Chemotaxis of larval soybean cyst nematode,Heterodera glycines Race 3, to root leachates and ions
Second-stage larvae of the soybean cyst nematodeHeterodera glycines Race 3 were attracted in an in vitro bioassay to pooled leachates of soybean roots that were expressed as root gram-hours (1 g of root/hr/vol). Their responses were dosage dependent with maximal attraction to a 5 root g-hr/ml source. Optimal bioassay conditions used 24 hr for gradient formation and 1.5 hr for larval movement. Individual plants produced leachate with little variation in biological activity. Production was constant for five days of preparation. The attractive activity of root leachate declined with storage at 4 °C and heating over 30 °C, but loss of activity was reduced by freezing. Extraction and Sep-Pak fractionation indicated that the attractions(s) was water-soluble. Larvae were attracted also to several ionic solutions.
Characterization of and male adaptation to pheromone of femaleTrichostrongylus colubriformis (Nematoda)
Males of the ruminant nematodeTrichostrongylus colubriformis were significantly attracted to an incubate from their females during in vitro assay. Exposure of males to sera from uninfected and infected animals or selected neurotransmitters had no effect on their subsequent responsiveness to the female's pheromone. In contrast, exposure to 1500 female-hours of pheromone decreased male responsiveness after moderate rinsing prior to bioassay. Rinsing of the males with larger volumes of Tyrode's solution prior to in vitro assay increased their subsequent response to the female's pheromone. High-performance liquid chromatography yielded a presumptive pheromone peak with a fivefold increase in biological activity. This peak was soluble in alcohols and tetrahydrofuran, based on elution from reverse-phase Sep-Pak cartridges. Stability of the peak was increased by EDTA or ascorbic acid (10 mM). Storage for six weeks in ascorbic acid at 4 °C allowed recovery of 47.3% of the original material.
The Effect of Root Diffusate and Pre-soaking Temperatures, and Pre-soaking Periods on the Hatching of Heterodera glycines ICHINOHE
1) ダイズシストセンチュウ(Heterodera glycines ICHINOHE)の卵(5°Cの湿った土壤中のシストから得た)を,インゲンの根の浸出液につけてふ化を促進する場合に,この卵をすぐ根の浸出液につけるよりも,まず温水に入れておいてから,根の浸出液に移す方がふ化率は高くなることがわかった。卵を温水につけないか,つけても短期間の場合は,根の浸出液に入れたあとのふ化率の高まりは遅く,最終的なふ化率も低かった。2) 前もってつけた水と,根の浸出液の浸漬温度をともに25°Cとした場合は,水につける期間が1∼4週間の時にふ化率が最も高くなった。また水につける期間を2週間とした場合は,その時の温度を25°Cか30°Cとすると,ふ化率を最も高くすることができた。前もって水につける処理の温度と期間の関係は,一般に温度が低ければ長期間の浸漬を必要とし,温度が高ければ短期間の浸漬でよかった。ただし35°Cの水につけた後では,25°Cの浸出液に入れてもふ化率は高くならなかった。3) 根の浸出液は25°Cの時に,その前の処理条件にかかわらず,ふ化率は最も高くなった。以上から,ふ化率を高めるための処理条件は卵をまず25°Cか30°Cの水に1∼2週間つけた後,25°Cの根の浸出液に移すのが最もよいと考えられる。4) ただし,前もって25°Cの水に卵をつけた場合には,30°Cの水につけた場合よりも,水中でふ化してしまう割合が高く,そのため浸出液に移してから後のふ化率は逆に少なくなった。根の浸出液に入れてから短期間にふ化率を高める目的の場合は,水の浸漬温度を30°Cとするほうがよいと思われる。この場合の浸漬期間は1週間で十分であると考えられる。