| Summary: | 碩士 === 國立中興大學 === 昆蟲學系所 === 103 === This study was conducted to culture the entomopathogenic nematode, Steinernema abbasi, on liquid media containing different components. There were two peaks of nematode adult production in the shaker flasks at 14 days after culturing. When changed the rotation speed at 70 and 90 rpm in these cultures, the yields of infective juveniles (IJs) were lower than those of the unchanged one. However, there was no significant difference between the changed and unchanged groups. When the OAK whole milk powder, low-fat milk powder, and non-fat milk powder were added into the liquid media, the IJ yields were 8×104, 2.6×104, and 4.5×103 IJs/ml, respectively. Among them, the IJ yield of the whole milk powder based medium was the highest one; however, as increased its concentration from 1.65％ to 6.6％, the nematode yields decreased from 1.7×105 to 125 IJs/ml. When inoculated with 500 IJs/ml and cultured for 17 days in the 1.65％ whole milk powder medium, the maximum yields reached at 16th day after culturing. The IJ yields of 1.65％ and 3.3％whole milk powder media were higher than those without adding milk powder. There were statistically significant differences among these media. When incubated 1.5, 3.0, or 4.5 ml of symbiotic bacteria in the culture medium for 48 h before inoculating nematodes, the IJ yields were 6.7×104, 2.2×104, and 1.8×104 IJs/ml, respectively. The yields between these three treatments were not significantly different. However, the yields by adding 1.5, 3.0, and 4.5 ml of symbiotic bacteria together with nematodes were less than those of the amount of their initial IJ inocula. Using one-on-one bioassay, the mortalities of 5th instar larvae of Spodoptera litura treated with in vivo- and in vitro-cultured S. abbasi were 23.3％ at 72 h after inoculation. There were no significant differences among the assayed time course. When applied 10, 20, and 30 IJs to each 5th instar larva of S. litura, the LT50 values of 10 IJs was significantly different with those of 20 and 30 IJs. However, the LT50 value of 20 IJs was not significantly different with that of 30 IJs. The LT50 values at the same inoculated dosage in both in vivo and in vitro cultures were not significantly different. The mortalities of 5th instar larvae of S. litura in all treatments were near 100％ after incubating for 72 h. In conclusion, our results showed that addition of whole milk powder to the liquid media could raise the yield of IJs and that the nematodes cultured in the liquid medium exhibited similar pathogenicity to S. litura as those cultured in vivo.
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