| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 101 === Bakanae disease is one of the oldest rice diseases, and is endemic in Taiwan for years. Typical symptoms are on the primary leaves with slender, chlorotic and elongated appearances, which is caused by gibberellin produced by the pathogen, Fusarium fujikuroi. Infected plants can be observed on the seedbed and in the field. This pathogen has long been considered to be seed-borne. Therefore, seed sterilization is the major approach to control this disease and has been proved effective. However, this disease still outbreaks from time to time and its occurrence is hardly predictable. There are still problems to be resolved, including (1) an effective method to detect F. fujikuroi on seeds, (2) the susceptibility of different rice varieties against F. fujikuroi, (3) the role of soil inoculum in the pathogenicity. In order to detect F. fujikuroi on seeds, a differential medium, designated as FFC medium, has been developed. FFC medium contains 20g Galactose, 2g L-asparagine, 1g K2HPO4, 0.5 g MgSO4．7H2O, 0.5 g KCl, 0.01 g Fe-Na-EDTA, 1 g Na2B4O7．10H2O, 20 g agar, 1 ppm Cycloheximide, 2 ppm Dichloran, 1 ppm Iprodine, 5 ppm Thiabendazole, 10 ppm Flutolanil, 1000 ppm lithium choloride, 200 ppm chloramphenicol and 1L distilled water. F. fujikuroi and F. proiferatum, the morphologically indistinguishable species, can be separated by FFC medium. F. proiferatum can be inhibited on FFC medium. To evaluate the susceptibility of rice toward F. fujikuroi, a standard screening methods for evaluating susceptibility of rice seedling has been established. High virulent isolate IL01 with the concentration of 1 ×103 spores/mL was inoculated to germinated seeds, which were then incubated at 28oC for 21 days. Susceptibility of rice can be evaluated by disease incidence. To investigate the infection capacity of soil inoculum, different growing stages of rice were inoculated. The results showed that adult rice plant could not be infected through soil inoculum, and infection on seeds could lead to the disease in the adult stage. The more we know about F. fujikuroi, the more questions we have in mind. It is expected that the ecology of F. fujikuroi can be fully understood after our dedication.
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