Indole Acetic Acid production by fluorescent Pseudomonas isolated from the rhizospheric soils of Malus and Pyrus

Abstract

Fluorescent Pseudomonas, a major component of rhizobacteria, promote  the plant growth  through their multifarious activities. In the present investigations, thirty   strains of fluorescent Pseudomonas were  isolated from the rhizosphere of apple and pear  plants of their  normal and  replant sites and found that the count of  Pseudomonas strains were  more  in normal site as compare to replant site. They were screened for auxins production (indole acetic acid or IAA) and it was found that the strains isolated from normal sites produced more auxins (7-30 µg/ml) as compared to the isolates of replant site (1-4µg/ml). Four strains viz PN-4-SAN, PN-10-SAN, AN-2-NAG and AN-4-NAG were selected on the basis of their higher auxin production. The maximum production of IAA was observed at 72 h incubation period at pH 7.0 under shaken condition at 28oC. The highest IAA was produced by strain AN-2-NAG (30 µg/ml) and PN-4-SAN (30 µg/ml) isolated from Malus (Apple) and Pyrus (Pear) rhizosphere soil, respectively. An attempt was made to extract, purify and evaluate IAA by thin layer chromatography and specific bioassay method. The IAA (Auxin) produced by both the isolates i.e. AN-2-NAG and PN-4-SAN showed Rf value of 0.81. The partially purified and extracted auxins were evaluated by bioassay. The auxins produced by isolates AN-2-NAG and PN-4-SAN showed highest increased in length of coleoptiles of avena. These isolates could be potential strains for bioinoculant production for apple and pear.