bursaphelenchus is a genus of nematodes ( roundworms ) in the order aphelenchida .

most are obligate mycophages , but some feed on wood , with two species , the red ring nematode ( b. cocophilus ) and the pine wood nematode ( b. xylophilus ) , economically significant as pests of coconut palms and of pine trees , respectively .

given that bursaphelenchus species are usually hard to distinguish from one another except by trained helminthologists with access to microscopes or dna sequence analysis , the entire genus is put under quarantine in some countries .

where this is not the case however , these nematodes are becoming established as model organisms for nematode developmental biology , ecology and genetics .

as of 2009 , there are about 70 to 90 species in the genus .

new taxa are described frequently .

bursaphelenchus

bursaphelenchus xylophilus ( pine wilt nematode ) ; distinctive spicule of male nematode . usa .
bursaphelenchus xylophilus ( pine wilt nematode ) ; vulva flap of female nematode . usa .
bursaphelenchus xylophilus ( pine wilt nematode ) ; general features of head region . japan .
bursaphelenchus xylophilus ( pine wilt nematode ) ; tail of male , showing characteristic spicule . japan .
bursaphelenchus vallesianus sp . n . has been found in wood samples from recently dead pine trees ( pinus sylvestris ) in several locations in canton valais , switzerland . the new species is described and illustrated . bursaphelenchus vallesianus sp . n . is morphologically most similar to bursaphelenchus sexdentati and bursaphelenchus borealis and clearly belongs to the bursaphelenchus sexdentati group , showing four lateral lines and the typical position of the caudal papillae of males . it can be differentiated from bursaphelenchus sexdentati by the shorter stylet , a conical female tail with a more or less rounded terminus ( bluntly rounded in b . sexdentati ) , shorter and slightly differently shaped spicules , the presence of a small cucullus and the lack of a distinct postvulval constriction of females . the post - uterine sac occupies 1 / 2 - 2 / 3 of the vulva - anus distance . bursaphelenchus vallesianus sp . n . sometimes shows a slight hook - like condylus of spicules like b . borealis . it differs from bursaphelenchus borealis by the shorter spicules and stylet , the presence of a cucullus , and the greater c value in males and females . the species differentiation is supported by the its - rflp patterns of bursaphelenchus vallesianus sp . n . , bursaphelenchus sexdentati , bursaphelenchus pinophilus , bursaphelenchus borealis and bursaphelenchus poligraphi , which are all members of the b . sexdentati group .
informations on bursaphelenchus xylophilus has been recorded for the following locations . click on the name for additional informations .
oepp / eppo , 2003 . national regulatory control systems bursaphelenchus xylophilus and its vectors . bulletin 33 , 301�304
pathogenicity of selected isolates of the quarantine pinewood nematode bursaphelenchus xylophilus to scots pine ( pinus sylvestris l . )
skarmoutsos , g . , and h . m . skarmoutsos . 2000 . pathogenicity of bursaphelenchus sexdentati , bursaphelenchus leoni , and bursaphelenchus hellenicus on european pine seedlings . forest pathology 30 : 149 - 156 . summary : information on description , economic importance , distribution , habitat , history , growth , and impacts and management of species .
morphology and description of bursaphelenchus platzeri n . sp . ( nematoda : parasitaphelenchidae ) , an associate of nitidulid beetles
bursaphelenchus xylophilus ( pine wilt nematode ) ; pine wilt symptoms , one year after death of tree . usa .
mortality of seedlings inoculated with bursaphelenchus xylophilus as affected by seedling species , age of larch seedlings and methods of inoculation .
mamiya y ( 1983 ) pathology of the pine wilt disease caused by bursaphelenchus xylophilus . annu rev phytopathol 21 : 201–220 .
futai k . pine wood nematode , bursaphelenchus xylophilus . ann rev phytopathol . 2013 ; 51 : 61–83 . pmid : 23663004
braasch h ; swart a ; tribe g ; burgermeister w , 1998 . first record of bursaphelenchus leoni in south africa and comparison with some other bursaphelenchus spp . bulletin oepp , 28 ( 1 / 2 ) : 211 - 216 ; 12 ref .
the contigs resulting from bursaphelenchus xylophilus assembly were deposited in the embl / genbank / ddbj databases under accession numbers cadv01000001 - cadv01010432 .
and oxidative enzyme in the interaction of different resistance pines and bursaphelenchus xylophilus . j nanjing univ natur sci . 2010 ; 06 .
bursaphelenchus xylophilus ( pine wilt nematode ) ; symptoms in a field setting - note dead trees and browning of foliage on others . china
kinn dn , 1986 . survival of bursaphelenchus xylophilus in wood chips . bulletin oepp / eppo bulletin , 16 : 461 - 464 .
recommended citation : global invasive species database ( 2018 ) species profile : bursaphelenchus xylophilus . downloaded from urltoken on 09 - 07 - 2018 .
a morphological key to the species of the xylophilus group of the genus bursaphelenchus has recently been published by braasch and schönfeld ( 2015 ) .
mamiya y , 1983 . pathology of the pine wilt disease caused by bursaphelenchus xylophilus . annual review of phytopathology , 21 : 201 - 220
pathogenicity of selected isolates of the quarantine pinewood nematode bursaphelenchus xylophilus to scots pine ( pinus sylvestris l . ) : journal of plant protection research
dwine ll , l . d . 1993 : first report of pinewood nematode ( bursaphelenchus xylophilus ) in mexico . plant disease 77 : 846 .
kiyohara t , bolla ri . pathogenic variability among populations of the pinewood nematode , bursaphelenchus xylophilus . forest sci . 1990 ; 36 : 1061–1076 .
bursaphelenchus xylophilus ( pine wilt nematode ) ; tee mortality on mason pine ( pinus massoniana ) , caused by the nematode . anhui province , china .
which described bursaphelenchus lignicolus as a new species from japan . subsequent research revealed that the species had been previously described from the usa as aphelenchoides xylophilus by
bursaphelenchus platzeri n . sp . is distinguished from all other described species of bursaphelenchus by the unique morphology of the spicules in males . also , the difference in the number of lines in the lateral field between propagative forms ( three lines ) and j iii ( four lines ) appears to be unique .
tanaka k . inoculation experiment with bursaphelenchus lignicolus to larix leptlepis . transactions of 89th annual meetings of the japanese forest society ; 1978 . pp . 293–295 .
scanning electron micrograph of cloaca with protracted tip of fused spicules of an adult male of bursaphelenchus cocophilus in subventral view ( scale bar = 1 μm ) .
bursaphelenchus xylophilus ( pine wilt nematode ) ; sem showing the spicule ( centre ) which identifies the species , a destructive pinewood nematode . original x 5000 .
oepp / eppo , 2001 . eppo standards pm7 / 4 diagnostic protocol for bursaphelenchus xylophilus . bulletin oepp / eppo bulletin , 31 : 61 - 69 .
hasegawa k , futai k , miwa s , miwa j ( 2004 ) early embryogenesis of the pinewood nematode bursaphelenchus xylophilus . dev growth differ 46 : 153–161 .
tomalak m . 2004 . ocena przydatności dostępnych metod do identyfikacji taksonomicznej kwarantannowego nicienia - węgorka sosnowca [ bursaphelenchus xylophilus ( steiner et bührer ) nickle ] . [ evaluation of methods available for taxonomic identification of the bursaphelenchus xylophilus ] . progress in plant protection / postępy w ochronie roślin 44 ( 1 ) : 452 - 461 .
a new species of bursaphelenchus was recovered as dauer juveniles ( j iii ) in the median oviducts and ovipositor sacs of adult females and the internal sacs of adult males of the pineapple beetle , carpophilus humeralis ( nitidulidae ) , from riverside , california ( giblin et al . , 1984 ; giblin , 1985 ) . this nematode is described herein as bursaphelenchus platzeri n . sp . it is the only described species of bursaphelenchus known to be associated with nitidulid beetles ( giblin , 1985 ) .
the pinewood nematode , bursaphelenchus xylophilus . proceedings of an international workshop . university of evora , porutugal august 20–22 , 2001 . nematology monographs and perspectives , volume 1 .
, but had been subsequently overlooked . later it was described again , as bursaphelenchus lignicolus , when recognized to be the causal agent of pine wilt disease in japan (
mcnamara dg ; støen m , 1988 . a survey for bursaphelenchus spp . in pine forests in norway . bulletin oepp , 18 ( 3 ) : 353 - 363
magnusson c , 1986 . potential for establishment of bursaphelenchus xylophilus and the pine wilt disease under nordic conditions . bulletin oepp / eppo bulletin , 16 : 465 - 471 .
ishibashi n , kondo e ( 1977 ) occurrence and survival of the dispersal forms of pine wood nematode , bursaphelenchus lignicolus mamiya and kiyohara . appl entomol zoolog 12 : 293–302 .
bursaphelenchus xylophilus ( pine wilt nematode ) ; the nematode is mycophagous and feeds on fungi in the wood , including bluestain fungi transmitted by engraver and other bark beetles . japan .
li h . 2008 . identification and pathogenicity of bursaphelenchus species ( nematoda : parasitaphelenchidae ) . ph . d . thesis , ghent university , ghent , belgium , 223 pp .
kiyohara t . , bolla r . i . 1990 . pathogenic variability among populations of the pinewood nematode , bursaphelenchus xylophilus . forest science 36 ( 4 ) : 1061 - 1076 .
oepp / eppo , 2003 . eppo standards pm 9 / 1 bursaphelenchus xylophilus and its vectors : procedures for official control . bulletin oepp / eppo bulletin , 33 : 301 - 312 .
tomminen j , 1990 . presence of bursaphelenchus mucronatus ( nematoda : aphelenchoididae ) fourth dispersal stages in selected conifer beetles in finland . silva fennica , 24 ( 3 ) : 273 - 278
light micrographs of spicules of bursaphelenchus platzeri n . sp . first three spicule photographs from left are different focal planes through the same specimen , and last two spicule photographs are of another specimen .
aikawa t . , kikuchi t . 2007 . estimation of virulence of bursaphelenchus xylophilus ( nematoda : aphelenchoididae ) based on its reproductive ability . nematology 9 ( 3 ) : 371 - 377 .
futai k . , furuno t . 1979 . the variety of resistances among pine species to pine wood nematode , bursaphelenchus lignicolous . bulletin of the kyoto university forests 51 : 23 - 26 .
mota m , braasch h , bravo m , penas a , burgermeister w , et al . ( 1999 ) first report of bursaphelenchus xylophilus in portugal and in europe . nematology 17 : 727–734 .
hasegawa k , mota mm , futai k , miwa j ( 2006 ) chromosome structure and behaviour in bursaphelenchus xylophilus ( nematoda : parasitaphelenchidae ) germ cells and early embryo . nematology 8 : 425–434 .
cabi / eppo , 2015 . bursaphelenchus xylophilus . [ distribution map ] . distribution maps of plant diseases , no . october . wallingford , uk : cabi , map 789 ( edition 2 ) .
the hermaphroditic b . okinawaensis is a laboratory model for aspects of the bursaphelenchus biology . here it has been demonstrated that the volatile pheromone produced by b . okinawaensis hermaphrodite and b . xylophilus is shared between species and precopulatory behavior is highly similar . the hermaphroditic b . okinawaensis seems useful for genetic analysis to understand the mating behavior of bursaphelenchus nematodes as well as the evolution of mating behavior among nematodes .
jones jt , moens m , mota m , li h , kikuchi t ( 2008 ) bursaphelenchus xylophilus : opportunities in comparative genomics and molecular host - parasite interactions thol mol plant pa 9 : 357–368 .
vicente csl , ikuyo y , mota m , hasegawa k . pinewood nematode - associated bacteria contribute to oxidative stress resistance of bursaphelenchus xylophilus . bmc microbiol . 2013 ; 13 : 299 . pmid : 24365493
kikuchi t , jones jt , aikawa t , kosaka h , ogura n ( 2004 ) a family of glycosyl hydrolase family 45 cellulases from the pine wood nematode bursaphelenchus xylophilus . febs lett 572 : 201–205 .
error bars represent standard deviation . different letters above the columns indicate significant differences ( p < 0 . 05 ) between bursaphelenchus sp . isolates h 2 o 2 neutralization , according to post - hoc duncan’s test .
braasch h ; burgermeister w ; pastrik kh , 1995 . differentiation of three bursaphelenchus species by means of rapd - pcr . nachrichtenblatt des deutschen pflanzenschutzdienstes , 47 ( 12 ) : 310 - 314 ; 21 ref .
mamiya y ; kiyohara t , 1972 . description of bursaphelenchus lignicolus n . sp . ( nematoda : aphelenchoididae ) from pine wood and histopathology of nematode - infested trees . nematologica , 18 : 120 - 124 .
aikawa t . , kikuchi t . , kosaka h . 2006 . population structure of bursaphelenchus xylophilus within single pinus thunbergii trees inoculated with two nematode isolates . forest pathology 36 ( 1 ) : 1 - 13 .
caroppo s . , cavalli m . , coniglio d . , ambrogioni l . 2000 . pathogenicity studies with various bursaphelenchus populations on conifer seedlings under controlled and open air conditions . redia 83 : 61 - 75 .
kozłowski m . w . 2003 . native and exotic sawyer beetles , monochamus spp . ( coleoptera , cerambycidae ) as the vectors of the pine wilt nematode , bursaphelenchus xylophilus . sylwan 1 : 24 - 34 .
the fungal feeding , hermaphroditic bursaphelenchus okinawaensis is a laboratory model to understand the biology of bursaphelenchus . the extent to which b . okinawaensis can be used to model bursaphelenchus xylophilus mating was investigated . a chemotaxis assay was conducted to examine whether b . xylophilus and b . okinawaensis produce and respond to volatile sex attractants . unmated b . xylophilus females were found to attract b . xylophilus males . similarly , old ( sperm depleted ) but not young ( sperm repleted ) b . okinawaensis hermaphrodites attract b . okinawaensis males . thus , in both species , sperm status corresponds to its ability to attract males . b . xylophilus males also produce a volatile pheromone that attracts both mated and unmated females . a second assay , in which the behavior of males on petri plates in the presence of different females or hermaphrodites of bursaphelenchus was observed , revealed that b . xylophilus unmated females attract b . okinawaensis males , and b . okinawaensis old hermaphrodites attract b . xylophilus males . these observations suggested that the pheromones of bursaphelenchus work to some extent across species . mating behavior through spicule insertion occurs across species , suggesting that postcopulatory mechanisms prevent production of interspecific progeny . the hermaphroditic b . okinawaensis will be a useful model to conduct genetic studies for the understanding of the molecular mechanisms underlying mating behavior in bursaphelenchus nematodes .
h 2 o 2 was used as oxidative agent at concentrations ranging between 15 and 40 mm for bursaphelenchus isolates . after nematode surface sterilization , the concentration of bursaphelenchus was adjusted to 150 nematodes per 50 μl of sterile water . mortality of nematodes was scored after 24h - stress exposure . nematodes were considered dead if no movements were observed after mechanical stimulation . this experiment was repeated three independent times , with two technical replications for each .
mamiya y ; enda n , 1979 . bursaphelenchus mucronatus n . sp . ( nematoda : aphelenchoididae ) from pine wood and its biology and pathogenicity to pine trees . nematologica , 25 ( 3 ) : 353 - 361
zhang jianjun ; zhang runzhi ; chen jingyuan , 2007 . species and their dispersal ability of monochamus as vectors to transmit bursaphelenchus xylophilus . journal of zhejiang forestry college , 24 ( 3 ) : 350 - 356 . urltoken
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lin s , jian h , zhao h , yang d , liu q ( 2011 ) cloning and characterization of a venom allergen - like protein gene cluster from the pinewood nematode bursaphelenchus xylophilus . exp parasitol 127 : 440–447 .
kikuchi t , jones jt , aikawa t , kosaka h , ogura n . a family of glycosyl hydrolase family 45 cellulases from pine wood nematode bursaphelenchus xylophilus . febs letters . 2004 ; 572 : 201–205 . pmid : 15304348
braasch h ; schönfeld u , 2015 . improved morphological key to the species of the xylophilus group of the genus bursaphelenchus fuchs , 1937 . bulletin oepp / eppo bulletin , 45 ( 1 ) : 73 - 80 . urltoken
braasch h . 2000 . influence of temperature and water supply on mortality of 3 - year - old pines inoculated with bursaphelenchus xylophilus and b . mucronatus . nachrichtenblatt des deutschen pflanzenschutzdienstes 52 ( 10 ) : 244 - 249 .
principal source : european and mediterranean plant protection organisation ( eppo ) . 2002 . bursaphelenchus xylophilus and its vectors : procedures for official control . bulletin oepp / eppo bulletin pine wilt disease university of illinois department of crop sciences , 1998
european and mediterranean plant protection organization ( eppo ) , 2002 . bursaphelenchus xylophilus and its vectors : procedures for official control . bulletin oepp / eppo bulletin 33 : 301 - 304 . summary : procedures for the control of species .
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error bars represent standard deviation . different letters above the columns indicate significant differences ( p < 0 . 05 ) between bursaphelenchus sp . isolates survival percentages in each h 2 o 2 treatment , according to post - hoc duncan’s test .
citation : vicente csl , ikuyo y , shinya r , mota m , hasegawa k ( 2015 ) catalases induction in high virulence pinewood nematode bursaphelenchus xylophilus under hydrogen peroxide - induced stress . plos one 10 ( 4 ) : e0123839 . urltoken
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bursaphelenchus platzeri n . sp . dauer juveniles in lateral view . a ) whole female . b ) whole male . c ) anterior region of female . d ) female gonad . e ) female tail . f ) male gonad . g ) male anus .
shinya r , morisaka h , kikuchi t , takeuchi y , ueda m , et al . secretome analysis of pine wood nematode bursaphelenchus xylophilus reveals the tangled roots of parasitism and its potential for molecular mimicry . plos one . 2012 ; 8 : e 67377 .
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citation : kikuchi t , cotton ja , dalzell jj , hasegawa k , kanzaki n , mcveigh p , et al . ( 2011 ) genomic insights into the origin of parasitism in the emerging plant pathogen bursaphelenchus xylophilus . plos pathog 7 ( 9 ) : e1002219 . urltoken
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scanning electron micrographs of adult females of bursaphelenchus platzeri n . sp . a ) en face view , aa = amphidial aperture , arrows = cephalic papillae . b ) head , nearly lateral view . c ) vulval region in lateral view . d ) anus in ventrosublateral view . e ) tail in lateral view .
animal and plant health inspection service ( aphis ) , 1999 . questionnaire on bursaphelenchus xylophilus . state administration of exit and entry & inspection and quarantine of the people s republic of china . summary : information on description , economic importance , distribution , habitat , history , growth , and impacts and management of species .
asai , e . , and k . futai . 2001 . the effects of long - term exposure to simulated acid rain on the development of pine wilt disease caused by bursaphelenchus xylophilus . forestry pathology 31 : 241 - 253 . summary : information on the affects of acid rain on the increased virulity of nematode .
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nematode : bursaphelenchus xylophilus ( strain s - 10 collected in shimane , japan ) was monoxenically cultured on the fungus botrytis cinerea grown on barley grains . nematodes were separated from the culture medium by the baermann funnel technique . a water suspension of nematodes was adjusted to a concentration of 10 5 nematodes / ml of tap water .
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gonz�lez , j . e . 2001 . bursaphelenchus xylophilus ( pine wilt nematode ) . university of texas at dallas : department of molecular and cell biology . summary : information on description , economic importance , distribution , habitat , history , growth , and impacts and management of species . available from : urltoken [ accessed 27 april 2004 ]
takemoto s . , kanzaki n . , futai k . 2005 . pcr - rflp image analysis : a practical method for estimating isolate - specific allele frequency in a population consisting of two different strains of the pinewood nematode , bursaphelenchus xylophilus ( aphelenchida : aphelencoididae ) . applied entomology and zoology ( jpn ) 40 : 529 - 535 .
braasch , helen and braasch - bidasak , rainulf . , 2002 . first record of the genus bursaphelenchus fuchs , 1937 in thailand and description of b . thailandae sp . n . ( nematoda : parasitaphelenchidae ) . nematology 4 ( 7 ) : 853 - 863 summary : available from : urltoken ; = 1 [ accessed 10 december 2004 ]
mota m . m . ; braasch h . ; bravo m . a . ; penas a . c . ; burgermeister w . ; metge k . ; sousa e . 1999 . first report of bursaphelenchus xylophilus in portugal and in europe . nematology , vol . 1 , no . 7 , pp . 727 - 734 ( 8 )
espada m . , silva a . c . , akker s . e . , cock p . j . a . , mota m . , jones j . t . 2015 . identification and characterization of parasitism genes from the pinewood nematode bursaphelenchus xylophilus reveals a multilayered detoxification strategy . molecular plant pathology . doi : 10 . 1111 / mpp . 12280
braasch , h . , c . tomiczek , k . metge , u . hoyer , w . burgermeister , i . wulfert , and u . schonfeld . 2001 . records of bursaphelenchus spp . ( nematoda , parasitaphelenchidae ) in coniferous timber imported from the asian part of russia forest pathology 31 : 129 - 140 . summary : a distribution record of species
irdani t ; caroppo s ; ambrogioni l , 1995 . molecular identification of pine wood bursaphelenchus species . nematologia mediterranea , 23 ( suppl ) : 99 - 106 ; [ ^ italic ~ paper presented at the 5th congress of the italian society of nematology , martina franca ( ta ) , 19 - 21 ottobre 1995 . ^ roman ~ ] ; 18 ref .
a systematic evolutionary study of plant cell wall modifying genes in tylenchoidea concluded that those genes were acquired by multiple hgt events from bacteria closely associated with the ancestors of these nematodes followed by gene duplication [ 61 ] . b . xylophilus is closely associated with fungi and it is likely that this feeding strategy is ancestral for this group as most bursaphelenchus species are solely fungal feeders .
diagrammatic representation of the en face pattern of a bursaphelenchus platzeri n . sp . female from scanning electron micrographs . aa = amphid aperture , cp = cephalic papilla , lcs = lateral cephalic sector , ld = labial disc , ls = lip sector plate , oa = oral aperture , ols = outer labial sensilla , sds = subdorsal cephalic sector , and svs = subventral cephalic sector .
the pinewood nematode , bursaphelenchus xylophilus is the causative agent of pine wilt disease . vectors of this nematode are long - horned beetles especially those belonging to the genus monochamus . the introduction of this nematode into japan had devastating effects on the native pines in that country . most species of conifers endemic to north america are resistant to the wilt disease , but many exotic species are highly susceptible .
population densities of bursaphelenchus xylophilus in the stems of dead 3 - yrear - old larch and pine seedlings inoculated with nematodes through the maturation feeding of jps adults . l , m , and u indicate the lower , middle , and upper part of the stem , respectively . values are means ( ±sd ) of nine dead larch seedlings and 12 dead pine seedlings . bars indicate standard errors of the mean .
cross sections of a dead 2 - year - old larch seedlings stem 15 days after nematode inoculation . bursaphelenchus xylophilus is located in the traumatic resin canals ( trc ) formed along the cambial zone . the parenchyma cells of trc are completely destroyed . a : the lower part of the stem . b : the middle part of the stem . arc is the axial resin canal . scale bar is 100 μm .
zamora p ; rodríguez v ; renedo f ; sanz av ; domínguez jc ; pérez - escolar g ; miranda j ; álvarez b ; gonzález - casas a ; mayor e ; dueñas m ; miravalles a ; navas a ; robertson l ; martín ab , 2015 . first report of bursaphelenchus xylophilus causing pine wilt disease on pinus radiata in spain . plant disease , 99 ( 10 ) : 1449 . urltoken
bowers ww ; hudak j ; raske ag ; magasi lp ; myren dt ; lachance d ; cerezke hf ; sickle gavan , 1992 . host and vector surveys for the pinewood nematode , bursaphelenchus xylophilus ( steiner and buhrer ) nickle ( nematoda : aphelenchoididae ) in canada . information report - newfoundland and labrador region , forestry canada , no . n - x - 285 : viii + 55 pp . ; 107 ref .
b . xylophilus is superficially similar to other species of the genus , although these are not regarded a pests . it can be distinguished from most of these by the unusual shape of the male spicules and the presence of a vulval flap in the female . however , there is a group of bursaphelenchus species sharing these characters and differentiating b . xylophilus from these species requires considerable expertise ( see the eppo diagnostic protocol for b . xylophilus ; oepp /
mating behavior of bursaphelenchus okinawaensis and b . xylophilus . the images show the stages of ( a ) pre - mating behavior of b . okinawaensis ; ( b ) spicule insertion behavior of b . okinawaensis ; ( c ) premating behavior of b . xylophilus ; and ( d ) spicule insertion behavior of b . xylophilus . m , male ; h , hermaphrodite ; f , female . white arrows indicate the position of male spicule inserted into vulva .
sousa , e . , p . naves , l . bonifacio , m . a . braveo , a . c . penas , j . pires , and m . serrao . 2002 . preliminary survey for insects associated with bursaphelenchus xylophilus in portugal . oepp / eppo , bulletin oepp / eppo bulletin 32 , 499 - 502 . summary : information on description , economic importance , distribution , habitat , history , growth , and impacts and management of species .
) . it is suggested that they constitute a species complex or supraspecies , separating from one another by reproductive isolation ; b . xylophilus is a native of north america , whereas the other two are palaearctic species , one colonizing coniferous trees , the other deciduous . b . xylophilus found in japan and other asian countries is obviously an introduction from north america . another apparently closely related species , bursaphelenchus kolymensis korenchenko , has been described from larix from the far east of russia (
recent molecular analyses of the near full - length small subunit ( ssu ) rdna , d2d3 expansion segments of the large subunit ( lsu ) rdna , and partial mitochondrial dna coi have provided a meaningful phy - logenetic framework for the genus bursaphelenchus , including b . platzeri n . sp . ( as b . sp . ex carpophilus humeralis 171 california ) , helping to justify its species status and placement relative to other nominal species ( giblin - davis et al . 2005 ; ye et al . , 2006 ) .
adult females and males of bursaphelenchus platzeri n . sp . in lateral view ( except where noted ) . a ) whole female . b ) whole male . c ) anterior body of female . d ) posterior region of female reproductive system . e ) vulva and vagina . f ) spicules ( ventral view ) . g ) female tail . h ) male tail . i ) male tail ( ventral view ) . j–m ) different focal planes through spicules of single male . n–o ) two focal planes through different male specimen .
the assembly is approximately 22 % repetitive , of which only around 1 . 3 % had characteristics of transposable elements ( tes , table 2 ) . a complete set of trna ( table s2 in text s2 ) and rrna genes were found in the genome . in common with other parasitic nematodes , including b . malayi and m . incognita [ 58 ] , sl2 trans - splicing appears not to exist in bursaphelenchus , but we find 25 sl1 - like sequences , found in the same tandem repeats as the 5s rrnas , as in c . elegans .
population densities of bursaphelenchus xylophilus in the stems of dead 3 - year - old larch and pine seedlings inoculated with a water suspension of cultured nematodes ( grown on botrytis cinerea ) or dj4 ( dispersal fourth stage juveniles obtained from jps beetles ) . l , m , and u indicate the lower , middle , and upper part of the stem , respectively . values are means ( ±sd ) of 15 dead larch seedlings inoculated with cultured nematodes , 25 dead larch seedlings inoculated with dj4 , 9 dead pine seedlings inoculated with cultured nematodes , and 5 dead pine seedlings inoculated with dj4 .
the pine wood nematode bursaphelenchus xylophilus is a migratory endoparasite that causes severe damage to forestry and forest ecosystems ( reviewed in [ 6 ] ) . b . xylophilus is native to north america such that trees there have evolved tolerance or resistance to the pathogen . however , at the start of the 20 th century it was introduced into japan and has subsequently spread to other countries in asia where no natural resistance is present , causing huge damage in an on - going epidemic of pine wilt disease . despite global quarantine efforts b . xylophilus was recently introduced into portugal [ 7 ] and has now also spread to spain .
sizes of each region are approximately proportional to the number of genes shared by the overlapping species , which are distinguished by different fill colour and different border styles . the selected genomes represent both taxonomically and ecologically diverse nematodes – c . elegans is a free - living bacteriovore , brugia malayi is an animal parasite , bursaphelenchus xylophilus and meloidogyne incognita are plant parasites , while pristionchus pacificus has a close ecological association with a beetle host , but is not parasitic . a phylogeny for these 5 species is shown in figure 5 . a number of overlapping regions are labelled with the number of gene families , as are a number of regions representing comparisons of particular ecological or taxonomic relevance .
statistical analysis was performed using spss version 11 . 5 . one - way anova analysis was performed in order to test if the different b . xylophilus and b . mucronatus isolates were equally tolerant to h 2 o 2 treatments for the parameters : nematode survival percentage , h 2 o 2 neutralization , and c . elegans survival percentage . post hoc multi - comparison duncan test ( significance level of 0 . 05 ) was used to group significantly different bursaphelenchus sp . isolates in the following parameters : nematode survival percentage , h 2 o 2 neutralization , and c . elegans survival percentage . levene’s test of homogeneity was performed a priori to infer anova assumption of homogeneity of variance .
bursaphelenchus xylophilus was first reported to infect l . laricina ( eastern larch ) in the northeastern united states ( bergdahl , 1982 ) . japanese larch growing in plantations has also been shown to be infected by b . xylophilus in the united states ( bergdahl and halik , 1987 ) . in japan , however , b . xylophilus has not been found in larch trees growing in natural forest stands , although b . xylophilus was found in dead and dying larch trees in an experimental forest located in an area of japan where pinewilt was spreading ( mamiya and shoji , 1985 ) . the latter report is the only record of a natural infection of larch trees by b . xylophilus in japan .
species of monochamus , the main vectors , are found throughout the northern hemisphere , and many have been recorded as having species of bursaphelenchus as associates ; it is assumed , therefore , that most , if not all , monochamus species would be capable of transmission to a greater or lesser extent . however , the only species known to transmit b . xylophilus and likely to carry the nematode on importation are those from north america and eastern asia . of the species recorded as carrying b . xylophilus , m . alternatus occurs in japan , china , taiwan , laos and the republic of korea , m . nitens and m . saltuarius in japan , siberia and northern china , and the others in canada and the usa .
a total of 18 , 074 protein coding genes were predicted in the assembly ( table 1 ) . this is fewer than the 20 , 416 in c . elegans ( wormbase ws221 ) and 19 , 212 in m . incognita , although it is higher than the number for m . hapla . the average protein length is similar to that of other nematodes , but b . xylophilus displays the largest average exon size ( 289 bp ) and the smallest average number of exons per gene ( 4 . 5 ) . the bursaphelenchus genome shows a number of characteristics of compact parasite genomes , for example having relatively few , short introns like m . hapla , but has a similar repetitive element content to other published nematode genomes , and is overall only slightly smaller .
the combined predicted proteins from b . xylophilus and 9 other nematode species were grouped into 27 , 547 families of orthologues and an additional 51 , 942 singleton proteins . we used a molecular phylogeny based on single - copy gene families to reconstruct the distribution and evolutionary dynamics of these gene families ( figure 5 ) , and find that the b . xylophilus genome has been relatively conserved over the long divergence from other plant parasitic nematodes . the pattern of sharing of gene families between genomes ( figure 6 ) shows little obvious phylogenetic pattern , but identifies relatively small numbers of genes - 202 genes shared by the two plant parasitic genomes , and 144 genes shared by pristionchus and bursaphelenchus that both show a close association with insects during their lifecycle – that could be implicated in these particular specializations .
most species within the bursaphelenchus genus , including the closest relatives of b . xylophilus [ 8 ] , are fungal feeders that are transmitted by vector insects only to dead or dying trees during oviposition . b . xylophilus and the few other pathogenic species described to date are unique in their capacity to feed on live trees as well as on the fungi that colonise dead or dying trees , so these species may represent a relatively recent , independent origin of plant parasitism . the nematode is a member of the aphelenchoididae and belongs to clade 10 [ 3 ] while most other major plant parasites including meloidogyne species belong to clade12 [ 3 ] ( figure 1 ) . the life cycle of b . xylophilus is summarised in figure 2 and the infection and disease process has been reviewed by mamiya [ 9 ] and by jones et al . [ 6 ] .
from 1905 until the present time , pine wilt disease ( pwd ) has been one of the most threatening diseases for worldwide forests [ 1 ] . pwd is considered a complex disease resulting from the interaction of three main elements : the pathogenic agent bursaphelenchus xylophilus ( pwn , pine wood nematode ) , the insect - vector monochamus spp . ( responsible for pwn dissemination ) , and the host tree , mostly from pinus spp . [ 2 – 3 ] . in a b . xylophilus population , there is intra - specific variability in the ability to cause pwd ( virulence ) [ 4 ] . the existence of different levels of virulence among pwn isolates , and their relation to pwn reproductive ability in vitro and in vivo were already reported [ 5 – 6 ] . in this context , the low virulence nematodes , often designated as avirulent , show lower reproduction rates and increased generation times that eventually affect their host invasion and colonization [ 7 – 9 ] .
bursaphelenchus nematodes are of great interest because b . xylophilus is the pathogen causing pine wilt disease , one of the most serious forest diseases in the world ( mamiya , 1988 ; futai , 2013 ) . we recently demonstrated the hermaphroditism and genetic tractability of the fungal feeding species b . okinawaensis ( shinya et al . , 2014 ) . mating experiments that used a visible recessive mutation to distinguish self - from cross - progeny showed that b . okinawaensis male mates only with the sperm - depleted old adult hermaphrodites . in the gonochoristic species b . xylophilus , males are attracted to volatile cues from virgin females , while not attracted to the volatile cues from mated or gravid females ( kiyohara , 1982 ) . also , liu et al . ( 2014 ) carefully observed the mating behavior in b . xylophilus and compared it with c . elegans . one major difference in mating among nematodes is whether the male coils around the female as in b . xylophilus or only contacts the female / hermaphrodite with his copulatory tail as in c . elegans .
population densities of bursaphelenchus xylophilus in diseased and dead seedlings : nematodes were extracted from wood samples collected from nematode - inoculated 2 - year - old larch seedlings at 6 - day intervals . all 3 - year - old dead larch and pine seedlings were collected on 10 september , 1984 . at each sampling time except 3 days after inoculation , 2 - year - old larch seedlings which showed external symptoms such as yellowing , wilting and falling leaves were chosen for nematode extraction . three days after inoculation seedlings were collected at random . stem sections ( 10 - cm long ) were cut from collected seedlings at each of the following positions : upper part ( the main shoot ) , middle part ( including the nematode inoculation point ) , and lower part ( 10 cm above ground level ) . stem samples were sliced thin and placed on baermann funnels to extract nematodes . after air drying for 3 days , each stem sample was dried for 8 h at 120 °c and weighed . the number of b . xylophilus was converted to the number / g dry wood .
after being introduced to japan from overseas , maybe from north america , in the early 1900s , the pinewood nematode , bursaphelenchus xylophilus ( steiner & buhrer ) nickle , has spread throughout japan and in many other countries , china , south korea , taiwan and portugal and has caused devastating damage to pine trees in the form of pine wilt disease ( pinewilt ) . annual loss caused by pinewilt was estimated 700 , 000 m 3 of pine wood , or about 5 million pine trees , in japan . in the last 3 decades , pinewilt has spread markedly , especially from the southwest and central parts of japan to the northeast and to pine forests distributed at higher elevations ( mamiya , 2004 ) . as a result of the spread of pinewilt to these areas , nearby larch forests have been threatened with infection by b . xylophilus . japanese larch , larix kaempferi , was extensively planted in the 1950s and 1960s throughout northeastern japan and in the high lands of central japan to provide wood resources . the total area of planted and managed larch forests in japan is 1 . 1 million ha .
pathogenicity of the pine wood nematode , bursaphelenchus xylophilus , to japanese larch , larix kaempferi , seedlings was tested with inoculation experiments under nursery conditions . water suspensions of nematodes ( mixed stages cultured on botrytis cinerea or dispersal fourth - stage juveniles ( dj4 ) extracted from the adult japanese pine sawyer , monochamus alternatus ) were injected into the stems of 2 - and 3 - year - old japanese larch and japanese black pine , pinus thunbergii , seedlings growing in a nursery . in another treatment , japanese pine sawyer adults holding dj4 were released under a net that covered the upper half of the seedlings . regardless of nematode inoculation method , japanese larch seedlings were as susceptible as japanese black pine seedlings to b . xylophilus under nursery conditions . the rate of disease development was similar on larch and pine seedlings . nematode population densities were lower in the stems of dead larch seedlings than in the stems of dead pine seedlings . histopathological observations revealed that the distribution of nematodes in the stems of dead larch seedlings was mostly limited to the cortex , phloem and cambial zone . traumatic resin canal formation was one of the most characteristic symptoms in larch seedlings which was dissimilar to that in pine seedlings .
effect of chemotaxis on males of a ) bursaphelenchus okinawaensis ( bok ) by the chemical cue of young hermaphrodites ( yh ) and old hermaphrodites ( oh ) of bok or unmated female ( uf ) and mated female ( mf ) of b . xylophilus ( bxy ) as compared to the water control ; b ) bxy by the chemical cue of yh and oh of bok or uf and mf of bxy as compared to the water control . chemotaxis index ( ci ) = ( [ number of nematodes at the test cue zone ] − [ number of nematodes at the control zone ] ) / ( [ number of nematodes at the test cue zone ] + [ number of nematodes at the control zone ] ) . sperm status of hermaphrodites or females are shown as ( + ) or ( − ) . sperm ( + ) indicates hermaphrodite having self - produced sperm or female having sperm supplied by male , while sperm ( − ) indicates hermaphrodite or female have no sperm at the preparation of the wcm . error bars indicate standard error . * * indicates significant difference ( p < 0 . 01 ) in ci between the tested chemical cue and water control based on dunnett’s test .
the pinewood nematode ( pwn ) , bursaphelenchus xylophilus , is the causal agent of pine wilt disease ( pwd ) . this nematode is considered to be an indigenous to north america and was introduced to japan in the late 19th century . subsequently , it has spread throughout japan and in many other countries , china , taiwan , and south korea . in 1999 , b . xylophilus was discovered in portugal , and in 2008 in spain . so far the studies have revealed that the pathogenicity of b . xylophilus varies between different isolates . the conducted study compared the pathogenicity of five isolates of b . xylophilus , originating from different parts of japan , to 3 - year - old pinus sylvestris , and their ability to reproduce in the seedlings . the results revealed diverse virulence of b . xylophilus resulting in plant mortality . three isolates s10 , ka4 , and t4 caused 100 % mortality of plants within three months while at the same time , the other two isolates , c14 - 5 and okd - 1 did not cause any disease symptoms on plants . after seven months , some dieback occurred on two seedlings , but similar symptoms were also found on the control plant . moreover , a significant positive correlation was found between nematode virulence and the number of nematodes reproducing on pine seedlings .
in addition to plant cell wall degrading enzymes , cazymes are present in b . xylophilus which potentially degrade the fungal cell wall . chitin is one of the main components of fungal cell walls . proteins related to chitin degradation were identified in the b . xylophilus genome . in comparison to the two meloidogyne species , p . pacificus and b . malayi the number of chitin - related cazymes in b . xylophilus is increased , likely reflecting its fungal feeding activity ( table 4 ) . c . elegans has a much larger number of gh18 proteins than b . xylophilus . this may be because those proteins have been used in c . elegans for specific biological features such as bacterial feeding . interestingly , six gh16 proteins which may degrade beta - 1 , 3 - glucan , another core component of the fungal cell wall , have been identified in the genome while no homologues have been found in other nematodes ( table 4 ) . because the b . xylophilus gh16 β - 1 , 3 - glucanase genes are most similar to those from bacteria , it has been suggested that they were acquired from bacteria which were closely associated with its ancestor [ 63 ] . this suggests that hgt processes , similar to those associated with plant cell wall modifying enzymes of other parasitic nematodes , have enhanced the ability of bursaphelenchus spp . to feed on fungi .
considered an eppo a2 quarantine pest , bursaphelenchus xylophilus is the causal agent of the pine wilt disease and the most devastating plant parasitic nematode attacking coniferous trees in the world . in the early stages of invasion , this nematode has to manage host defence mechanisms , such as strong oxidative stress . only successful , virulent nematodes are able to tolerate the basal plant defences , and furthermore migrate and proliferate inside of the host tree . in this work , our main objective was to understand to what extent b . xylophilus catalases are involved in their tolerance to oxidative stress and virulence , using as oxidant agent the reactive oxygen species hydrogen peroxide ( h 2 o 2 ) . after 24 hours of exposure , high virulence isolates of b . xylophilus could withstand higher h 2 o 2 concentrations in comparison with low virulence b . xylophilus and b . mucronatus , corroborating our observation of bxy - ctl - 1 and bxy - ctl - 2 catalase up - regulation under the same experimental conditions . both catalases are expressed throughout the nematode intestine . in addition , transgenic strains of caenorhabditis elegans overexpressing b . xylophilus catalases were constructed and evaluated for survival under similar conditions as previously . our results suggest that catalases of high virulence b . xylophilus were crucial for nematode survival under prolonged exposure to in vitro oxidative stress , highlighting their adaptive response , which could contribute to their success in host conditions .