| The bark beetle is one of the important pests that damage trees.It has a large number of hosts and is found all over the world.Many bark beetles are vectors of pathogenic fungi,and their interactions with related fungi are complicated.The co-invasion of bark beetles and associated fungi led to a rapid decline of host trees,which eventually resulted in the death of trees,causing massive ecological and economic losses.When bark beetles and associated fungi infest a host,a defensive response is triggered.To help the bark beetle colonize the host,associated fungi may consume the host’s defensive chemicals.In this study,we focused on the diversity of Geosmithia associated bark beetles in China and the diversity of ophiostomatoid fungi associated with Cryphalus piceae in Shandong coastal areas.We also studied the effects of plant defensive compounds on ophiostomatoid fungi.The main research contents of this thesis are as follows:(1)A total of 12 beetle species were collected from Fujian,Guangdong,Guangxi,Hunan,Jiangsu,Jiangxi,Shandong,Shanghai and Yunnan.In total,178 strains of Geosmithia were isolated from the beetles and their galleries.The ITS,TUB2,TEF1-α,and RPB2 sequence fragments were sequenced.Identification was conducted by using phylogenetic analyses and morphological characteristics.A total of 12 species were identified,of which three were known species,namely G.xerotolerans,G.putterillii,and G.pallida;nine were new species that were described as G.luteobrunnea,G.radiata,G.brevistipitata,G.bombycina,G.granulata(Geosmithia sp.20),G.subfulva,G.pulverea(Geosmithia sp.3 and Geosmithia sp.23),G.fusca,and G.pumila.The dominant species are G.luteobrunnea and G.pulverea.This study systematically studied Geosmithia in China,which made an important contribution to understanding the distribution and diversity of Geosmithia in the world and also filled the gap in the study of this kind of fungi in China.(2)The diversity of the ophiostomatoid fungi associated with Cryphalus piceae in Shandong Province was explored.The fungal strains were isolated from the bark beetles and their galleries which collected from Weihai,Qingdao,and Yantai,and then identified by multigene(TUB2,TEF1-α,CAL and LSU)phylogenetic analyses and morphological characters.A total of 254 fungal strains were obtained,including 175 ophiostomatoid strains,which were divided into seven species,belonging to five genera: Ophiostoma,Sporothrix,Graphilbum,Graphium,and Ceratocystiopsis.Two of them are known species: Graphium pseudormiticum and O.ips.The rest of five species are new to science and described as C.yantaiensis,C.weihaiensis,Gr.translucens,Gr.niveum,and S.villosa.Ophiostoma ips is a dominant species with 141 strains.These new ophiostomatoid fungi increased the number of known fungi in China.(3)The effects of ethanol on ophiostomatoid fungi,the most common fungi associated bark beetle,were tested.Our results showed that some ophiostomatoid benefited(or at least not be harmed)from the presence of ethanol.This confirmed the competitive advantage of ophiostomatoid fungi in bark beetles’ preferred ethanol-containing hosts.In addition,we tested the tolerance of ophiostomatoid fungi to turpentine,a metabolite of pine trees,and its main components α-pinene and β-pinene.Results suggested that these compounds could promote the growth of some ophiostomatoid fungi.This study laid a foundation for the thorough studies on the interaction between bark beetle-and their associated fungal symbionts.In this study,the diversity of Geosmithia spp.in China and the ophiostomatoid fungi in Shandong Province were studied.A total of 1000 strains were isolated and 20 species were identified,including 14 new species.In addition,the effects of plant chemical defence substances on ophiostomatoid fungi were studied.This study can deepen the understanding of the biological and ecological characteristics of bark beetles and provide new ideas for the prevention and control of bark beetles.It provides a basis for further revealing the interaction between associated fungi and tree hosts. |
