PHYSIOLOGICAL STUDIES ON HALOTOLERANT AZOTOBACTER IN DESERT SOIL

Abstract

This study was carried out to isolate halotolerant azotobacters from ditTerent local saline soils and find out the most favourable environmental conditions (temperature and incubation period) and nutritional factors (carbon and nitrogen sources) needed for maximizing the microbial growth. Different carrier materials (peat moss, vermiculite and alginate) were compared for obtaining high microbial viability and N2 - fixtion activity after 16 weeks of storage at room temperature. The effect of some external osmolytes (glutamate, proline and trehalose) in addition to some grain extracts (barley and wheat) on the growth of selected azotohacters was also studied. Internal osmolytes were also estimated within bacterial cells to throw light on the mechanism of osmoprotection of such halotolerant azotobacters. A pot experiment for cultivating wheat plants in sandy soil irrigated with saline solution (0.1 or 0.2% NaCI) and inoculated with halotolerant and (or) non­ halotolerant strains of Azotobacter as well as rhizobacterin was also carried out. The obtained results clearly reveal that osmolytes play an important role for resisting high salinity level. The selected halotolerant inoculant mostly gave the highest growth and yield of wheat plants grown under high salinity stress.