| Peanut scorch spot disease caused by Leptosphaerulina arachidicola is a very common disease in peanut production.The pathogen of peanut scorch spot was identified and its biological characteristics were studied in this paper.In order to further study the population characteristics of peanut scorch spot pathogen in Henan Province,the genetic diversity of 42 peanut scorch fungus strains were studied from six regions(Xinxiang,Sanmenxia,Luoyang,Zhoukou,Kaifeng and Nanyang)of Henan.The main results are as follows:(1)The isolation and identification of pathogenic fungi,morphological observation and pathogenicity determination were studied.The multilocus sequence analysis of the transcriptional spacer(ITS),of the rRNA gene,partial large subunit28 S rDNA region and part ? tubulin gene(?-tubulin)region were analyzed.The results showed that the pathogen of scorch spot disease was(Leptosphaerulina arachidicola).The study of biological characteristics showed that the strain could grow on a variety of media,and the best medium was on the medium supplemented with peanut leaves,the optimum temperature was 25?,the optimum pH was 6,the alternative of light and dark was beneficial to the mycelium growth,the best carbon nutrition was starch,and the nitrogen nutrition was beef extract and peptone.(2)Using RAPD molecular markers,8 primers were selected from 68 primers for DNA amplification of 42 peanut scorch spot pathogens,a total of 51 DNA bands were amplified,48 polymorphic bands,the polymorphic band ratio was 94.12%.The results showed that there was rich genetic diversity in isolates of L.arachidicola in Henan.The results of cluster analysis showed that when the genetic similarity coefficient was 0.70,the preliminary analysis indicated that the genetic similarity of the strains was related to the geographical sources.The results of principal component analysis showed that most of the strains in cluster I and II of UPGMA cluster analysis were clustered together.The strains JYL2 and NC3-1 were far away from other groups,and the results were basically consistent with those of cluster analysis.(3)The results of genetic diversity analysis of L.arachidicola in Henan Province showed that the order of genetic diversity of 6 populations from high to low was zks > lys > kfs > nys > smx > jxx.The Gst value of Nei's genetic differentiation degree was 0.1647,indicating that 16.47% of the variation occurred amongpopulations and 83.53% of the variation occurred within the population.The gene flow value was 2.5352(Nm > 1),which indicated that there was a certain gene flow among the six populations.(4)Nei's genetic identity(GI)and Nei's genetic distance(GD)between two populations in 6 populations of L.arachidicola in Henan Province were calculated.The smx and kfs population strains had the highest genetic identity(GI=0.9782),the lowest genetic distance(GD=0.0220),zks and nys population strain genetic identity)(GI=0.9163),and the longest genetic distance(GD=0.0874).The genetic structure of L.arachidicola in Henan Province was analyzed.The results showed that it could be classified into two groups.The results showed that most of the strains(85.71%)had a relatively single genetic component and less exchange of genetic material among subgroups.In this study,the pathogen was identified by morphological identification,pathogenicity test and multilocus phylogeny,and the biological characteristics of L.arachidicola were further studied systematically.This is the first study for the genetic diversity of L.arachidicola in Henan province,which could provide reference for further study and control of peanut leaf spot disease. |
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