Effects of rhizobia species on the growth and symbiotic performance of Arachis hypogaea under salt stress

MEDEOT, D; MEYER, J; PAULUCCI, N; BUENO, M; GARCÍA, M; DARY, M; DARDANELLI, M

Marruecos

Conferencia; Conférence Internationale sur: les Biotechnologies Microbiennes et leurs Applications; 2007

Association Marocaine de Microbiologie

In order to study the effect of saline stress on the rhizobia-peanut symbiosis, we investigated the response of partners, and in symbiosis. At the Rhizobium level, two strains previously selected for their salt tolerance: were used: Rhizobium ATCC10317 and Bradyrhizobium TAL1000. The fast-growing strain TAL 1000 was able to multiply in 400 mM NaCl and so was the slow-growing strain ATCC 10317, although both strains diminished their viability. However, tolerance of the legume host to salt is the most important factor in determining the success of compatible Rhizobium strains to form successful symbiosis under conditions of high soil salinity. In logarithmic and early stationary-phase cells from strain ATCC 10317 the accumulation of trehalose was highly significant, but not in TAL000.In peanut, only the roots were able to accumulate proline, indicating a possible protective paper of this molecule. The effect of salinity on bacteria–plant association was studied by using the tolerant variety Blanco Manfredii M68 inoculated separately with both strains. In the absence of salinity, the strains induced a significantly higher number of nodules on the roots and both strains were similarly effective. Salinity (100 mM) affected the nodulation development more than it affected the infection steps. Neither of the two strains was able to nodulate BM68 under saline conditions, in spite of the fact that TAL1000 was considered the most salt-tolerant strains. The unsuccessful nodulation could be related to the inhibition by salt of one or more steps of the early events of the infection process.