In an attempt to elucidate toxin production in pine seedlings by the pine wood nematode, Bursaphelenchus xylophilus, and an associated bacterium, young seedlings of Pinus thunbergii which had formed callus tissues on root tips were inoculated with aseptic nematodes or bacterium-contaminated nematodes in test tubes. In the former most of inoculated seedlings collapsed by the nematode invasion. Several seedlings remained healthy in appearance although the nematodes propagated on root callus and/or invaded the stems.
Bacterium-contaminated nematodes did not affect the seedlings.
Culture filtrate of three bacterial isolates from the dispersal forth-stage larvae of the nematode showed toxicity to young seedlings, but the cell suspension of an isolate, of which culture filtrate showed the strongest toxicity, did not affect three-year-old Pinus densiflora seedlings while aseptic nematodes killed them. Jpn. J. Nernatol. 13:1-5(1983)

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On 17 tree species, which included five pine species, the effect of wood tissues on the molting rate of the dauerlarvae (a dispersal 4th stage) of Bursaphelenchus xylophilus was studied using three methods. The active substance which induced the dauerlarvae to molt exuded from the wood tissues and infiltrated the agar plates (agar plate method). This substance can be extracted by acetone (acetone extact method). Differences in the molting rate of dauerlarvae directly invading wood tissues were observed among tree species (direct method). Throughout the experiments based on each of the three methods, species of Pinus and Larix leptolepis showed the highest molting rate. Abies firma and Cedrus deodara followed them. In every tree species some effect on the molting rate was demonstrated. Since there was no significant difference in the molting effect among pines, which consisted of species both resistant and susceptible to B. xylophilus, we concluded that variability of molting could not be a factor of resistance of pine trees to pine wilt disease. Jpn. J. Nematol. 13:6-13(1983)

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Four species of Criconematidae were detected from soil around the roots of mulberry in warm climate regions of Japan; Hachijo-shima Is., To-shima Is., Nebukawa of Kanagawa, and Yaku-shima Is. Two of them were identified to be Hemicriconemoides chitwoodi and Crossonema dryum, and the rest two species were found to be new. Nothocriconema yakushimense n. sp. resembles N. loofi but differs in possessing a wider distinctive saucer-shaped first annule, a longer stylet, and a smaller number of body annules. Ogma brevistylum n. sp. is closely related to O. lentiforme but can be distinguished by the sharp scales on body annules, the stylet knobs with slight forwardly directed processes, slightly wider first annule than the second one, and a smaller number of body annules. Morphology of H. chitwoodi and C. dryum from mulberry fields mostly agreed with their original descriptions. JPn. J. Nematol. 13:14-19 (1983)

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Oogenesis and spermatogenesis of Bursaphelenchus xylophilus followed the generalpattern of bisexual nematodes. Gonial cell multiplication occurred in the germinal zone of the gonad through regular mitotic division. Oocytes and spermatocytes underwent two regular maturation divisions. The diploid chromosome number was restored by fusion of sperm and egg pronuclei. In uninseminated females, the oocytes collapsed after passed through the spermatheca. The haploid chromosome number was determined to be 6 during the metaphase of the first meiotic division for both male and female. Sex chromosomes could not be recognized. Jpn. J. Nematol. 13:20-25(1983).

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