Effect Of Two Vineyard Ground Covers On Rhizobium Leguminosarum Bv Trifolii Populations

0. Domergue, J. Colette, V. Chareyron, L. Maure, J. Cleyet-Marel

Laboratoire des Symbioses Tropicales et Méditerranéennes INRA/IRD/CIRAD/AGRO-M, Montpellier, France

During the past 50 years, herbicides use in vineyard has induced major disturbances in soil with a dramatic decrease in microbial activity and organic matter content. Actually, to reduce erosion and to increase organic matter rate in vineyard soils, ground cover with herbaceous plants is more and more practiced. Among the plant species available, subterraneum clover (Trifolium subterraneum) with its nitrogen-fixing capacity is a very useful legume species as biological soil activator. However, the absence of Rhizobium leguminosarum bv. trifolii, the subterraneum clover symbiotic partner, could limit the plant development. Therefore, the relative abundance of rhizobial populations associated to subterraneum clover in soils from three different plots was evaluated in three different situations: (i) soil without plant cover; (ii) plots with perennial grass cover during three years; (iii) plots with subterraneum clover during three years.

The determination of microbial diversity based on genetic and phenotypic characterization of isolated and cultivated strains after trapping on Trifolium subterraneum as a plant host was performed by PCR restriction analysis of 16S-IGS and nifKD genes. Marked differences were observed between rhizobial isolates trapped from soil without grass cover and isolates from soil cropped with perennial grass or with subterraneum clover.

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