SYMBIOSIS IN NITROGEN-FIXING FABALES TREES OF DRY REGIONS OF RAJASTHAN - A REVIEW

Research on tree legume-Rhizobium/Bradyrhizobium (root nodulating bact eria) symbiosis has been done to synthesize knowledge on the highly co ordinate sequence of interaction between the two symbionts, which culm inates in biological nitrogen fixation. Genetic, microbiotic, and envi ronmental factors greatly influence the process of symbiosis. Periodic ally revised taxonomies and systematics of nodulating bacteria have be en traced since 1838, along with evolutionary relatedness among member s of Rhizobiaceae. Rhizobial identification based upon morphological a nd physiological characteristics has been well demonstrated. Variabili ty in the adaptability of the bacterial strains as free-living microbe s in saline alkaline soil and conditions of environmental stress in th e desert have been studied extensively. The hot arid and semiarid regi ons of the state of Rajasthan, having nutrient-deficient sandy oil, is dominated by woody tree species of Acacia and Prosopis, which play an important role in the conservation and improvement of the desert soil .