Isolation and characterization of a multiple herbicide resistant strain [<i style="">Av</i>(MHR)^Ar,Al,B,D] of diazotrophic cyanobacterium <i>Anabaena</i><i style=""> variabilis</i>

Abstract

The present study was aimed to isolate a multiple herbicide resistant strain [(MHR)^Ar,Al,B,D]of <i style="">Anabaena variabilis</i> exhibiting resistance against four common rice-field herbicides, viz., Arozin, Alachlor, Butachlor and 2,4-D. The multiple herbicide resistant (MHR) strain was isolated by spontaneous mutational techniques. Of the four spontaneously occurring mutants, Arozin resistant mutant (Ar-R) exhibited 92-98% survival in lethal concentrations of Arozin, Alachlor, Butachlor and 2,4-D, and was designated as MHR strain, <i style="">Av</i>(MHR)^Ar,Al,B,D. The MHR strain exhibited faster growth rate, substantial increase in macromolecular contents, photosynthesis, nitrogenase and glutamine synthetase (GS) activity not only in graded concentration of herbicides but below (0-25 mg L^-1) and above the lethal dosages (25-80 mg L^-1), and even in the presence of combined lethal dosages of all four herbicides as compared to wild type as well as Alachlor, Butachlor and 2,4-D resistant strains. The cross resistance relationship in Arozin resistant (Ar-R) mutant strain of<i style=""> A. variabilis </i>with lethal dosages of Alachlor, Butachlor and 2,4-D did indicate that it was a single mutational event and resistance to Arozin was associated with the acquisition of resistance to Alachlor, Butachlor and 2,4-D. Evidently such improved <i style="">Av</i>(MHR)^Ar,Al,B,D strain of diazotrophic cyanobacterium <i>A. variabilis</i> under herbicide(s) stressed agro-ecosystem, particularly rice-fields, would likely to serve as efficient biofertilizer.