Morphological And Molecular Identification Of Aphelenchoides Populations Isolated From Imported Plant Materials At Ningbo Port

There are about 200 species in genus Aphelenchoides having been reported.Among these species,several important plant parasitic nematodes are included,such as A.besseyi causing the "white tip disease" on rice,A.ritzemabosi causing damage on buds and leaves of strawberry,and A.fragariae causing leaf lesion.on chrysanthemum.In this paper,five Aphelenchoides populations were isolated from Lilium orientalis imported from the Netherlands and from plant materials imported from Japan at Ningbo Port.The morphological identification and molecular characterizations based on rDNA 18S,28S D2-D3 and mtDNA-COI genes were carried out to determine their taxonomic status.The main results are as following:The preliminarily morphological identification revealed that five Aphelenchoides populations all having single mucro,which belong to the Group 2 category of Aphelenchoides species sensu Shahina(1996).The detailed morphological and molecular characterization confirmed the population from Lilium orientalis of The Netherlands as a new species and described as A.smolae n.sp.The population from medium soil of Acer palmatum from Japan was identified as A.heidelbergi.Three Japanese populations from medium soil of Olea europaea and Podocarpus macrophyllus plants,as well as from wood packaging materials,respectively,were confirmed as unknown species of Aphelenchoides.Aphelenchoides smolae n.sp.is characterised by the female body length of 826(672-1002)?m and male body length of 785(683-844)?m.lateral field with four lines(three bands),stylet 13.0-14.9 ?m long with small basal swellings,excretory pore situated slightly posterior to nerve ring,vulval flap absent,post-uterine sac well developed and extending for about 35.7-62.4%of vulva to anus distance,conical tail with terminus bearing a single mucro with many tiny nodular protuberances,males common,with spicules 25.7-29.8 ?m long(median curved line),the condylus and rostrum rounded,well developed,the dorsal limb with a hook-like tip,and tail bearing three pairs(2+2+2)of caudal papillae and a sharply pointed mucro.The 18S,28S and mtCOI phylogenetic trees all revealed that the new species closely related to A.blastophthorus?A.eldaricus and A.fragariae,however,they were distinguished from each other on the morphological characters.The A.heidelbergi population from Japanese Acer palmatum is characterized by lateral field with three lines,excretory pore situated slightly posterior to nerve ring,post-uterine sac less developed and two small continuous protrusions on ventral limb.Its morphological characters are similar to the A.heidelbergi population isolated from Pinus radiata in Australia.The 18S and mtCOI trees both revealed that the Japanese population was clustered with Australia population in a branch.Three Japanese Aphelenchoides populations from O.europaea,P.macrophyllus,and the wood packaging materials respectively,are characterized by lateral field with four lines,excretory pore situated posterior to metacorpus,vulval flap absent,spicule dorsal limb with a distinct bend at about 1/3 of total length from anterior end.The 18S and 28S trees both revealed that three populations were clustered with Aphelenchoides sp.Asp7763,Aphelenchoides sp.13Asp,and Aphelenchoides sp.Asp6753,respectively.The results not only enriched the taxonomic information for species in genus Aphelenchoides,but also provided the theoretical basis for phytosanitary inspection of plant nematodes at ports in China.