Genotypic characterization and symbiotic properties of slow-growing native isolates obtained from peanut root nodules

MUÑOZ, V., IBAÑEZ, F., FABRA, A

Carlos Paz, Córdoba, Argentina

Congreso; VI Congreso Argentino de Microbiología General; 2009

Sociedad Argentina de Microbiología General

Peanut (Arachis hypogaea L.) is a widespread leguminous plant of great economical significance. Argentina is one of the main peanut producer countries in the world and 94% of its production is concentrated in Córdoba province. The native bacterial population associated with peanut nodules in Córdoba is highly heterogeneous and includes both slow- and fast-growing rhizobia. In this work, the genetic diversity and the symbiotic effectiveness of a population of slow-growing isolates obtained from nodules of peanut growing in seven different locations (Pizarro, Suco, Río Cuarto, Charras, Santa Eufemia and Las Higueras) in Córdoba, Argentina, were determined. The analysis of the symbiotic properties revealed differences among the isolates, even when all of them were capable to induce the formation of several nodules in peanut and to significantly increase the shoot dry weight of plants. The genotypic characterization was performed by ERIC-PCR, using primers E1 and E2. ERIC-PCR profiles were analyzed with Cross Checker and FAMD softwares, using the Dice similarity coefficient and UPGMA clustering method to construct a dendrogram. The analysis of the tree revealed that, at a 60% similarity, three clusters could be recognized. Cluster I grouped the four isolates from Charras, as well as two isolates from Pizarro. Cluster II included isolates from Pizarro, Suco, Las Higueras, and the reference strain SEMIA 6144, recommended as inoculant. Cluster III grouped isolates obtained from Pizarro, Rio Cuarto and Santa Eufemia.   The results obtained in this work indicate that the population of slow-growing native isolates from Córdoba is genetically diverse, and it encompass isolates that exhibit different symbiotic properties. The understanding of the genetic diversity and the symbiotic effectiveness of the slow growing population can result in the selection of rhizobial strains to develop an inoculant. This work was supported by SECyT-UNRC, CONICET, MINCyT Córdoba.