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Alcea rosea L. are herbaceous plants with several cultivars and a wide range of flower types and colors. They are commonly grown for their ornamental value and are widely cultivated worldwide. However, the lack of genetic diversity and effective molecular markers has hindered efforts to improve and identify A. rosea cultivars. In this study, specific-locus amplified fragment sequencing (SLAF-seq) was employed to develop markers for 38 samples of A. rosea (17 samples from Chengdu Botanical Garden, 19 samples from Flower Valley, and 2 samples from wild species) using the Hibiscus syriacus L. genome as a reference for enzyme digestion prediction. A total of 1,345,364 SLAF tags were obtained by high-throughput sequencing, with an average sequencing depth of 31.80X. There were 162,476 polymorphic SLAF tags and a total of 425,098 single nucleotide polymorphism (SNP) markers were discovered and used for phylogenetic tree, population structure, principal component, and genetic diversity analyses. The results showed that relatedness among samples was generally correlated with plant type, flower type, and flower color. At the same time, the population genetic structure and phylogenetic relationships of high-stem A. rosea in the Flower Valley were more complex. Besides, the genetic diversity of the wild species was higher than cultivated species. At last, 26 variant loci were also screened and identified as core markers for DNA fingerprinting for A. rosea identification. The development of SNP markers and the construction of DNA fingerprints in this study provide references for future analyses in A. rosea cultivar identification, genetic diversity, and molecular breeding. [ABSTRACT FROM AUTHOR]

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Garlic is an important vegetable and condiment that has good medical and health care effects. At present, the origin of Chinese garlic and its association with other types of quality are limited to the molecular marker level, and there are few reports at the genome level. Therefore, this study is based on the specific length amplified fragment sequencing (SLAF-seq) of 102 copies of garlic germplasm resources, the group structure, and further screening of the core germplasm. SLAF-seq of 102 garlic cultivars yielded 1949.85 Mb of clean data and 526,432,275 SNPs. Through principal component analysis, evolutionary tree, population structure, and genetic relationship analysis, all garlic cultivars were divided into 3 groups. Among them, Group 1 contains 45 Chinese cultivars and 1 Egyptian cultivar, which are distributed mainly in the coastal and central areas of China. Group 2 contains 36 Chinese cultivars and 1 U.S. cultivar, which are distributed mainly in Northwest China. Group 3 contains 19 Chinese cultivars, which are distributed mainly in Xinjiang, China. The genetic diversity results indicate that the fixation index (Fst) values of Group 1 and Group 2 are lower than those of Group 1 and Group 3 and that the diversity of nucleotides (π) of Group 3 is greater than those of Group 2 and Group 1. Finally, the 30 parts of the cultivars were used as the core germplasms, and there was no difference between the two cultivars in terms of core quality. In summary, this study provides tags for the determination of garlic molecular markers and genotypes and provides a theoretical basis for subsequent resource protection and utilization, genetic positioning of important agronomic traits, and molecular marking agglomeration breeding. [ABSTRACT FROM AUTHOR]

Alicella gigantea, the largest amphipod scavengers found to date, play key roles in the food web of the hadal ecosystem. However, the genetic structure of A. gigantea populations among different trenches has not been reported yet. In this study, SNP (single-nucleotide polymorphism) markers were developed for three A. gigantea geographic populations collected from the southern Mariana Trench (SMT), the central New Britain Trench (CNBT), and the eastern New Britain Trench (ENBT), based on the SLAF-seq (specific locus amplified fragment sequencing) technology. A total of 570,168 filtered SNPs were screened out for subsequent population genetic analysis. Results showed that the inbreeding levels across the three geographic populations were relatively low, and the genomic inbreeding coefficients of the three populations were similar in magnitude. Based on the results of phylogenetic analysis, population structure analysis, and principal component analysis, it is believed that the three A. gigantea geographic populations belong to the same population, and the kinship relationship between the ENBT and CNBT populations is close. Moreover, the differential candidate adaptive sites on the SNPs suggest that there may be variations in metabolic rates among the three geographic populations, possibly linked to differences in food availability and sources in different trenches, ultimately resulting in different survival strategies in A. gigantea populations within distinct trenches. Compared with the Mariana Trench, the New Britain Trench has a richer organic matter input, and it is speculated that the A. gigantea Mariana Trench population may adopt a lower metabolic rate to cope with the harsher environment of nutrient deficiency. [ABSTRACT FROM AUTHOR]

Abstract Background Carcass traits are essential economic traits in the commercial pig industry. However, the genetic mechanism of carcass traits is still unclear. In this study, we performed a genome-wide association study (GWAS) based on the specific-locus amplified fragment sequencing (SLAF-seq) to study seven carcass traits on 223 four-way intercross pigs, including dressing percentage (DP), number of ribs (RIB), skin thinkness (ST), carcass straight length (CSL), carcass diagonal length (CDL), loin eye width (LEW), and loin eye thickness (LET). Results A total of 227,921 high-quality single nucleotide polymorphisms (SNPs) were detected to perform GWAS. A total of 30 SNPs were identified for seven carcass traits using the mixed linear model (MLM) (p

Abstract Objective The objective of this study was to examine the genetic diversity within and between farmed populations of Onychostoma macrolepis, and to establish a foundation for enhancing the genetic resources of breeding groups through the introduction of new individuals and crossbreeding. A total of 49 individuals were subjected to sequencing using Specific-Locus Amplified Fragment Sequencing (SLAF-seq), one of the restriction site-associated DNA sequencing technologies. The single nucleotide polymorphisms(SNPs)were identified to conduct the analyzation of phylogeny population structure, principal component and genetic diversity. Results A total of 853,067 SNPs were identified. The results of the phylogenetic analysis revealed that each sample was genetically clustered into three distinct groups: ZhenPing (ZP), LanGao parents (LG), and their progeny population (LG-F1). Each population was observed to be clustered together. Analysis of population genetic diversity revealed that the observed heterozygosity (Ho) ranged from 0.200 to 0.230, the expected heterozygosity (He) ranged from 0.280 to 0.282, and the polymorphic information content (PIC) ranged from 0.228 to 0.230. These results indicate that the genetic diversity of the population is low and the signs of long-term interbreeding are obvious, but there are differences between the populations, and the genetic diversity of the population can be improved by hybridization in different regions.

Abstract Coix lacryma-jobi L. is one of the most economically and medicinally important corns. This study constructed a high-density genetic linkage map of C. lacryma-jobi based on a cross between the parents 'Qianyi No. 2' × 'Wenyi No. 2' and their F2 progeny through high-throughput sequencing and the construction of a specific-locus amplified fragment (SLAF) library. After pre-processing, 325.49 GB of raw data containing 1628 M reads were obtained. A total of 22,944 high-quality SLAFs were identified, among which 3952 SLAFs and 3646 polymorphic markers met the requirements for the construction of a genetic linkage map. The integrated map contained 3605 high-quality SLAFs, which were grouped into ten genetic linkage groups. The total length of the map was 1620.39 cM, with an average distance of 0.45 cM and an average of 360.5 markers per linkage group. This report presents the first high-density genetic map of C. lacryma-jobi. This map was constructed using an F2 population and SLAF-seq approach, which allows the development of a large number of polymorphic markers in a short period. These results provide a platform for precise gene/quantitative trait locus (QTL) mapping, map-based gene separation, and molecular breeding in C. lacryma-jobi. They also help identify a target gene for tracking, splitting quantitative traits, and estimating the phenotypic effects of each QTL for QTL mapping. They are of great significance for improving the efficiency of discovering and utilizing excellent gene resources of C. lacryma-jobi.

Objective: The objective of this study was to examine the genetic diversity within and between farmed populations of Onychostoma macrolepis, and to establish a foundation for enhancing the genetic resources of breeding groups through the introduction of new individuals and crossbreeding. A total of 49 individuals were subjected to sequencing using Specific-Locus Amplified Fragment Sequencing (SLAF-seq), one of the restriction site-associated DNA sequencing technologies. The single nucleotide polymorphisms(SNPs)were identified to conduct the analyzation of phylogeny population structure, principal component and genetic diversity. Results: A total of 853,067 SNPs were identified. The results of the phylogenetic analysis revealed that each sample was genetically clustered into three distinct groups: ZhenPing (ZP), LanGao parents (LG), and their progeny population (LG-F1). Each population was observed to be clustered together. Analysis of population genetic diversity revealed that the observed heterozygosity (Ho) ranged from 0.200 to 0.230, the expected heterozygosity (He) ranged from 0.280 to 0.282, and the polymorphic information content (PIC) ranged from 0.228 to 0.230. These results indicate that the genetic diversity of the population is low and the signs of long-term interbreeding are obvious, but there are differences between the populations, and the genetic diversity of the population can be improved by hybridization in different regions. [ABSTRACT FROM AUTHOR]

Background: Carcass traits are essential economic traits in the commercial pig industry. However, the genetic mechanism of carcass traits is still unclear. In this study, we performed a genome-wide association study (GWAS) based on the specific-locus amplified fragment sequencing (SLAF-seq) to study seven carcass traits on 223 four-way intercross pigs, including dressing percentage (DP), number of ribs (RIB), skin thinkness (ST), carcass straight length (CSL), carcass diagonal length (CDL), loin eye width (LEW), and loin eye thickness (LET). Results: A total of 227,921 high-quality single nucleotide polymorphisms (SNPs) were detected to perform GWAS. A total of 30 SNPs were identified for seven carcass traits using the mixed linear model (MLM) (p < 1.0 × 10− 5), of which 9 SNPs were located in previously reported quantitative trait loci (QTL) regions. The phenotypic variation explained (PVE) by the significant SNPs was from 2.43 to 16.32%. Furthermore, 11 candidate genes (LYPLAL1, EPC1, MATN2, ZFAT, ZBTB10, ZNF704, INHBA, SMYD3, PAK1, SPTBN2, and ACTN3) were found for carcass traits in pigs. Conclusions: The GWAS results will improve our understanding of the genetic basis of carcass traits. We hypothesized that the candidate genes associated with these discovered SNPs would offer a biological basis for enhancing the carcass quality of pigs in swine breeding. [ABSTRACT FROM AUTHOR]

To ascertain the effect of low-light stress (80 μmol·m−2·s−1) on cucumbers, we report on improving and breeding low-light-tolerant varieties by mining genes related to low-light tolerance. In this study, the quantitative trait locus (QTL) mapping of cucumber plant height and internode length under low-light stress was conducted using the F2 population, employing specific-length amplified fragment sequencing (SLAF-seq) and phenotypic analysis. A genetic map with a total length of 1114.29 c M was constructed from 1,076,599 SNPs, and 2233 single-nucleotide polymorphism (SNP) markers were distributed on seven linked groups, with an average map distance of 0.50 c M. Two QTLs related to plant height, CsPlH5.1 and CsPlH6.1, were detected on Chr.5 and Chr.6, with a cumulative contribution rate of 16.33%. The contribution rate (PVE), max LOD value, additive effect (ADD), and dominant effect (DOM) of CsPlH5.1 were 9.446%, 4.013, 1.005, and 0.563, respectively. CsPlH5.1 was located between 4,812,907 and 5,159,042 in the Gy14_V2.0 genome of cucumber, with a genetic distance of 0.32 Mb; the interval contained 41 candidate genes, and CsPlH6.1 was found to be located between Marker537985 (171.10 c M) and Marker537984 (171.55 c M), a range containing only one candidate gene. A total of 42 candidate genes related to photosynthesis, chloroplast development, abiotic stress, and plant growth were found in the location range associated with plant height. Simultaneously, a QTL (Csnd2_NdL6.1) for the second internode length was detected, and the max LOD, ADD, and DOM values were 5.689, 0.384, and −0.19, respectively. Csnd2_NdL6.1 was located between 29,572,188 and 29,604,215, with 0.03 Mb on Chr.6 including seven candidate genes. The molecular function of the CsGy6G032300 gene is involved with the binding of calcium ions, which may be related to the elongation and growth of plants; however, the population needs to be further expanded for acceptable localization verification. The results of this study provide a preliminary basis for the mining of essential genes of cucumber's low-light tolerance and identifying low-light-tolerance genes. [ABSTRACT FROM AUTHOR]

Coix lacryma-jobi L. is one of the most economically and medicinally important corns. This study constructed a high-density genetic linkage map of C. lacryma-jobi based on a cross between the parents 'Qianyi No. 2' × 'Wenyi No. 2' and their F2 progeny through high-throughput sequencing and the construction of a specific-locus amplified fragment (SLAF) library. After pre-processing, 325.49 GB of raw data containing 1628 M reads were obtained. A total of 22,944 high-quality SLAFs were identified, among which 3952 SLAFs and 3646 polymorphic markers met the requirements for the construction of a genetic linkage map. The integrated map contained 3605 high-quality SLAFs, which were grouped into ten genetic linkage groups. The total length of the map was 1620.39 cM, with an average distance of 0.45 cM and an average of 360.5 markers per linkage group. This report presents the first high-density genetic map of C. lacryma-jobi. This map was constructed using an F2 population and SLAF-seq approach, which allows the development of a large number of polymorphic markers in a short period. These results provide a platform for precise gene/quantitative trait locus (QTL) mapping, map-based gene separation, and molecular breeding in C. lacryma-jobi. They also help identify a target gene for tracking, splitting quantitative traits, and estimating the phenotypic effects of each QTL for QTL mapping. They are of great significance for improving the efficiency of discovering and utilizing excellent gene resources of C. lacryma-jobi. [ABSTRACT FROM AUTHOR]

Abstract Background Soybean is one of the most important oil crops in the world, and its protein and fat are the primary sources of edible oil and vegetable protein. The effective components in soybean protein and fat have positive effects on improving human immunity, anti-tumor, and regulating blood lipids and metabolism. Therefore, increasing the contents of protein and fat in soybeans is essential for improving the quality of soybeans. Results This study selected 292 soybean lines from different regions as experimental materials, based on SLAF-seq sequencing technology, and performed genome-wide association study (GWAS) on the phenotype data from 2019–2021 Planted at the experimental base of Jilin Agricultural University, such as the contents of protein and fat of soybeans. Through the GLM model and MLM model, four SNP sites (Gm09_39012959, Gm12_35492373, Gm16_9297124, and Gm20_24678362) that were significantly related to soybean fat content were associated for three consecutive years, and two SNP sites (Gm09_39012959 and Gm20_24678362) that were significantly related to soybean protein content were associated. By the annotation and enrichment of genes within the 100 Kb region of SNP loci flanking, two genes (Glyma.09G158100 and Glyma.09G158200) related to soybean protein synthesis and one gene (Glyma.12G180200) related to lipid metabolism were selected. By the preliminary verification of expression levels of genes with qPCR, it is found that during the periods of R6 and R7 of the accumulation of soybean protein and fat, Glyma.09G158100 and Glyma.09G158200 are positive regulatory genes that promote protein synthesis and accumulation, while Glyma.12G180200 is the negative regulatory gene that inhibits fat accumulation. Conclusions These results lay the basis for further verifying the gene function and studying the molecular mechanisms regulating the accumulation of protein and fat in soybean seeds.

In order to reveal the genetic diversity of wild Medicago falcata L. in Xinjiang, SLAF-seq technology was used to develop SNP materials. The results showed that the average Q30 value and GC value were 96.32% and 37.99%, respectively. A total of 376 641 SLAF tags and 119 331 polymorphic SLAF tags were developed. The average integrity of SNP was 24.77% and the average heterozygosity was 5.53%. The average values of effective allele number, observed allele number, expected heterozygosity, observed heterozygosity, and Shnnon Wiener index were 1.380, 1.594, 0.220, 0.117, and 0.327, respectively. The study indicates that cluster analysis divides the materials into seven categories, PCA divides the materials into three categories, but the samples come from the same ancestor. [ABSTRACT FROM AUTHOR]

Tamarix chinensis Lour. is native to China and has characteristics such as heat resistance and salt alkali resistance. It is mostly distributed in coastal or inland desert areas of China. In this article, 36 samples of Tamarix chinensis collected from the Bohai Rim region (11 samples from Shandong, 5 samples from Tianjin, 15 samples from Hebei, and 5 samples from Liaoning) were sequenced by specific locus amplified fragment sequencing (SLAF-seq). Based on the willow genome as a reference, the system design of the experimental scheme was carried out by bioinformatics analysis. The specific length of DNA fragments was screened, and the SLAF-seq library was constructed. A large number of sequences were obtained by high-throughput sequencing. Then, polymorphic SLAF tags were obtained by software analysis and comparison. Finally, a large number of specific single nucleotide polymorphisms (SNPs) were developed on the polymorphic SLAF tags. A total of 2,341,663 SLAF tags were obtained, including 51,985 polymorphic SLAF tags. All SNPs were filtered according to integrity > 0.5 and MAF > 0.05, and 157,821 highly consistent SNPs were obtained. The SNPs were analyzed by statistical methods, and 36 Tamarix samples from four regions were obtained. Phylogenetic tree, population structure, and principal component analyses were completed, which revealed the genetic differentiation between individuals at the genome level. The results showed that the Tamarix chinensis from the four regions all originated from the same ancestor, but due to the different growth environment and geographical location, genetic differentiation occurred in the process of growth and development. However, the genetic differences among the individuals were small. Through cluster analysis, clustering phenomenon was observed for some varieties. [ABSTRACT FROM AUTHOR]

Taxus cuspidata is a rare plant with important medicinal and ornamental value. Aiming at the obvious differences between wild and cultivated populations of T. cuspidata from Northeast China, a total of 61 samples, that is, 33 wild yews and 28 cultivated yews were used to analyze the differences and correlations of the kinship, genetic diversity, and genetic structure between them by specific length amplified fragment sequencing (SLAF-seq). Finally, 470725 polymorphic SLAF tags and 58622 valid SNP markers were obtained. Phylogenetic analysis showed that 61 samples were classified into 2 clusters: wild populations and cultivated populations, and some wild yews were categorized into the cultivated populations; the genetic diversity analysis showed that the Nei diversity index of wild populations (0.4068) was smaller than that of cultivated populations (0.4414), and the polymorphic information content (PIC) of wild populations (0.2861) was smaller than that of cultivated populations (0.3309). The genetic differentiation analysis showed that the total populations of gene diversity (Ht) of cultivated and wild populations were respectively 0.8159 and 0.5685, the coefficient of gene differentiation (Gst) of cultivated and wild populations was respectively 0.3021 and 0.1068, and the gene flow (Nm) (2.4967) of wild populations was larger than cultivated populations (0.8199). The molecular variance (AMOVA) revealed that inter-population variation accounted for 29.57% of the total genetic variation, while intra-population variation accounted for 70.42% of the total genetic variation (p < 0.001), this suggested that the genetic variation in the T. cuspidata is mainly attributed to within-population factors. In conclusion, the genetic distance between geographical ecological groups of wild populations was generally smaller than that of cultivated populations, and the degree of genetic diversity and genetic differentiation was smaller than that of cultivated populations. As evident, the utilization of SLAF-seq technology enables efficient and accurate development of SNP markers suitable for genetic analysis of T. cuspidata species. These developed SNP markers can provide a molecular foundation for T. cuspidata breeding, construction of genetic maps, variety identification, and association analysis of agronomic traits. [ABSTRACT FROM AUTHOR]

Alicella gigantea, the largest amphipod scavengers found to date, play key roles in the food web of the hadal ecosystem. However, the genetic structure of A. gigantea populations among different trenches has not been reported yet. In this study, SNP (single-nucleotide polymorphism) markers were developed for three A. gigantea geographic populations collected from the southern Mariana Trench (SMT), the central New Britain Trench (CNBT), and the eastern New Britain Trench (ENBT), based on the SLAF-seq (specific locus amplified fragment sequencing) technology. A total of 570,168 filtered SNPs were screened out for subsequent population genetic analysis. Results showed that the inbreeding levels across the three geographic populations were relatively low, and the genomic inbreeding coefficients of the three populations were similar in magnitude. Based on the results of phylogenetic analysis, population structure analysis, and principal component analysis, it is believed that the three A. gigantea geographic populations belong to the same population, and the kinship relationship between the ENBT and CNBT populations is close. Moreover, the differential candidate adaptive sites on the SNPs suggest that there may be variations in metabolic rates among the three geographic populations, possibly linked to differences in food availability and sources in different trenches, ultimately resulting in different survival strategies in A. gigantea populations within distinct trenches. Compared with the Mariana Trench, the New Britain Trench has a richer organic matter input, and it is speculated that the A. gigantea Mariana Trench population may adopt a lower metabolic rate to cope with the harsher environment of nutrient deficiency.

Soybean fat contains five principal fatty acids, and its fatty acid composition and nutritional value depend on the type of soybean oil, storage duration, and conditions. Among the fat contents, polyunsaturated fatty acids, such as linoleic acid and linolenic acid, play an essential role in maintaining human life activities; thus, increasing the proportions of the linoleic acid and linolenic acid contents can help improve the nutritional value of soybean oil. Our laboratory completed SLAF-seq whole genome sequencing of the natural population (292 soybean varieties) in the previous growth period. In this study, genome-wide association analysis (GWAS) was performed based on the natural population genotypic data and three-year phenotypic data of soybean linoleic acid and linolenic acid contents, and a significant single nucleotide polymorphisms (SNPs) locus (Gm13_10009679) associated with soybean oleic acid content was repeatedly detected over a span of 3 years using the GLM model and MLM model. Additionally, another significant SNP locus (Gm19_41366844) correlated with soybean linolenic acid was identified through the same models. Genes within the 100 Kb interval upstream and downstream of the SNP loci were scanned and analyzed for their functional annotation and enrichment, and one gene related to soybean linoleic acid synthesis (Glyma.13G035600) and one gene related to linolenic acid synthesis (Glyma.19G147400) were screened. The expressions of the candidate genes were verified using qRT-PCR, and based on the verification results, it was hypothesized that Glyma.13G035600 and Glyma.19G147400 positively regulate linoleic acid and linolenic acid synthesis and accumulation, respectively. The above study lays the foundation for further validating gene functions, and analyzing the regulatory mechanisms of linoleic acid and linolenic acid synthesis and accumulation in soybean. [ABSTRACT FROM AUTHOR]

Background: Glycine soja Sieb. & Zucc. is the wild ancestor from which the important crop plant soybean was bred. G. soja provides important germplasm resources for the breeding and improvement of cultivated soybean crops, however the species is threatened by habitat loss and fragmentation, and is experiencing population declines across its natural range. Understanding the patterns of genetic diversity in G. soja populations can help to inform conservation practices. Methods: In this study, we analyzed the genetic diversity and differentiation of G. soja at different sites and investigated the gene flow within the species. We obtained 147 G. soja accessions collected from 16 locations across the natural range of the species from China, Korea and Japan. Samples were analyzed using SLAF-seq (Specific-Locus Amplified Fragment Sequencing). Results: We obtained a total of 56,489 highly consistent SNPs. Our results suggested that G. soja harbors relatively high diversity and that populations of this species are highly differentiated. The populations harboring high genetic diversity, especially KR, should be considered first when devising conservation plans for the protection of G. soja, and in situ protection should be adopted in KR. G. soja populations from the Yangtze River, the Korean peninsula and northeastern China have a close relationship, although these areas are geographically disconnected. Other populations from north China clustered together. Analysis of gene flow suggested that historical migrations of G. soja may have occurred from the south northwards across the East-Asia land-bridge, but not across north China. All G. soja populations could be divided into one of two lineages, and these two lineages should be treated separately when formulating protection policies. [ABSTRACT FROM AUTHOR]

Background: Soybean is one of the most important oil crops in the world, and its protein and fat are the primary sources of edible oil and vegetable protein. The effective components in soybean protein and fat have positive effects on improving human immunity, anti-tumor, and regulating blood lipids and metabolism. Therefore, increasing the contents of protein and fat in soybeans is essential for improving the quality of soybeans. Results: This study selected 292 soybean lines from different regions as experimental materials, based on SLAF-seq sequencing technology, and performed genome-wide association study (GWAS) on the phenotype data from 2019–2021 Planted at the experimental base of Jilin Agricultural University, such as the contents of protein and fat of soybeans. Through the GLM model and MLM model, four SNP sites (Gm09_39012959, Gm12_35492373, Gm16_9297124, and Gm20_24678362) that were significantly related to soybean fat content were associated for three consecutive years, and two SNP sites (Gm09_39012959 and Gm20_24678362) that were significantly related to soybean protein content were associated. By the annotation and enrichment of genes within the 100 Kb region of SNP loci flanking, two genes (Glyma.09G158100 and Glyma.09G158200) related to soybean protein synthesis and one gene (Glyma.12G180200) related to lipid metabolism were selected. By the preliminary verification of expression levels of genes with qPCR, it is found that during the periods of R6 and R7 of the accumulation of soybean protein and fat, Glyma.09G158100 and Glyma.09G158200 are positive regulatory genes that promote protein synthesis and accumulation, while Glyma.12G180200 is the negative regulatory gene that inhibits fat accumulation. Conclusions: These results lay the basis for further verifying the gene function and studying the molecular mechanisms regulating the accumulation of protein and fat in soybean seeds. [ABSTRACT FROM AUTHOR]

Geodorum eulophioides is a unique and endangered species belonging to the Orchidaceae family in China. It has great potential as an ornamental horticultural plant. However, little is known about its genetic diversity and reasons for being endangered due to its narrow distribution and few populations in the wild. To effectively evaluate and conserve available resources, the genetic diversity and population structure of G. eulophioides were analyzed in this study. A total of 94 individuals from 10 natural populations were studied using site-specific amplified fragment sequencing (SLAF-seq). Based on the 76,340 SNPs detected by SLAF-seq, genetic diversity analysis was performed and markers associated with environmental variables were determined. The results showed that the level of genetic diversity in the 10 natural populations studied was low, with PIC values ranging from 0.1874 to 0.2156. FIS values ranged from −0.2376 to 0.2658, with excess and deficiency in heterozygotes. FST values ranged from 0.0482 to 0.3144, with genetic variation among populations. AMOVA results showed that the genetic variation among populations accounted for 21.35% of the total variation, and the remaining genetic variation among individuals within populations was 78.65%. The results of the population structure analysis showed that 94 individuals were classified into three major groups and two subgroups. Environmental association analysis using Bayenv2 and LFMM yielded thirty and eighteen putative adaptive loci, respectively, and five specific functional genes were annotated. In summary, this study provides further insight into the genetic structure of G. eulophioides and provides a reference for protection and restoration. [ABSTRACT FROM AUTHOR]

Nitrogen is essential for crop production. It is a critical macronutrient for plant growth and development. However, excessive application of nitrogen fertilizer is not only a waste of resources but also pollutes the environment. An effective approach to solving this problem is to breed rice varieties with high nitrogen use efficiency (NUE). In this study, we performed a genome-wide association study (GWAS) on 419 rice landraces using 208,993 single nucleotide polymorphisms (SNPs). With the mixed linear model (MLM) in the Tassel software, we identified 834 SNPs associated with root surface area (RSA), root length (RL), root branch number (RBN), root number (RN), plant dry weight (PDW), plant height (PH), root volume (RL), plant fresh weight (PFW), root fractal dimension (RFD), number of root nodes (NRN), and average root diameter (ARD), with a significant level of p < 2.39×10-7. In addition, we found 49 SNPs that were correlated with RL, RBN, RN, PDW, PH, PFW, RFD, and NRN using genome-wide efficient mixed-model association (GEMMA), with a significant level of p < 1×10-6. Additionally, the final results for eight traits associated with 193 significant SNPs by using multilocus random-SNP-effect mixed linear model (mrMLM) model and 272 significant SNPs associated with 11 traits by using IIIVmrMLM. Within the linkage intervals of significantly associated SNP, we identified eight known related genes to NUE in rice, namely, OsAMT2;3, OsGS1, OsNR2, OsNPF7.4, OsPTR9, OsNRT1.1B, OsNRT2.3, and OsNRT2.2. According to the linkage disequilibrium (LD) decay value of this population, there were 75 candidate genes within the 150-kb regions upstream and downstream of the most significantly associated SNP (Chr5_29804690, Chr5_29956584, and Chr10_17540654). These candidate genes included 22 transposon genes, 25 expressed genes, and 28 putative functional genes. The expression levels of these candidate genes were measured by real-time quantitative PCR (RT-qPCR), and the expression levels of LOC_Os05g51700 and LOC_Os05g51710 in C347 were significantly lower than that in C117; the expression levels of LOC_Os05g51740, LOC_Os05g51780, LOC_Os05g51960, LOC_Os05g51970, and LOC_Os10g33210 were significantly higher in C347 than C117. Among them, LOC_Os10g33210 encodes a peptide transporter, and LOC_Os05g51690 encodes a CCT domain protein and responds to NUE in rice. This study identified new loci related to NUE in rice, providing new genetic resources for the molecular breeding of rice landraces with high NUE. [ABSTRACT FROM AUTHOR]

Abstract Background Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is prevalent in the main wheat-producing regions of China, resulting in severe yield losses in recent years. Mining and utilization of resistant genes from wild relatives of wheat is the most environmentally sound measure to control disease. Aegilops geniculata Roth (2n = 2x = 28, UgUgMgMg) is an essential and valuable disease-resistance gene donor for wheat improvement as a close relative species. Results In this study, to validate powdery mildew resistance locus on chromosome 7Mg, two genetic populations were constructed and through crossing wheat – Ae. geniculata 7Mg disomic addition line NA0973-5-4-1-2-9-1 and 7Mg (7 A) alien disomic substitution line W16998 with susceptible Yuanfeng175 (YF175, authorized varieties from Shaanxi province in 2005), respectively. Cytological examination, in situ hybridization (ISH), and functional molecular markers analysis revealed that the plants carrying chromosome 7Mg showed high resistance to powdery mildew in both F1 and F2 generation at the seedling stage. Besides, 84 specific markers were developed to identify the plants carrying chromosome 7Mg resistance based on the specific-locus amplified fragment sequencing (SLAF-seq) technique. Among them, four markers were selected randomly to check the reliability in F2 segregating populations derived from YF175/NA0973-5-4-1-2-9-1 and YF175/W16998. In summary, the above analysis confirmed that a dominant high powdery mildew resistance gene was located on chromosome 7Mg of Ae. geniculata. Conclusion The results provide a basis for mapping the powdery mildew resistance gene mapping on chromosome 7Mg and specific markers for their utilization in the future.

The genetic relationship of the collected Dendrobium germplasm resources was analyzed by SNP marker technology to provide theoretical basis for the selection of new varieties breeding parents. Total 60 Dendrobium germplasm resources were used for SNP marker development and genetic relationship analysis using specific-locus amplified fragment sequencing technology（SLAF-seq）. The sequencing data of each sample were statistically analyzed, and 157.34 Mb Clean Reads data were obtained. The Reads data of each sample ranged from 576 195 to 5 359 710. The average sequencing quality value（Q30）and GC content of samples was 93.85% and 40.16%. Through sequencing data analysis, a total of 1 337 217 SLAF tags and 1 049 638 polymorphic SLAF tags were obtained. The average sequencing depth of the tags was 9.63×.A total of 11 248 186 population SNP markers were developed. The number of SNP markers in each sample ranged from 694 015 to 6 367 379. The integrity ratio was 2.71% to 24.89%, and the hetloci ratio was 1.13% to 5.74%. The population SNPs were filtered, and a total of 31 499 highly consistent and effective SNP markers were obtained. The phylogenetic tree was constructed by using the SNP markers obtained. The 60 Dendrobium germplasm resources were divided into 3 subgroups. These three subgroups contained germplasm resources: Q1（3）, Q2（21）, and Q3（36）. The results of germplasm clustering were basically consistent with the morphological classification. Using SLAF-seq technology can efficiently and accurately develop SNP markers suitable for the genetic analysis of Dendrobium. The SNP markers developed may provide molecular basis for Dendrobium breeding, genetic map construction, variety identification and association analysis of agronomic traits. [ABSTRACT FROM AUTHOR]

Key message: Common loci and candidate genes for controlling salt-alkali tolerance and yield-related traits were identified in Brassica napus combining QTL mapping with transcriptome under salt and alkaline stresses. The yield of rapeseed (Brassica napus L.) is determined by multiple yield-related traits, which are susceptible to environmental factors. Many yield-related quantitative trait loci (QTLs) have been reported in Brassica napus; however, no studies have been conducted to investigate both salt-alkali tolerance and yield-related traits simultaneously. Here, specific-locus amplified fragment sequencing (SLAF-seq) technologies were utilized to map the QTLs for salt-alkali tolerance and yield-related traits. A total of 65 QTLs were identified, including 30 QTLs for salt-alkali tolerance traits and 35 QTLs for yield-related traits, accounting for 7.61–27.84% of the total phenotypic variations. Among these QTLs, 18 unique QTLs controlling two to four traits were identified by meta-analysis. Six novel and unique QTLs were detected for salt-alkali tolerance traits. By comparing these unique QTLs for salt-alkali tolerance traits with those previously reported QTLs for yield-related traits, seven co-localized chromosomal regions were identified on A09 and A10. Combining QTL mapping with transcriptome of two parents under salt and alkaline stresses, thirteen genes were identified as the candidates controlling both salt-alkali tolerance and yield. These findings provide useful information for future breeding of high-yield cultivars resistant to alkaline and salt stresses. [ABSTRACT FROM AUTHOR]

Magnolia odoratissima is a highly threatened species, with small distribution and scattered populations due to habitat fragmentation and human activity. In this study, the genetic diversity and population structure of the five remaining natural populations and two cultivated populations of M. odoratissima were analyzed using single nucleotide polymorphisms (SNPs) derived from specific-locus amplified fragment sequencing. A total of 180,650 SNPs were identified in seventy M. odoratissima individuals. The Nei's and Shannon-Wiener diversity index across all M. odoratissima population were 0.35 and 0.51, respectively, while the observed heterozygosity (Ho) and expected heterozygosity (He) were 0.27 and 0.34, respectively. Our results suggest that M. odoratissima has relatively high genetic diversity at the genomic level. The FST and AMOVA indicated that high genetic differentiation exists among populations, and a phylogenetic neighbor-joining tree, Bayesian model–based clustering and discriminant function analysis of principal component all divided the M. odoratissima individuals into three distinct clusters. The Treemix analysis showed that there was low gene flow among the natural populations. Demographic history inferences indicated show that three clusters of M. odoratissima experienced at least three bottlenecks and resulted in a decrease of effective population size. Our results suggest that three distinct evolutionary significant units should be set up to conserve this critically endangered species. [ABSTRACT FROM AUTHOR]

Fruit cracking decreases the total production and the commercial value of watermelon. The molecular mechanisms of fruit cracking are unknown. In this study, 164 recombinant inbred lines (RILs) of watermelon, derived from the crossing of the WQ1 (cracking-sensitive) and WQ2 (cracking-tolerant) lines, were sequenced using specific length amplified fragment sequencing (SLAF-seq). A high-density genetic linkage map was constructed with 3,335 markers spanning 1,322.74 cM, at an average 0.40 cM across whole-genome flanking markers. The cracking tolerance capacity (CTC), depth of fruit cracking (DFC), rind thickness (RT), and rind hardness (RH) were measured for quantitative trait locus (QTL) analysis. Of the four traits analyzed, one major QTL with high phenotypic variation (41.04%-61.37%) was detected at 76.613-76.919 cM on chromosome 2, which contained 104 annotated genes. Differential gene expression analysis with RNA sequencing (RNA-seq) data between the two parents identified 4,508 differentially expressed genes (DEGs). Comparison of the genes between the QTL region and the DEGs obtained eight coexisting genes. Quantitative real-time PCR (qRT-PCR) analysis revealed that these genes were significant differentially expressed between the two parents. These results provide new insights into the identification of QTLs or genes and marker-assisted breeding in watermelon. [ABSTRACT FROM AUTHOR]

Long-day length and high temperature inhibit sex expression in pumpkin (Cucurbita moschata Duch.), and therefore directly impact the production potential. In this study, female flowering patterns in photoperiod-insensitive (PPIS) and photoperiod-sensitive (PPS) germplasms differed significantly in a moderately long day and high temperature environment. However, both germplasms exhibited a similar response in short day with either low temperature or high temperature environment. Photoperiod sensitivity led to this difference in sex expression between the germplasms. For the traits of 1st female flowering node (FFFN) and number of female flowers (NFF), high-density linkage map construction and quantitative trait locus (QTL) mapping were performed using SLAF-seq technology and 162 F2 individuals generated from PPIS and PPS. In total, 4 655 SLAFs were selected and mapped on 20 linkage groups (LGs). The total map length was 2 502.01 cM with an average interval distance of 0.75 cM. Major QTLs for both FFFN and NFF were detected on LG6 with intervals of 7.89 and 17.67 cM and PVE values of 30.5% and 22.9%, respectively. Further analyses of the major locus for FFFN revealed 73 protein-coding genes. Among them, 4 were related to sex expression, photoperiod flowering, and hormone response. An InDel (insertion and deletion) marker partially correlated with FFFN of the F2 population was also developed. Our study identified the QTL for the sex expression response to environmental factors using the high-density linkage map. The identified candidate genes and markers will provide useful information about the molecular interaction between the environment and sex expression and for marker-assisted selection of pumpkin environment-insensitive resources.

Erect milkvetch (Astragalus adsurgens) is a perennial legume forage crop with economic and ecological value in livestock grazing and soil-erosion control in arid and semiarid areas worldwide. Genomic information and molecular tools to support breeding and research in the species are limited. The objectives of this investigation were to map its genome using DNA markers and to identify quantitative trait loci (QTL) in the species. An F1 mapping population of 250 plants was developed from a cross between two parents with differing flowering-related traits. A high-density genetic linkage map containing 4821 markers on eight linkage groups (LGs) with a total genetic length of 1395 cM and a mean interval of 0.29 cM between adjacent markers was constructed with SLAF-seq technology. Comparative genomic analyses revealed the highest genome sequence similarity (8.71%) between erect milkvetch and Medicago truncatula, followed by Glycine max (7.65%), Cicer arietinum (7.53%), and Lupinus angustifolius (5.21%). A total of 64 significant QTL for flowering-related traits on six LGs were detected, accounting for 9.38 to 19.1% of the associated phenotype variation. Five and 48 key candidate genes for floret number and inflorescence length were identified based on the Glycyrrhiza uralensis genome. These candidate genes were involved in ubiquitination/degradation, pollen development, cell division, cytokinin biosynthetic process, and plant flowering. These findings shed light on the regulation of flowering traits in erect milkvetch and provide genomic resources for future molecular breeding of the crop.

Abstract Background Carcass backfat thickness (BFT), carcass lean percentage (CLP) and carcass fat percentage (CFP) are important to the commercial pig industry. Nevertheless, the genetic architecture of BFT, CLP and CFP is still elusive. Here, we performed a genome-wide association study (GWAS) based on specific-locus amplified fragment sequencing (SLAF-seq) to analyze seven fatness-related traits, including five BFTs, CLP, and CFP on 223 four-way crossbred pigs. Results A total of 227, 921 highly consistent single nucleotide polymorphisms (SNPs) evenly distributed throughout the genome were used to perform GWAS. Using the mixed linear model (MLM), a total of 20 SNP loci significantly related to these traits were identified on ten Sus scrofa chromosomes (SSC), of which 10 SNPs were located in previously reported quantitative trait loci (QTL) regions. On SSC7, two SNPs (SSC7:29,503,670 and rs1112937671) for average backfat thickness (ABFT) exceeded 1% and 10% Bonferroni genome-wide significance levels, respectively. These two SNP loci were located within an intron region of the COL21A1 gene, which was a protein-coding gene that played an important role in the porcine backfat deposition by affecting extracellular matrix (ECM) remodeling. In addition, based on the other three significant SNPs on SSC7, five candidate genes, ZNF184, ZNF391, HMGA1, GRM4 and NUDT3 were proposed to influence BFT. On SSC9, two SNPs for backfat thickness at 6–7 ribs (67RBFT) and one SNP for CLP were in the same locus region (19 kb interval). These three SNPs were located in the PGM2L1 gene, which encoded a protein that played an indispensable role in glycogen metabolism, glycolysis and gluconeogenesis as a key enzyme. Finally, one significant SNP on SSC14 for CLP was located within the PLBD2 gene, which participated in the lipid catabolic process. Conclusions A total of two regions on SSC7 and SSC9 and eight potential candidate genes were found for fatness-related traits in pigs. The results of this GWAS based on SLAF-seq will greatly advance our understanding of the genetic architecture of BFT, CLP, and CFP traits. These identified SNP loci and candidate genes might serve as a biological basis for improving the important fatness-related traits of pigs.

Meat quality traits (MQTs) have gained more attention from breeders due to their increasing economic value in the commercial pig industry. In this genome-wide association study (GWAS), 223 four-way intercross pigs were genotyped using the specific-locus amplified fragment sequencing (SLAF-seq) and phenotyped for PH at 45 min post mortem (PH45), meat color score (MC), marbling score (MA), water loss rate (WL), drip loss (DL) in the longissimus muscle, and cooking loss (CL) in the psoas major muscle. A total of 227, 921 filtered single nucleotide polymorphisms (SNPs) evenly distributed across the entire genome were detected to perform GWAS. A total of 64 SNPs were identified for six meat quality traits using the mixed linear model (MLM), of which 24 SNPs were located in previously reported QTL regions. The phenotypic variation explained (PVE) by the significant SNPs was from 2.43% to 16.32%. The genomic heritability estimates based on SNP for six meat-quality traits were low to moderate (0.07-0.47) being the lowest for CL and the highest for DL. A total of 30 genes located within 10 kb upstream or downstream of these significant SNPs were found. Furthermore, several candidate genes for MQTs were detected, including pH45 (GRM8), MC (ANKRD6), MA (MACROD2 and ABCG1), WL (TMEM50A), CL (PIP4K2A) and DL (CDYL2, CHL1, ABCA4, ZAG and SLC1A2). This study provided substantial new evidence for several candidate genes to participate in different pork quality traits. The identification of these SNPs and candidate genes provided a basis for molecular marker-assisted breeding and improvement of pork quality traits. [ABSTRACT FROM AUTHOR]

Black spot disease (PBS) caused by Alternaria alternata is an economic disease of pear (Pyrus pyrifolia Nakai). Developing cultivars with durable PBS resistance traits is an important research objective for improving pear germplasm. The Deshengxiang is a popular pear variety in China and resistant to PBS. This study aimed to detect quantitative trait loci (QTL) associated with PBS resistance trait in pear and determine closely linked molecular markers by specific locus amplified fragment sequencing (SLAF-seq). F1 population resulting from a cross between "Deshengxiang" (female) and "Guiguan," a susceptible (male) variety, was developed and evaluated in 2016 and 2017. SLAF technology was used to discover SNPs in the F1 individuals and subsequently a high-density genetic linkage map for PBS resistance was constructed which contained 17,604 SNP markers. Based on the linkage map, the markers were distributed into 17 linkage groups, spanning 1548.48 cM, with a mean marker distance of 0.09 cM, representing the densest genetic map of the genus Pyrus. QTL analysis of PBS resistance identified a locus strongly related to PBS resistance at 77.68 ~ 112.99 cM on linkage group 15, which was further narrowed down to 93.79 ~ 112.99 cM. Two markers, Marker94293 and Marker94206, located at 97.47 and 102.93 cM, were closely associated with PBS resistance, with a Δ (SNP index) value of 0.46. Co-localization of QTL interval, bioinformatics analysis, and functional annotation revealed PBS putative candidate genes. Overall, the high-density pear linkage map is a suitable reference for mapping PBS resistance trait, QTL, and genes identified in this study contribute information that could be useful for PBS improvement in pear. [ABSTRACT FROM AUTHOR]

Microspore embryogenesis is widely used in plant breeding to obtain homozygous lines. It is an important way of obtaining haploids and it is valuable for QTL (Quantitative Trailt Locus) mapping and genetic research. We analyzed the microspore embryogenesis ability of 142 recombinant inbred lines (RIL) and mapped QTLs for microspore embryogenesis based on a genetic map constructed using specific-locus amplified fragment sequencing SLAF-seq technology. Results revealed that microspore embryogenesis ability in pepper is a quantitative character. Seven QTLs were detected on linkage groups LG2, LG6, LG8, LG11 and LG12. The peak logarithm of odds (LOD) score of the seven QTLs ranged from 3.51 to 6.66, and the range of phenotypic variation explained by a single QTL ranged from 4.76 to 18.30%. We identified a major QTL, Me2.2, located in the region of 116.5–118.5 cM on LG2; the corresponding physical segment was 166,621,667–167,038,758 bp, and 24 candidate genes were predicted in this region. Functional annotation indicated that these genes are closely related to the initiation of cell division, symmetrical or asymmetric cell division, and other life processes. The study laid a good foundation for further research on the mechanism of microspore embryogenesis. [ABSTRACT FROM AUTHOR]

Simple Summary: The population genomic study of seven populations of Bellamya aeruginosa across three river systems in China was conducted by specific-locus amplified fragment sequencing (SLAF-seq). A clear division was found among populations from the Yellow River basin and the Pearl River basin, as well as population YC from the Yangtze River basin using the SNPs data. However, there existed no distinct population structure using the mitochondrial DNA. Anthropogenic translocation from the Yangtze River to the Pearl River basin and the passive dispersion from the Yangtze River basin to the Yellow River basin by flooding have weakened the phylogeographic pattern of B. aeruginosa. These results provide useful guidance for the effective selective breeding of Bellamya, which is very important for the development of the industry of LZRSRN. Clarifying the genetic structure can facilitate the understanding of a species evolution history. It is crucial for the management of germplasm resources and providing useful guidance for effective selective breeding. Bellamya is an economically and ecologically important freshwater snail for fish, birds and even humans. Population genetic structures of the Bellamya species, however, were unknown in previous studies. Population genomics approaches with tens to hundreds of thousands of single nucleotide polymorphisms (SNPs) make it possible to detect previously unidentified structures. The population genomic study of seven populations of B. aeruginosa across three river systems (Yellow River, Yangtze River and Pearl River) in China was conducted by SLAF-seq. SLAF-seq obtained a total of 4737 polymorphisms SLAF-tags and 25,999 high-consistency genome-wide SNPs. The population genetic structure showed a clear division among populations from the Yellow River basin (YH and WL) and the Pearl River basin (QSH and LB), as well as population YC from the Yangtze River basin using the SNPs data. However, there existed no distinct population structure using the mitochondrial DNA (mtDNA). The anthropogenic translocation from the Yangtze River basin to the Pearl River basin and the passive dispersion from the Yangtze River basin to the Yellow River basin by flooding have weakened the phylogeographic pattern of B. aeruginosa. The divergence of B. aeruginosa in the three river systems suggests that the anthropogenic dispersal for aquaculture and breeding requires serious consideration of the population structure for the preservation of genetic diversity and effective utilization of germplasm resources. [ABSTRACT FROM AUTHOR]

Medicago polymorpha L. (bur clover), an invasive plant species of the genus Medicago, has been traditionally used in China as an edible vegetable crop because of its high nutritive value. However, few molecular markers for M. polymorpha have been identified. Using the recently published high-quality reference genome of M. polymorpha, we performed a specific-locus amplified fragment sequencing (SLAF-seq) analysis of 10 M. polymorpha accessions to identify molecular markers and explore genetic diversity. A total of 52,237 high-quality single nucleotide polymorphisms (SNPs) were developed. These SNPs were mostly distributed on pseudochromosome 3, least distributed on pseudochromosome 7, and relatively evenly distributed on five other pseudochromosomes of M. polymorpha. Phenotypic analysis showed that there was a great difference in phenotypic traits among different M. polymorpha accessions. Moreover, clustering all M. polymorpha accessions based on their phenotypic traits revealed three groups. Both phylogenetic analysis and principal component analysis (PCA) of all M. polymorpha accessions based on SNP markers consistently indicated that all M. polymorpha accessions could be divided into three distinct groups (I, II, and III). Subsequent genetic diversity analysis for the 10 M. polymorpha accessions validated the effectiveness of the M. polymorpha germplasm molecular markers in China. Additionally, SSR mining analysis was also performed to identify polymorphic SSR motifs, which could provide valuable candidate markers for the further breeding of M. polymorpha. Since M. polymorpha genetics have not been actively studied, the molecular markers generated from our research will be useful for further research on M. polymorpha resource utilization and marker-assisted breeding. [ABSTRACT FROM AUTHOR]

Abstract Background Simao pine is one of the primary economic tree species for resin and timber production in southwest China. The exploitation and utilization of Simao pine are constrained by the relatively lacking of genetic information. Construction a fine genetic linkage map and detecting quantitative trait locis (QTLs) for growth-related traits is a prerequisite section of Simao Pine's molecular breeding program. Results In our study, a high-resolution Simao pine genetic map employed specific locus amplified fragment sequencing (SLAF-seq) technology and based on an F1 pseudo-testcross population has been constructed. There were 11,544 SNPs assigned to 12 linkage groups (LGs), and the total length of the map was 2,062.85 cM with a mean distance of 0.37 cM between markers. According to the phenotypic variation analysis for three consecutive years, a total of seventeen QTLs for four traits were detected. Among 17 QTLs, there were six for plant height (Dh.16.1, Dh16.2, Dh17.1, Dh18.1–3), five for basal diameter (Dbd.17.1–5), four for needle length (Dnl17.1–3, Dnl18.1) and two for needle diameter (Dnd17.1 and Dnd18.1) respectively. These QTLs individually explained phenotypic variance from 11.0–16.3%, and the logarithm of odds (LOD) value ranged from 2.52 to 3.87. Conclusions In our study, a fine genetic map of Simao pine applied the technology of SLAF-seq has been constructed for the first time. Based on the map, a total of 17 QTLs for four growth-related traits were identified. It provides helpful information for genomic studies and marker-assisted selection (MAS) in Simao pine.

Abstract Background Miscanthus, which is a leading dedicated-energy grass in Europe and in parts of Asia, is expected to play a key role in the development of the future bioeconomy. However, due to its complex genetic background, it is difficult to investigate phylogenetic relationships in this genus. Here, we investigated 50 Miscanthus germplasms: 1 female parent (M. lutarioriparius), 30 candidate male parents (M. lutarioriparius, M. sinensis, and M. sacchariflorus), and 19 offspring. We used high-throughput Specific-Locus Amplified Fragment sequencing (SLAF-seq) to identify informative single nucleotide polymorphisms (SNPs) in all germplasms. Results We identified 257,889 SLAF tags, of which 87,162 were polymorphic. Each tag was 264–364 bp long. The obtained 724,773 population SNPs were used to investigate genetic relationships within three species of Miscanthus. We constructed a phylogenetic tree of the 50 germplasms using the obtained SNPs and grouped them into two clades: one clade comprised of M. sinensis alone and the other one included the offspring, M. lutarioriparius, and M. sacchariflorus. Genetic cluster analysis had revealed that M. lutarioriparius germplasm C3 was the most likely male parent of the offspring. Conclusions As a high-throughput sequencing method, SLAF-seq can be used to identify informative SNPs in Miscanthus germplasms and to rapidly characterize genetic relationships within this genus. Our results will support the development of breeding programs with the focus on utilizing Miscanthus cultivars with elite biomass- or fiber-production potential for the developing bioeconomy.

The main topic of population genetics and evolutionary biology is the influence of the ecological environment, geographical isolation, and climatic factors on population structure and history. Here, we estimated the genetic diversity, genetic structure, and population history of two subspecies of Tolai hares (Lepus tolai Pallas, 1778), L. t. lehmanni inhabiting Northern and Northwest Xinjiang and L. t. centrasiaticus inhabiting Central and Eastern Xinjiang using SNP of specific-length amplified fragment sequencing (SLAF-seq) and four mitochondrial DNA (mtDNA). Our results showed a relatively high degree of genetic diversity for Tolai hares, and the diversity of L. t. lehmanni was slightly higher than that of L. t. centrasiaticus, likely due to the more favorable ecological environment, such as woodlands and plains. Phylogenetic analysis from SNP and mtDNA indicated a rough phylogeographical distribution pattern among Tolai hares. Strong differentiation was found between the two subspecies and the two geographical groups in L. t. centrasiaticus, possibly due to the geographical isolation of mountains, basins, and deserts. However, gene flow was also detected between the two subspecies, which might be attributed to the Tianshan Corridor and the strong migration ability of hares. Tolai hare population differentiation occurred at approximately 1.2377 MYA. Population history analysis based on SNP and mtDNA showed that the Tolai hare population has a complex history and L. t. lehmanni was less affected by the glacial event, possibly because its geographic location and terrain conditions weaken the drastic climate fluctuations. In conclusion, our results indicated that the joint effect of ecological environment, geographic events, and climatic factors might play important roles in the evolutionary process of L. t. lehmanni and L. t. centrasiaticus, thus resulting in differentiation, gene exchange, and different population history.

Soybean fat contains five principal fatty acids, and its fatty acid composition and nutritional value depend on the type of soybean oil, storage duration, and conditions. Among the fat contents, polyunsaturated fatty acids, such as linoleic acid and linolenic acid, play an essential role in maintaining human life activities; thus, increasing the proportions of the linoleic acid and linolenic acid contents can help improve the nutritional value of soybean oil. Our laboratory completed SLAF-seq whole genome sequencing of the natural population (292 soybean varieties) in the previous growth period. In this study, genome-wide association analysis (GWAS) was performed based on the natural population genotypic data and three-year phenotypic data of soybean linoleic acid and linolenic acid contents, and a significant single nucleotide polymorphisms (SNPs) locus (Gm13_10009679) associated with soybean oleic acid content was repeatedly detected over a span of 3 years using the GLM model and MLM model. Additionally, another significant SNP locus (Gm19_41366844) correlated with soybean linolenic acid was identified through the same models. Genes within the 100 Kb interval upstream and downstream of the SNP loci were scanned and analyzed for their functional annotation and enrichment, and one gene related to soybean linoleic acid synthesis (Glyma.13G035600) and one gene related to linolenic acid synthesis (Glyma.19G147400) were screened. The expressions of the candidate genes were verified using qRT-PCR, and based on the verification results, it was hypothesized that Glyma.13G035600 and Glyma.19G147400 positively regulate linoleic acid and linolenic acid synthesis and accumulation, respectively. The above study lays the foundation for further validating gene functions, and analyzing the regulatory mechanisms of linoleic acid and linolenic acid synthesis and accumulation in soybean.

Salt stress severely affects crop growth and development and reduces the yield of Brassica napus. Exploring natural genetic variations for high salt tolerance in B. napus seedlings is an effective approach to improve productivity under salt stress. Using 10,658 high-quality single nucleotide polymorphic (SNP) markers developed by specific-locus amplified fragment sequencing (SLAF-seq) technology, genome-wide association studies (GWAS) were performed to investigate the genetic basis of salt tolerance and yield-related traits of B. napus. The results revealed that 77 and 497 SNPs were significantly associated with salt tolerance and yield-related traits, of which 40 and 58 SNPs were located in previously reported QTLs/SNPs, respectively. We identified nineteen candidate genes orthologous with Arabidopsis genes known to be associated with salt tolerance and seven potential candidates controlling both salt tolerance and yield. Our study provides a novel genetic resource for the breeding of high-yield cultivars resistant to salt stress. [ABSTRACT FROM AUTHOR]

The main topic of population genetics and evolutionary biology is the influence of the ecological environment, geographical isolation, and climatic factors on population structure and history. Here, we estimated the genetic diversity, genetic structure, and population history of two subspecies of Tolai hares (Lepus tolai Pallas, 1778), L. t. lehmanni inhabiting Northern and Northwest Xinjiang and L. t. centrasiaticus inhabiting Central and Eastern Xinjiang using SNP of specific-length amplified fragment sequencing (SLAF-seq) and four mitochondrial DNA (mtDNA). Our results showed a relatively high degree of genetic diversity for Tolai hares, and the diversity of L. t. lehmanni was slightly higher than that of L. t. centrasiaticus, likely due to the more favorable ecological environment, such as woodlands and plains. Phylogenetic analysis from SNP and mtDNA indicated a rough phylogeographical distribution pattern among Tolai hares. Strong differentiation was found between the two subspecies and the two geographical groups in L. t. centrasiaticus, possibly due to the geographical isolation of mountains, basins, and deserts. However, gene flow was also detected between the two subspecies, which might be attributed to the Tianshan Corridor and the strong migration ability of hares. Tolai hare population differentiation occurred at approximately 1.2377 MYA. Population history analysis based on SNP and mtDNA showed that the Tolai hare population has a complex history and L. t. lehmanni was less affected by the glacial event, possibly because its geographic location and terrain conditions weaken the drastic climate fluctuations. In conclusion, our results indicated that the joint effect of ecological environment, geographic events, and climatic factors might play important roles in the evolutionary process of L. t. lehmanni and L. t. centrasiaticus, thus resulting in differentiation, gene exchange, and different population history. [ABSTRACT FROM AUTHOR]

Paeonia lactiflora Pall. (P. lactiflora) is a famous ornamental plant with showy and colorful flowers that has been domesticated in China for 4,000 years. However, the genetic basis of phenotypic variation and genealogical relationships in P. lactiflora population is poorly understood due to limited genetic information, which brings about bottlenecks in the application of effective and efficient breeding strategies. Understanding the genetic basis of color-related traits is essential for improving flower color by marker-assisted selection (MAS). In this study, a high throughput sequencing of 99 diploid P. lactiflora accessions via specific-locus amplified fragment sequencing (SLAF-seq) technology was performed. In total, 4,383,645 SLAF tags were developed from 99 P. lactiflora accessions with an average sequencing depth of 20.81 for each SLAF tag. A total of 2,954,574 single nucleotide polymorphisms (SNPs) were identified from all SLAF tags. The population structure and phylogenetic analysis showed that P. lactiflora population used in this study could be divided into six divergent groups. Through association study using Mixed linear model (MLM), we further identified 40 SNPs that were significantly positively associated with petal color. Moreover, a derived cleaved amplified polymorphism (dCAPS) marker that was designed based on the SLAF tag 270512F co-segregated with flower colors in P. lactiflora population. Taken together, our results provide valuable insights into the application of MAS in P. lactiflora breeding programs. [ABSTRACT FROM AUTHOR]

Background: Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is prevalent in the main wheat-producing regions of China, resulting in severe yield losses in recent years. Mining and utilization of resistant genes from wild relatives of wheat is the most environmentally sound measure to control disease. Aegilops geniculata Roth (2n = 2x = 28, UgUgMgMg) is an essential and valuable disease-resistance gene donor for wheat improvement as a close relative species. Results: In this study, to validate powdery mildew resistance locus on chromosome 7Mg, two genetic populations were constructed and through crossing wheat – Ae. geniculata 7Mg disomic addition line NA0973-5-4-1-2-9-1 and 7Mg (7 A) alien disomic substitution line W16998 with susceptible Yuanfeng175 (YF175, authorized varieties from Shaanxi province in 2005), respectively. Cytological examination, in situ hybridization (ISH), and functional molecular markers analysis revealed that the plants carrying chromosome 7Mg showed high resistance to powdery mildew in both F1 and F2 generation at the seedling stage. Besides, 84 specific markers were developed to identify the plants carrying chromosome 7Mg resistance based on the specific-locus amplified fragment sequencing (SLAF-seq) technique. Among them, four markers were selected randomly to check the reliability in F2 segregating populations derived from YF175/NA0973-5-4-1-2-9-1 and YF175/W16998. In summary, the above analysis confirmed that a dominant high powdery mildew resistance gene was located on chromosome 7Mg of Ae. geniculata. Conclusion: The results provide a basis for mapping the powdery mildew resistance gene mapping on chromosome 7Mg and specific markers for their utilization in the future. [ABSTRACT FROM AUTHOR]

Growth traits are crucial economic traits in the commercial pig industry and have a substantial impact on pig production. However, the genetic mechanism of growth traits is not very clear. In this study, we performed a genome-wide association study (GWAS) based on the specific-locus amplified fragment sequencing (SLAF-seq) to analyze ten growth traits on 223 four-way intercross pigs. A total of 227,921 highly consistent single nucleotide polymorphisms (SNPs) uniformly dispersed throughout the entire genome were used to conduct GWAS. A total of 53 SNPs were identified for ten growth traits using the mixed linear model (MLM), of which 18 SNPs were located in previously reported quantitative trait loci (QTL) regions. Two novel QTLs on SSC4 and SSC7 were related to average daily gain from 30 to 60 kg (ADG30–60) and body length (BL), respectively. Furthermore, 13 candidate genes (ATP5O, GHRHR, TRIM55, EIF2AK1, PLEKHA1, BRAP, COL11A2, HMGA1, NHLRC1, SGSM1, NFATC2, MAML1, and PSD3) were found to be associated with growth traits in pigs. The GWAS findings will enhance our comprehension of the genetic architecture of growth traits. We suggested that these detected SNPs and corresponding candidate genes might provide a biological foundation for improving the growth and production performance of pigs in swine breeding. [ABSTRACT FROM AUTHOR]

Guizhou is one of the centers of origin for the tea plant (Camellia sinensis (L.) Kuntze). The location contains highly diverse ancient tea plant germplasms in its Sandu Aquarium Autonomous County. After a prolonged course of continuous evolution, these ancient plants have gained a wealth of genetic diversity. Their resources could be harnessed for the selection and breeding of fine varieties of tea plant, as well as for the effective utilization and protection of germplasm resources. In this study, the specific locus-amplified fragment (SLAF) sequencing method was used to analyze the population structure and conduct a genome-wide association study (GWAS) for the three traits of 125 ancient tea plants in the Sandu County of Guizhou province, China. A total of 807,743 SLAF tags and 9,428,309 population single-nucleotide polymorphism (SNP) tags were obtained. The results of the phylogenetic tree analysis, cluster analysis, and principal component analysis showed that 125 germplasms were clustered into four groups, and the heterozygosity rates for groups I, II, III, and IV, were 0.211, 0.504, 0.144, and 0.192, respectively. Additionally, GWAS analysis suggested that seven candidate genes were related to altitude at the origin of the plants, eight were related to tree shape, and three were associated with leaf color. In this study, we clarified genetic relationships between four ancient tea plant-producing areas in Sandu County and obtained candidate genes related to their development associated with altitude, tree shape, and leaf color. The study provides useful information for tea plant-breeding development and molecular identification. [ABSTRACT FROM AUTHOR]

Soybeans are essential crops that supply protein and oil. The composition and contents of soybean fatty acids are relevant to human health and have a significant relationship with soybean oil processing and applications. Identifying quantitative trait locus (QTL) genes related to palmitic acid could facilitate the development of a range of nutritive soybean cultivars using molecular marker-assisted selection. In this study, we used a cultivar with higher palmitic acid content, 'Dongnong42', and a lower palmitic acid content cultivar, 'Hobbit', to establish F2:6 recombinant inbred lines. A high-density genetic map containing 9980 SLAF markers was constructed and distributed across 20 soybean chromosomes. The genetic map contained a total genetic distance of 2602.58 cM and an average genetic distance of 0.39 cM between adjacent markers. Two QTLs related to palmitic acid content were mapped using inclusive composite interval mapping, explaining 4.2–10.1% of the phenotypic variance in three different years and environments, including the QTL included in seed palmitic 7-3, which was validated by developing SSR markers. Based on the SNP/Indel and significant differential expression analyses of Dongnong42 and Hobbit, two genes, Glyma.15g119700 and Glyma.15g119800, were selected as candidate genes. The high-density genetic map, QTLs, and molecular markers will be helpful for the map-based cloning of palmitic acid content genes. These could be used to accelerate breeding for high nutritive value cultivars via molecular marker-assisted breeding. [ABSTRACT FROM AUTHOR]

Abstract Background Aegilops geniculata Roth is closely related to common wheat (Triticum aestivum L.) and is a valuable genetic resource for improvement of wheat. Results In this study, the W19513 line was derived from the BC1F10 progeny of a cross between wheat ‘Chinese Spring’ and Ae. geniculata SY159. Cytological examination showed that W19513 contained 44 chromosomes. Twenty-two bivalents were formed at the first meiotic metaphase I in the pollen mother cellsand the chromosomes were evenly distributed to opposite poles at meiotic anaphase I. Genomic in situ hybridization demonstrated that W19513 carried a pair of alien chromosomes from the M genome. Fluorescence in situ hybridization confirmed detection of variation in chromosomes 4A and 6B. Functional molecular marker analysis using expressed sequence tag–sequence-tagged site and PCR-based landmark unique gene primers revealed that the alien gene belonged to the third homologous group. The marker analysis confirmed that the alien chromosome pair was 3Mg. In addition, to further explore the molecular marker specificity of chromosome 3Mg, based on the specific locus amplified fragment sequencing technique, molecular markers specific for W19513 were developed with efficiencies of up to 47.66%. The W19513 line was inoculated with the physiological race E09 of powdery mildew (Blumeria graminis f. sp. tritici) at the seedling stage and showed moderate resistance. Field inoculation with a mixture of the races CYR31, CYR32, CYR33, and CYR34 of the stripe rust fungus (Puccinia striiformis f. sp. triticii) revealed that the line W19513 showed strong resistance. Conclusions This study provides a foundation for use of the line W19513 in future genetic research and wheat improvement.

The cyprinid Aral barbel L. brachycephalus is endemic to the Aral Sea of Uzbekistan and was introduced in China in 2003. With increased cultivation, there is a need for more effective breeding strategies. We sequenced 146 individuals from a full-sib family and obtained 66,771 single nucleotide polymorphisms (SNPs) using specific locus amplified fragment sequencing (SLAF-seq). Among these, 31,019 SNPs were assigned to 50 linkage groups. The linkage map contained 4304 unique loci and spanned 2419.2 cM in total, with an average length of 48.4 cM. The length for each linkage group ranged from 5.2 cM to 76.2 cM, with an average distance of 0.4 cM to 0.8 cM. Using the linkage map, 72 QTL regions were predicted to be significantly associated with three breeding-related traits: body height (BH), total length (TL), and head breadth (HB). This study provides useful tools for the molecular mark-assisted breeding of L. brachycephalus.