Filipiak, A.

Tomalak, M.

English

JKI Open Journal Systems (Julius Kühn-Institut)

  IUFRO / REPHRAME International Conference on Pine Wilt Disease 2013  Berichte aus dem Julius Kühn-Institut 169. 2013 70 Tomalak M, Filipiak A, Inter-specific competition of Bursaphelenchus xylophilus with native populations of B. mucronatus in pine. In: Schröder, T. (ed.), Pine Wilt Disease Conference 2013, pp. 70-71, Braunschweig, ISSN: 1866-590X Inter-specific competiton of Bursaphelenchus xylophilus with native populations of B. mucronatus in pine Tomalak MInstitute of Plant Protection – National Research Inst., Węgorka 20, 60-318 Poznań, Poland , Filipiak A Email: M.Tomalak@iorpib.poznan.pl  Both the quarantine pest nematode, Bursaphelenchus xylophilus and native to Eurasia, unnharmful B. mucronatus are genetically closely related and present similar bionomics. They develop and reproduce in pine, can use the same insect vectors, and with contiuous colonization of new localities by B. xylophilus, the overlap of their geographic distribution continues to increase. The laboratory and field study in natural ecosystems of the Far East revealed a competitive displacement of the native B. mucronatus by the invasive B. xylophilus (Cheng et al., 2009), which could be attributed to faster population development in the later species (Futai 1980). Considering the observed genetic and phenotypic variation among European populations of B. mucronatus we have undertaken a research on interactions between selected strains of B. xylophilus (both European and Asiatic) and a series of native Polish isolates of B. mucronatus during concurrent invasion and development in the same host.   MATERIALS AND METHODS  In our quarantine glasshouse study, conducted on 2-3-year old seedlings and 20-cm-long logs of P. silvestris, reproduction of a single Chinese (Nanjing) and two Portuguese (Mad25c and Pt67OL) strains of B. xylophilus, five geographically distant isolates of B. mucronatus collected in Poland, and the recently constructed multi-strain intra-specific hybrid of the later species (MT-Rol-01) marked with a Roller Bmrol-1(mt4) mutation, were compared when reared separately or in two-species mixed populations. The seedlings were inoculated with a dose of 2500 or 5000 nematodes for single-species cultures, and of 2500 nematodes for each species in mixed populations. In logs the dose was reduced to 500 and 1000 nematodes, respectively. The nematodes were incubated for 1 month at 20oC. Then, the wood was chopped and subjected to water extraction of nematodes. The nematodes were identified based on the shape of female tail terminus. The proportions of phenotypes present in the offspring were counted for each species/strain variant. Selected populations were also subjected to molecular (ITS-RFLP) analysis to confirm the taxonomic status of the offspring.    IUFRO / REPHRAME International Conference on Pine Wilt Disease 2013  Berichte aus dem Julius Kühn-Institut 169. 2013 71 RESULTS AND DISCUSSION Phenotypic examination of the nematode offspring revealed that in single-species populations of B. xylophilus the range of morphological variation of the female tail has increased when compared to nematodes of the parental populations, which were originally reared in vitro, on Botritis cinerea. This was particularly obvious in the Chinese strain (Nanjing), where in 28-42% individuals the tail terminus had a conical projection or a small mucro, compared to mostly broadly rounded terminus of in vitro-reared females. The shape of mucro was, however, distinctive from that in B. mucronatus. In B. mucronatus the female tail was similar in both the nematodes reared in vitro and in wood.  In the offspring of two-species mixed populations the proportions of females with B. xylophilus- and B. mucronatus-like tail generally drifted to one of the parental phenotypes. Interestingly, not only B. xylophilus but also B. mucronatus could dominate and contribute to significant reduction of the second species. Among five isolates of B. mucronatus examined in logs, one (Mdz-1) proved to dominate B. xylophilus (Nanjing and Pt67 OL) in 73 and 63% of replicates, respectively, while the isolate Maz-02 dominated these strains in almost 50% of replicates. B. xylophilus (Mad 25c) dominated in all experimental variants, however, in individual seedlings or logs these nematodes could also be outperformed by local isolates of B. mucronatus. Insertion of the Roller mutation into the intra-specific hybrid population of B. mucronatus (MT-Rol-01) clearly simplified the process of phenotypic examination of the offspring in two-species mixed cultures. By producing the unique phenotype in all developmental stages of B. mucronatus the Roller mutation seems to be a very handy marker for any intra- and inter-specific hybridization and controlled rearing of this nematode.   In similar environmental conditions the results of the inter-specific competition in the host differed among species / strain combinations and were apparently related with variation in innate characteristics of the nematode populations. We speculate that the observed phenomenon may have some retarding effect on early success of B. xylophilus in colonization of new regions where native populations of B. mucronatus are present. These observations need, however, further substantiation in field experiments.  REFERENCES Futai K (1980). Developmental rate and population growth of Bursaphelenchus lignicolus (Nematoda: Aphelenchoididae) and B. mucronatus. Applied Entomology and Zoology 15, 115-122.  Chen X-Y; Xie P-Z; Cheng F-X; Xu R-M; Xie B-Y (2009). Competitive displacement of the native species Bursaphelenchus mucronatus by an alien species Bursaphelenchus xylophilus (Nematoda: Aphelenchida; Aphelenchoididae): a case of successful invasion. Biological Invasions 11, 205-213.  

Inter-specific competition of Bursaphelenchus xylophilus with native populations of B. mucronatus in pine

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Inter-specific competition of Bursaphelenchus xylophilus with native populations of B. mucronatus in pine

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