Genotyping pepper varieties using Target SNP-seq reveals that population structure clusters according to fruit shape

Abstract

Background The widely cultivated pepper (Capsicum spp.) is one of the most diverse vegetables; however, little research has characterized the genetic diversity and relatedness of commercial varieties grown in China. In this study, a panel of single-nucleotide polymorphisms (SNPs) was created that consisted of 97 perfect SNPs, which were identified using re-sequencing data from 35 diverse C. annuum lines. Based on this panel, a Target SNP-seq was designed that combined the multiplex amplification of the perfect SNPs with Illumina sequencing to detect polymorphisms across 271 commercial pepper varieties. Results The perfect SNPs panel had a high discriminating capacity due to the average value of polymorphism information content (PIC), observed heterozygosity (Ho), expected heterozygosity (He), and minor allele frequency (MAF), which were 0.31, 0.28, 0.4, and 0.31, respectively. Notably, the studied pepper varieties were morphologically categorized based on fruit shape; blocky, long horn, short horn, and linear-fruited. The long horn-fruited population exhibited the most genetic diversity followed by the short horn, linear, and blocky-fruited populations. A set of 35 core SNPs were then used as KASPar markers, another robust genotyping technique for variety identification. Analysis of genetic relatedness using principal component analysis (PCA) and phylogenetic tree construction indicated that the four fruit shape populations clustered separately with limited overlaps. Based on STRUCTURE clustering, it was possible to divide the varieties into five subpopulations, which correlated with fruit shape. Further, the subpopulations were statistically different according to a randomization test and Fst statistics. Notably, two SNP loci, CaSNP118 and CaSNP053, which are located on chromosome 11 and 6 were significantly associated with fruit shape (p < 1.0 × 10 -4) Conclusions Target SNP-seq developed in this study appears as an efficient power tool to detect the genetic diversity, population relatedness and molecular breeding in pepper. Moreover, this study demonstrates that the genetic structure of the pepper varieties is significantly influenced by breeding programs focused on fruit shape.

Identification of elite fiber quality loci in upland cotton based on the genotyping-by-target-sequencing technology

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Development of the maize 5.5K loci panel for genomic prediction through genotyping by target sequencing

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