Selection of Tn5 :: lacZ mutants isogenic to wild type Azospirillum brasilense strains capable of growing at sub-optimal temperature

Azospirillum brasilense strains, CDJA and A40, capable of growing at sub-op timal temperature were tagged with stable chromogenic marker Tn5-lacZ. Muta nts were screened for plant growth promoting activities at 20, 22, 25, 30 a nd 37 degreesC. Mutants MC48 and MA3 were found to fix nitrogen upto 85% an d produced indole acetic acid (IAA) and siderophore in isogenic manner to t heir respective wild type strains, CDJA and A40, at sub-optimal temperature s. Co-inoculation of mutants with their respective parent (1:1 ratio) to th e wheat revealed that colonization potential of the mutants was affected gr eatly. Tn5-lacZ tagged mutants MC48 and MA3 were found isogenic to their re spective wild type Azospirillum strain, with regards to plant growth promot ing activities and root colonization ability.