Research into the Rhizobium/Leguminosae symbiosis in Latin America

Freire, J. R. Jardim

doi:10.1007/978-94-009-7639-9_20

Cited by 5 publications

(9 citation statements)

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“…Brazilian soils are usually very poor in N and are originally free of soybean bradyrhizobia [8,13,15,16,29,30]. Therefore, with the introduction of the soybean crop to the country, inoculants containing foreign strains were used.…”

Section: Discussionmentioning

confidence: 99%

“…The country today has specific legislation for quality control of commercial inoculants, which can only contain strains recommended by a committee of microbiologists. Four approved strains exist for soybean, SEMIA 587, 29w, CPAC 7 and CPAC 15, all obtained by reisolation from previously inoculated soils after a long or short period of adaptation [8,12,13,28,32].…”

Section: Discussionmentioning

confidence: 99%

“…Until now, the identification of strains by the Brazilian laboratories has been based exclusively on the serological properties and well defined groups with different serological reactions have been established. It is possible that foreign inoculants used in Brazil during the first years of the crop's introduction carried contaminant strains, but for years the serological analysis of nodules collected in the field showed that the known strains occupied most of the nodules [8,10–13,16–20,29–32]. To be able to establish in the soil in such high proportions, these contaminant strains should be extremely competitive and dissemination from other producing areas would have occurred.…”

Section: Discussionmentioning

confidence: 99%

“…Soybean was introduced into Brazil in the last century, but large‐scale commercial crop production started in the early 1960s. As Brazilian soils are originally free from soybean bradyrhizobia [8,13,15,16,29,30], during the establishment of the crop, the seeds had to be inoculated with strains. The inoculant strains were initially brought from the USA, but a search for strains adapted to Brazilian conditions started concomitantly with the expansion of commercial soybean crop production [6,8,15,16,18,19].…”

Section: Introductionmentioning

confidence: 99%

“…As Brazilian soils are originally free from soybean bradyrhizobia [8,13,15,16,29,30], during the establishment of the crop, the seeds had to be inoculated with strains. The inoculant strains were initially brought from the USA, but a search for strains adapted to Brazilian conditions started concomitantly with the expansion of commercial soybean crop production [6,8,15,16,18,19]. The selection of adapted strains usually consisted of inoculation of an area, followed, after a short period of time, by reisolation of bacteria from nodules of soybean trap plants.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of soybean Bradyrhizobium strains adapted to the Brazilian savannas

Santos

Vargas

Hungría

1999

FEMS Microbiology Ecology

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Brazilian soils are originally free from soybean bradyrhizobia and the first inoculants were brought to the country in this century, but a search for adapted strains started immediately and still continues. A strain selection program was established at Embrapa based on the reisolation of strains after a long period of adaptation to the soils followed by a search for variant genotypes with higher N(2) fixation capacity and competitiveness. A second approach of this program consists of searching for variant colonies of a single strain with higher N(2) fixation rates and competitiveness, following a short period of adaptation to the soil. In this study, using both approaches, strains belonging to three serogroups, CB 1809, 532C and SEMIA 5020, were obtained. In general, the variant strains showed differences in colony morphology (mucoidy) but produced similar protein and lipopolysaccharide profiles. Within serogroup CB 1809, containing variants obtained via the second approach, a low level of DNA polymorphism was detected relative to the parental genotype by ERIC and REP-PCR. However, within the two other serogroups, containing variant strains obtained via the first approach, a high level of polymorphism in ERIC and REP-PCR fingerprints was observed relative to the putative serologically related parental genotypes. These results show that a great variability can be detected following adaptation of Bradyrhizobium strains to the soil, although other potential explanations for the DNA polymorphisms observed are discussed. Some of the variant strains obtained by both methodologies were found to have higher rates of N(2) fixation and almost all were more competitive than the parental genotypes, suggesting that it is possible to select variant strains which can contribute to an improved plant N nutrition status.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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