Construction of an SNP fingerprinting database and population genetic analysis of 329 cauliflower cultivars

An initial exploration of core collection construction and DNA fingerprinting in Elymus sibiricus L. using SNP markers

Elymus sibiricus L., an excellent forage and ecological restoration grass, plays a key role in grassland ecological construction and the sustainable development of animal husbandry. In China, the wild germplasm resources of E. sibiricus are abundant, and they are shaped by similar and contrasting climatic conditions to form distinct populations, which enrich the genetic diversity of E. sibiricus. To more comprehensively aggregate E. sibiricus germplasm resources at a lower cost and to more accurately utilize its genetic variation, this study conducted a preliminary exploration of core germplasm collections and fingerprinting of E. sibiricus using single nucleotide polymorphism (SNP) markers. By combining multiple evaluation measures with weighted processing, we successfully identified 36 materials from 90 wild E. sibiricus samples to serve as a core collection. Genetic diversity assessments, allele evaluations, and principal component analyses of the 36 core germplasm samples all indicate that these 36 samples accurately and comprehensively represent the genetic diversity of all 90 E. sibiricus germplasm accessions. Additionally, we identified 290 SNP loci from among the high-quality SNP loci generated by whole-genome sequencing of the 90 E. sibiricus samples as candidate markers. Of these, 52 SNP loci were selected as core markers for DNA fingerprinting of E. sibiricus. Using kompetitive allele-specific PCR (KASP) technology, we also performed population origin identification for 60 wild E. sibiricus germplasm accessions based on these core markers. The core SNP markers screened in this study were able to accurately distinguish between E. sibiricus germplasms from the Qinghai-Tibet Plateau and those from elsewhere. This study not only provides a reference for the continued collection and identification of E. sibiricus germplasm resources but also offers a scientific basis for their conservation and utilization.

Genetic Variation Analysis and Development of KASP Marker for Leaf Area and Hight in Southern-Type Populus deltoides

Populus deltoides holds significant ecological and economic importance and is a crucial gene donor for the world's staple poplar varieties. To select and breed P. deltoides with improved agronomic traits, nine growth and leaf traits were examined in 375 different genotypes, assessing their genetic diversity and performing correlation and comprehensive ranking analyses. Phenotyping results were then utilized to screen a total of 2,009,263 SNP (single nucleotide polymorphism) loci significantly associated with the nine phenotypic traits. A total of 45 SNP loci exhibited significant associations with growth traits based on a general linear model (GLM) analysis. By analyzing the Linkage disequilibrium (LD) block of five SNP loci with significant leaf area and height, we identified five candidate genes related to leaf area and height. Three of the five SNP loci were successfully validated using KASP (kompetitive allele-specific PCR) assays. One loci Chr08_16007979 was closely linked with leaf area, and two loci Chr05_12148738, and Chr05_17106547 were closely linked with height. The developed functional KASP markers offer valuable insights for subsequent further marker-assisted breeding and genetic improvement studies in southern-type poplars.

Development of KASP markers, SNP fingerprinting and population genetic analysis of Cymbidium ensifolium (L.) Sw. germplasm resources in China

Cymbidium ensifolium (L.) Sw. is a valuable ornamental plant in the genus Cymbidium, family Orchidaceae, with high economic and ecological significance. However, the lack of population genetic information and molecular markers has hindered the development of the sales market and genetic breeding of C. ensifolium despite the abundance of commercial cultivars available. In this study, we aimed to develop a set of single nucleotide polymorphism (SNP) markers to distinguish the main cultivated C. ensifolium cultivars in China and provide technical support for domestic cultivar protection, registration, and market rights protection. A total of 1,280,516 high-quality loci were identified from 10,021,591 SNPs obtained by sequencing 50 C. ensifolium commercial cultivars using double digest restriction site-assisted DNA sequencing technology. A total of 7,599 SNPs were selected for kompetitive allele-specific PCR (KASP) primer design, and 4,360 were successfully designed as KASP markers. Population structure analysis revealed that the 50 commercial cultivars were best divided into four populations, with some correlation between the group distribution and the morphological and geographical characteristics of the germplasm. Using the genotyping results from 28 KASP markers screened from the cultivars, a minimum set of 11 markers was identified that could distinguish 83 C. ensifolium commercial cultivars completely, with the remaining 17 markers serving as extended markers. The average PIC value of the 11 markers was 0.345, which was considered medium polymorphism. DNA fingerprints were constructed for the 83 cultivars on the basis of the 11 KASP markers, providing a new approach for mapping DNA fingerprints in C. ensifolium cultivars with high efficiency, accuracy, and low cost compared with traditional methods.

SNP loci identification and KASP marker development system for genetic diversity, population structure, and fingerprinting in sweetpotato (Ipomoea batatas L.)

Sweetpotato (Ipomoea batatas L.), an important food and industrial crop in the world, has a highly heterozygous hexaploid genome, making the development of single nucleotide polymorphism (SNP) markers challenging. Identifying SNP loci and developing practical SNP markers are crucial for genomic and genetic research on sweetpotato. A restriction site-associated DNA sequencing analysis of 60 sweetpotato accessions in this study yielded about 7.97 million SNPs. Notably, 954 candidate SNPs were obtained from 21,681 high-quality SNPs. Based on their stability and polymorphism, 274 kompetitive allele specific PCR (KASP) markers were then developed and uniformly distributed on chromosomes. The 274 KASP markers were used to genotype 93 sweetpotato accessions to evaluate their utility for assessing germplasm and analyzing genetic diversity and population structures. These markers had respective mean values of 0.24, 0.34, 0.31, and 0.25 for minor allele frequency, heterozygosity, gene diversity, and polymorphic information content (PIC). Their genetic pedigree led to the division of all accessions into three primary clusters, which were found to be both interrelated and independent. Finally, 74 KASP markers with PIC values greater than 0.35 were selected as core markers. These markers were used to construct the DNA fingerprints of 93 sweetpotato accessions and were able to differentiate between all accessions. To the best of our knowledge, this is the first attempt at the development and application of KASP markers in sweetpotato. However, due to sweetpotato's polyploidy, heterozygosity and the complex genome, the KASP marker conversion rate in this study was relatively low. To improve the KASP marker conversion rate, and accuracies in SNP discovery and marker validation, further studies including more accessions from underrepresented regions are needed in sweetpotato.

Establishment and application of a SNP molecular identification system in Grifola frondosa

Germplasm resources of edible mushrooms are essential for the breeding of varieties with improved traits. Analysis of the genetic diversity of Grifola frondosa germplasm resources and clarification of the genetic relationships among strains can provide valuable information for the selection of breeding parents. A total of 829,488 high-quality SNP loci were screened from 2,125,382 SNPs obtained by sequencing 60 G. frondose. Phylogenetic analysis, PCA, and population structure analysis based on the high-quality SNPs showed that the 60 strains could be divided into five subgroups, and the clustering results were consistent with the geographical distributions of these strains. Based on high-quality SNP loci, a core collection containing 18 representative germplasm resources was constructed, and 1,473 Kompetitive Allele-Specific PCR markers were obtained. A total of 722 SNP markers in the exonic regions were screened using KASP-genotyping experiments, and 50 candidate SNP markers and 12 core SNP markers were obtained. Genetic fingerprints of G. frondosa germplasm resources were constructed based on the selected SNP markers; these fingerprints provide an accurate, rapid, convenient, and efficient method for the identification of G. frondosa germplasm resources. The results of this study have important implications for the preservation and utilization of G. frondosa germplasm resources and the identification of varieties.

Genetic Analysis and Construction of a Fingerprint for Licensed Triadica sebifera Cultivars Using SSR Markers

Triadica sebifera is an important landscaping tree species because of its colorful autumn leaves. In recent years, some cultivars have been bred and licensed, but it can be difficult to identify them from their morphological traits due to their similar phenotypes. To explore the genetic relationships and construct a fingerprint of the cultivars, the licensed T. sebifera cultivars were analyzed using SSR markers. A total of 179 alleles were identified among the 21 cultivars at 16 SSR loci, and these alleles exhibited a high level of genetic diversity (He = 0.86). The genetic variations mainly occurred among cultivars based on an analysis of molecular variance (AMOVA). According to phylogenetic analysis, principal coordinate analysis (PCoA), and Bayesian clustering analysis, the genetic relationships were independent of geographic distances, which may be mainly due to transplantations between regions. Some cultivars with different leaf colors showed obvious genetic differentiation and may be preliminary candidates for cross-breeding. Finally, the fingerprint for the licensed cultivars was constructed with two SSR markers. The results of this study can provide technical support for the application and legal protection of licensed Triadica sebifera cultivars.

Genetic Diversity Analysis and Core Germplasm Construction of Rubus chingii Hu

Rubus chingii Hu is the only species that is used for both edible and medicinal purposes among the 194 species of the genus Rubus in China. It is well known for its sweet and sour fresh fruits that are rich in vitamins and for its dried immature fruits that are used to treat kidney-related ailments. This study aims to evaluate genetic diversity and population structure and build a core germplasm repository of 132 R. chingii accessions from the provinces of Jiangxi and Fujian, using Hyper-seq-derived single-nucleotide polymorphism (SNP) markers. This is the first genetic study of R. chingii based on SNP molecular markers, and a total of 1,303,850 SNPs and 433,159 insertions/deletions (InDels) were identified. Low values for observed heterozygosity, nucleotide diversity (Pi) and fixation indexes (Fis) indicated low genetic diversity within populations, and an analysis of molecular variance (AMOVA) showed that 37.4% and 62.6% of the variations were found between populations and within samples, respectively. Four main clusters were identified by means of neighbor-joining (NJ) trees, the ADMIXTURE program and principal component analysis (PCA). Based on the genetic diversity, we finally constructed 38 representative core collections, representing 50% of the total core germplasm samples and 95.3% of the genotypes. In summary, the results of our study can provide valuable information on the genetic structure of R. chingii germplasm resources, which is helpful for further explorations of potential high-quality genes and for formulating future breeding and conservation strategies.

Construction of SNP fingerprints and genetic diversity analysis of radish (Raphanus sativus L.)

Radish (Raphanus sativus L.) is a vegetable crop with economic value and ecological significance in the genus Radish, family Brassicaceae. In recent years, developed countries have attached great importance to the collection and conservation of radish germplasm resources and their research and utilization, but the lack of population genetic information and molecular markers has hindered the development of the genetic breeding of radish. In this study, we integrated the radish genomic data published in databases for the development of single-nucleotide polymorphism (SNP) markers, and obtained a dataset of 308 high-quality SNPs under strict selection criteria. With the support of Kompetitive Allele-Specific PCR (KASP) technology, we screened a set of 32 candidate core SNP marker sets to analyse the genetic diversity of the collected 356 radish varieties. The results showed that the mean values of polymorphism information content (PIC), minor allele frequency (MAF), gene diversity and heterozygosity of the 32 candidate core SNP markers were 0.32, 0.30, 0.40 and 0.25, respectively. Population structural analysis, principal component analysis and genetic evolutionary tree analysis indicated that the 356 radish materials were best classified into two taxa, and that the two taxa of the material were closely genetically exchanged. Finally, on the basis of 32 candidate core SNP markers we calculated 15 core markers using a computer algorithm to construct a fingerprint map of 356 radish varieties. Furthermore, we constructed a core germplasm population consisting of 71 radish materials using 32 candidate core markers. In this study, we developed SNP markers for radish cultivar identification and genetic diversity analysis, and constructed DNA fingerprints, providing a basis for the identification of radish germplasm resources and molecular marker-assisted breeding as well as genetic research.