The Genetic Diversity Analysis Using ISSR And Identification Of Two Kinds Of Pathogenic Funguse On Carya Illinoemis

In this study,33 Carya illinoemis germplasms resources were ISSR-PCR molecular markers,relationship tree maps between different varieties were established,and dry rot and leaf spot of thin shell pecan were studied to identify the pathogens,providing theoretical basis for genetic diversity analysis and disease control of thin shell pecan germplasm resources.The results of the studies are as follows:1.The optimal PCR reaction system for the molecular markers of Carya illinoemis was established: pre-denaturation at 94 °C for 4 minutes,denaturation at 94 °C for 30 seconds,annealing temperature between 50 °C and 53 °C for 45 seconds,and 72 °C for 35 seconds.After that,the repair was carried out again at 72 ° C for 10 minutes,and stored in a refrigerator at 4 ° C after the completion of the amplification.2.The PCR reaction products were detected by electrophoresis,and a total of 58 bands with clear bands were obtained,of which 45 were polymorphic sites,and the percentage of polymorphic sites(PPB)was 77.59%,the genetic diversity(H)of Nei's is 0.3010,and the Shannon Information Index(I)is 0.4182.The results of the study are rich in genetic diversity.According to the NTSYS software,we calculated the UPGMA genetic distance between the 33 varieties of Carya illinoemis in the range of 0.67-0.84,and plotted the cluster analysis tree.All varieties are divided into five groups,namely A,B,C,D,E,of which there are up to 11 types of D varieties,and E class contains at least one species of haihetao,indicating that haihetao has the longest genetic similarity.3.The branches and diseased leaves of Carya illinoemis lesions were isolated and purified,and two strains were obtained.Both pathogens were pathogenic strains by Koch's law.Combined with morphology and rDNA-ITS molecular biology analysis,the pathogen of Carya illinoemis dry rot was identified as Botryosphaeria dothidea,and the pathogen of leaf spot was Alternaria.