| Summary: | Orchid was belonged to one of popular ornamental plant dispersed around
the world. Orchids growth process takes long time to reach generative phase and
existence of soft rot disease would became as factor of deficit production of
orchids. Recently, many researches could be done to find some associated
microorganism which promotes plant growth and controlling the disease. The aim
of this study was to analyze the capability of orchid associated bacteria to produce
phytohormone and its capacity to promote plantlet of P. amabilis growth.
Furthermore, analyzing the suppression of soft rot disease incidence and severity
by orchids associated bacteria on plantlet was done in this study.
Phytohormone productions of orchids associated bacteria were done by
colorimetric assay and the concentration was estimated by Elisa Reader at
absorbance 550 nm. Out of 106 isolates, 79 isolates have been able to produce
IAA with addition of tryptophan in growth medium. Then, 20 selected bacteria
was evaluated their antagonistic activity against to Pectobacterium sp. using
double layer method. Screening antagonistic activity of 20 isolates showed
inhibition haloes ranging from 3 to 7.2 cm. Ten isolates were selected to
characterize by rep-PCR technique using BOX-A1R primer. Five isolated
bacteria that displayed different rep-PCR patterns were selected for further assay.
Introduction of isolates AkOc1 to plantlet P. amabilis showed significant
difference on height, length and roots number of plantlet compared to control.
Furthermore, all inoculated plantlet of P. amabilis showed suppression of soft rot
disease incidence and severity after 3 weeks inoculation with Pectobacterium sp.
Characterization by partial gen 16S rRNA revealed that four isolates (IbtPhm1,
DnDr2, AkOc1 and DnAr4) were closely related to genera of Klebsiella and
isolate TbPh7 were belonging to genera of Bacillus. These results suggested that
inoculation of plantlet by orchid associated bacteria could promote growth of
plantlet P. amabilis and suppress the development of soft rot disease on P.
amabilis plantlet.
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