Genetic Diversity And Pathogenicity Of Downy Mildew Disease Of Foxtail Millet In Shanxi Province

Downy mildew disease of foxtail millet caused by Sclerospora graminicola(Sacc.),is one of the most destructive diseases on foxtail millet,and could result in a total yield loss and the lower quality.Preliminary investigation shows that the symptoms and pathogenicity of the disease caused by S.graminicola in different regions are different.In order to preliminarily explore the pathogenicity and genetic characteristics of S.graminicola in different regions of Shanxi Province,the genetic diversity of S.graminicola is analyzed by using specific sequence analysis and SSR molecular markers.The main physiological composition,pathogenicity and distribution characteristics of S.graminicola are determined.To provide reference for the research of S.graminicola and rational distribution of regional varietiety planting.The main research findings were as follows:1.In order to establish an early detection system for S.graminicola,ITS,β-tubulin and EF-1α coding genes based on S.graminicola are designed to design specific primers,which can be used for the specific detection of S.graminicola.The determination of loop mediated isothermal amplification showes that the detection system established in this experiment is highly sensitive,with a minimum DNA detection concentration of 100 fg/μL,100 times that of ordinary PCR,65℃ water bath for 30 min,which is easy to operate and suitable for rapid detection in the field.2.In order to evaluate the pathogenicity of S.graminicola in different regions,the strains from 7 areas in Shanxi Province and 5 millet varieties with different resistance were treated with oospore dressing.The incidence rate of JG21 is high sensitive and JG59 is high resistant.According to the difference of pathogenicity between the two strains collected from different areas,it was found that the pathogenicity of the strains collected from Xinzhou,Changzhi and Linfen was stronger.3.The SSR molecular markers were developed for the S.graminicola genome sequence,and 3442 repeated SSR loci from single nucleotide to hexanucleotide were searched,which were located in 2742 sequences.The number of SSR types on chromosomes is randomly distributed.Followed by the number of dinucleotide to hexanucleotide repeats: 1293,1262,172,87,14.The number of SSRs of each type decreased with the increase of repetition.4.A versatility of seventeen strains was analyzed by using fifty pairs of primers,of which 18 paris had good polymorphism.A total of 55 alleles(Na)were detected in 18 pairs of primers,and an average of3.1 loci per pair.There were 42.5 effective alleles(Ne),accounting for 77.33% of the observed alleles.The average of Shannon Information Index(I)and Polymorphic Information Content(PIC)was 0.9269 and0.6077.A total of 240 loci were amplified from seventeen strains from seven regions.The average of Ne,I,PIC and Nei’s expected of heterozygosity was 31.2722,10.3283,0.7622 and 6.8881.5.According to the SSR markers,seventeen strains can be clustered into two categories,among which category I includes YQ-3,TZ-1,FY-7,TG-17,XJ-4 and FS-15;category II includes FY-8,YC-16,QX-5,DX-11/12/13/14,HS-9,HQ-10,GL-2 and CZ-6.According to Nei’s genetic distance analysis,the closer genetic distance of S.graminicola was correlated with the geographic distance.Because of the large area planting of millet,the outbreak of S.graminicola,the germ was affected by geography and so on in the evolution process,and the physiological race was produced.Based on its genetic structure,the epidemic characteristics of the disease were analyzed to provide basis for disease control and disease resistance breeding.