Host responses and nematode dispersion in Pinus strobus and P. densiflora infected with the pine wood nematode, Bursaphelenchus xylophilus.

Abstract

The pine wood nematode, Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, causes serious mortality of Japanese black pine, Pinus thunbergii Parl., and Japanese red pine, P. densi flora Sieb. et Zucc., in Japan. The inoculation test revealed that P. thunbergii and P. densiflora were susceptible to the infection of B. xylophilus, and some Pinus spp. including eastern white pine, P. strobus L., were resistant1,2). Pine wilt disease caused by B. xylophilus is characterized by rapid loss of xylem water con ductivity. Increase in resistance to water flow in P. thunbergii and blockage of xylem water conduction in P. densiflora following the nematode inoculation were reported3,4). Relationship between wilt-resistance and blockage of water conduction, however, has not documented. Cotton plant infected with Verticillium dahliae Kleb. or Meloidogyne incognita (Kofoid et White) Chit. produces terpenoid aldehydes, gossypol and related compounds, as the results of host responses5-8). These compounds are considered to be involved in the mechanism of resist ance, and are detected with SbCl3 reagent by specific coloration. SbCl3 reaction was found in Scots pine, Pinus sylvestris L., inoculated with B. xylophilus9). In this report, we compare P. strobus with P. densiflora in reference to the relationships between nematode dispersion and SbCl3 reaction or blockage of water conduction in the early stage of the infection. B. xylophilus (isolate S-10) was reared on Botrytis cinerea Pers. growing on potato dextrose agar at 25 C. Six-year-old P. strobus and 5-year-old P. densiflora seedlings growing in a nursery were used. Three or 4-year-old branches of P. strobus and 2 or 3-year-old ones of P. densiflora were inoculated with the nematode on July 14 or 15, 1984. A water suspension of nematodes, 1,800 nematodes in 0.2ml, were introduced into cotton placed in a shallow, 1-2cm long, slit on the branch, and the inoculation site was wrapped with parafilm. Inoculated branches were cut off 5, 10 and 15 days after inoculation. At each sampling

Physiological Process of the Symptom Development and Resistance Mechanism in Pine Wilt Disease

“…5c). Similar results have been obtained by many researchers (Ikeda, 1996a;Ikeda and Kiyohara, 1995;Ikeda et al, 1994;Kuroda et al, 1991b;Odani et al, 1985b;Sasaki et al, 1984;Tamura et al, 1988). The cambium seemed to be degraded by cellulase activity of the virulent nematodes (Kusunoki, 1987).…”

“…However, symptom development of pine wilt disease is so rapid that many physiological changes appear at the same time. To avoid this problem, some researchers used resistant pine species and families to compare symptom development with susceptible ones (Ikeda et al, 1994;Kuroda et al, 1991b;Tamura et al, 1988;Yamada and Ito, 1993ab). Kiyohara (1989) and Kiyohara and Bolla (1990) reported a wide range of variation in the pathogenicity among pinewood nematode isolates, some of which never kilt pine trees.…”

Pest Risk Analysis (PRA) for the territories of the European Union (as PRA area) on Bursaphelenchus xylophilus and its vectors in the genus Monochamus

“…In both cases survival of the nematode is possible but, following transmission by feeding, the likelihood of spread of the nematode into the trunk of the tree depends on the susceptibility of the tree, infestation being restricted to the branches in native North American Pinus spp. (Wingfield & Blanchette, 1984;Bedker, 1987;Bedker et a[., 1987;Tamura et al, 1988). If the nematode is present in the trunk, it is capable of surviving and reproducing for at least one year and can thus be expected to be present on arrival in Europe.…”

Bursaphelenchus xylophilus induced pine wilt: Factors associated with resistance

“…Nematode migration from inoculated branches to the top and base of trunks is very rapid comparable to that seen in P. thunbergii. TAMURA et al (1988) reported that larger numbers of B. xylophilus invaded the tissue of P. strobus than in susceptible P. densiflora. Following the primary distribution of nematodes, however, there was a clear decrease followed by slow increase in the size of the nematode population which differed from the continual increase seen in susceptible species.…”