Preliminary Study On Peanut Scab Disease Pathogen (Elsino(?) Arachidis) In Fujian Province

Peanut scab is a common peanut disease,caused by arachidis(Bitanc.&Jenkins)Rossman&WC Allen(the anamorph is Sphaceloma arachidis Bitanc.&Jenkins).Because of late discovery in China,there have been few research reported about this fungus.Because of this,the pathogen of peanut scab was systematically studied in this study,including morphological and molecular identification,biological characters of E.arachidis,its phylogenetic relationships with other Elsinoe species and the anamorphs,and the establishment of a rapid diagnosis technique of this disease.The results of this study are as follows:(1)Scab-like peanut samples were collected from Fuzhou and Longyan in Fujian province.The samples were checked for identification.5 fungal strains were obtained after isolation and purification of the samples.The strains were identified by morphological characters and phylogenetic analyses of ITS sequences.The results showed that peanut scab in Fujian province is also caused by E.arachidis.(2)The results of biological characters of E.arachidis(strain LY-HS-1,collected from Longyan)showed that the optimum growth temperature of E.arachidis are 23℃-27℃,the optimal carbon sources for mycelial growth are dextrose,sucrose and starch,and the optimal nitrogen source of mycelial growth is yeast extract.E.arachidis grew faster in acidic environment(pH 4.5-6.5).The temperature and the nutrients had a significant impact on the colony morphology and mycelial growth rate,and the pH only affect mycelial growth rate.(3)The phylogenetic analyses of Elsinoe and its anamorph with multiple-loci sequences(including ITS,LSU,SSU,TEF,CHS,mtSSU,actin and β-tublin)showed that SSU and LSU genes did not separate different species in Elsinoe and its anamorphs.Therefore,the two genes are not suitable for species identification in Elsinoe and its anamorphs.ITS and TEF genes separated different species in Elsinoe and its anamorphs,and reflected the relationships among them to some extent,but the relationships were not very clear.Therefore,the two genes can be used for identification of Elsinoe species and the anamorphs,but need to be analysed with other genes when investigating the phylogenetic relationships among different species.Because of the lacking of reference sequences of Elsinoe and its anamorphs for other 4 genes,the sequences obtained in this study for the 4 genes were analyzed.Species variation was found in E.arachidis and for CHS gene.This shows CHS gene may be used to study variation within species of E.fawcettii and E.arachidis.For the other 3 genes,there were differences between arachidis and E.fawcettii,but the species variation is not very obvious.(4)A rapid detection technique for E.arachidis was established.By using this technique,the sample without obvious scab symptom or decomposed and not suitable for artificial isolation could be diagnosed.The sensitivity of the method could reach 0.1pg/mL.And rotted peanut stems were preliminarily proofed to be one of the overwintering places of E.arachidis by this method.In summary,the results of this study provide the basis for understanding occurrence regularity,prevention and control and more researchs of this disease.