線虫の薬剤感受性実験法としての薬液浸漬法の検討

Abstract

In order to estimate analytically the susceptibility of nematodes of different stages, an immersion test proposed by Moje (1959) was examined. The standard procedure by the present authors is as follows: 1) to immerse nematodes in the solution of a given chemical for 24 hours 2) remove the solution of the chemical (needed two hours) and store the treated nematodes in sterile water for 22 hours and 3) separate mobile nematodes from the immobile by cotton wool filter for 24 hours and calculate mortality of the nematodes. Temperature during experiments is 25°.As a test nematode, the southern root-knot nematode, Meloidogyne incognita (Kofoid & White) was used. Larvae were obtained from egg-masses or infected soils by Baermann funnel technique or sieving plus Baermann method. It is convenient to use about a hundred nematodes for a treatment. Loss of M. incognita larvae during test process is considered to be about ten per cent. From 70 to 90 % of mobile larvae of M. incognita were isolated by the cotton wool filter specially designed, where the coefficient of the variation was less than twenty per cent in most experiments. The rate of separation reached the maximum within 24 hours. An example is given in Table 1.Storing treated nematodes in sterile water leads them to death or recovery from anesthetization. Relation of procedure to remove EDB emulsion and period for maintaining the nematodes treated with EDB in water, to the mortality of M. incognita larvae is shown in Table 2. Mortality due to 24 hours store was near to that for 46 hours.In most experiments, linear correlation was observed between concentrations in logarithm of EDB and mortality in probit at the level of 95 % confidence, except some lower concentrations (Figs. 2 and 3). Results of experiments conducted by the same person in August, September and October with M. incognita larvae from egg-masses on the roots of sweet potato in the same field are shown in Figs. 2 and 3. The figures indicate the reproductivity in a sense of the experiments by the present method. LC-50 of the nematodes from sweet potato to EDB was 86 and 80 ppm in August (from Figs. 2 and 3), 54 ppm in September and 77 ppm in October (Fig. 2). The relation between temperatures during immersion in EDB emulsion and the mortality of M. incognita larvae was also examined (Table 3).