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Gibberellins (GAs) play an important role in plant growth and development. Fifteen fungi were isolated from Physalis alkekengi var. francheti plant roots, and among them, four isolates showed GA-production activity. A bioassay using waito-c rice was carried out with the culture fluid of the GA-producing fungi. The GA-producing fungi were cultured for 7 days in Czapek’s liquid medium at 30oC, 120 rpm, under dark conditions. The culture broth was concentrated 30-fold and 10 μl of that concentrate was applied to 2-leaf rice sprouts. The height of the rice seedlings treated with the culture fluid of isolate PA08 was 26 cm high, while that of the seedlings treated with the wild-type Gibberella fujikuroi was 13 cm high. As such the plant growth-promoting activity exhibited by isolate PA08 was 2 times stronger than that exhibited by the wild-type G. fujikuroi. The amounts of GA1, GA3, GA4, GA7, GA9, GA20, and GA24 in the medium were measured using gas chromatography-mass spectrometry (GCMS), and the quantities produced by isolate PA08 were 4.85 ng/ml, 4.79 ng/ml, 17.30 ng/ml, 6.01 ng/ml, 16.61 ng/ ml, 0.08 ng/ml, and 17.30 ng/ml, respectively. Isolate PA08 was also identified as Fusarium proliferatum KGL0401 by a genetic analysis of the nucleotide sequences of the internal transcribed spacer region of the ribosomal DNA.
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