Abstract:
Plant growth promoting traits like production of indoleacetic acid (IAA), ammonia, hydrogen cyanide (HCN),
siderophore, and like the enzyme activities of catalase, ACC deaminase, cellulase, chitinase and protease were
assayed in vitro for twenty one phosphorus solubilizing bacteria isolated from soil isolates. Except SPP-5 and
SPP-15 strains, all the other isolated strains produced IAA in various amounts of 10 to 23 µg ml-1. All strains
showed positive response for ammonia production and ACC deaminase activity implying that they are capable
of growing in a N-free basal medium. Catalase activity was found to be superior in SPP-2, SPP-7, SPP-12 and
SPP-17 compared to the other strains tested. HCN production was detected by 15 strains and among them
SPP-9, SPP-15, SAph-11, and SAph-24 were found to be strong HCN producers. Except the isolates SPP-10,
SPP-12, SPP-13 and SPP-14, all the other isolates produced more than 80% siderophore units. None of the
strains showed cellulose and chitinase activity. SAph-8, SAPh-11, SAPh-24 and SPP-15 strains showed
35.84, 50.33, 56.64 and 34.78 U/ml protease activities, respectively. SPP-1, SPP-2, SPP-3, SPP-11, SPP-17,
SPP-18, SAph-11 and SAph-24 strains showed positive response for all the tested plant growth promotion
traits except cell wall degrading enzyme activities. According to the results, all the tested phosphorus
solubilizing isolates could exhibit more than three or four plant growth promoting traits, which may promote
plant growth directly or indirectly or synergistically. Therefore, these phosphorus solubilizing strains could be
employed as bio-inoculants for agriculture soils
