Screening of earthworm cast actinobacteria for plant growth promoting properties and production of indole acetic acid (IAA) from selected actinobacterial isolates

Author(s): N.Malliga, S.Bharathi, M.Radhakrishnan, R.Balagurunathan

Actinobacteria are the diverse group of bacteria which are widely distributed in various natural and man-made environments. This present study is attempted for the isolation of actinobacteria from earth worm cast and the production of indole acetic acid (IAA) from selected isolates. Totally 10 actinobacterial colonies were isolated using starch casein agar and cast extract agar fromearthwormcastmaterial collected fromAgricultural area, Kanchipuram. All the isolated were confirmed as actinobacteria based on their colonial and microscopic appearance. All the isolates were screened for the production of ammonia, acetoin, phosphate solubilisation and indole acetic acid production. Out of 10 isolates, 5 showed acetoin production, 9 showed phosphate solubilisation and six isolates showed indole acetic acid production. Further study was concentrated on IAA production fromtwo actinobacterial isolates namelyCA4 and CA6. Production, extraction, separation and assay of IAA were performed by adopting standard procedures. The quantity of IAA produced by the strain CA4 and CA6 was estimated as 15.4µg/ml and 19.8 µg/ml, respectively. Microscopic, cultural and physiological characteristics of actinobacterial isolates were studied by adopting standard procedures. Based on the phenotypic characteristics both the actinobacterial isolates (CA4 and CA6) are suspected as Streptomyces species. Finding of the present work concludes that cast soil is a potential source for plant growth promoting actinobacteria (PGPA). Optimization studies are needed to prove the potential of cast soil actinobacteria such as CA4 and CA6 as producer of Indole Acetic Acid (IAA).

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