Identification Of Pathogen And Genetic Diversity Of Curvularia Leaf Spot In Henan Province

Corn Curvularia Leaf Spot is an important leaf spot disease on cornfollowing Northern corn leaf blight and Southern leaf blight corn. The disease haveoccurred in Huanghuai, northeast and southwest corn-producing areas. The leaves cancovered with lesions when Curvularia leaf spot is serious and it affects filling andyield of corn. Since Curvularia leaf spot is a new disease in recent years, the studies inthis disease are relatively less. In this study,the authors identify the pathogen speciesand pathogenicity in Curvularia leaf spot in Henan province. In addition RAPD andISSR molecular marker technique are used to analyze the genetic diversity of isolatedpathogen strains. The main findings are as following:(1)The standard samples of Corn Curvularia leaf spot were collected fromZhengzhou,Shangqiu,Xunxian,Puyang,Lushi and other places in Henan province,andthen54strains were isolated.The morphology of colonies,conidia and conidiophoresof54strains were observed.The results show that54strains are Curvularia lunatareference to Demodex conidial fungi in China fungi Chi which editor-in-chief isZhang Tianyu.(2) Using the universal primers ITS1and ITS4,Gpd and ACT, the internaltranscribed spacer(ITS) and5.8S rDNA of the54strains were cloned and sequenced.The rDNA ITS sequences homologies were100%; the Gpd sequences homologieswere99.74%~100%;the ACT sequences homologies were99.80%~100%.Thedifferences of sequences performance in deletion or mutation of the individualnucleotides. The obtained sequence were compared with published sequences inGenBank database. The ITS sequences homologies were100%of the strain XX01and Curvularia lunata; the homologies were low between the strain XX01and othergenus. The Gpd sequences homologies were more than99%between the strain XX01and Curvularia lunata, and the Gpd sequences homologies were high among speciesin Curvularia.There is no ACT sequences can be compared with of Curvularia lunatain GeneBank. The ACT sequences homologies were low between the strain XX01andC. pallescens or Bipolaris maydis.According to the molecular identification, the54strains were identified to be the same species--Curvularia lunata. (3) Two maize cultivars,Xundan20and Zhengdan958were used to evaluate forthe pathogenic responses of54strains using the Manual spray inoculation technique.These strains were divided into four groups based on the Relative index ofpathogenic:super strong pathogenicity, strong pathogenicity, moderate pathogenicityand weak pathogenicity. The results indicate that there exists obvious diversities inpathogenicity in Corn Curvularia leaf spot Pathogens of Henan. In the maize varietiesXundan20, there was twenty strong pathogenicity strains including SQ01,SS02,LY04and LS06, accounting for37.04%,eighteen moderate pathogenicity strains includingZZ01, SS01and PY02, accounting for33.33%, sixteen weak pathogenicity strainsincluding YC02, PY04and LS04, accounting for29.63%. In the maize varietiesZhengdan958, there were seventeen strong pathogenicity strains including SQ01,PY05,NZ04and NZ02, accounting for31.48%, eighteen moderate pathogenicitystrains including ZZ02and XX02, accounting for33.33%, nineteen weakpathogenicity strains including YC01and ZZ06, accounting for35.19%. Thepathogenicity of strains were not linked to geographic distribution.(4)According to genetic diversity analysis of54strains with RAPD and ISSRmakers, the results show that there was relatively rich genetic variations withinC.lunata population in Henan. The result of the clustering and analysis showed54strains were clustered into4~5distinct groups. No close correlation was foundbetween genetic diversity and pathogenicity. And every group had differentpathogenicity. There was certain correlation between genetic diversity andgeographical distribution, and7strains of Lushi region were clustered into one group.