Abstract

Rhizobium spp. retains a symbiotic relationship with leguminous plants including Sesbania bispinosa by fixing N2 through nodule formation. Several researches suggest that Exopolysaccharides (EPSs) are required for nodule formation. Rhizobial growth parameters as well as the EPS production are affected by the presence of pesticides. The present investigation was performed using three different pesticides which were Imitaf 20SL (Insecticide), Tafgor 40EC (Insecticide) and Tilt 250EC (Fungicide). Production of EPS was exceptionally increasing with the escalating concentrations of pesticides. The effects of pesticides were also observed on the antibiotic resistance of these organisms. Some gained resistance against Kanamycin while some got more sensitive than before. Detection of nodC gene and nifH gene ensured the fact that they are the residents of rhizobia bacteria. This study uncovers the fact that extensive use of pesticides may cause an unfavourable environment for survival of rhizobia and a decrease in EPS production resulting in poor N2 fixation and thus affecting the whole agricultural economy of a country.

Key words: Pesticides, Rhizobia, exopolysaccharide, symbiosis, Sesbania bispinosa, antibiotics.

Abbreviation

EPS, Exopolysaccharide; SL, soluble liquid; EC, emulsifiable concentrate; nod, nodulation; nif, nitrogen fixation.