Identification And Phylogeny Of Ophiostomatoid Fungi Associated With Ips Subelonsatus In China

Ips subelongatus was the main pest which infected the Larix spp. in our country.As thepioneer species, the bark-beetles can infect the felled trees,the dying trees, and also can lead thehealthy wood to die. It had been reported that Ips subelongatus had happened in northeast andnorth China, including Heilongjiang, Jilin, Inner Mongolia, Shanxi, Liaoning and Hebeiprovince. Mainly, the I. subelongatus infected the three allopatric larchs, L.gmelini, L.olgensisand L. prineipis-rupprechtii.I. subelongatus was a pioneer pest threatening the larch plantationin China. Universally, the ophiostomatoid fungi can form a kind of stable associated relations.Unfortunately, the associated community can make stronger damages than single bark-beetlesor the single fungi. The study on the associations between the bark-beetles and theophiostomatoid fungi, clearly to determine the associated fungi flora composition, it canprovide scientific basis to make the policies and measures for the government to prevent andcontrol thecompositedamages of diseases and pests effectively.Fungi were recovered from and around the gallery of Ips subelongatus attacking the Larixspp. plants. Over40genera of fungi were isolated during the sampling. In order to identify themain associated fungi, the ophiostomatoid, morphological and physiological observation,multiple DNA sequences comparisons and phylogenetic analyses were conducted. The studyaimed at inventorying the ophiostomatoid fungi associated with the I. subelongatus, todetermine the species specific associations between I. subelongatus and the ophiostomatoidfungi.Samples were collected from17places in north-easten China.1036strains including150ophiostomatoid fungi strains were isolated from the galleries or the body surface of the beetles.Totally,4genera of ophiostomatoid fungi were abtained, they were Ophiostoma, Ceratocystis,Grosmannia, and Ceratocystiopsis. The number and type of Ophiostoma spp. were the most,earned a total123strains,7species during the isolation. Observations of the colony, physiology and morphology characteristics, and comparisonsof anamorph and teleomorph structures of the ophiostomatoid fungi, a new species withuncertained name, O. cf. bicolor was discovered. The colony characters was samed toOphiostoma bicolor, but the microscopic features was different. It growed fast on the2%MEAmedium, colorless to white at first,then reverse to pale yellowish or olivaceous. The myceliumsuperficial and immersed,hyaline. This species was discovered on the L.gmelini and L.prineipis-rupprechtii. At the same time, the new species with uncertain name,O.cf.saponiodorum were found from the Pinus sylvestris.Grosmannia spp., Ophiostoma abietinum, O. kryptum, O. floccosum, O. minus, O.cf.saponiodorum, O. brunneo-ciliatum, Ceratocystisfujiensis and Ceratocystiopsisminuta werealso isolated from the samples collected from the larch logs infected by Ipssubelongatus.O.abietinum，O.kryptum，O. brunneo-ciliatumand O. floccosum were considered as newrecords species in China. The results found that the number of O. brunneo-ciliatum was morethan the other fungi, constant association with Ipssubelongatus.The phylogenetic analysis based on sequences derived from the ITS regions of the rDNAoperon, the partial β-tubulin gene and the MAT-2HMG box gene, further determined a total ofnineteen fungal strains as species ofCeratocystis fujiensis. The study first determinedCeratocystis fujiensis extensively existed in three allopatric larch forests innortheast and northChina, which formed a stable association relationship with I. subelongatus under suchecological conditions.Ceratocystisfujiensis was proved as a dominant fungus associated with Ipssubelongatus inJapan, and a pioneer species and the strongest pathogenic fungus in all the bark-beetlesassociated fungi. Because C.fujiensis widely infestedLarix spp. plants in China, inevitably, thisphenomenon should be paid high attention. The study provides scientific basis to make thepolicies and measures for the government to prevent and control thecompositedamages ofdiseases and pests effectively. The result in this paper provides support to the hypothesis ofspecies specific association between Ips beetles and ophiostomatoid fungi. Meanwhile, themulti-gene sequences characteristicindicates that I.subelongatus and C. fujiensis exist significant genetic diversity in different geographic populations, which probably predict thepossibility of the species specific association occurred under species levels. The associationsbetween Ips beetles and ophiostomatoid fungi exhibit an ideal insight into completelyunderstanding the symbiotic relationship between the bark beetles and ophiostomatoid fungi,and species specific association as well.