Relation of IAA production with drought and salinity tensions and tryptophan variability in isolated bacteria from saline and saline-sodic soils

This investigation was carried out because of the importance of IAA production by bacteria and its role in rooting induction in drought, saline and saline-sodic soils., especially.In this investigation, 400 bacteria were isolated from soils with different levels of electrical conductivity (EC) and sodium adsorption ratio (SAR) and analyzed the variability of their ability in IAA production and the effects of different amounts of tryptophan and drought-salinity tensions on IAA production.Results indicated that the effects of drought and salinity tensions on variability of IAA production were significant, statistically. One of bacterial species as Arthrobacter siccitolerans that was isolated from saline-sodic soils, was IAA producer and had the highest dtability in tensions. Also, this bacterium was osmotolerant and halotolerant and continued to IAA production up to EC of 40 dS.m-1 and OP (Osmosis pressure) of -20 bar. A. siccitolerans has a high efficiency in tryptophan consumption in tension conditions. So, IAA production per unit of consumed tryptophan was 0.1, and reported as the most efficient bacterium in drought-salinity conditions. So, According to the tests on isolates, A. siccitolerans was proposed for field experiments in drought, salinity and salinity-sodicity affected soils.