RESUMEN
Transposon Tn5 induced, four Mesorhizobium ciceri auxotroph were isolated and characterized. Unlike its wild type parent (TL 620), all four mutants were found defective for amino acid and pyramiding biosynthesis. The auxotroph mutants were characterized and found TL130 as cytosine and uracil, TL 196 for guanine, cytocine, uracil and riboflavin, TL 141 as serine and TL 38 as argentine defective. Symbiotic characterization of these mutants revealed phenotypic deformities and deficiencies in biological nitrogen fixation. All the four auxotrophic mutants were characterized as nod+/fix+ nature with reduced nitrogenase activity of 42.2, 26.3 and 17.13% respectively as compared to the wild type which is further supported by sub cellular examination of the nodules section by TEM study.