Identification of stress tolerant rhizobial strains inhabiting <em>Gliricidia sepium</em> in Polonnaruwa district, Sri Lanka

Abstract

Rhizobia are well-reputed biological nitrogen fixing organisms due to their proficiency in symbiotic root nodule formation with leguminous plants. Gliricidia sepium is a widely distributed legume which hosts a wide range of rhizobia. Few studies have been carried out to identify the stress tolerant rhizobial populations inhabiting G. sepium in Sri Lanka. This study was focused on the characterization and identification of stress tolerant rhizobial strains residing in the root nodules of G. sepium growing in seven selected locations of Polonnaruwa district, Sri Lanka. Isolated rhizobial strains were separately subjected to stress conditions (pH, temperature, salinity, and drought) and to a combination of given stress conditions. Most of the strains were tolerant to 25-45 ºC temperature range, extreme drought conditions and 1.5 % and 2.0 % salinity levels. However all the strains were adversely affected by acidic pH. Among the fifteen strains that were selected from the statistical analysis, fourteen displayed higher survival capacity when the combinations of physiological conditions were applied. There was great genetic diversity within these isolates and they belonged to 10 clusters. Cross inoculation of these isolated stress tolerant strains into crop legumes can be used as an ideal alternative for chemical nitrogen fertilizers.

Rhizobia inhabiting <em>Clitoria ternatea</em> L. in Anuradhapura District, Sri Lanka: An assessment of stress tolerance and genetic diversity

“…Furthermore, similar rhizobial strains can be found in different geographical locations. These results are further supported by the studies carried out by Udupamunuwa et al (2020) and Samarakoon and Rajapakse (2020). Even though some of the strains belong to similar clusters, their physiological behaviors are different due to the difference in their genetic makeup.…”

Mecanismos de inducción de rizobios para reducir el estrés por sequía en las leguminosas

“…Entre estos microorganismos, algunos rizobios, además de establecer simbiosis con las leguminosas para obtener nitrógeno asimilable, también poseen rasgos de ser promotores del crecimiento de plantas (Flores-Félix et al, 2020). Esta capacidad les permite inducir, en las leguminosas, tolerancia al estrés por sequía (Ojuederie et al, 2019;Yanni et al 2016), a través de diferentes mecanismos como la síntesis de exopolisacáridos, fitohormonas, enzimas, sideróforos, solubilización de fosfatos (Samarakoon y Rajapakse, 2020;Ullah et al, 2017), secuestro de carbono y remediación de suelos áridos y semiáridos (Ayangbenro y Babalola, 2021).…”