Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali-8602, Bangladesh

Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan

Use of eco-friendly area specific salt tolerant bio-inoculants is better alternatives to chemical fertilizer for sustainable agriculture in the coastal saline soils. The study was conducted to isolate and characterize salinity tolerant bacteria like Rhizobium sp. which can be used as biofertilizer. Soil samples were collected from two salinity affected districts namely Khulna and Patuakhali situated in the southern part of Bangladesh. Nine colonies were isolated from pore-plate containing yeast extract mannitol agar (YEMA) medium. All the isolates were rod-shaped, motile and gram negative. Biochemical tests indicated that they were obligate aerobes, catalase and starch hydrolysis positive. They were fast and slow growers on the YEMA medium having different pH levels. The obtained results exhibited that all the isolates tolerated at higher salt concentration (up to 4% NaCl). Among the isolates examined in this study, the KNR4 isolate was found maximum absorbance (1.265) indicating most tolerant to salinity whereas, KNR5 isolate was recorded the lowest absorbance (0.8449) resulting most sensitive. Other isolates were moderate tolerance to salinity. Therefore, KNR4 isolate may become a promising source for salinity tolerant Rhizobiumsp in Bangladesh.

Keywords: coastal soil,Rhizobium, isolation,salinity, Bangladesh.