| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 97 === Fusarium species of the Section Liseola could produce fumonisins. This mycotoxin was associated with equine leukoencephalomacia, procine pulmonary edema nephrotoxicity, liver or kidney cancer in rats, immunosuppression in poultry, and high rate of human esophageal cancer. Seventeen Fusarium isolates in the Section Liseola were isolated from rice and corn by Nash-PCNB selective medium, and evaluated their ability of producing FB1 by Fumonisin kit and HPLC. Five isolates, ST-P01(from corn feed), PR-14, PR-33, PR-44, and PR-143(from rice), were able to produce FB1, especially isolate ST-P01 was able to produce the highest amount of FB1, up to 581.52 ppm. Isolates ST-P01, PR-14, PR-33, PR-44, and PR-143 were identified as Fusarium proliferatum (Matsushima) Nirenberg by conidia morphology, conidigenous cells, and ITS sequencing. Furthermore, the factors affecting FB1 production were evaluated including temperature, culture time, culture substrates, culture methods, pH value of culture medium, relative humidity, and inoculum density. The FB1 production by isolate ST-P01 could be detected five days after its static culturing, and FB1 yield was the highest at 32℃ compared to the other temperature treatment. Isolate ST-P01 produced the highest amount of FB1 up to 431 ppm in purple glutinous rice meal liquid media among nine substrates, including purple glutinous rice, unpolished rice, rice, millet, wheat, corn, oat, naked barley, and buckwheat. Isolate ST-P01 cultured in corn meal liquid media produced 351 ppm. The less one was 75 ppm when isolate ST-P01 cultured in oat meal liquid media. In addition, isolate ST-P01 cultured staticly in corn solid media produced 5000 times more FB1 than in liquid media. Isolate ST-P01 produced more amount of FB1 cultured in corn meal liquid with shaking compared to with static. Isolate ST-P01 cultured in corn meal liquit media with pH 2 produced the highest amount of FB1 at 453 ppm. On the contrary, it cultured in corn meal liquid media with pH 6 produced the lowest amount of FB1 at 19 ppm. Among five relative humidities including 7, 20, 34.5, 75.5 and 97.5%, isolate ST-P01 could produce FB1 only at RH 97.5%. Three initial inoculum density of isolate ST-P01, 105, 106, and 107 conidia/ml, inoculated into liquid corn meal media did not make difference on producing FB1. In our studies, among four isolates tested, ST-P01 was able to produce largest amount of FB1 when it was cultured at 32℃ in medium with pH 2. However, isolate PR-44 was suitable for FB1 production at 28℃ in medium with pH 6. By manipulalting the conditions for corn storage, it was found that the inoculated corn kernels stored at 4 ℃ for 15 days did not grow out the fungal mycelia and produce FB1. In addition, amendment of FB1-solution with teamine could reduce 34% of FB1.
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