Abstract:
Legume-Rhizobial symbiosis plays a greater agronomical and ecological
significance as it provides fixed nitrogen through Biological Nitrogen
Fixation. Clitoria ternatea is a leguminous plant that hosts a wide
range of rhizobial strains. Even though it is a widely distributed plant,
comprehensive information and studies conducted on the rhizobial - C.
ternatea symbiosis is lacking in Sri Lanka. This study aimed to identify
different stress-tolerant rhizobial strains inhabiting root nodules of C.
ternatea growing in seven selected locations of Anuradhapura district of
Sri Lanka. Twenty-eight pure rhizobial colonies were isolated and they
were separately grown in ½ Lupin broths and were subjected to four
different physiological conditions, pH, temperature, salinity, and drought.
Most of the isolates were well-grown within the pH range of 5.0-8.0, the
temperature range of 30-35 °C and at 0.2% Polyethylene glycol-8000 (PEG) concentration. There was no observable pattern in the growth of
rhizobial strains in different physiological conditions. The twelve rhizobial
strains which showed high tolerance to extreme physiological conditions
were subjected to a combination of physiological stress conditions of pH
8.0, temperature 36 °C, 3.0 % NaCl and 0.4 % PEG. The maximum growth
in combination physiological study was observed in a strain collected
at the Palugaswewa site. According to the dendrogram prepared by the
Enterobacterial Repetitive Intergenic Consensus (ERIC) profile, twelve
strains are genetically diverse, as they belonged to11 clusters at 69.89 %
of similarity level. These stress-tolerant rhizobial strains could be used for
further studies on cross-inoculation of crop legumes as an alternative to
the nitrogenous fertilizers.
