STUDIES ON DIVERSE PLANT GROWTH PROMOTING RHIZOBACTERIA ASSOCIATED WITH RHIZOSPHERE OF KIWI VINES
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Date
2015
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ABSTRACT
Plant hormones are chemical messengers that affect a plant's ability to respond to its
environment. Hormones are organic compounds that are effective at very low concentration; they are
usually synthesized in one part of the plant and are transported to another location. Botanists
recognize five major groups of hormones: auxins, gibberellins, ethylene, cytokinins, and abscisic acid.
IAA (indole-3-acetic acid) is the member of the group of phytohormones and is generally considered
the most important native Auxin. It functions as an important signal molecule in the regulation of
plant development including organogenesis, tropic responses, cellular responses such as cell
expansion, division, differentiation, and gene regulation. Therefore, the objective of the present study
was to isolate and screen IAA producing rhizobacteria from kiwi vines and to optimize cultural
conditions for maximum production of IAA. One hundred and fifty seven isolates (sixty three
rhizospheric and ninety four root endophytic isolates were isolated from different cultivars of kiwi
vines and were screened for IAA production. These IAA producing isolates were further screened for
P-solubilization on PVK media, siderophore production on CAS medium and their ability to grow on
nirtrogen free medium. Overall maximum IAA producing twenty isolates were selected for screening
of other PGP traits. Variation was also observed in their plant growth promoting (PGP) activities such
as IAA production, P-solubilization and siderophore production. Out of twenty, majority isolates
exhibited antifungal activity and showed enzyme production. Overall six most efficient bacterial
isolates were finally selected and evaluated for plant growth promotion of tomato and kiwi seedlings
under net house conditions. The most efficient isolate B2S10 was further subjected to optimization of
cultural conditions for IAA production. Maximum IAA production of (55μg/ml) was observed after
96 hours of incubation at 35⁰C temperature, pH 9 in LB broth amended with 1.00 (%) tryptohan. The
most efficient isolate was identified as Serratia marcescens by 16SrRNAgene sequence analysis