Isolation and partial structure elucidation of gibberillin produced by plant growht promoting bacteria (PGPB) and its effect on the growth of hybrid rice (Oryza sativa L.)

Issue Date

8-2010

Abstract

Forty plant growth promoting bacteria (PGPB) were screened for gibberellin (GA) production through the dwarf rice (cv. Tanginbozu) bioassay. Among the GA-producing isolate, TCeR 48 produced the highest amount of GA (81.70 μg GA₃ equiv mL¯¹ culture). The peak of GA production by TCeR 48 was at 15 days after inoculation. Extracts from TCeR 48 were purified by high performance liquid chromatography (HPLC) and analyzed through gas chromatography coupled with mass spectrometry (GC-MS). The production of ent-kaur-16-ene, an intermediate in the biosynthesis of gibberellin, is indicated by the peaks at m/z 91 and m/z 105. There is a hint that GA₂₀, a 13-hydroxy gibberellin. Further analysis by ultraviolet (UV) spectroscopy revealed the presence of a strong peak at λ of 215 nm which indicated the presence of unconjugated -OH bond and a low intensity single bond at λ of 260 nm which suggest the presence of isolated C=0 and -COOH. Fourier transform infrared (FTIR) spectroscopy confirmed the functional groups present in the unknown GA structure. Peaks at 3377.95 cm¯¹ and 1411.99 cm¯¹ suggest the presence of -COOH and -CH₃ groups, respectively. All of the observed functional groups in the UV and FTIR spectra are characteristics of the structure of GA₂₀. However, a distinct peak at 1116.98 cm¯¹ of the TCeR 48 spectrum indicates the presence of a double bond in the structure of the unknown GA which is absent in GA₂₀.

Application of the PGPB-derived GA was explored in hybrid rice seed production. At five days after sowing (DAS), germination of seeds treated with strains TCeR 48, TCeRe 37w, BTToaRe and farmer's practice (incubation at 60 ˚C for 5 days) were significantly higher compared to the control. Seedling height of rice treated with the PGPB isolates was higher than the control and the oven-incubated seeds at 21 DAS. Shoot and root dry weights of the seedlings treated with BTToRe were higher compared to the control. Transplanted seedlings showed significant increase in plant height when treated with GA₃ and the PGPB isolates at 3 months after transplanting. Tillering was significantly enhanced by treatment with TCeR 48.

Source or Periodical Title

Philippine Journal of Crop Science

ISSN

0115-463x

Volume

35

Issue

2

Page

12-22

Document Type

Article

Frequency

tri-quarterly

Physical Description

tables, graphs, pictures

Language

English

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