RESUMEN
The distribution of chloroplast DNA (cpDNA) variation in Italian beech ( Fagus sylvatica L.) populations was studied using PCR-RFLP and microsatellite markers. In total, 67 populations were analysed, and 14 haplotypes were identified by combining the two marker types. A remarkable subdivision of cpDNA diversity in Italian beech was found, as indicated by a high level of genetic differentiation ( G(st)=0.855). The highest level of total haplotype diversity ( h(t)=0.822) was estimated for southern Italian populations. The highest number of haplotypes was found in the central-southern region of the peninsula. The nested clade analysis provided evidence for past fragmentation events that may have been occurred during the Quaternary glaciations and had a major role in defining the genetic structure of the central-southern Italian beech populations. Only one haplotype apparently spread towards the north of Italy along the Apennine chain and reached the Italian slope of the western part of the Alps (Maritime Alps, Liguria). All haplotypes found along the Apennines remained trapped in the Italian peninsula. Southern and central Italy represent hotspots of haplotype diversity for Italian beech.
Asunto(s)
ADN de Cloroplastos/genética , Fagus/genética , Variación Genética , Filogenia , Análisis de Varianza , Secuencia de Bases , Cartilla de ADN , Demografía , Geografía , Haplotipos/genética , Italia , Repeticiones de Microsatélite/genética , Datos de Secuencia Molecular , Polimorfismo de Longitud del Fragmento de Restricción , Dinámica Poblacional , Análisis de Secuencia de ADNRESUMEN
We analyzed the genetic diversity of 531 Sinorhizobium meliloti strains isolated from nodules of Medicago sativa cultivars in two different Italian soils during 4 years of plant growth. The isolates were analyzed for DNA polymorphism with the random amplified polymorphic DNA method. The populations showed a high level of genetic polymorphism distributed throughout all the isolates, with 440 different haplotypes. Analysis of molecular variance allowed us to relate the genetic structure of the symbiotic population to various factors, including soil type, alfalfa cultivar, individual plants within a cultivar, and time. Some of these factors significantly affected the genetic structure of the population, and their relative influence changed with time. At the beginning of the experiment, the soil of origin and, even more, the cultivar significantly influenced the distribution of genetic variability of S. meliloti. After 3 years, the rhizobium population was altered; it showed a genetic structure based mainly on differences among plants, while the effects of soil and cultivar were not significant.
Asunto(s)
Variación Genética , Medicago sativa/microbiología , Sinorhizobium meliloti/crecimiento & desarrollo , Sinorhizobium meliloti/genética , ADN Bacteriano/análisis , ADN Bacteriano/genética , Italia , Técnica del ADN Polimorfo Amplificado Aleatorio/métodos , Suelo , SimbiosisRESUMEN
We analysed the genetic diversity of 270 Sinorhizobium meliloti strains isolated from nodules of three different Medicago sativa varieties, planted in three different Italian soils, combining the Analysis of Molecular Variance (AMOVA) with the Random Amplified Polymorphic DNA (RAPD) technique to estimate variance among RAPD patterns with the aim to draw an objective description of the population genetic structure. Results indicated that a general intraspecific genetic diversity was globally distributed among all the population, however a very high level of diversity was found among strains nodulating different Medicago sativa varieties. Moreover the distribution of the RAPD haplotypes among the plant varieties also showed to be non-random. The overall data indicated that the plant genotype is a major factor in shaping the genetic structure of this natural Rhizobium population.
Asunto(s)
Variación Genética , Medicago sativa/microbiología , Rhizobiaceae/genética , Análisis de Varianza , ADN Bacteriano/análisis , Genotipo , Haplotipos , Italia , Medicago sativa/genética , Filogenia , Técnica del ADN Polimorfo Amplificado Aleatorio , Rhizobiaceae/clasificación , Rhizobiaceae/aislamiento & purificación , Rhizobiaceae/fisiología , Microbiología del SueloRESUMEN
A Burkholderia cepacia population naturally occurring in the rhizosphere of Zea mays was investigated in order to assess the degree of root association and microbial biodiversity at five stages of plant growth. The bacterial strains isolated on semiselective PCAT medium were mostly assigned to the species B. cepacia by an analysis of the restriction patterns produced by amplified DNA coding for 16S rRNA (16S rDNA) (ARDRA) with the enzyme AluI. Partial 16S rDNA nucleotide sequences of some randomly chosen isolates confirmed the ARDRA results. Throughout the study, B. cepacia was strictly associated with maize roots, ranging from 0.6 to 3.6% of the total cultivable microflora. Biodiversity among 83 B. cepacia isolates was analyzed by the random amplified polymorphic DNA (RAPD) technique with two 10-mer primers. An analysis of RAPD patterns by the analysis of molecular variance method revealed a high level of intraspecific genetic diversity in this B. cepacia population. Moreover, the genetic diversity was related to divergences among maize root samplings, with microbial genetic variability markedly higher in the first stages of plant growth; in other words, the biodiversity of this rhizosphere bacterial population decreased over time.
Asunto(s)
Burkholderia cepacia/genética , Zea mays/microbiología , Secuencia de Bases , Burkholderia cepacia/aislamiento & purificación , ADN Ribosómico/química , Variación Genética , Datos de Secuencia Molecular , ARN Ribosómico 16S/genética , Técnica del ADN Polimorfo Amplificado AleatorioRESUMEN
We investigated the genetic diversity of 96 Rhizobium meliloti strains isolated from nodules of four Medicago sativa varieties from distinct geographic areas and planted in two different northern Italian soils. The 96 isolates, which were phenotypically indistinguishable, were analyzed for DNA polymorphism with the following three methods: (i) a randomly amplified polymorphic DNA (RAPD) method, (ii) a restriction fragment length polymorphism (RFLP) analysis of the 16S-23S ribosomal operon spacer region, and (iii) an RFLP analysis of a 25-kb region of the pSym plasmid containing nod genes. Although the bacteria which were studied constituted a unique genetic population, a considerable level of genetic diversity was found. The new analysis of molecular variance (AMOVA) method was used to estimate the variance among the RAPD patterns. The results indicated that there was significant genetic diversity among strains nodulating different varieties. The AMOVA method was confirmed to be a useful tool for investigating the genetic variation in an intraspecific population. Moreover, the data obtained with the two RFLP methods were consistent with the RAPD results. The genetic diversity of the population was found to reside on the whole bacterial genome, as suggested by the RAPD analysis results, and seemed to be distributed on both the chromosome and plasmid pSym.
Asunto(s)
Medicago sativa/microbiología , Sinorhizobium meliloti/genética , Sinorhizobium meliloti/aislamiento & purificación , Análisis de Varianza , Secuencia de Bases , Mapeo Cromosómico , Cromosomas Bacterianos/genética , Cartilla de ADN/genética , ADN Bacteriano/genética , ADN Ribosómico/genética , Variación Genética , Italia , Datos de Secuencia Molecular , Plásmidos/genética , Polimorfismo de Longitud del Fragmento de Restricción , ARN Bacteriano/genética , ARN Ribosómico 16S/genética , ARN Ribosómico 23S/genética , Técnica del ADN Polimorfo Amplificado Aleatorio , Microbiología del Suelo , SimbiosisRESUMEN
Random amplified polymorphic DNA (RAPD) analysis was applied to genomic DNA from nineteen yeast strains belonging to the genera Saccharomyces and Zygosaccharomyces. Results obtained with five primers indicated that this technique is a powerful tool for yeast differentiation and identification. The data were consistent with those derived from restriction fragment length polymorphism (RFLP) using two S. cerevisiae DNA probes. We conclude that RAPD fingerprinting, combined with the analysis of RFLP, can provide unambiguous type assignment in yeasts.