Pathogenicity Differentiation And Genetic Diversity Of Curvularia Lunata

Curvularia leaf spot of maize is one of the most serious corn diseases.Due to monoculture of resistant cultivars,the change of farming system,the influence of climate and other environmental factors,the pathogenicity of Curvularia lunata has been significantly differentiated in different regions of China and thus promotes the epidemics of Curvualria leaf spot.The cause of pathogenicity differentiation of pathogens is the change of pathogen genotype,which is closely related to genes differential expression,so,the cause of pathogenicity differentiation of Curvularia lunata in maize should be explored from the perspective of genetic differentiation.In this study,the genetic diversity of Curvularia lunata was studied by AFLP technique,and the correlation between the genetic diversity of Curvularia lunata and the pathogenicity of the strains was analyzed.In addition,the differences of genomic DNA between different strains were analyzed.It is expected to find the differential genes related to pathogenicity differentiation,and provide a theoretical basis for the study of the pathogenic mechanism of Curvularia lunata.The main results are as follows:1.The corn leaf spot samples were collected from China,2 genera and 3 species were isolated and identified.A total of 36 samples were collected from corn growing areas in Liaoning,Yunnan,Sichuan,Hubei,Anhui,Shandong,Hebei,Jilin and Heilongjiang provinces.32 strains were isolated and identified by a combination of morphological and molecular biology methods.30 C.lunata,1 C.geniculata and 1 B.setariae were identificated.The two new diseases were described and reported for the first time in China.2.In this study,the pathogenicity differentiation of 111 strains of C.lunata was studied.According to the average disease index of the strains on 9 identification hosts,the tested strains were divided into three pathogenic types: strong(83),medium(26)and weak(2)pathogenic type.According to the reaction type of the tested strains in 9 identified hosts,the strains were clustered into four toxic groups,namely PGI,PGII,PGIII and PGIV.The results showed that there was obvious pathogenicity differentiation in the strain population,and the pathogenicity of the strain had a certain correlation with the geographical origin.3.The genetic diversity of 111 C.lunata strians was analyzed by AFLP technique.Using the selected 8 pairs of polymorphic primers,the genetic diversity of 111 C.lunata strains were analyzed.When the similarity coefficient is 0.78,the strain was divided into two main groups,GDI and GDII.The similarity coefficient is 0.88,the GDI group is further divided into 21 subgroups GDI-A,GDI-B,GDI-C,GDI-D,GDI-E,GDI-F,GDI-G,GDI-H,GDI-I,GDI-J,GDI-K,GDI-L,GDI-M,GDI-N,GDI-O,GDI-P,GDI-Q,GDI-R,GDI-S,GDI-T,GDI-U,when the similarity coefficient is 0.91,the GDI-A subgroup is further divided into 8 subgroups GDIA-1,GDIA-2,GDIA-3,GDIA-4,GDIA-5,GDIA-6,GDIA-7,GDIA-8,indicating that the strain population has a high level genetic differentiation.AFLP cluster analysis was not correlated with the geographical origin and was correlated with the pathogenicity of the strain.4.The AFLP fingerprints of three pathotypes of C.lunata were analyzed.A total of 41 differential fragments were identified,24 differential fragments were cloned and sequenced successfully,15 differential fragments were found in the NCBI database.The genes is known to be related to basal metabolism,transcription,transport,protein synthesis,signal transduction and so on.Differential genes: Transcriptional repressor rco-1,c2h2 finger domain-containing protein,Asparagine synthetase B,MFS transporter may be related to the pathogenic differentiation of C.lunata.