Analysis Of Population Genetic Structure,mating Type And Sensitivity Of Exserohilum Turcicum In Henan Province

Corn is an important food crop,which is second only to rice and wheat in China.Henan Province is a large province for corn cultivation.It is one of the key steps to ensure high yield and stable yield of corn that promptly follow up the evolution information of corn diseases and formulate countermeasures in Henan Province.Northern Corn Leaf Blight is an important disease on corn,which has great harm to corn yield and quality.In order to effectively prevent and control corn spot disease in Henan Province,this study systematically studied the population genetic structure,mating type and sensitivity to pyraclostrobin and iprodione in the strain of Exserohilum turcicum in Henan Province.The main findings are as follows:（1）Successfully developed 23 pairs of SSR primers from the genome of Exserohilum turcicum.The genetic diversity and genetic structure of 48 strains of Exserohilum turcicum in Henan Province were analyzed with 6 pairs of SSR primers.UPGMA clustering can divide 48 strains into 2 groups at a similarity coefficient of0.66,group I contains 38 strains,and group II contains 10 strains.There was no significant correlation between the clustering of strains and geographic sources.The total genetic diversity of Exserohilum turcicum in Henan Province is rich.The Nei’s gene diversity index and the Shannon diversity index are 0.6694 and 1.3121,respectively.The genetic level of some of the populations of Exserohilum turcicum in Henan Province is very high.The genetic diversity Hs in the population is 0.5294,which is significantly higher than the 0.222 of the genetic diversity Dst between populations.Genetic structure analysis showed that 48 strains were most likely to be derived from two ancestral subgroups.Among them,the proportion of subgroup I in 21strains reached more than 90%,and the proportion of subgroup II in 18 strains reached more than 90%.Most（83.3%）strains have relatively single genetic components,and there are few genetic material exchanges between the two subgroups.（2）The mating type of 48 strains was determined by two methods,normal PCR and multiplex PCR.The results showed that A was a dominant mating type with 34 A mating strains;a was a weak mating type with 14 a mating strains.Seven of the eight geographical populations contain two mating strains,and only six strains of the Sanmenxia population are all A mating type.（3）The sensitivity of Exserohilum turcicum strains to pyraclostrobin and iprodione in Henan Province was determined by mycelial growth rate method.The results showed that the EC₅₀0 value of pyraclostrobin was 0.0001⁰.4146 mg/L and the average EC₅₀0 was 0.0362 mg/L.The EC₅₀0 value of iprodione in the range of0.0035⁰.9823 mg/L,the average EC₅₀0 value is 0.1900 mg/L.The Exserohilum turcicum in Henan Province is highly sensitive to the commonly used pyraclostrobin and iprodione fungicide.This study is the first comprehensive analysis of Exserohilum turcicum in Henan Province,and clarifies the genetic diversity,mating composition,and resistance levels of pyraclostrobin and iprodione in Henan Province.These findings are of great significance for scientific guidance in the prevention and treatment of Northern Corn Leaf Blight in Henan Province.