Molecular Identification and In Vitro Plant Growth-Promoting Activities of Culturable Potato (Solanum tuberosum L.) Rhizobacteria in Tanzania (original) (raw)
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Frontiers in plant science, 2016
Rhizosphere engineering with beneficial plant growth promoting bacteria offers great promise for sustainable crop yield. Potato is an important food commodity that needs large inputs of nitrogen and phosphorus fertilizers. To overcome high fertilizer demand (especially nitrogen), five bacteria, i.e., Azospirillum sp. TN10, Agrobacterium sp. TN14, Pseudomonas sp. TN36, Enterobacter sp. TN38 and Rhizobium sp. TN42 were isolated from the potato rhizosphere on nitrogen-free malate medium and identified based on their 16S rRNA gene sequences. Three strains, i.e., TN10, TN38, and TN42 showed nitrogen fixation (92.67-134.54 nmol h(-1)mg(-1) protein), while all showed the production of indole-3-acetic acid (IAA), which was significantly increased by the addition of L-tryptophan. Azospirillum sp. TN10 produced the highest amount of IAA, as measured by spectrophotometry (312.14 μg mL(-1)) and HPLC (18.3 μg mL(-1)). Inoculation with these bacteria under axenic conditions resulted in differenti...
Using Plant Growth Promoting Rhizobacteria to Improve Potato Production and Plant Health
Plant Growth Promoting Rhizobacteria (PGPR) have shown their potential in various crops to improve yield and plant health. In this respect PGPR could be developed into an alternative inexpensive bio-fertilizer to increase potato yields of small scale subsistence farmers and/or to improve organic crop production systems in the Central Andean Highlands of Peru. In 2005/06 commercially available PGPR were applied in field trails with potatoes, resulting in yield increases of 20-30% and partial control of Rhizoctonia solani. Increased yields were due to greater sink size and sink strength of the inoculated potato crop. Populations of Azotobacter and Bacillus subtilis in the rhizosphere of the potato were greater during the entire growth period as compared with non-inoculated control potato plants. Based on these results PGPR research will be continued and native bacteria in the major potatogrowing regions of Peru will be sampled, identified, tested and selected. PGPR shows a clear potential to increase nutrient use efficiency of potato that could be developed as an important element in low and high input crop production systems.
Evaluating soil rhizobacteria for their ability to enhance plant growth and tuber yield in potato
Annals of Applied Biology, 2010
The objectives of this study were to identify promising microorganisms to improve potato productivity in low-input systems of tropical highlands and to compare results from in vitro, greenhouse and field experiments to advance the development of a screening method for rhizobacteria and develop an efficient assessment of their effect on plant growth in field conditions. A total of 150 bacterial strains were screened in vitro, in greenhouse and field trials. The series of experiments confirmed the plant growth-promoting ability of a range of rhizobacteria. Although in vitro and greenhouse results were promising, the field experiment showed variability and the results require further verification. The in vitro tests might have limited value for screening as no correlation could be found between in vitro tests and pot trial results. However, trials in controlled conditions produced insights into the mechanisms causing better plant growth in potato, such as early tuberisation, fast development of leaf area and probably greater photosynthetic rates.
Rhizobacteria-Based Technology for Sustainable Cropping of Potato (Solanum tuberosum L.)
Potato Research, 2019
Potato (Solanum tuberosum L.) is one of the most important food crops worldwide but its cultivation is affected by numerous challenges including pests, diseases and high fertiliser requirements which have associated environmental problems. The exploitation of plant rhizospheres and their associated rhizobacterial interactions has gathered momentum worldwide in search of environmentally-friendly approaches to crop cultivation. A lot of literature exists on rhizobacterial associations and their biofertilisation or bioprotection roles in many plants. However, very scanty information is available on rhizobacterial functions and communities of the potato, an indication that they are still understudied. In this regard, more research is needed to understand and exploit them for the successful application of rhizobacteria-based technology in potato cropping. This review updates our knowledge of the beneficial rhizobacteria of the potato and documents their roles in its bioprotection, phytostimulation and biofertilisation while highlighting their potential in enhancing its production and productivity. The future prospects regarding the research on these important potato microflora are further discussed as a guide and a baseline for future research on them. This review shows that rhizobacteria-based technology is a viable option for potato biofertilisation and bioprotection and could be the missing link in its sustainable cropping. The adoption and full exploitation of this technology can be fast-tracked if we increase our understanding of the subject matter.
A gnotobiotic bioassay, using potato plantlets derived from single-node explants and grown in test tubes containing potato nodal cutting medium (PNCM), was found to be highly useful for investigations of direct growth promotion by a nonfluorescent Pseudomonas sp. strain PsJN. Strain PsJN was used to optimize and evaluate this bioassay for purposes of screening other rhizosphere bacteria and identification of Tn5 mutants of strain PsJN deficient in growth-promoting properties. The selection of potato cultivar used in this bioassay was critical, as growth promotion of potatoes by strain PsJN was cultivar specific. Inoculated plantlets of cultivars Norchip, Kennebec, Shepody, and Chaleur showed, in root dry weight, a five- to eight-fold increase, two- to three-fold increase, no response, and a decrease of SO%, respectively. Haulm dry weight followed similar trends but was not as consistent an indicator of growth promotion. Bioassay results were not altered to any extent by minor changes in PNCM composition or by slight changes in temperature and light conditions. A rapid method for preparation of bacterial suspensions and inoculation of explants was developed. Inoculation of three explants taken from 6-week-old stock plantlets of cv. Kennebec for each Tn5 transconjugate of strain PsJN (total of 1500 transconjugates) enabled the elimination of 93% of those isolates that retained growth-promoting activity. The remaining 7% of isolates were retested and seven were confirmed to have lost growth-promoting ability. Bacteria from different genera were also screened with this bioassay. None of these bacteria increased the growth of potato plantlets, but several inhibited root and haulm growth.
Effect of Rhizobacterial Strain Enterobacter Cloacae Strain Pglo 9 on Potato Plant Growth and Yield
2018
To assess functional potentialities of rhizobacteria in relation to plant growth promoting activities, rhizobacterial strain Enterobacter cloacae PGLO9 was obtained from rhizosphere soil of potato plant (Solanum tuberosum L.) root. The result of in vitro assays showed that strain PGLO9 solubilize phosphate as well as produce siderophore and amylase. This strain having abilities for phosphate solubilization, siderophores and amylase production, were tested as bioinoculant to potato tubers via pot trail experiment. The results of inoculated potato plants showed significant increase in vegetative growth parameters such as root length, shoot length, root biomass and shoot biomass, compared with control and found better response in potato plant growth and yield against uninoculated control. Whereas potatoes harvested was healthy as well as not infected with any pathogen. Strain PGLO9 can be recommended as biofertilizer for reducing the dependence on chemical fertilizers and providing a s...
African Journal of Microbiology Research, 2009
Laboratory study was conducted to characterize the beneficial properties of plant growth-promoting rhizobacterial (PGPR) strains isolated from sweet potato rhizosphere. Fifteen rhizobacterial (PGPR) strains were screened for indole acetic acid (IAA) production with and without addition of the precursor L-tryptophan (L-TRP), phosphate-solubilizing activity, and nitrogen production, antagonistic activity against fungal pathogens, siderophore production and intrinsic antibiotic resistance. Results of the laboratory study showed that 15 rhizobacterial isolates were able to produce indole acetic acid (IAA). The concentration of IAA produced ranged from 3.84-13.33 mg L-1. Addition of L-tryptophan (L-TRP) to the bacterial isolates increased the production of IAA ranging from 4.94-46.66 mg L-1. Six isolates (40%) were able to solubilize insoluble phosphate as evident by production of clear zone on calcium phosphate medium. All isolates were able to grow in N-free media indicating their abilities to produce nitrogen which ranged from 0.74-1.32 ppm. Three of the isolates produced fluorescent pigment on agar plate indicated their abilities to produce siderophores. Four isolates were able to inhibit the fungal pathogens Rhizoctonia sp. and Pythium sp. The intrinsic antibiotic test showed that all isolates were resistant against Chloramphenicol (10 and 30 µg mL-1), Streptomycin (10 µg mL-1), Kanamycin (5 and 30 µg mL-1), Penicillin (10 µg mL-1) and Tetracyclin (30 µg mL-1). The rhizobacterial isolates showed the several beneficial traits that could improve plant growth.
The Central Andean Highlands are the center of origin of the potato plant (Solanum tuberosum). Ages of mutualism between potato plants and soil bacteria in this region support the hypothesis that Andean soils harbor interesting plant growth-promoting (PGP) bacteria. Therefore, the aim of this study was to isolate rhizobacteria from Andean ecosystems, and to identify those with PGP properties. A total of 585 bacterial isolates were obtained from eight potato fields in the Andes and they were screened for suppression of Phytophthora infestans and Rhizoctonia solani. Antagonistic mechanisms were determined and antagonistic isolates were further tested for phosphate solubilization, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and production of NH3- and indole-3-acetic acid (IAA). PGP was studied in healthy and R. solani diseased plantlets under growth room conditions. Performance was compared to the commercial strain B. subtilis FZB24® WG. Isolates were dereplicated with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), and identified with 16S rRNA gene sequencing and multi locus sequence analysis (MLSA). A total of 10% of the isolates were effective antagonists, of which many were able to solubilize phosphate, and produce IAA, ACC deaminase, NH3 and hydrogen cyanide (HCN). During growth room experiments, 23 antagonistic isolates were associated with plant growth-promotion and/or disease suppression. Ten isolates had a statistically significant impact on test parameters compared to the uninoculated control. Three isolates significantly promoted plant growth in healthy plantlets compared to the commercial strain, and seven isolates outperformed the commercial strain in in vitro R. solani diseased plantlets.
Beneficial effect of plant growth promoting bacteria isolated from the roots of potato plant
Annals of Agricultural Sciences, 2013
This study was conducted with a view to isolate bacteria associated with the roots of sweet potato plants (Ipomoea batatas (L.) Lam.) and to assess their functional potentialities in relation to plant growth promoting activities. Seven bacterial isolates namely P18, P19, P31, P32, P35, P39, and P42 were obtained from surface sterilized healthy roots of sweet potato. The isolates were tested for morphological and biochemical characteristics. The results of in vitro assays showed that all isolates can produce IAA, while four isolates i.e. P18, P31, P35, and P42) solubilize rock phosphate. These isolates having abilities for IAA production and phosphate solubilization were tested as bioinoculant to potato tubers. The results of inoculated plants showed significant differences in vegetative growth parameters as well as photosynthetic pigments and N, P, and K concentrations compared with control. Consequently, the more efficient isolates namely P31 and P35 were identified by 16S ribosomal DNA sequencing analysis as Bacillus cereus and Achromobacter xylosoxidans, respectively. These can be recommended as biofertilizers for reducing the dependence on chemical fertilizers and providing a step forward toward sustainable agriculture.
International Journal of Scientific & Technology Research, 2015
Plant Growth Promoting Rhizobacteria (PGPR) are a group of bacteria that colonize the rhizosphere and can enhance plant growth directly or indirectly. Bacteria rhizoshere can induce substances like IAA and GA that can contribute to the improvement of potato growth, is crucial for sustainable potato cultivation. The present study was undertaken to screen the rhizosphere bacteria isolated from potato var. Hartapel growing regions of Buru Island for their physiological characteristics, including IAA and GA production. Of these isolates, 36 isolates were capable of producing IAA, and GA. Among the selective isolates, HB8 produced the highest amount of IAA (5.816 mg l -1 ), while isolate HB32 produced the highest amount of GA (6.879 mg l -1 ).