For identifying Pratylencus penetrans, species-specific primers (PP1 and PP2) were developed, based on the sequences of the interscribed spacer regions (ITS1 and ITS2) of the rDNA. When the purified DNA from seven Pratylenchus species was subjected to PCR using these primers, the 462 bp fragment was generated only for P. penetrans. The same fragment was obtained with DNA from the crude lysate of single juvenile and of adult (male and female) P. penetrans.

View full abstract

Effects of precedent infection of Steinernema carpocapsae and S. glaseri on subsequent nematode invasion were investigated at 25°C. Behavior of Galleria mellonella larvae infected through injection with ca. 50 S. carpocapsae infective juveniles did not change 6 hr post-infection, but invasion of both nematode species decreased by ca. 50%, compared to previously uninfected hosts. Precedent infection with S. glaseri promptly suppressed subsequent invasion of the two nematode species. Subsequent invasion was also significantly decreased by symbiotic Xenorhabdus bacteria: invasion rates to insects killed by X. nemato-philus injection, X. poinarii injection, and by hot water treatments were 1.8, 0, and 5.4% for S. carpocapsae and 1.8, 5.0 and 7.8% for S. glaseri, respectively, while invasion rates to the non-treated live insects were 16.5% for S. carpocapsae and 15.1% for S. glaseri. At the early stage of the subsequent invasion, the sex ratio (% male) of the invading S. carpocapsae in the hosts with and without the precedent infections were 5.3% and 12.3%, respectively. These results indicated that insects infected with a Steinernema/Xenorhabdus complex may emanate suppressive substance (s) against subsequent nematode invaders.

View full abstract

In the preceding papers, the authors showed that the genuine pathogen of the pine wilt disease is the phenylacetic acid-producing bacteria accompanying the pine wood nematodes. However, the difference in pathogenicity between nematode isolates (OKD-1 and OKD-3) could not be explained solely by the accompanying bacteria because weakly pathogenic isolate OKD-1 also was accompanied by the bacteria. The facts that the pine wilt disease is prevented by injection of a nervous action inhibitor to the pine trunk made the authors suppose that inherent mobility of the isolates is also important for expressing pathogenicity. In this paper, the authors have compared the mobility of the nematodes in mycelia of Botrytis cinerea grown on crushed barley grains in a microtube among a weakly pathogenic isolate OKD-1, a strongly pathogenic isolate OKD-3, and its bacteria-free nematode OKD-3-BF. The strongly pathogenic isolates OKD-3 showed larger mobility irrespective of accompanying bacteria than the weakly pathogenic isolate OKD-1. This finding suggests that the different pathogenicity of the two isolates is explained by the difference in mobility between these isolates.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract