| Summary: | 碩士 === 國立中興大學 === 昆蟲學系 === 89 === Artificial culture of the entomopathogenic nematode, Steinernema abbasi
Ju-Chuan Lo
Abstract
The entomopathogenic nematode, Steinernema abbasi, was isolated from Taiwan. Its symbiotic bacterium, Xenorhabdus sp. cultured in nutrient broth (NB) was biphasic growth and it grew well at 25-30℃. The concentration of Xenorhandus sp. after culturing in NB for 48 hr at 25℃ was 108 CFUs/ml. The relationship of bacterial concentration (X) and the optical density (OD) at 550 nm (Y) was Y = 0.01 + 5.78e-9X (r2 = 0.99). Using optical density (OD550) is thought to be a tool for measuring the bacterial concentration.
Monoxenic culture of S. abbasi was carried out with its symbiotic bacteria (in NB, 5ml) in the media containing peptone, yeast extract, lard, soy flour, water and sponge, and mixing them with other materials including duck liver powder, Spodoptera litura larval powder, Bombyx mori pupal powder, Bactrocera dorsalis pupal powder, chicken egg or milk powder, respectively. The nematodes cultured in the medium containing milk powder grew best, with a yield of 2.8 × 105 IJs/g. The medium contained duck liver powder produced the lowest yield, 4.5 × 103 IJs/g. The IJs produced from those artificial media were not significantly different from those produced in vivo in terms of body length and body width. By one-on-one bioassay, the IJs cultured with B. dorsalis puapl powder caused the highest mortality (46.7%) to the last instars of the great wax moth, Galleria mellonella. But, in higher nematode dosage (5-10 IJs/larva), the mortality caused by the IJs produced from artificial media and living insects to the common cutworm, S. litura, was not significantly different.
The nematode was cultured at different temperatures. It did not develop well at 15℃, and the growth rate increased with the temperature. Culturing at 25 and 30℃, the nematode yields were 2.9 and 2.1 × 105 IJs/g, respectively. The nematode concentrations from 30 to 30,000 IJs per treatment were inoculated into the media. After 14 days, the yield inoculed with 30,000 IJs was the highest at a concentration of 6.5 × 105 IJs/g. However, after 21 days, the yields were not significantly different between 300 and 30,000 IJs .
Virulence of S. abbasi produced from S. litura and S. exigua was tested. The IJs from S. exigua were more virulent to S. exigua (95.6-100%) than S. litura (40-62.2%). But the IJs cultured in S. litura caused similar mortality to those in S. litura and to S. exigua.
The IJs from artificial media applied on sweetpotato leaves were more virulent than those applied on sand and peat moss. However, the mortality of S. litura 5th instar larvae infected with the nematodes on the sand and peat moss was different.
中文摘要…………………………………………………….1
英文摘要…………………………………………………….3
前言………………………………………………………….5
文獻摘述…………………………………………………….7
材料與方法……………………………………………….. 18
結果與討論………………………………………………...26
參考文獻………………………………………………...…38
圖表………………………………………………………...47
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