Transposon-derived mutants of Pseudomonas strains altered in indole acetic acid production: Effect on nodulation and plant growth in green gram (Vigna radiata L.).

Pseudomonas strains CPS63 and MPS78 produced 18.1 and 19.2 μg ml(-1) of indole acetic acid (IAA) at 2 days of growth. Low producers as well as over producer IAA mutants were derived from Pseudomonas strains CPS63 and MPS78 by Tn5 mutagenesis. Inoculation of selected IAA mutants on green gram (Vigna radiata) seeds showed stunting effect on root and shoot growth of seedlings at 5 and 10 days. Coinoculation studies of Pseudomonas strains with Bradyrhizobium strain S24 and IAA over producer mutants, i.e. CPS63-20 and MPS78-107 resulted in more nodule formation in green gram as compared to wild type Bradyrhizobium strain at 50 days of growth. Significant gains in plant dry weights, i.e. 2.0-3.06 times increase in comparison to uninoculated control plants, were observed on coinoculation of IAA low producer mutants CPS63-27, MPS78-92 and MPS78-166. Better performance of IAA low producer mutants in enhancing plant dry weights of green gram than to IAA over producer mutants indicated that overproduction of IAA by bacteria might inhibit shoot growth in green gram.