Variation of soil populations of Rhizobium leguminosarum bv. Trifolii and the occurrence of inoculant rhizobia in nodules of subterranean clover after pasture renovation in north-eastern victoria

Slattery, J. F.; Coventry, David

doi:10.1016/0038-0717(93)90176-c

Cited by 29 publications

(13 citation statements)

References 29 publications

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“…Interestingly, in a field study over three growing seasons, the populations of Rhizobium trifolii were found to vary from ca. 10 3 to 10 6 g of soil Ϫ1 according to soil and seasons (29). These numbers are comparable to those found in the present study.…”

Section: Discussionsupporting

confidence: 81%

Seasonal Fluctuations and Long-Term Persistence of Pathogenic Populations of Agrobacterium spp. in Soils

Krimi

Petit

Mougel³

et al. 2002

Appl Environ Microbiol

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Short-and long-term persistence of pathogenic (i.e., tumor forming) agrobacteria in soil was investigated in six nursery plots with a history of high crown gall incidence. No pathogenic Agrobacterium strains were isolated in soil samples taken in fall and winter in any plots, but such strains were isolated from both bulk soils and weed rhizospheres (over 0.5 ؋ 10 5 pathogenic CFU/g of bulk soil or rhizosphere) in three out of six plots in spring and summer. PCR amplifications of a vir sequence from DNA extracted from soil confirmed the presence of Ti plasmids in summer and their absence in fall and winter. The results indicate that strains that harbor a Ti plasmid had an unforeseen positive fitness versus Ti plasmid-free strains in soil and rhizosphere in spring and summer in spite of the apparent absence of tumor, and hence of opines. The gain of fitness occurred during a bloom of all cultivable agrobacteria observed only in conducive soils. An evolution of the pathogenic population was recorded during a 4-year period in one particularly conducive soil. In 1990, the pathogenic population in this soil consisted of only biovar 1 strains harboring both octopine-and nopaline-type Ti plasmids. In 1994, it consisted of only nopaline-type Ti plasmids equally distributed among biovar 1 and 2 strains. These results suggest that nopaline-type Ti plasmids conferred a better survival ability than octopinetype Ti plasmids to biovar 2 agrobacteria under the present field conditions. Agrobacterium spp. are a genus in the family Rhizobiaceae. Strains of Agrobacterium harboring a tumor-inducing (Ti) plasmid cause the plant disease crown gall, which is characterized by uncontrolled proliferation of plant tissues (e.g., tumors). In the course of the infection process, a region of the Ti plasmid, the T-DNA, is transferred to and integrated into the plant genome (13, 34). In the transformed plant cell, T-DNA genes encode enzymes responsible for the uncontrolled synthesis of the plant hormones auxin and cytokinin, which account for the appearance of plant tissue hyperplasia. Other T-DNA genes encode enzymes responsible for the biosynthesis of particular compounds by the transformed plant cells, called opines. Opines are utilized as energy sources by strains harboring a Ti plasmid. Some opines induce the conjugal transfer of the Ti plasmids. Opines are relatively specific niches for strains harboring Ti plasmids, and tumors that produce opines are favorable habitats for both the proliferation of agrobacteria and the conjugal spread of Ti plasmids (10).Ti plasmids are large genetic elements, representing about 5% of the agrobacterial genome (1). As a consequence, they might negatively affect the fitness of Agrobacterium in the absence of opines. When population dynamics were monitored in the presence of opines, the closely related Ri plasmid was found to improve the growth and thus the fitness of a strain harboring this plasmid over those of a plasmid-free strain. Conversely, in the absence of opine, Ri and related plasmids hampered t...

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Section: Discussionsupporting

confidence: 81%

Seasonal Fluctuations and Long-Term Persistence of Pathogenic Populations of Agrobacterium spp. in Soils

Krimi

Petit

Mougel³

et al. 2002

Appl Environ Microbiol

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“…In such situations, seed, soil or aerial contamination will usually lead to some initial nodule formation, and over a period of 4-5 years, to a gradual buildup in the soil rhizobial population. The number of soil rhizobia that result will vary with a number of factors, as discussed in subsequent sections, but can range from 10 2 to 10 7 cells g-l soil Carter et 01., 1995;Ellis et al, 1984;Hirsch, 1996;Rougbley et al, 1995;Singleton and Tavares, 1986;Slattery and Coventry, 1993;Strain et al, 1994;Triplett et al, 1993). Most field or ecological studies designed to count or measure the diversity of these organisms involve a serial dilution of the soil, trapping the rhizobia by nodule formation on sterile seedlings, and the isolation of the rhizobia directly from nodules (Somasegaran and Hoben, 1994).…”

Section: N Soil Populations Of the Rhizobia And Their Diversitymentioning

confidence: 97%

“…This may be due to: a) the relatively non-specific enhancement of rhizobia because of their ability to metabolize a substance present in root exudate; b) the result of multiplication and release of rhizobia from the nodule; or c) the ability of the host legume to select particular groups of rhizobia from a mixed population. While both Rhizobium and B. japonieum strains can exist in soils for a relatively long time in the absence of a host plant (Bottomley, 1992;BruneI et al, 1988;Kucey and Hynes 1989;Sanginga et al, 1994;Slattery and Coventry, 1993;Weaver et al, 1972), specific biovars of Rhizobium have been shown to be influenced by the host. For example, Kucey and Hynes (1989) showed that under pea, population densities of R. leguminosarum bv.…”

Section: Influence Of the Legume Host On Rhizobial Populations Anmentioning

confidence: 97%

Soil Biology of the Rhizobiaceae

Sadowsky¹,

Graham²

1998

The Rhizobiaceae

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“…The sites where the rainfall was recorded were about 10 km from the experimental site in each case. The rainfall data have been presented previously in Slattery and Coventry (1993).…”

Section: Experimental Design Treatments and Site Managementmentioning

confidence: 99%

“…The acidification of these pastoral soils may affect the growth of the clover (Ridley et al, 1990;Ridley and Coventry, 1992). In addition, increased soil acidity may result in problems with clover nodulation and effectiveness of the native soil Rhizobia Slattery and Coventry, 1993). Finally, root diseases have been recognised as important contributing factors to subterranean clover decline (Taylor and Greenhalgh, 1987).…”

Section: Introductionmentioning

confidence: 99%

Subterranean clover decline in permanent pastures in north-eastern Victoria

Burnett¹,

Coventry²,

Hirth³

et al. 1994

Plant Soil

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Experimental sites were established at two locations in north-eastern Victoria to define factors limiting the establishment and growth of Trifolium subterranean L. (subterranean clover). Liming the soil, seed inoculation and fungicide application were used in renovating subterranean clover pasture on two acidic soils (Longwood: brown/grey sandy loam DY 3.14 and Seymour: grey brown light clay DY 3.22, Northcote classification) with mean annual rainfall of 650 mm and 600 mm respectively. Soil acidity, low available soil phosphorus and plant disease were identified as factors limiting clover yield on these soils. Significant yield responses to lime (35-140%) were obtained with subterranean clover at both sites, with corresponding decreases in A1 in the 0-10 cm soil horizon. Liming the soil, when combined with seed inoculation, increased the number and effectiveness of root nodules at both sites. Soil P available for plant growth was low at both sites (6.1 and 8.4/~g g-~) resulting in sub-optimal P concentrations in the clover herbage (45 mmol kg-1 at Longwood). Levels of root disease were low but Aphanomyces euteiches and Phytophthora clandestina (causal agents of lateral and tap root rot) were detected frequently on roots. Application of fungicide resulted in higher dry matter yields (p= 0.05) at both sites.An assessment of the relative contributions of these limiting factors and the benefits to be obtained from better management would provide a clearer picture of the profitability and sustainability of this farming system.

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Variation of soil populations of Rhizobium leguminosarum bv. Trifolii and the occurrence of inoculant rhizobia in nodules of subterranean clover after pasture renovation in north-eastern victoria

Cited by 29 publications

References 29 publications

Seasonal Fluctuations and Long-Term Persistence of Pathogenic Populations of Agrobacterium spp. in Soils

Seasonal Fluctuations and Long-Term Persistence of Pathogenic Populations of Agrobacterium spp. in Soils

Soil Biology of the Rhizobiaceae

Subterranean clover decline in permanent pastures in north-eastern Victoria

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