Phvlogenv Of Some Botryosphaeriaceae Species And Genetic Diversity Of Type Botryosphaeria Dothidea In China

The species-rich family, Botryosphaeriaceae (Ascomycota, Dothideomycetes), has acosmopolitan distribution and causes canker and die-back on branches and stems of variouseconomically important trees including poplar and fruit trees in China. The pathogens arecommonly nominated according to diseases and host plants for long, which brings the sameorganism with different names or different organisms with the same name, and confusion ofnomination and taxonomy of Botryosphaeriaceae. These problems hindered the effectivecontrol and management of the disease. The type species, Botryosphaeria dothidea, is one ofthe most common speices in this family. This species has been found in many climate regions.It is significant to find out genetic diversity and differerciation of B. dothidea populations fordetecting and managing disease.This study investigate the pathogens of canker and die-back and the diversity ofBotryosphaeriaceae in China, especially the botryosphaeriaceous fungi on poplar androsaceous fruit trees. The morphological and phylogenetic analyses showed that the58isolateson poplar and37isolates on rosaceous fruit trees from five typical climate regions in Chinawere considered as8or9species of Botryosphaeriaceae afflicting to five genera.Botryosphaeria dothidea populations had moderate genetic diversity (Nei's genetic diversityindex H=0.6777).B. dothidea, Neofusicoccum parvum, Diplodia seriata, D. mutila, Dothiorella viticola andan undescribed new species, Fusicoccum sp.1on poplar were identified based on morphologycombined comparisons of DNA sequences for the ITS, β-tubulin and EF1-α regions. Fifty-threeisolates were regarded as B. dothidea. B. dothidea, Lasiodiplodia pseudotheobromae, Neof.parvum/Neof. ribis complex and another undescribed new species, Fusicoccum sp.2on fruittrees were identified. There were15isolates were reported as B. dothidea,3isolates as L.pseudotheobromae, Neof. parvum/Neof. ribis complex each, and the other6isolates asFusicoccum sp.2. D. seriata was firstly reported on poplar in China, and Dothiorella viticola was observed on from Cyclobalanopsis glaucoides in this study as well as on poplar in aprevious study. There was reason to suspect the corresponding relation between B. rhodina andL. theobromae acorrding to the phylogenetic results based on β-tubulin sequence, and considerthat the anamorphic B. rhodina is L. pseudotheobromae. Distribution of most isolates had nodirect correlation with climate regions, except that L. pseudotheobromae was only found insouth subtropical in China.Comparison of cultural characteristics and phylogenetic relationships based on LSUregion and ITS/EF1-α combined sequences supported the phylogenetic position of Fusicoccumsp.1and Fusicoccum sp.2belonging to Botryosphaeria complex. Fusicoccum sp.1was theclosest to Fusicoccum fabicercianum. Fusicoccum sp.1and Fusicoccum sp.2appearedobviously different from the other species in Botryosphaeria complex based on culturalcharacteristics.Botryosphaeria dothidea, the dominant species on both poplar and fruit trees, was locatedfrom mid-temperate to south semitropical zone, which indicated the differentiation potencyadapting to different host and geography. To find out genetic differences and genetic diversityof B. dothidea population, ten polymorphic SSR (Simple Sequence Repeat) loci were selectedfor investigating genetic diversity and structure of77isolates from5climate regions, namelymid-temperate sub-humid climate region (12B), warm-temperate sub-humid climate region(13B), north-subtropical humid climate region (21A), mid-subtropical sub-humid climateregion (22A) and south-subtropical humid climate region (23A). In this study on the77isolates,5populations were found to have a moderate gene diversity and a low genetic variation(Fst=0.0758). Most of genetic variation was from inner population, while those betweenpopulations were low. Except12B, the other4populations had unique alleles, and the numberwas21,2,2and3. The reason for low genetic differentiation and high gene flow in5populations were probably that the locations of77isolates were the places with frequenthuman activities, and were directly assisted by movement with their host plant, especiallypoplar. Meanwhile, the unique alleles were found in different populations, including407bp and425bp of21A,424bp and429bp of22A,234bp,408bp and416bp of23A, and313bp,333bp, etc. of13B. These unique alleles were very significant for detecting B. dothidea when latent intissues.