A Study On The Stress Tolerant Rhizobial Isolates From Sesbania bispinosa
Najmun Nahar, Nusrat Nahar, Anowara Begum, Humaira Akhter*
Departmrent of Microbiology, University of Dhaka, Dhaka - 1000
ABSTRACT: The present investigation was carried out to study the extremely diversified characteristics of rhizobial strains isolated from locally produced legume
Sesbania bispinosa, a well-known green manure of Bangladesh, commonly known as Dhaincha. It was important to study the rhizobial isolate of this less studied plant
of Bangladesh in order to learn about its association and to increase soil fertility. An attempt had been made to evaluate the effect of abiotic constraints
(salt, pH and temperature) on the growth of rhizobia isolated from Sesbania bispinosa growing in different region of Bangladesh with a view to screen out stress
tolerant isolates. Growth of pure rhizobial isolates on Yeast Mannitol Agar (YMA) medium having different concentration of NaCl (2%, 2.5%, 3%, 4%, 5%, 6% and 8%)
and variable range of pH (4.5, 5.5, 6.5, 8.5, 9.5 and 10.5) were recorded after incubation at 30˚C for 24-48 hours. The growth of rhizobial isolates were also
observed after incubation at 25˚C, 30˚C, 37˚C, 45˚C and 55˚C temperature, respectively. All the 46 isolates were able to tolerate up to 3% salt concentration. However
it was observed that with increasing salt concentration isolates were found to be decreasing. It was further observed that, acidic and alkaline pH could not suppress
the growth of these isolates. All isolates were found to grow upto 37˚C. However, 42 out of 46 isolates were able to tolerate 45˚C. The highest temperature (55˚C)
was found to inhibit growth of about 43% isolates. The stress tolerant traits of these rhizobia are of potential value from the point of view for using Sesbania sp.
as bio-fertilizer in different region of Bangladesh.
KEYWORDS: Sesbania, stress tolerant, bio-fertilizer