Genetic diversity of Rhizobium present in nodules of Phaseolus vulgarisL. cultivated in two soils of the central region in Chile

Abstract

Although Phaseolus vulgaris L. is native from the Americas and is currently cultured in diverse areas, verylittle is known about the diversity of symbiotic nitrogen fixing Rhizobium (mycrosymbiont) in many ofthose cultures. Therefore, the aim of this study was to assess the genetic diversity of Rhizobium presentin nodules of P. vulgaris in the central region of Chile. A method to extract DNA from surface-sterilizednodules was applied to two populations of the same seed variety grown in different fields. The 16SrRNA and nifH genes were amplified directly from the DNA extracted. DGGE analysis and clone librariesshowed a restricted genetic diversity of the microsymbiotic populations that nodulate P. vulgaris. Bothmolecular markers revealed the presence of a microsymbiont closely related to Rhizobium etli in all theplants from the soils studied, indicating that the populations of Rhizobium sp. nodulating P. vulgaris inthe central region of Chile displayed an extremely low genetic diversity. The level of genetic diversityin microsymbiont populations in plants grown in soils with different origin suggested that other factorsrather than the indigenous soil rhizobial populations play a major role in the selection of the symbioticpartner in P. vulgaris.