Physiological Differentiation And Phylogeny Of Botryosphaeria Dothidea Causing Poplar Canker

Poplar is wide ranging in northeast, northwest, north China and the Yangtze river’smiddle and lower reaches, and plays significant roles in wind prevention and sand resistance,as well as in the conservation of soil and water. Poplar canker, a major forest diseasescaused by Botryosphaeria dothidea, is an important branch and stem disease damaging thewhole tree, leading to death and inflicting economic damage. Therefore, investigating on thegeographical distribution of poplar canker in northwest China such as Shannxi and Gansu andresearching in physiological differentiation and phylogenetic analysis of Botryosphaeriadothidea have the important theoretical and practical significance.The cultural characteristics, anamorph morphology and pathogenicity of B. dothideaisolates collected from Shannxi and Gansu province were investigated. The ITS rDNA region,partial β-tubulin and EF-1α gene fragment of62isolates were amplified, using primers ofITS1/ITS4, EF1-728F/EF1-986R and Bt2a/Bt2b, respectively, and the molecular phylogenyof the aligned sequences was analysed. The research consequences were as follows:1. According to colony characteristics on the PDA medium,62isolates could be dividedinto two colonial groups: groupⅠ showed flat colony, groupⅡ showed typical fountain. Thegrowth rate of isolates Flnh, Fnbl2and Ffnw were much higher than others, in contrast,growth rate of isolates Fzwh2, Fzwh3, Fhyx and Fymp1were lower, therefor the testedisolates could be divided into three groups. Conidial size of the tested isolates were overlapand no significant difference. Based on the characteristics of conidium and culture, theseisolates are identified Fusicoccum aesculi, that is anamorph of Botryosphaeria dothidea.2. Pathogenicity identification indicated that the tested isolates existed obviouspathogenicity differentiation, and could be divided into three groups, the lesions Fzwh3、Fzwh6、Fcsh、Ffhn and Fhsz displayed strong pathogenicity, while pathogenicities of isolatesFnbl1、Flxj and Fhmx were weak, most other isolates were center.3. Meanwhile tested isolates were clustered into two, three, and three groups in terms ofthe partial rDNA-ITS, β-tubulin and EF-1α gene sequence phylogenetic trees structured bythe neighbor joining (NJ) method respectively. The isolates of GroupⅠ, included most strains,were clustered together with B. dothidea retrieved from GenBank, which was confirmedmorphological identification results; the isolates Fyxn, Fyrg and Fyxj from Yangling ofShaanxi were classified as one group in the β-tubulin and EF-1α gene phylogenetic trees, displaying far away phylogenetic relationship from other isolates of B. dothidea; three isolatesFxfh, Fxdh1and Fxdh2from Xianyang of Shaanxi province were classified as one group Ⅲin the EF-1α gene phylogenetic trees. Overall there is no one-to-one relationship amongphylogeny, morphology, cultural characteristics, and pathogenicity differences of the testedisolates.