Isolation of fungi producing gibberellins from the several plant roots

摘要

Gibberellins (GAs) are a large family of isoprenoid plant hormones, that control many aspects of plant development, including seed germination, shoot elongation, flower formation and development, fruit- setting, seed development, sex determination, and chlorophyll content. It was first report on GAs in 1828 that disease of rice plants could affect on the elongation of stem excessively. The cause of rice disease was identified as fungus Gibberella fujikuroi by Hori in 1898. GAs are secondary metabolites of the fungus G. fujikuroi. The commercial source of the bio-active GAs was known as GA1, GA3, GA4> and GA7 by fermentation of the fungus G. fujikuroi. 238 fungi were isolated from the 25 plant roots, and the production of GAs was spectrophotometrically examined. As a result sixty nine fungi were shown to produce GAs. A bioassay using waito-c rice was carried out with the culture fluid of the sixty nine GA-producing fungi. The GA-producing fungi were cultured for 7 days in Czapek's liquid medium at 30℃, 120 rpm under dark conditions. 10μl of lyophilized culture fluid concentrated to 30 folds was treated on the 2-leaf rice sprout and the height was measured with scale. Fifteen of these showed plant growth promoting activity and the amount of each GAs in the medium was measured by Gas chromatography-mass spectrometer (GC-MS). The fifteen fungi were shown activity of gibberellin by GC-MS. Ten of these fungi were also identified by genetic analysis of the nucleotide sequences in the internal transcribed spacer region of the ribosomal DNA. As a result isolated fungi showed high similarity to the strain Cladosporium oxysporium, Didymella cucurbitacearum, Penicillium venetum, Neosartorya fischeri, Fusarium Oxysporum, Penicillium canescens, Leptosphaeria sp., Phoma glomerata, and Fusarium proliferatum. So the strains were named Cladosporium oxysporium KGL0402, Didymella cucurbitacearum KGL0403, Penicillium venetum KGL0404, Neosartorya fischeri KGL0407, Fusarium Oxysporum KGL0409, Penicillium canescens KGL0405, Leptosphaeria sp. KGL0419, Phoma glomerata KGL0406, Phoma glomerata KGL0408, and Fusarium proliferatum KGL0401.