STUDIES ON SYMBIOTIC NITROGEN FIXATION UNDER SOIL STRESS CONDITIONS

Abstract

Until perhaps l 0 years, studies of environmental stress and the legume-Rhizobium or Bradyrhizobium symbiosis were restricted to defining the problem, and to using physical or chemical amendments to overcome it, i.e., mulching to reduce soil temperature or liming to ameliorate soil acidity. The identification of bacterial strains and in some cases host cultivars that are tolerant to these stresses opens the way for altemate, lower cost solutions to these problems. Therefore, in the present study, the ability of 25 local and foreign Rhizobium and Bradyrhizobium strains represent R. meliloti (5 strains), R. leguminosarum bv. viceae (5 strains), R. leguminosarum bv. trifolii (2 sJrains), Bradyrhizobium w nodulating peanut (5 strains) and

Bradyrhizobium japonicum ( 5 strains) to tolerate increased concentrations of NaCl, high temperature, high levels of nitrogen, high pH values and desiccation was investigated•. Rhizobia!strains tolerant to • the above mentioned stress conditions were selected and the symbiotic

performance of the obtained strains was evaluated as well.