| Potato is an important food and vegetable crop in the world.Late blight caused by the oomycete Phytophthora infestans(Mont.)de Bary(P.infestans)is the most destructive disease for potato worldwide.It has been proved that the most efficient way to control late blight is the use of resistant cultivars.However,cultivated potato resistant resources are lacking,and the resistance genes are easily overcome by new P.infestans isolates,the breeding process against late blight is slow.Therefore,screening for excellent germplasm resources,mining good resistance genes,and clarifying the interaction mechanism between potato and P.infestans are particularly important for guiding disease resistance breeding.This paper carried out a series of work on potato germplasm resources evaluation for late blight resistance,genetic diversity assessment and late blight resistance-related gene analysis.The main results are as follows:1.The resistance of late blight of 192 potato accessions including species of wild tuberosum species,S.andigena,and S.tuberosum L.was evaluated by using five different P.infestans isolates.Ten accessions with excellent resistance to late blight,e.g.BCP1-3,JAM1-4,CPH1-14,TRD2-1,were obtained.It is of great significance and useful to explore novel late blight resistance genes,select the parents for potato late blight resistance breeding,and broaden the genetic background of potato cultivars in future.2.Thirty SSR markers which covered all the 12 chromosomes of potato genome were used to analyze the genetic diversity of 189 potato accessions.A total of 173 alleles were amplified,of which 171 were polymorphic.Alleles amplified by each marker ranged from 3 to 12,with a mean of 5.77.The polymorphic information content values(PIC)ranged from 0.1975 to 0.5329,with a mean of 0.3559.Based on the Neighbor-Joining tree construction,all the 189 accessions tested were clustered into 3 general groups(Group 1,Group 2 and Group 3).Group 1 consisted of 44 accessions,of which 35 belong to wild tuberosum species,and group 2 included 21 accessions,of which 17 belong to wild tuberosum species;Group 3 included 124 accessions,mainly gathered by cultivated potato accessions.Group 3 could be further divided into three sub-groups of A,B and C.Among them,the A sub-group mainly consisted of S.andigena genotypes,and the B and C subgroups mainly gathered cultivated potato accessions.The results of this study show that the use of SSR molecular marker can clearly distinguish wild tuberosum species,S.andigena,and S.tuberosum L.Compared with the evaluation results of disease resistance,it was found that the resistance of 189 accessions to the five P.infestans isolates was scattered among the clusters classified by SSR markers,showing that there was no obvious genetic relationship between different resistant accessions.3.A 20 K SNP chip was used to genotype 72 potato accessions,and the phylogenetic tree was constructed to reveal the evolutionary relationship between 71 germplasm accessions,which were well genotyped.71 accessions were divided into 4 groups(Q1,Q2,Q3,and Q4)based on group structure and principal component analysis.Q1 and Q2 were mainly consisted of wild tuberosum species genotypes,Q3 contained genotypes of wild tuberosum species,S.andigena and diploid accessions derived from wild tuberosum species and S.tuberosum L.,and Q4 was mainly gathered by S.tuberosum L.genotypes.The accessions of wild tuberosum species and S.tuberosum L.were divided into different groups using SNP chip.The resistance of the 71 accessions to the five P.infestans isolates was relatively concentrated in the clusters classified by the SNP markers.4.The resistance-related gene expression profiles of S.andigena genotype 03112-233 were established.Almost 20% and 16% genes in 03112-233 were differentially expressed in response to 90128 and CN152,respectively Further analysis revealed that in compatible and incompatible interactions,SA-and ET-mediated disease resistance signaling pathways are involved in the resistance of 03112-233 to P.infestans isolates 90128 and CN152,while JA-mediated signaling pathways are inhibited.Sixteen and three candidate genes related to incompatible and compatible interactions were also predicted,respectively,and the molecular mechanism of incompatible and compatible interactions was characterized.Our results provide a valuable resource for understanding the compatible and incompatible interactions between different P.infestans isolates and potato. |
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