Ventorino Valeria, Chiurazzi Mario, Aponte Maria, Pepe Olimpia, Moschetti Giancarlo
Dipartimento di Scienza degli Alimenti, Sezione di Microbiologia Agraria, Alimentare ed Ambientale e di Igiene, Università degli Studi di Napoli Federico II, Portici, Italy.
Curr Microbiol. 2007 Dec;55(6):512-7. doi: 10.1007/s00284-007-9024-5. Epub 2007 Sep 27.
A total of 98 rhizobial strains, isolated during the winter of the years 2003 (35 isolates), 2004 (33 isolates), and 2005 (30 isolates) were analyzed to determine the genetic diversity of the natural population nodulating Vicia faba plants and to identify dominant genotypes. All isolates were identified as Rhizobium leguminosarum bv. viciae by biovar-specific polymerase chain reaction amplification of the nodC gene. Intraspecific DNA polymorphism was evaluated through the restriction endonucleases analysis combined with pulsed-field gel electrophoresis. Four genotypes characterized 53% of the isolates, showing a high occurrence; moreover, they were recovered over the 3 years, thus showing a lasting persistence in the soil, which could mean a high degree of saprophytic competitiveness. The richness, diversity, and dominance indexes of genotypes were calculated to monitor the evolution of the rhizobial population during the 3 years. The genetic diversity of the analyzed strains decreased along the 3 years. In fact, the biodiversity index H' decreased from 2.6 in the first and second year to 1.9 in the third year; probably, as a result of bean monocropping, specific genotypes of Rh. leguminosarum bv. viciae were naturally selected.
对2003年冬季（35株分离物）、2004年冬季（33株分离物）和2005年冬季（30株分离物）分离得到的总共98株根瘤菌菌株进行了分析，以确定蚕豆结瘤自然群体的遗传多样性并鉴定优势基因型。通过对nodC基因进行生物型特异性聚合酶链反应扩增，所有分离物均被鉴定为豌豆根瘤菌蚕豆生物型。通过限制性内切酶分析结合脉冲场凝胶电泳评估种内DNA多态性。四种基因型占分离物的53%，出现频率较高；此外，它们在这3年中均被检出，表明在土壤中持续存在，这可能意味着具有高度的腐生竞争力。计算基因型的丰富度、多样性和优势度指数，以监测3年期间根瘤菌群体的演变。分析菌株的遗传多样性在这3年中有所下降。事实上，生物多样性指数H'从第一年和第二年的2.6降至第三年的1.9；这可能是由于蚕豆连作，豌豆根瘤菌蚕豆生物型的特定基因型被自然选择的结果。
