Influence of pH and calcium on the growth, polysaccharide production and symbiotic association of Sinorhizobium meliloti SEMIA116 with alfalfa rots

DELAVECHIA,C.; HAMPP,E.; FABRA, ADRIANA; CASTRO,S.

BIOLOGY AND FERTILITY OF SOILS

SPRINGER

Lugar: Berlin; Año: 2003 vol. 38 p. 110 - 114

0178-2762

The Sinorhizobium -legume interaction is sensitiveto a number of environmental factors, soil aciditybeing one of the most important. In the typic Hapludollsoil of the central-southern region of Crdoba (Argentine)it was found that the nodulation of alfalfa ( Medicagosativa L.) roots was impaired with a reduction in shootdry matter under conditions of soil acidity (pH 5.5) Ourresults showed that the addition of lime as dolomiticlimestone at a concentration of 1 t ha-1 to acid soil causeda significant increase in the nodulation of alfalfa rootsinoculated with the strain Sinorhizobium meliloti SEMIA116 (recommended inoculum for alfalfa) in the greenhouseexperiments. The success of the lime treatment maybe related not only to an increase in the pH values but alsoto an increase in the Ca concentration, improving thegrowth of S. meliloti and its nodulation ability underacidic conditions. In this study, we also demonstrated anincrement in the bacterial growth rate as well as in theproduction of exopolysaccharides and lipopolysaccharidesunder low pH (5.5) and a high Ca concentration(5 mM) in the culture medium.