorescens were evaluated for their potential in promoting plant growth and in the control of late leaf spot caused by Cercosporidium personatum in groundnut under greenhouse conditions. Seed treatment with P. fluorescens strain Pf1 recorded the highest germination percentage and the maximum plant height. Seed treatment with P. fluorescens Pf1 significantly controlled late leaf spot disease of groundnut and increased the pod yield. When the treated seeds were sown in soil, the antagonist colonized well in the groundnut rhizosphere. P. fluorescens Pf1 showed the maximum production of indole acetic acid in in vitro.
Study and comparison of efficiency of the antagonist species Trichoderma atroviride, T. harzianum and T. longibrachiatum against Fusarium wilt were carried out using in vitro and in vivo based bioassay. Significant decrease of both growth and conidia production of the pathogen are obtained compared to the control. Thus, the highest percentages of diameter colony reduction and conidial production were obtained with the T. atroviride isolate (Ta.13), causing 65.64% reduction in colony diameter (direct confrontation), 48.71% reduction in colony diameter (indirect confrontation), and a complete inhibition of conidial production. Once more in direct confrontation, T. atroviride overgrowth the pathogen colony and sporulate above. The seed treatment by Trichoderma spp. isolates before sowing in a soil already infested by the pathogen led to a significant decrease of disease severity compared to the untreated control. The weakest index of disease severity is obtained with the T. atroviride isolates (Ta.13), which cause 83.92% reduction compared to the control. The most effective isolates in protection chickpea seedlings against the disease were the three strains of T. atroviride species (Ta.3, Ta.7 and Ta.13) as well as the isolate T. harzianum (Th.16). Reduction of disease severity obtained was associated with an increase of the vegetal growth including the stem height as well as the plant fresh and dry weight.
230 Leinhos, V., Bergmann, H. (1995): Influence of auxin producing rhizobacteria on root morphology and nutrient accumulation of crops. II. Root growth promotion and nutrient accumulation of
Dubeikovsky, A. N., Mordukhova, E. A., Kochethov, V. V., Polikarpova, F. Y., Boronin, A. M. (1993): Growth promotion of black currant soft cuttings by recombinant strain Pseudomonas fluorescens BS53a synthesizing an increased amount of indole-3-acetic
T-sejtes lymphoma közönséges variábilis immunhiány talaján. Esetismertetés és irodalmi áttekintés
Presence of T-cell lymphoma in patient with common variable immunodeficiency. Case report and review of literature
features of 248 patients. Clin Immunol. 1999; 92: 34–48. 12 Ensoli B, Sturzl M, Monini P. Cytokine-mediated growth promotion of Kaposi’s sarcoma and primary effusion lymphoma
