Rhizobium population dynamics in the pea rhizosphere of rhizobial inoculant strain applied in different formulations

2001 ◽  
Vol 47 (7) ◽  
pp. 595-600 ◽  
Author(s):  
Russell K Hynes ◽  
Desirée C Jans ◽  
Eric Bremer ◽  
Newton Z Lupwayi ◽  
Wendell A Rice ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Rhizobium Leguminosarum ◽  
Sampling Period ◽  
Resistant Mutant ◽  
Nodule Occupancy ◽  
Colony Forming Units ◽  
Inoculant Strain ◽  
Rhizosphere Population ◽  
Lag Period ◽  
Seed Yields

The effect of inoculant formulation on the population dynamics of rhizobia in the pea rhizosphere was investigated using a streptomycin-resistant mutant of Rhizobium leguminosarum bv. viceae NITRAGIN128C56G (128C56G strR). The isolate was formulated into liquid, peat powder, and granular peat carriers, and was tested on pea at field sites near Saskatoon, Saskatchewan, and Beaverlodge, Alberta, in 1996 and 1997. The liquid and peat powder formulations were applied to seed while the granular inoculant was applied to soil. In three out of four site years, population dynamics were similar among formulations: an initial decline or lag period lasting 2–5 days followed by an increase to approximately 105 colony-forming units (CFU)/seedling by 14–28 days after planting (DAP) and, where sampled, a continuing increase from 107 to 108 CFU/plant at 63 DAP. In these same site years, nodule number (not determined at Beaverlodge in 1997) and nodule occupancy at 60 days were not significantly different among formulations. In contrast, soil populations of 128C56G strR from the liquid formulation declined to near zero by 28 DAP at Beaverlodge in 1996, when soil moisture was excessive in spring because of high rainfall. Populations increased in this treatment after this time, but remained significantly lower than the populations of the other two formulations throughout the sampling period. Pea seed yields were not significantly different among treatments in either year at Beaverlodge, but were significantly higher with granular inoculant than the noninoculated control in Saskatoon. Within inoculated treatments at Saskatoon, there were no significant differences in grain yield.Key words: Rhizobium leguminosarum, rhizosphere, population dynamics.

Competitiveness of inoculant strains of Rhizobium leguminosarum bv. trifolii in red clover using repeated inoculation and increased inoculum levels

1990 ◽  
Vol 36 (2) ◽  
pp. 136-139 ◽  
Author(s):  
Anna M. Mårtensson
Keyword(s):  
Biological Activity ◽  
Dry Matter ◽  
Rhizobium Leguminosarum ◽  
Red Clover ◽  
Field Studies ◽  
Nodule Occupancy ◽  
Inoculum Concentration ◽  
Matter Production ◽  
Inoculant Strain ◽  
Matter Basis

The effects of inoculation of red clover with Rhizobium leguminosarum bv. trifolii strains 285 and 7612 were studied. In greenhouse experiments repeated inoculations were made. Strain 285 occupied all nodules when included, and strain 7612 increased its nodule occupancy with repeated inoculation. In field studies, where native, ineffective red clover bacteria were present, increased levels of inoculum were added, which increased dry matter production and nitrogen content of the plants. Yields from plants inoculated with strain 7612 were higher but dependent on inoculum concentration. The number of early nodules occupied by inoculant bacteria increased with increasing inoculum concentrations of strain 7612 but not of strain 285. The inoculant strain occupancy of late nodules was unaffected by inoculum levels in both cases. Acetylene reduction and accumulation of 14C-labelled metabolites in nodules situated at different distances from the shoots and in nodules of different ages, including overwintering nodules, were studied. Nodule placement did not influence the biological activity of the nodules. Old nodules were less active on a dry matter basis, but since they are larger, they may have contributed to the nitrogen balance of the plants as much as young nodules. Overwintering the plants did not change this pattern. Key words: competition, inoculation, nodule life cycle, Rhizobium.

Effects of crop sequence and rainfall on population dynamics of Fusarium solani f.sp. phaseoli in soil

1992 ◽  
Vol 70 (10) ◽  
pp. 2005-2008 ◽  
Author(s):  
Robert Hall ◽  
Lana Gay Phillips
Keyword(s):  
Population Dynamics ◽  
Phaseolus Vulgaris ◽  
Population Density ◽  
Fusarium Solani ◽  
Population Densities ◽  
Total Rainfall ◽  
Colony Forming Units ◽  
Bean Crop ◽  
Previous Summer ◽  
Crop Sequence

Evidence is presented that population dynamics of Fusarium solani f.sp. phaseoli in soil depend on the effects of crop sequence and rainfall on parasitic activities of the pathogen. In a rotation trial started in 1978 and conducted over 14 years, population densities (colony-forming units/g) of the fungus in soil remained below 50 in treatments (fallow, repeated corn, repeated soybean) where the preferred host plant (common bean, Phaseolus vulgaris) was not grown. Where bean was grown every 3rd year or every year, population densities reached 475 and 660, respectively, by 1984. Thereafter, population densities of the fungus fluctuated widely from year to year in both rotation and repeated bean treatments. In the rotation treatment, peaks in population density of the pathogen coincided with the years of bean production. In repeated bean plots between 1985 and 1991, population density of the fungus in June was significantly correlated (r = 0.77, p = 0.04) with total rainfall received during the previous summer (June–August). It is postulated that higher rainfall during the growing season of the bean crop stimulated root growth and root infection, leading to the accumulation of higher levels of potential inoculum in infected tissue and the release of higher levels of inoculum into the soil by the following June. Key words: Fusarium solani f.sp. phaseoli, bean, Phaseolus vulgaris, rainfall, crop rotation.

scholarly journals Competitiveness of a native Rhizobium leguminosarum biovar trifolii strain for nodule occupancy is manifested during infection

2008 ◽  
Vol 318 (1-2) ◽  
pp. 117-126 ◽  
Author(s):  
Samuel Duodu ◽  
Caroline Brophy ◽  
John Connolly ◽  
Mette M. Svenning
Keyword(s):  
Rhizobium Leguminosarum ◽  
Nodule Occupancy ◽  
Rhizobium Leguminosarum Biovar Trifolii

Diversity and symbiotic effectiveness of Rhizobium leguminosarum bv. trifolii isolates from pasture soils in south-western Australia

Soil Research ◽  
2002 ◽  
Vol 40 (8) ◽  
pp. 1319 ◽  
Author(s):  
M. T. Collins ◽  
J. E. Thies ◽  
L. K. Abbott
Keyword(s):  
Western Australia ◽  
Rhizobium Leguminosarum ◽  
Subterranean Clover ◽  
Most Probable Number ◽  
Enzyme Linked Immunosorbent Assay ◽  
Symbiotic Effectiveness ◽  
Probable Number ◽  
Pcr Fingerprinting ◽  
Rapd Pcr ◽  
Inoculant Strain

The abundance of the Australian inoculant strain of Rhizobium leguminosarum bv. trifolii for subterraneum clover (WU95) and the diversity of naturalised rhizobia were assessed in 3 subterranean clover pastures in the Albany region of south-western Western Australia. Most probable number, enzyme linked immunosorbent assay (ELISA), and polymerase chain reaction (PCR) techniques were used. A putative strain similar to inoculant strain WU96 was uncommon at one site (South Stirling) and not isolated at 2 other sites. Randomly amplified polymorphic DNA (RAPD) PCR fingerprinting using the RPO1 primer identified 45 different profiles amongst the 208 isolates examined. RAPD-PCR fingerprinting using the primers RPO4 and RPO5 confirmed most groupings based on RPO1 fingerprint patterns and revealed further genetic diversity within some groups. Overall, 54 putative strains were defined by RAPD-PCR fingerprint profiles across the 3 sites. Subterranean clover rhizobia at the Manypeaks and Mount Shadforth sites were dominated by isolates with 1 or 2 RPO1 RAPD profiles at 2 sampling times, while the population at South Stirling was much more diverse. The symbiotic effectiveness of 11 rhizobial isolates, representing the major RPO1 RAPD profile groups within naturalised rhizobial populations, were compared in pot culture with those of the 2 commercial inoculant strains for subterranean clover, WU95 and TA1, on 3 cultivars. Differences in effectiveness among 3 of the 11 isolates were observed in comparison to both the commercial strains and other naturalised isolates. The nitrogen fixing effectiveness of 8 isolates representing different subgroups from one RP01 group was not the same. The use of all 3 primers increased the precision in defining putative strains of Rhizobium leguminosarum bv. trifolii, and although naturalised rhizobia from these pastures are saprophytically competent, their dominance in nodules does not appear to be linked to symbiotic effectiveness.

Effects of aphids and moth caterpillars on epiphytic microorganisms in canopies of forest trees

2000 ◽  
Vol 30 (4) ◽  
pp. 631-638 ◽  
Author(s):  
Bernhard Stadler ◽  
Thomas Müller
Keyword(s):  
Population Dynamics ◽  
Functional Groups ◽  
Filamentous Fungi ◽  
Growing Season ◽  
Aphid Species ◽  
Growth Media ◽  
Forest Trees ◽  
Epiphytic Microorganisms ◽  
Colony Forming Units ◽  
Different Types

Different types of herbivores were investigated for their effects on microorganisms in the phyllosphere of forest trees during the growing season. Aphids on spruce, beech, and oak produced honeydew, which was readily consumed by microorganisms and resulted in two to three orders of magnitude higher densities (colony forming units) of bacteria, yeasts, and filamentous fungi on leaves of infested trees. The amounts of honeydew excreted by different aphid species and their mode of excretion (large droplets, tiny droplets scattered over leaves, production of wax wool) affected the degree to which honeydew could be processed by epiphytic microorganisms. All groups of microorganisms appeared to be energy limited. These results were consistent for different growth media offered to the microorganisms. Leaf-feeding moth caterpillars also positively affected the growth of microorganisms on leaves of beech and oak. The effects were more pronounced for bacteria and yeasts especially on oak. Thus, different functional groups of herbivores positively affected the growth of microorganisms in the phyllosphere of trees. It is suggested that the population dynamics of herbivores and their feeding characteristics are important features, which should be considered when the population dynamics of microorganisms in the canopies of trees is studied.

Persistence of introduced strains of Rhizobium leguminosarum bv trifolii in acidic soils of north-eastern Victoria

1999 ◽  
Vol 39 (7) ◽  
pp. 829 ◽  
Author(s):  
J. F. Slattery ◽  
D. R. Coventry
Keyword(s):  
Rhizobium Leguminosarum ◽  
Soil Amendments ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Nodule Occupancy ◽  
Acidic Soils ◽  
High Background ◽  
Poor Tolerance ◽  
Acidic Sites ◽  
Commercial Inoculant

Summary. A 5-year study was undertaken to establish if introduced rhizobia with higher tolerance to Al than the current inoculant Rhizobium can persist and continue nodulating subterranean clover (Trifolium subterraneum L.) in acidic soils. Two Rhizobium leguminosarum bv trifolii strains were introduced as seed inoculants with subterranean clover at 2 acidic sites (pHCa 4.1 and pHCa 4.3), where lime and gypsum had been applied as soil amendments. Strain NA3001 was selected for its tolerance to high Al concentrations when grown on an agar medium and WU95, which is a widely used commercial inoculant strain, for its relatively poor tolerance to Al when grown on agar. Liming the soil increased its pH and reduced the concentration of extractable Al at both sites. In the year the subterranean clover was sown, strain WU95 had nodule occupancy of 20–49%, decreasing with time to 4–7% after 5 seasons (1991–95). The nodule occupancy of strain NA3001 was initially lower than strain WU95 (14–16%), but its occupancy did not vary with time (significant strain x time interactions, P<0.05). These data indicate that the acid-tolerant strain NA3001 has the potential to persist in these strongly acidic soils and, despite the presence of high background populations of naturalised rhizobia, to continue initiating nodulation. The use of soil amendments (lime and gypsum) to increase pH and reduce soluble Al concentrations did not affect the nodule occupancy of either NA3001 or WU95 with time, nor did it slow the rate of decline in nodule occupancy of WU95.

scholarly journals Competition, Nodule Occupancy, and Persistence of Inoculant Strains: Key Factors in the Rhizobium-Legume Symbioses

2021 ◽  
Vol 12 ◽  
Author(s):  
Marcela Mendoza-Suárez ◽  
Stig U. Andersen ◽  
Philip S. Poole ◽  
Carmen Sánchez-Cañizares
Keyword(s):  
Nitrogen Fixation ◽  
Current Knowledge ◽  
Local Environment ◽  
Nitrogen Fertilizers ◽  
Superior Performance ◽  
Nodule Occupancy ◽  
Inoculant Strain ◽  
Native Strains ◽  
Biological Nitrogen ◽  
Rhizobial Inoculants

Biological nitrogen fixation by Rhizobium-legume symbioses represents an environmentally friendly and inexpensive alternative to the use of chemical nitrogen fertilizers in legume crops. Rhizobial inoculants, applied frequently as biofertilizers, play an important role in sustainable agriculture. However, inoculants often fail to compete for nodule occupancy against native rhizobia with inferior nitrogen-fixing abilities, resulting in low yields. Strains with excellent performance under controlled conditions are typically selected as inoculants, but the rates of nodule occupancy compared to native strains are rarely investigated. Lack of persistence in the field after agricultural cycles, usually due to the transfer of symbiotic genes from the inoculant strain to naturalized populations, also limits the suitability of commercial inoculants. When rhizobial inoculants are based on native strains with a high nitrogen fixation ability, they often have superior performance in the field due to their genetic adaptations to the local environment. Therefore, knowledge from laboratory studies assessing competition and understanding how diverse strains of rhizobia behave, together with assays done under field conditions, may allow us to exploit the effectiveness of native populations selected as elite strains and to breed specific host cultivar-rhizobial strain combinations. Here, we review current knowledge at the molecular level on competition for nodulation and the advances in molecular tools for assessing competitiveness. We then describe ongoing approaches for inoculant development based on native strains and emphasize future perspectives and applications using a multidisciplinary approach to ensure optimal performance of both symbiotic partners.

scholarly journals Cloning and Characterization of a Rhizobium leguminosarum Gene Encoding a Bacteriocin with Similarities to RTX Toxins

1999 ◽  
Vol 65 (7) ◽  
pp. 2833-2840 ◽  
Author(s):  
Ivan J. Oresnik ◽  
Sunny Twelker ◽  
Michael F. Hynes
Keyword(s):  
Amino Acid ◽  
Sinorhizobium Meliloti ◽  
Insertional Mutagenesis ◽  
Rhizobium Leguminosarum ◽  
Nodule Occupancy ◽  
Bacteriocin Activity ◽  
Gene Encoding ◽  
Reading Frame ◽  
Rtx Toxins ◽  
Culture Supernatants

ABSTRACT A 3-kb region containing the determinant for bacteriocin activity from Rhizobium leguminosarum 248 was isolated and characterized by Tn5 insertional mutagenesis and DNA sequencing. Southern hybridizations showed that this bacteriocin was encoded on the plasmid pRL1JI and that homologous loci were not found in other unrelated R. leguminosarum strains. Tn5 insertional mutagenesis showed that mutations in the C-terminal half of the bacteriocin open reading frame apparently did not abolish bacteriocin activity. Analysis of the deduced amino acid sequence revealed that, similarly to RTX proteins (such as hemolysin and leukotoxin), this protein contains a characteristic nonapeptide repeated up to 18 times within the protein. In addition, a novel 19- to 25-amino-acid motif that occurred every 130 amino acids was detected. Bacteriocin bioactivity was correlated with the presence of a protein of approximately 100 kDa in the culture supernatants, and the bacteriocin bioactivity demonstrated a calcium dependence in bothR. leguminosarum and Sinorhizobium meliloti. A mutant of strain 248 unable to produce this bacteriocin was found to have a statistically significant reduction in competitiveness for nodule occupancy compared to two test strains in coinoculation assays. However, this strain was unable to compete any more successfully with a third test strain, 3841, than was wild-type 248.

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