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Soybean plant architecture has a significant impact on yield potential, but the genetic underpinnings of key architectural traits remain elusive. The primary objective of this study was to explore the genetic foundations underlying main stem node number (MSN) in soybeans. Recombinant inbred lines (RILs) contained a 234 individual derived from crosses between two cultivars Zhonghuang35 (ZH35) and Jindou21 (JD21) was evaluated for seed hardness across 3 years (2013, 2014, and 2015 in Gansu). Markedly, the parent varieties, shown significant differences in MSN. Also, the RIL population exhibited a wide range of genetic variation in MSN. A high-density genetic map composed of 8,078 specific-locus amplified fragment (SLAF) markers, spanning 3,480.98 centimorgans (cM) with an average inter-marker distance of 0.59 cM were used to construct linkage map. Using ICIM analysis identified a total of 23 Quantitative Trait Loci (QTLs) across the 20 chromosome, of which five QTLs were detected in multiple years in Chr.6. Notably, we identified a stable major QTL, qMSN-6-4, explaining up to 24.81% of phenotypic variation. This QTL govern seven candidate genes with potential roles in regulating MSN development in soybean, including Glyma.06G027500 with a domain of unknown function, Glyma.06G027600 involved in proton transport, Glyma.06G027700 linked to proteolysis, Glyma.06G027900 related to transcriptional regulation, and Glyma.06G028000 and Glyma.06G028050 associated with membrane functions. The RT-PCR analysis confirmed that these genes were expressed differently between the parental lines this supports the idea that they may play a role in determining MSN. Glyma.06G027500 and Glyma.06G027600 showing higher expression in JD21 leaves and nodes, while Glyma.06G027700 and Glyma.06G028000 exhibited increased expression in ZH35 stems, highlighting their distinct roles in transcription regulation, membrane activities, and protein degradation that contribute to MSN formation in soybean. This study offers valuable insights into the genetic mechanisms governing soybean MSN, providing a foundation for future research and crop improvement efforts.

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.

Upland cotton accounts for a high percentage (95%) of the world's cotton production. Plant height (PH) and branch number (BN) are two important agronomic traits that have an impact on improving the level of cotton mechanical harvesting and cotton yield. In this research, a recombinant inbred line (RIL) population with 250 lines developed from the variety CCRI70 was used for constructing a high-density genetic map and identification of quantitative trait locus (QTL). The results showed that the map harbored 8298 single nucleotide polymorphism (SNP) markers, spanning a total distance of 4876.70 centimorgans (cMs). A total of 69 QTLs for PH (9 stable) and 63 for BN (11 stable) were identified and only one for PH was reported in previous studies. The QTLs for PH and BN harbored 495 and 446 genes, respectively. Combining the annotation information, expression patterns and previous studies of these genes, six genes could be considered as potential candidate genes for PH and BN. The results could be helpful for cotton researchers to better understand the genetic mechanism of PH and BN development, as well as provide valuable genetic resources for cotton breeders to manipulate cotton plant architecture to meet future demands. [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]

Maize is an important food and industrial material resource. We constructed a high-density genetic map using the whole-genome resequencing and specific-locus amplified fragments sequencing (SLAF-seq) techniques for the "HZS" and "X224M" elite maize inbred lines, and 196 F2 individuals from a cross between "HZS" and "X224M." In our study, the average resequencing depth of the maternal and paternal parents was 13.30-fold and 11.94-fold, respectively. In the F2 population, the sequencing depth ranged from 9.64-fold to 45.16-fold with an average of 23.18-fold. In total, 12, 354, 021 SNPs were detected in the F2 population, and 87.78% of which were polymorphic. Among these SNPs, 2, 843, 917 (53.96%) were included in the segregation pattern aa × bb. Finally, 6, 186 SNPs were used to construct a high-density genetic map. The length of this map included all 10 chromosomes in maize and was 1, 667.36 cM, with an average distance of 0.318 cM between markers. The number of mapped SNPs in different linkage groups (LGs) ranged from 254 to 960, and the genetic distance of each LGs ranged from 157.22 to 192.72 cM. Based on the evaluation of haplotype and heat maps, the results indicated that our genetic map is of high quality, and we now have more detailed information for gene mapping and marker-assisted breeding. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China Agricultural University is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Upland cotton accounts for a high percentage (95%) of the world’s cotton production. Plant height (PH) and branch number (BN) are two important agronomic traits that have an impact on improving the level of cotton mechanical harvesting and cotton yield. In this research, a recombinant inbred line (RIL) population with 250 lines developed from the variety CCRI70 was used for constructing a high-density genetic map and identification of quantitative trait locus (QTL). The results showed that the map harbored 8298 single nucleotide polymorphism (SNP) markers, spanning a total distance of 4876.70 centimorgans (cMs). A total of 69 QTLs for PH (9 stable) and 63 for BN (11 stable) were identified and only one for PH was reported in previous studies. The QTLs for PH and BN harbored 495 and 446 genes, respectively. Combining the annotation information, expression patterns and previous studies of these genes, six genes could be considered as potential candidate genes for PH and BN. The results could be helpful for cotton researchers to better understand the genetic mechanism of PH and BN development, as well as provide valuable genetic resources for cotton breeders to manipulate cotton plant architecture to meet future demands.

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Grain shape is an important agronomic trait directly associated with yield in rice. In order to explore new genes related to rice grain shape, a high-density genetic map containing 2193 Bin markers (526957 SNP) was constructed by whole-genome resequencing of 208 recombinant inbred (RILs) derived from a cross between ZP37 and R8605, with a total genetic distance of 1542.27 cM. The average genetic distance between markers was 0.76 cM, and the physical distance was 201.29 kb. Quantitative trait locus (QTL) mapping was performed for six agronomic traits related to rice grain length, grain width, length-to-width ratio, thousand-grain weight, grain cross-sectional area, and grain perimeter under three different environments. A total of 39 QTLs were identified, with mapping intervals ranging from 8.1 kb to 1781.6 kb and an average physical distance of 517.5 kb. Among them, 15 QTLs were repeatedly detected in multiple environments. Analysis of the genetic effects of the identified QTLs revealed 14 stable genetic loci, including three loci that overlapped with previously reported gene positions, and the remaining 11 loci were newly identified loci associated with two or more environments or traits. Locus 1, Locus 3, Locus 10, and Locus 14 were novel loci exhibiting pleiotropic effects on at least three traits and were detected in multiple environments. Locus 14, with a contribution rate greater than 10%, influenced grain width, length-to-width ratio, and grain cross-sectional area. Furthermore, pyramiding effects analysis of three stable genetic loci showed that increasing the number of QTL could effectively improve the phenotypic value of grain shape. Collectively, our findings provided a theoretical basis and genetic resources for the cloning, functional analysis, and molecular breeding of genes related to rice grain shape. [ABSTRACT FROM AUTHOR]

Grape berry shape is an important agricultural trait. Clarifying its genetic basis is significant for cultivating grape varieties that meet market demands. However, the current study by forward genetics has not achieved in-depth results. Here, a high-density map was constructed to identify quantitative trait loci (QTLs) for berry shape. A total of 358 709 polymorphic SNPs were obtained using whole-genome resequencing (WGS) based on 208 F2 individuals derived from round grape 'E42-6' and oblong grape 'Rizamat'. The 1 635.65 cM high-density map was divided into 19 linkage groups with an average distance of 0.37 cM. Using this map, three significant QTLs for fruit shape index (ShI: ratio of berry length to berry width) identified over three years were mapped onto LG4 and LG5, including one stable QTL on Chr5 with the genomic region of 0.47e1.94 Mb. Combining with gene annotation and expression patterns based on RNA-seq data from two contrasting F2 individuals with round and oblong berry (their average ShI was 1.89 and 1.10, respectively) at four developmental stages, four candidate genes were selected from the above QTLs. They were mainly involved in DNA replication, cell wall modification, and phytohormone biosynthesis. Further analysis of RNAseq data revealed that several important phytohormone synthesis and metabolic pathways were enriched based on differentially expressed genes (DEGs), which was consistent with the results of QTL mapping for genes related to plant hormone biosynthesis in the F2 population. Furthermore, a comparison of plant hormone content showed that there were significant differences in IAA and tZ content between the two contrasting F2 individuals at different developmental stages. Our findings provide molecular insights into the genetic variation in grape berry shape. Stable QTLs and their tightly linked markers offer the possibility of marker-assisted selection to accelerate berry shape breeding. [ABSTRACT FROM AUTHOR]

Faba bean (Vicia faba L.) is a valuable legume crop and data on its seed-related traits is required for yield and quality improvements. However, basic research on faba bean is lagging compared to that of other major crops. In this study, an F2 faba bean population, including 121 plants derived from the cross WY7×TCX7, was genotyped using the Faba_bean_130 K targeted next-generation sequencing genotyping platform. The data were used to construct the first ultra-dense faba bean genetic map consisting of 12,023 single nucleotide polymorphisms markers covering 1,182.65 cM with an average distance of 0.098 cM. The map consisted of 6 linkage groups, which is consistent with the 6 faba bean chromosome pairs. A total of 65 quantitative trait loci (QTL) for seedrelated traits were identified (3 for 100-seed weight, 28 for seed shape, 12 for seed coat color, and 22 for nutritional quality). Furthermore, 333 candidate genes that are likely to participate in the regulation of seed-related traits were also identified. Our research findings can provide a basis for future faba bean marker-assisted breeding and be helpful to further modify and improve the reference genome. [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.

The seed size of castor (Ricinus communis L.) directly affects the yield, and there is a great difference in seed size among different castor varieties. It is of great significance to further study the genetic mechanism of castor seed size traits for the development of castor seed industry. In this study, we used monoecious inbred lines SL1 as male parent, pistillate line HCH1 as female parent 1 (Combination 1), and pistillate line HCH3 as female parent 2 (Combination 2) to construct F2 and BC1 populations, respectively. Firstly, the correlations between seed size traits were analyzed by phenotypic statistics of the two genetic populations. Secondly, based on the phenotypic data of 150 individual plants in F2 population from Combination 1, a high-density genetic map was constructed using genotyping by whole genome sequencing technology (WGS), and QTL analysis was performed for the seed size traits. Finally, the KEGG pathway enrichment and BLAST comparison were performed to determine the candidate genes in the definite QTL region. The results showed that the correlation between seed traits was different among different combinations and populations, and the correlation between seed length and width was the most significant by the pheno-typic analysis. And a total of 18 QTLs were detected for four traits including 2 QTLs for seed length, 5 QTLs for seed width, 4 QTLs for seed thickness, and 7 QTLs for hundred-grain weight, which were distributed on linkage groups 1, 4, 7, 8, 9, and 10, respectively. The LOD values ranged from 3.77 to 7.40, and the contribution of variation rate ranged from 0.71% to 86.20%. Based on these results, six candidate genes (28470.m000435, 29908.m006143, 29848.m004589, 27752.m000045, 29683.m000480, and 29848.m004611) for regulating seed size were screened. This study lays a theoretical foundation for further research on fine mapping and gene cloning, molecular marker-assisted breeding and gene function analysis of castor seed size traits. [ABSTRACT FROM AUTHOR]

Rice is a major food crop that sustains approximately half of the world population. Recent worldwide improvements in the standard of living have increased the demand for high-quality rice. Accurate identification of quantitative trait loci (QTLs) for rice grain quality traits will facilitate rice quality breeding and improvement. In the present study, we performed highresolution QTL mapping for rice grain quality traits using a genotyping-bysequencing approach. An F2 population derived from a cross between an elite japonica variety, Koshihikari, and an indica variety, Nona Bokra, was used to construct a high-density genetic map. A total of 3,830 single nucleotide polymorphism markers were mapped to 12 linkage groups spanning a total length of 2,456.4 cM, with an average genetic distance of 0.82 cM. Seven grain quality traits--the percentage of whole grain, percentage of head rice, percentage of area of head rice, transparency, percentage of chalky rice, percentage of chalkiness area, and degree of chalkiness--of the F2 population were investigated. In total, 15 QTLs with logarithm of the odds (LOD) scores >4 were identified, which mapped to chromosomes 6, 7, and 9. These loci include four QTLs for transparency, four for percentage of chalky rice, four for percentage of chalkiness area, and three for degree of chalkiness, accounting for 0.01%-61.64% of the total phenotypic variation. Of these QTLs, only one overlapped with previously reported QTLs, and the others were novel. By comparing the major QTL regions in the rice genome, several key candidate genes reported to play crucial roles in grain quality traits were identified. These findings will expedite the fine mapping of these QTLs and QTL pyramiding, which will facilitate the genetic improvement of rice grain quality. [ABSTRACT FROM AUTHOR]

The tolerance of rice anaerobic germination (AG) is the main limiting factor for direct seeding application, yet the genetics mechanism is still in its infancy. In the study, recombinant inbred lines population of TD70 Japonica cultivar and Kasalath Indica cultivar, was employed to construct a high-density genetic map by whole genome re-sequencing. As a result, a genetic map containing 12,328 bin-markers was constructed and a total of 50 QTLs were then detected for CL (coleoptile length), CD (coleoptile diameter), CSA (coleoptile surface area) and CV (coleoptile volume) related traits in the two stages of anaerobic treatment using complete interval mapping method (inclusive composite interval mapping, ICIM). Among the four traits associated with coleoptile, coleoptile volume had the largest number of QTLs (17), followed by coleoptile diameter (16), and coleoptile length had 5 QTLs. These QTLs could explain phenotypic contribution rates ranging from 0.34% to 11.17% and LOD values ranging from 2.52 to 11.57. Combined with transcriptome analysis, 31 candidate genes were identified. Furthermore, 12 stable QTLs were used to detect the aggregation effect analysis. Besides, It was found that individuals with more aggregation synergistic alleles had higher phenotypic values in different environments. Totally, high-density genetic map, QTL mapping and aggregation effect analysis of different loci related to the anaerobic germination of rice seeds were conducted to lay a foundation for the fine mapping of related genes in subsequent assisted breeding. [ABSTRACT FROM AUTHOR]

Soybean plant architecture has a significant impact on yield potential, but the genetic underpinnings of key architectural traits remain elusive. The primary objective of this study was to explore the genetic foundations underlying main stem node number (MSN) in soybeans. Recombinant inbred lines (RILs) contained a 234 individual derived from crosses between two cultivars Zhonghuang35 (ZH35) and Jindou21 (JD21) was evaluated for seed hardness across 3 years (2013, 2014, and 2015 in Gansu). Markedly, the parent varieties, shown significant differences in MSN. Also, the RIL population exhibited a wide range of genetic variation in MSN. A high-density genetic map composed of 8,078 specific-locus amplified fragment (SLAF) markers, spanning 3,480.98 centimorgans (cM) with an average inter-marker distance of 0.59 cM were used to construct linkage map. Using ICIM analysis identified a total of 23 Quantitative Trait Loci (QTLs) across the 20 chromosome, of which five QTLs were detected in multiple years in Chr.6. Notably, we identified a stable major QTL, qMSN-6-4 , explaining up to 24.81% of phenotypic variation. This QTL govern seven candidate genes with potential roles in regulating MSN development in soybean, including Glyma.06G027500 with a domain of unknown function, Glyma.06G027600 involved in proton transport, Glyma.06G027700 linked to proteolysis, Glyma.06G027900 related to transcriptional regulation, and Glyma.06G028000 and Glyma.06G028050 associated with membrane functions. The RT-PCR analysis confirmed that these genes were expressed differently between the parental lines this supports the idea that they may play a role in determining MSN. Glyma.06G027500 and Glyma.06G027600 showing higher expression in JD21 leaves and nodes, while Glyma.06G027700 and Glyma.06G028000 exhibited increased expression in ZH35 stems, highlighting their distinct roles in transcription regulation, membrane activities, and protein degradation that contribute to MSN formation in soybean. This study offers valuable insights into the genetic mechanisms governing soybean MSN, providing a foundation for future research and crop improvement efforts., Competing Interests: The authors declare that they have no competing interests., (© 2024 Ren et al.)

Abstract Background Genetic and functional genomics studies require a high-quality genome assembly. Tomato (Solanum lycopersicum), an important horticultural crop, is an ideal model species for the study of fruit development. Results Here, we assembled an updated reference genome of S. lycopersicum cv. Heinz 1706 that was 799.09 Mb in length, containing 34,384 predicted protein-coding genes and 65.66% repetitive sequences. By comparing the genomes of S. lycopersicum and S. pimpinellifolium LA2093, we found a large number of genomic fragments probably associated with human selection, which may have had crucial roles in the domestication of tomato. We also used a recombinant inbred line (RIL) population to generate a high-density genetic map with high resolution and accuracy. Using these resources, we identified a number of candidate genes that were likely to be related to important agronomic traits in tomato. Conclusion Our results offer opportunities for understanding the evolution of the tomato genome and will facilitate the study of genetic mechanisms in tomato biology.

Due to its fast deterioration, soybean (Glycine max L.) has an inherently poor seed vigor. Vigor loss occurring during storage is one of the main obstacles to soybean production in the tropics. To analyze the genetic background of seed vigor, soybean seeds of a recombinant inbred line (RIL) population derived from the cross between Zhonghuang24 (ZH24, low vigor cultivar) and Huaxia3hao (HX3, vigorous cultivar) were utilized to identify the quantitative trait loci (QTLs) underlying the seed vigor under −20 °C conservation and accelerated aging conditions. According to the linkage analysis, multiple seed vigor-related QTLs were identified under both −20 °C and accelerated aging storage. Two major QTLs and eight QTL hotspots localized on chromosomes 3, 6, 9, 11, 15, 16, 17, and 19 were detected that were associated with seed vigor across two storage conditions. The indicators of seed vigor did not correlate well between the two aging treatments, and no common QTLs were detected in RIL populations stored in two conditions. These results indicated that deterioration under accelerated aging conditions was not reflective of natural aging at −20 °C. Additionally, we suggest 15 promising candidate genes that could possibly determine the seed vigor in soybeans, which would help explore the mechanisms responsible for maintaining high seed vigor.

Grain shape is an important agronomic trait directly associated with yield in rice. In order to explore new genes related to rice grain shape, a high-density genetic map containing 2193 Bin markers (526957 SNP) was constructed by whole-genome resequencing of 208 recombinant inbred (RILs) derived from a cross between ZP37 and R8605, with a total genetic distance of 1542.27 cM. The average genetic distance between markers was 0.76 cM, and the physical distance was 201.29 kb. Quantitative trait locus (QTL) mapping was performed for six agronomic traits related to rice grain length, grain width, length-to-width ratio, thousand-grain weight, grain cross-sectional area, and grain perimeter under three different environments. A total of 39 QTLs were identified, with mapping intervals ranging from 8.1 kb to 1781.6 kb and an average physical distance of 517.5 kb. Among them, 15 QTLs were repeatedly detected in multiple environments. Analysis of the genetic effects of the identified QTLs revealed 14 stable genetic loci, including three loci that overlapped with previously reported gene positions, and the remaining 11 loci were newly identified loci associated with two or more environments or traits. Locus 1, Locus 3, Locus 10, and Locus 14 were novel loci exhibiting pleiotropic effects on at least three traits and were detected in multiple environments. Locus 14, with a contribution rate greater than 10%, influenced grain width, length-to-width ratio, and grain cross-sectional area. Furthermore, pyramiding effects analysis of three stable genetic loci showed that increasing the number of QTL could effectively improve the phenotypic value of grain shape. Collectively, our findings provided a theoretical basis and genetic resources for the cloning, functional analysis, and molecular breeding of genes related to rice grain shape.

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. [ABSTRACT FROM AUTHOR]

Pumpkin is a popular vegetable crop and exhibits a broad diversity in fruit shape and size. Fruit-related traits are the decisive factors determining consumer acceptance and market value of pumpkin cultivar. As a result, deciphering the genetic basis of fruit-related traits is of great importance for pumpkin breeding. To address this problem, a F2 population was generated by two Cucurbita moschata inbred lines with contrasting fruit shapes, and genotyping by sequencing approach was used to construct a genetic map and localize the QTLs underlying the fruit-related traits in this study. The results showed that a high-quality genetic map was constructed for pumpkin, which comprised of 2413 bins and spanned a total length of 2252.10 cM with an average genetic distance of 0.94 cM. Thirty significant QTLs with moderate or small effects were identified for seven fruit-related traits, including fruit length, fruit diameter, fruit shape index, fruit weight, fruit flesh thickness, seed cavity size, and total soluble solids content. Co-locations were observed between the QTLs underlying different traits, demonstrating that pleiotropic effect plays an important role in genetic control of fruit-related traits. The identified QTLs provide valuable information for further fine mapping of the related genes and pumpkin breeding programs with the aim of improving fruit quality. [ABSTRACT FROM AUTHOR]

Seed coat color is a typical evolutionary trait. Identification of the genetic loci that control seed coat color during the domestication of wild soybean could clarify the genetic variations between cultivated and wild soybean. We used 276 F10 recombinant inbred lines (RILs) from the cross between a cultivated soybean (JY47) and a wild soybean (ZYD00321) as the materials to identify the quantitative trait loci (QTLs) for seed coat color. We constructed a high-density genetic map using re-sequencing technology. The average distance between adjacent markers was 0.31 cM on this map, comprising 9,083 bin markers. We identified two stable QTLs (qSC08 and qSC11) for seed coat color using this map, which, respectively, explained 21.933 and 26.934% of the phenotypic variation. Two candidate genes (CHS3C and CHS4A) in qSC08 were identified according to the parental re-sequencing data and gene function annotations. Five genes (LOC100786658, LOC100801691, LOC100806824, LOC100795475, and LOC100787559) were predicted in the novel QTL qSC11, which, according to gene function annotations, might control seed coat color. This result could facilitate the identification of beneficial genes from wild soybean and provide useful information to clarify the genetic variations for seed coat color in cultivated and wild soybean. [ABSTRACT FROM AUTHOR]

The genetic architecture of resistance for witches' broom disease of cacao (WBD) was reexamined in an F2 population (Sca-6 × ICS-1), addressing symptom-specificity and possible genetic basis for the differences in disease scores from terminal and cushion brooms. A high-density genetic linkage map was constructed with 494 individuals and 2968 SNPs, obtaining 10 linkage groups comprising 1595 centiMorgans. The trees were evaluated under field conditions with high WBD pressure from 2015 to 2019, with low spatial autocorrelation tested by Moran's I. Five WBD symptoms and one tree growth trait were mapped, resulting in 23 minor-effects QTLs, primarily arranged in clusters and distributed in all linkage groups except 4 and 6, indicating that WBD has a polygenic inheritance. Terminal and cushion brooms shared a genomic region in linkage group 9, suggesting pleiotropy. In these conditions, the ICS-1 grandparent contributed with more QTLs than Sca-6 to WBD resistance, indicating that the resistance pattern has changed and confirming the susceptible parent's importance. Few QTLs were identified in the same or proximal loci comparing the 5-year, annual, or biennial periods. Several candidate genes such as glutathione peroxidases, threonine-serine receptors, and endochitinases were potentially associated with WBD resistance. These findings strongly suggest that WBD resistance is more complex than previously postulated, and future directions are presented and suggested to investigate further and improve the insights into WBD resistance. [ABSTRACT FROM AUTHOR]

A high-density genetic map is a prerequisite for marker-assisted selection of crop species. Here, we developed a high-density genetic map of Vitis using 92 F1 progeny derived from the cross between two wine grape cultivars, 'Shuanghong' and 'Italian Riesling'. Whole genome resequencing (WGS) technology was used to generate SNP markers for the map. The map consisted of 1351 recombination bin markers (210,873 SNPs), distributed on 19 linkage groups (LGs), with an average distance of 0.65 cM between adjacent bin markers and a map distance of 860.46 cM. The high levels of uniform coverage and collinearity between the 19 LGs and the grape reference genome indicated that the map is of high quality and can serve as a powerful platform for evaluating grapevines and deciphering the genetic mechanism of important economic and agronomic traits. Our findings will facilitate the process of mapping quantitative trait loci (QTL) that control important horticultural and economic traits of grape. [ABSTRACT FROM AUTHOR]

Iron deficiency chlorosis (IDC) under calcareous and alkaline soils is a significant abiotic stress affecting the growth and yield of peanut. In this study, the genomic regions governing IDC tolerance were mapped using a recombinant inbred line (RIL) population derived from TMV 2 (susceptible to IDC) and TMV 2-NLM (tolerant to IDC), which was phenotyped during the rainy seasons of 2019 and 2020 in the iron-deficient calcareous plots. The best linear unbiased prediction (BLUP) values for IDC tolerance traits like visual chlorotic rating (VCR), and SPAD chlorophyll meter reading (SCMR) were used for QTL analysis along with a genetic map carrying 700 GBS-derived SNP, AhTE and SSR markers. In total, 11 and 12 main-effect QTLs were identified for VCR and SCMR, respectively. Among them three QTLs were major with the phenotypic variance explained (PVE) of 10.3–34.4% for VCR, and two QTL were major for SCMR with PVE of 11.5–11.7%. A region (159.3–178.3 cM) on chromosome Ah13 carrying two QTLs (one each for VCR and SCMR) was consistent with the previous report. A SNP marker, Ah14_138037990 identified from single marker analysis for VCR was located in the intronic region of the gene Arahy.QA0C1, which is important for protein-binding. Overall, this study identified new QTLs and also validated QTL for IDC tolerance. These genomic resources could be useful for genomics-assisted breeding of peanut for IDC tolerance. [ABSTRACT FROM AUTHOR]

Abstract Background Goji (Lycium spp., 2n = 24) is a fruit bearing woody plant popular as a superfood for extensive medicinal and nutritional advantages. Fruit size associated attributes are important for evaluating small-fruited goji berry and plant architecture. The domestication traits are regulated quantitatively in crop plants but few studies have attempted on genomic regions corresponding to fruit traits. Results In this study, we established high-resolution map using specific locus amplified fragment (SLAF) sequencing for de novo SNPs detection based on 305 F1 individuals derived from L. chinense and L. barbarum and performed quantitative trait loci (QTL) analysis of fruit size related traits in goji berry. The genetic map contained 3495 SLAF markers on 12 LGs, spanning 1649.03 cM with 0.47 cM average interval. Female and male parents and F1 individuals` sequencing depth was 111.85-fold and 168.72-fold and 35.80-fold, respectively. The phenotype data were collected for 2 successive years (2018–2019); however, two-year mean data were combined in an extra year (1819). Total 117 QTLs were detected corresponding to multiple traits, of which 78 QTLs in 2 individual years and 36 QTLs in extra year. Six Promising QTLs (qFW10–6.1, qFL10–2.1, qLL10–2.1, qLD10–2.1, qLD12–4.1, qLA10–2.1) were discovered influencing fruit weight, fruit length and leaf related attributes covering an interval ranged from 27.32–71.59 cM on LG10 with peak LOD of 10.48 and 14.6% PVE. Three QTLs targeting fruit sweetness (qFS3–1, qFS5–2) and fruit firmness (qFF10–1) were also identified. Strikingly, various traits QTLs were overlapped on LG10, in particular, qFL10–2.1 was co-located with qLL10–2.1, qLD10–2.1 and qLA10–2.1 among stable QTLs, harbored tightly linked markers, while qLL10–1 was one major QTL with 14.21 highest LOD and 19.3% variance. As LG10 harbored important traits QTLs, we might speculate that it could be hotspot region regulating fruit size and plant architectures. Conclusions This report highlights the extremely saturated linkage map using SLAF-seq and novel loci contributing fruit size-related attributes in goji berry. Our results will shed light on domestication traits and further strengthen molecular and genetic underpinnings of goji berry; moreover, these findings would better facilitate to assemble the reference genome, determining potential candidate genes and marker-assisted breeding.

Abstract Background Transcription factor (TF) GAMYB, belonging to MYB family (named after the gene of the avian myeloblastosis virus) is a master gibberellin (GA)-induced regulatory protein that is crucial for development and germination of cereal grain and involved in anther formation. It activates many genes including high-molecular-weight glutenin and α-amylase gene families. This study presents the first attempt to characterize the rye gene encoding GAMYB in relation to its sequence, polymorphisms, and phenotypic effects. Results ScGAMYB was mapped on rye chromosome 3R using high-density Diversity Arrays Technology (DArT)/DArTseq-based maps developed in three mapping populations. The ScGAMYB sequences were identified in RNA-seq libraries of four rye inbred lines. The transcriptome used for the search contained almost 151,000 transcripts with a median contig length of 500 nt. The average amount of total base raw data was approximately 9 GB. Comparative analysis of the ScGAMYB sequence revealed its high level of homology to wheat and barley orthologues. Single nucleotide polymorphisms (SNPs) detected among rye inbred lines allowed the development of allele specific-PCR (AS-PCR) markers for ScGAMYB that might be used to detect this gene in wide genetic stocks of rye and triticale. Segregation of the ScGAMYB alleles showed significant relationship with α-amylase activity (AMY). Conclusions The research showed the strong similarity of rye GAMYB sequence to its orthologues in other Graminae and confirmed the position in the genome consistent with the collinearity rule of cereal genomes. Concurrently, the ScGAMYB coding sequence (cds) showed stronger variability (24 SNPs) compared to the analogous region of wheat (5 SNPs) and barley (7 SNPs). The moderate regulatory effect of ScGAMYB on AMY was confirmed, therefore, ScGAMYB was identified as a candidate gene for partial control of α-amylase production in rye grain. The predicted structural protein change in the aa region 362–372, caused by a single SNP (C/G) at the 1100 position in ScGAMYB cds and single aa sequence change (S/C) at the 367 position, is the likely cause of the differences in the effectiveness of ScGAMYB regulatory function associated with AMY. The development of sequence-based, allele-specific (AS) PCR markers could be useful in research and application.

Abstract Background Berry color is an important trait in grapes and is mainly determined by the anthocyanin content and composition. To further explore the coloring mechanism of grape berries, the F1 population of Vitis vinifera ‘Red Globe’ × ‘Muscat Hamburg’ was used to map the color locus, and transcriptome analysis was performed to assist in screening candidate genes. Results A total of 438,407 high-quality single-nucleotide polymorphisms (SNPs) were obtained from whole-genome resequencing (WGS) of the population, and 27,454 SNPs were selected to construct a high-density genetic map. The selected SNPs were clustered into 19 linkage groups (LGs) spanning a genetic distance of 1442.638 cM. Berry color was evaluated by color grade, chromatic aberration, total anthocyanin content and anthocyanin composition. The Pearson correlation coefficients of these phenotypes in 2017 and 2018 were significant at the 0.01 level. The major color locus of MYBA1 and MYBA2 on LG2 was identified, explaining between 26 and 63.6% of all phenotypic variance. Furthermore, 9 additional QTLs with smaller effects were detected on Chr2, Chr4, Chr6, Chr11 and Chr17. Combined with the gene annotation and RNA-seq data, multiple new candidate genes were selected from the above QTLs. Conclusion These results indicated that grape berry color is a quantitative trait controlled by a major color locus and multiple minor loci. Though the major color locus was consistent with previous studies, several minor QTLs and candidate genes associated with grape berry color and anthocyanin accumulation were identified in this study. And the specific regulatory mechanism still needs to be further explored.

Background: Genetic and functional genomics studies require a high-quality genome assembly. Tomato (Solanum lycopersicum), an important horticultural crop, is an ideal model species for the study of fruit development. Results: Here, we assembled an updated reference genome of S. lycopersicum cv. Heinz 1706 that was 799.09 Mb in length, containing 34,384 predicted protein-coding genes and 65.66% repetitive sequences. By comparing the genomes of S. lycopersicum and S. pimpinellifolium LA2093, we found a large number of genomic fragments probably associated with human selection, which may have had crucial roles in the domestication of tomato. We also used a recombinant inbred line (RIL) population to generate a high-density genetic map with high resolution and accuracy. Using these resources, we identified a number of candidate genes that were likely to be related to important agronomic traits in tomato. Conclusion: Our results offer opportunities for understanding the evolution of the tomato genome and will facilitate the study of genetic mechanisms in tomato biology. [ABSTRACT FROM AUTHOR]

Salinity tolerance plays an important role in direct seeding cultivation since tolerance to salinity at the bud burst stage of rice directly affects seedling formation and yield. However, information on the quantitative trait loci (QTL) associated with salinity tolerance at the bud burst stage is limited. Here, a recombinant inbred line (RIL) population, derived from a cross between Kongyu131 (salinity-sensitive) and Xiaobaijingzi (salinity-tolerant), was used to identify QTLs for salinity tolerance at the bud burst stage using a high-density genetic map. Four QTLs were identified. The threshold LOD score for QTL identification was 3.0. Among the four QTLs detected, two QTLs namely qRSL3 (PVE, 22.59%) and qRRL3 (PVE, 21.21%) were considered to be one QTL, named qST3, which was the major QTL related to salinity tolerance on chromosome 3. This major QTL was located within an interval of 2.55 Mb and contained 253 candidate genes. Using RNA-seq data, 51 differentially expressed genes (DEGs) were detected among the candidate region. According to Rice Annotation Project and quantitative real-time PCR (qRT-PCR) analysis, Os03g0664800 was accepted as the most likely candidate gene for qST3. These results will be useful for improving salinity tolerance of rice and for developing rice cultivars suitable for direct seeding in salinized soil. [ABSTRACT FROM AUTHOR]

Plant height is a crucial element related to plant architecture that influences the seed yield of oilseed rape (Brassica napus L.). In this study, we isolated a natural B. napus mutant, namely a semi-dwarf mutant (sdw-e), which exhibits a 30% reduction in plant height compared with Zhongshuang 11-HP (ZS11-HP). Quantitative trait locus sequencing (QTL-seq) was conducted using two extreme DNA bulks in F2 populations in Wuchang-2017 derived from ZS11-HP ×sdw-e to identify QTLs associated with plant height. The result suggested that two QTL intervals were located on chromosome A10. The F2 population consisting of 200 individuals in Yangluo-2018 derived from ZS11-HP × sdw-e was used to construct a high-density linkage map using whole-genome resequencing. The high-density linkage map harbored 4323 bin markers and covered a total distance of 2026.52 cM with an average marker interval of 0.47 cM. The major QTL for plant height named qPHA10 was identified on linkage group A10 by interval mapping and composite interval mapping methods. The major QTL qPHA10 was highly consistent with the QTL-seq results. And then, we integrated the variation sites and expression levels of genes in the major QTL interval to predict the candidate genes. Thus, the identified QTL and candidate genes could be used in marker-assisted selection for B. napus breeding in the future. [ABSTRACT FROM AUTHOR]

Ancherythroculter nigrocauda is a fish endemic to the upper areas of the Changjiang (Yangtze) River in China. Quantitative trait locus (QTL) mapping is a powerful tool to identify potential genes affecting traits of economic importance in domestic animals. In this study, a high-density genetic map was constructed with 5 901 single nucleotide polymorphism (SNP) makers by sequencing 92 individual fish from a F1 family using the specific-locus amplified fragment sequencing approach. Initially, 48 QTLs for total length, body length, body height, and body weight were identified according to the high density of the genetic map with 24 LGs, a total length of 3 839.4 cM, and marker spacing of about 0.82 cM. These QTLs explained 27.1%–49.9% of phenotypic variance. The results of this study suggest that major QTLs are responsible for the growth of A. nigrocauda, and these are potentially useful in comparative genomics research, genome assembly, and marker-assisted breeding programs for this species. [ABSTRACT FROM AUTHOR]

Pepper (Capsicum annuum L.) is an economically significant global crop and condiment. Its yield can be severely reduced by the oomycete plant pathogen, Phytophthora capsici (P. capsici). Here, a high-density genetic map was created with a mapping panel of F2 populations obtained from 150 individuals of parental lines PI201234 and 1287 and specific-locus amplified fragment sequencing (SLAF) that was then utilized to identify loci that are related to resistance to P. capsici. The sequencing depth of the genetic map was 108.74-fold for the male parent, 126.25-fold for the female parent, and 22.73-fold for the offspring. A high-resolution genetic map consisting of 5565 markers and 12 linkage groups was generated for pepper, covering 1535.69 cM and an average marker distance of 0.28 cM. One major quantitative trait locus (QTL) for the P. capsici resistance (CQPc5.1) was identified on Chr05 that explained the observed 11.758% phenotypic variance. A total of 23 candidate genes located within the QTL CQPc5.1 interval were identified, which included the candidate gene Capana05g000595 that encodes the RPP8-like protein as well as two candidate genes Capana05g000596 and Capana05g000597 that encodes a RPP13-like protein. Quantitative reverse-transcription PCR (qRT-PCR) revealed higher expression levels of Capana05g000595, Capana05g000596, and Capana05g000597 in P. capsici resistance accessions, suggesting their association with P. capsici resistance in pepper. [ABSTRACT FROM AUTHOR]

Gray leaf spot (GLS) caused by Cercospora zeae-maydis or Cercospora zeina is one of the devastating maize foliar diseases worldwide. Identification of GLS-resistant quantitative trait loci (QTL)/genes plays an urgent role in improving GLS resistance in maize breeding practice. Two groups of recombinant inbred line (RIL) populations derived from CML373 × Ye107 and Chang7-2 × Ye107 were generated and subjected to genotyping-by-sequencing (GBS). A total of 1,929,222,287 reads in CML373 × Ye107 (RIL-YCML) and 2,585,728,312 reads in Chang7-2 × Ye107 (RIL-YChang), with an average of 10,961,490 (RIL-YCML) and 13,609,096 (RIL-YChang) reads per individual, were got, which was roughly equal to 0.70-fold and 0.87-fold coverage of the maize B73 RefGen_V4 genome for each F7 individual, respectively. 6418 and 5139 SNP markers were extracted to construct two high-density genetic maps. Comparative analysis using these physically mapped marker loci demonstrated a satisfactory colinear relationship with the reference genome. 11 GLS-resistant QTL have been detected. The individual QTL accounted for 1.53–24.00% of the phenotypic variance explained (PVE). The new consensus QTL (qYCM-DS3-3/qYCM-LT3-1/qYCM-LT3-2) with the largest effect was located in chromosome bin 3.05, with an interval of 2.7 Mb, representing 13.08 to 24.00% of the PVE. Further gene annotation indicated that there were four candidate genes (GRMZM2G032384, GRMZM2G041415, GRMZM2G041544, and GRMZM2G035992) for qYCM-LT3-1, which may be related to GLS resistance. Combining RIL populations and GBS-based high-density genetic maps, a new larger effect QTL was delimited to a narrow genomic interval, which will provide a new resistance source for maize breeding programs. [ABSTRACT FROM AUTHOR]

Resveratrol (trans-3,4′,5-trihydroxystilbene) is a natural stilbene phytoalexin which is also found to be good for human health. Cultivated peanut (Arachis hypogaea L.), a worldwide important legume crop, is one of the few sources of human's dietary intake of resveratrol. Although the variations of resveratrol contents among peanut varieties were observed, the variations across environments and its underlying genetic basis were poorly investigated. In this study, the resveratrol content in seeds of a recombination inbred line (RIL) population (Zhonghua 6 × Xuhua 13, 186 progenies) were quantified by high performance liquid chromatography (HPLC) method across four environments. Genotypes, environments and genotype × environment interactions significantly influenced the resveratrol contents in the RIL population. A total of 8,114 high-quality single nucleotide polymorphisms (SNPs) were identified based on double-digest restriction-site-associated DNA sequencing (ddRADseq) reads. These SNPs were clustered into bins using a reference-based method, which facilitated the construction of high-density genetic map (2,183 loci with a total length of 2,063.55 cM) and the discovery of several chromosome translocations. Through composite interval mapping (CIM), nine additive quantitative trait loci (QTL) for resveratrol contents were identified on chromosomes A01, A07, A08, B04, B05, B06, B07, and B10 with 5.07–8.19% phenotypic variations explained (PVE). Putative genes within their confidential intervals might play roles in diverse primary and secondary metabolic processes. These results laid a foundation for the further genetic dissection of resveratrol content as well as the breeding and production of high-resveratrol peanuts.

Resveratrol (trans-3,4′,5-trihydroxystilbene) is a natural stilbene phytoalexin which is also found to be good for human health. Cultivated peanut (Arachis hypogaea L.), a worldwide important legume crop, is one of the few sources of human's dietary intake of resveratrol. Although the variations of resveratrol contents among peanut varieties were observed, the variations across environments and its underlying genetic basis were poorly investigated. In this study, the resveratrol content in seeds of a recombination inbred line (RIL) population (Zhonghua 6 × Xuhua 13, 186 progenies) were quantified by high performance liquid chromatography (HPLC) method across four environments. Genotypes, environments and genotype × environment interactions significantly influenced the resveratrol contents in the RIL population. A total of 8,114 high-quality single nucleotide polymorphisms (SNPs) were identified based on double-digest restriction-site-associated DNA sequencing (ddRADseq) reads. These SNPs were clustered into bins using a reference-based method, which facilitated the construction of high-density genetic map (2,183 loci with a total length of 2,063.55 cM) and the discovery of several chromosome translocations. Through composite interval mapping (CIM), nine additive quantitative trait loci (QTL) for resveratrol contents were identified on chromosomes A01, A07, A08, B04, B05, B06, B07, and B10 with 5.07–8.19% phenotypic variations explained (PVE). Putative genes within their confidential intervals might play roles in diverse primary and secondary metabolic processes. These results laid a foundation for the further genetic dissection of resveratrol content as well as the breeding and production of high-resveratrol peanuts. [ABSTRACT FROM AUTHOR]

Seed traits are agronomically important for Cucurbita breeding, but the genes controlling seed size, seed weight and seed number have not been mapped in Cucurbita maxima (C. maxima). In this study, 100 F2 individual derived from two parental lines, “2013-12” and “9-6”, were applied to construct a 3,376.87-cM genetic map containing 20 linkage groups (LGs) with an average genetic distance of 0.47 cM using a total of 8,406 specific length amplified fragment (SLAF) markers in C. maxima. Ten quantitative trait loci (QTLs) of seed width (SW), seed length (SL) and hundred-seed weight (HSW) were identified using the composite interval mapping (CIM) method. The QTLs affecting SW, SL and HSW explained a maximum of 38.6%, 28.9% and 17.2% of the phenotypic variation and were detected in LG6, LG6 and LG17, respectively. To validate these results, an additional 150 F2 individuals were used for QTL mapping of SW and SL with cleaved amplified polymorphic sequence (CAPS) markers. We found that two major QTLs, SL6-1 and SW6-1, could be detected in both SLAF-seq and CAPS markers in an overlapped region. Based on gene annotation and non-synonymous single-nucleotide polymorphisms (SNPs) in the major SWand SL-associated regions, we found that two genes encoding a VQ motif and an E3 ubiquitin-protein ligase may be candidate genes influencing SL, while an F-box and leucinerich repeat (LRR) domain-containing protein is the potential regulator for SW in C. maxima. This study provides the first high-density linkage map of C. maxima using SNPs developed by SLAF-seq technology, which is a powerful tool for associated mapping of important agronomic traits, map-based gene cloning and marker-assisted selection (MAS)-based breeding in C. maxima.

Developing new population types based on interspecific introgressions has been suggested to facilitate the discovery of novel allelic sources for traits of agronomic importance. In this study, a chromosome segment substitution line (CSSL) rice population carrying contiguous chromosomal segments of japonica Nipponbare in the genetic background of indica 9311 was developed. Meanwhile, a high-density genetic map including 655 bins covering a distance of 1480.2 Mb, with an average of 0.60 Mb between markers, was generated through a whole-genome resequencing approach. Compared with previous CSSL populations constructed from 9311 or Nipponbare, this population has a higher marker density and can effectively meet the requirements of high QTL mapping resolution. On the basis of the newly constructed high-density genetic map, a total of three major QTLs (qGP4, qGP5, and qBL4) conferring seed growth capacity after low-temperature (5 °C) treatment were detected. Among these, two QTLs shared by Nipponbare, qGP4 and qGP5, could increase germination percentage, while one QTL shared by Nipponbare, qBL4, could increase bud length after cold stress; qGP4 and qBL4 were first reported in our study. These QTLs could be highly valuable genetic factors for cold tolerance improvement in rice lines. The CSSLs carrying these QTLs not only provide an opportunity for map-based cloning of important cold tolerance QTLs but also supply useful inbred lines to improve cold tolerance in 9311. These CSSLs represent good sources of japonica tolerance QTLs (genes) for use in improving cold tolerance in indica rice directly, avoiding the genetic drag arising from incompatible epistasis effects. [ABSTRACT FROM AUTHOR]

Phytophthora root rot attributable to infection by the soil-borne oomycete Phytophthora sojae causes serious damage to susceptible soybeans grown in poorly drained soil. Management of this disease depends primarily on Rps (resistance to P. sojae) resistance genes. The objective of this study was to map resistance to two P. sojae isolates (40412 and 2457) in a Daepung × Socheong2 recombinant inbred line population. Of these two varieties, Socheong2 is resistant to the two isolates, whereas Daepung is susceptible. Single-marker analysis of variance and linkage analyses using a high-density genetic map identified different resistance loci for each isolate. A genomic region of 36.2~37.4 Mbp on chromosome 3 was identified as being associated with resistance to isolate 40412, explaining 18% of the phenotypic variance (PV), whereas, a 2.1~2.6-Mbp region on chromosome 18 was significantly associated with resistance to isolate 2457, accounting for approximately 26% of the PV. An additional region of 53.1~53.3 Mbp on chromosome 18 was also significantly associated with resistance to isolate 2457. All three loci coincide with genomic regions where an Rps gene or partial resistance have been mapped in previous studies. The respective locus showed significance for only one or the other of the isolates, indicating an isolate-specific interaction. From this finding, it can be inferred that isolates 40412 and 2457 are characterized by different avirulence genes, and that Socheong2 has at least two Rps genes that interact with each isolate. The finding of multiple Rps loci specific to an isolate within a single soybean genotype is a unique discovery. Socheong2 will accordingly be a useful genetic source for breeding resistance to multiple P. sojae isolates. [ABSTRACT FROM AUTHOR]

Luffa cylindrica L. is a cash crop which has important health, medicinal and industrial value, but no high saturation genetic map has been constructed owing to a lack of efficient markers. Furthermore, no genes were reportedly responsible for CMV resistance in Luffa spp. Specific length amplified fragment sequencing (SLAF-seq) is a valuable tool for large-scale discovery of markers and genetic mapping. The present study reported the construction of a high-density genetic map and the mapping of CMV resistant genes by using an F2 population of 130 individuals and their two inbred line parents. A total of 271.01 Mb pair-end reads were generated. 100,077 high-quality SLAFs were detected, and 7404 of them were polymorphic. Finally, 3701 of the polymorphic markers were selected for genetic map construction, and 13 linkage groups were generated. The map spanned 1518.56 cM with an average distance of 0.41 cM between adjacent markers. Based on the newly constructed high-density map, one gene located on chromosome 1 (100.072–100.457 cM) was identified to regulate CMV resistance in L. cylindrica. A gag-polypeptide of LTR copia-type retrotransposon was predicted as the candidate gene responsible for CMV resistance in L. cylindrica. The high-density genetic map and the CMV resistant gene mapped and predicted in this study will be useful in future research. [ABSTRACT FROM AUTHOR]

The knowledge about the genetic basis of alkaline salt stress and neutral salt stress in rice is limited. Here, we located quantitative trait loci (QTL) for seed germination rate (GR) under alkaline salt stress (NaHCO3) and neutral salt stress (NaCl) using backcross inbred lines population, which was derived from a cross between indica cv. Changhui 891 (CH891) and japonica cv. 02428 with 3057 bins markers. A total of ten QTL for five salt stress-related traits were detected. The QTL detected for control condition, NaCl stress, and NaHCO3 stress were quite different, which suggested that the genes controlling the transport of the Na+, in the form of NaCl and the NaHCO3, may be different or induced incoordinately by salt stress. Furthermore, on the basis of the high-density genetic map, the ten QTL were mapped on 40–980 kb chromosomal regions on Nipponbare genome, and 16 candidate genes related to stress or metal transport were found. These results contribute to the fine mapping and use of these GR-related QTL. [ABSTRACT FROM AUTHOR]

Background: Berry color is an important trait in grapes and is mainly determined by the anthocyanin content and composition. To further explore the coloring mechanism of grape berries, the F1 population of Vitis vinifera 'Red Globe' × 'Muscat Hamburg' was used to map the color locus, and transcriptome analysis was performed to assist in screening candidate genes. Results: A total of 438,407 high-quality single-nucleotide polymorphisms (SNPs) were obtained from whole-genome resequencing (WGS) of the population, and 27,454 SNPs were selected to construct a high-density genetic map. The selected SNPs were clustered into 19 linkage groups (LGs) spanning a genetic distance of 1442.638 cM. Berry color was evaluated by color grade, chromatic aberration, total anthocyanin content and anthocyanin composition. The Pearson correlation coefficients of these phenotypes in 2017 and 2018 were significant at the 0.01 level. The major color locus of MYBA1 and MYBA2 on LG2 was identified, explaining between 26 and 63.6% of all phenotypic variance. Furthermore, 9 additional QTLs with smaller effects were detected on Chr2, Chr4, Chr6, Chr11 and Chr17. Combined with the gene annotation and RNA-seq data, multiple new candidate genes were selected from the above QTLs. Conclusion: These results indicated that grape berry color is a quantitative trait controlled by a major color locus and multiple minor loci. Though the major color locus was consistent with previous studies, several minor QTLs and candidate genes associated with grape berry color and anthocyanin accumulation were identified in this study. And the specific regulatory mechanism still needs to be further explored. [ABSTRACT FROM AUTHOR]

Seed traits are agronomically important for Cucurbita breeding, but the genes controlling seed size, seed weight and seed number have not been mapped in Cucurbita maxima (C. maxima). In this study, 100 F2 individual derived from two parental lines, "2013-12" and "9-6", were applied to construct a 3,376.87-cM genetic map containing 20 linkage groups (LGs) with an average genetic distance of 0.47 cM using a total of 8,406 specific length amplified fragment (SLAF) markers in C. maxima. Ten quantitative trait loci (QTLs) of seed width (SW), seed length (SL) and hundred-seed weight (HSW) were identified using the composite interval mapping (CIM) method. The QTLs affecting SW, SL and HSW explained a maximum of 38.6%, 28.9% and 17.2% of the phenotypic variation and were detected in LG6, LG6 and LG17, respectively. To validate these results, an additional 150 F2 individuals were used for QTL mapping of SW and SL with cleaved amplified polymorphic sequence (CAPS) markers. We found that two major QTLs, SL6-1 and SW6-1, could be detected in both SLAF-seq and CAPS markers in an overlapped region. Based on gene annotation and non-synonymous single-nucleotide polymorphisms (SNPs) in the major SWand SL-associated regions, we found that two genes encoding a VQ motif and an E3 ubiquitin-protein ligase may be candidate genes influencing SL, while an F-box and leucinerich repeat (LRR) domain-containing protein is the potential regulator for SW in C. maxima. This study provides the first high-density linkage map of C. maxima using SNPs developed by SLAF-seq technology, which is a powerful tool for associated mapping of important agronomic traits, map-based gene cloning and marker-assisted selection (MAS)-based breeding in C. maxima. [ABSTRACT FROM AUTHOR]

Key message: Genetic dissection of GPC and TKW in tetraploid durum × WEW RIL population, based on high-density SNP genetic map, revealed 12 GPC QTLs and 11 TKW QTLs, with favorable alleles for 11 and 5 QTLs, respectively, derived from WEW. Wild emmer wheat (Triticum turgidum ssp. dicoccoides, WEW) was shown to exhibit high grain protein content (GPC) and therefore possess a great potential for improvement of cultivated wheat nutritional value. Genetic dissection of thousand kernel weight (TKW) and grain protein content (GPC) was performed using a high-density genetic map constructed based on a recombinant inbred line (RIL) population derived from a cross between T. durum var. Svevo and WEW acc. Y12-3. Genotyping of 208 F6 RILs with a 15 K wheat single nucleotide polymorphism (SNP) array yielded 4166 polymorphic SNP markers, of which 1510 were designated as skeleton markers. A total map length of 2169 cM was obtained with an average distance of 1.5 cM between SNPs. A total of 12 GPC QTLs and 11 TKW QTLs were found under five different environments. No significant correlations were found between GPC and TKW across all environments. Four major GPC QTLs with favorable alleles from WEW were found on chromosomes 4BS, 5AS, 6BS and 7BL. The 6BS GPC QTL coincided with the physical position of the NAC transcription factor TtNAM-B1, underlying the cloned QTL, Gpc-B1. Comparisons of the physical intervals of the GPC QTLs described here with the results previously reported in other durum × WEW RIL population led to the discovery of seven novel GPC QTLs. Therefore, our research emphasizes the importance of GPC QTL dissection in diverse WEW accessions as a source of novel alleles for improvement of GPC in cultivated wheat. [ABSTRACT FROM AUTHOR]

Key message: A QTL for resistance to several races of black spot co-located with the known Rrd1 locus in Rosa. A polymorphism in muRdr1A linked to black spot resistance was identified and molecular markers were designed. Black spot, caused by Diplocarpon rosae, is one of the most serious foliar diseases of landscape roses that reduces the marketability and weakens the plants against winter survival. Genetic resistance to black spot (BS) exists and race-specific resistance is a good target to implement marker-assisted selection. High-density single nucleotide polymorphism-based genetic maps were created for the female parent of a tetraploid cross between 'CA60' and 'Singing in the Rain' using genotyping-by-sequencing following a two-way pseudo-testcross strategy. The female linkage map was generated based on 227 individuals and included 31 linkage groups, 1055 markers, with a length of 1980 cM. Race-specific resistance to four D. rosae races (5, 7, 10, 14) was evaluated using a detached leaf assay. BS resistance was also evaluated under natural infection in the field. Resistance to races 5, 10 and 14 of D. rosae and field resistance co-located on chromosome 1. A unique sequence of 32 bp in exon 4 of the muRdr1A gene was identified in 'CA60' that co-segregates with D. rosae resistance. Two diagnostic markers, a presence/absence marker and an INDEL marker, specific to this sequence were designed and validated in the mapping population and a backcross population derived from 'CA60.' Resistance to D. rosae race 7 mapped to a different location on chromosome 1. [ABSTRACT FROM AUTHOR]

Abstract: General combining abilities (GCAs) are very important in utilization of heterosis in maize breeding. However, its genetic basis is unclear. In the present study, a set of 118 doubled haploid (DH) lines were induced from F1 generations produced from the cross between the inbred line Zheng 58 and the inbred line W499 belonging to the Reid subgroup. Using the MaizeSNP50 BeadChip, a high-density genetic map was constructed based on the DH population which included 1 147 bin markers with an average interval length of 2.00 cM. Meanwhile, the DH population was crossed with three testers including W16-5, HD568, and W556, which belong to the Sipingtou subgroup. The GCAs of the ear height (EH), the kernel moisture content (KMC), the kernel ratio (KR), and the yield per plant (YPP) were estimated using these hybrids in three environments. Combining the high-density genetic map and the GCAs, a total of 14 QTLs were detected for the GCAs of the four traits. Especially, one pleiotropic QTL was identified on chromosome 1 between the SNP SYN16067 and the SNP PZE-101169244 which was simultaneously associated with the GCAs of the EH, the KR, and the YPP. These QTLs pave the way for further dissecting the genetic architecture underlying GCAs of the traits, and they may be used to enhance GCAs of inbred lines under the fixed heterotic pattern Reid×Sipingtou in China through a marker-assisted selection approach.

Plant growth habit is an important and complex agronomic trait and is associated with yield, disease resistance, and mechanized harvesting in peanuts. There are at least two distinct growth habits (erect and prostrate) and several intermediate forms existing in the peanut germplasm. A recombinant inbred line population containing 188 individuals was developed from a cross of “Jihua 5” and “M130” for genetically dissecting the architecture of the growth habit. A new high-density genetic linkage map was constructed by using specific locus amplified fragment sequencing technology. The map contains 2,808 single-nucleotide polymorphism markers distributed on 20 linkage groups with a total length of 1,308.20 cM and an average inter-marker distance of 0.47 cM. The quantitative trait locus (QTL) analysis of the growth habit-related traits was conducted based on phenotyping data from seven environments. A total of 39 QTLs for growth habit-related traits was detected on 10 chromosomes explaining 4.55–27.74% of the phenotypic variance, in which 6 QTLs were for lateral branch angle, 8 QTLs were for extent radius, 7 QTLs were for the index of plant type, 11 QTLs were for main stem height, and 7 QTLs were for lateral branch length. Among these QTLs, 12 were co-localized on chromosome B05 spanning an approximately 0.17 Mb physical interval in comparison with the allotetraploid reference genome of “Tifrunner.” Analysis of the co-localized genome region has shown that the putative genes are involved in light and hormones and will facilitate peanut growth habit molecular breeding and study of peanut domestication.

The tassel architecture of maize (Zea mays L.), which plays an important role in F1 hybrid seed production and yield performance, is genetically controlled by quantitative trait loci (QTLs). Here, we constructed a high-density SNP-based genetic map using an F2 population containing 148 individuals. This genetic map included 7613 SNPs whose average genetic distance was 0.19 cM. On account of the F2 population, we detected 14 QTLs responsible for tassel branch number (TBN), tassel weight (TW), central spike length (CSL), and meristem length (ML); eight of these QTLs demonstrated a relatively high level of phenotypic variation explanation (PVE) (PVE ≥ 10%), at a high level of significance. qTW-2 was a major QTL (LOD = 10.11 and PVE = 28.82%), and this QTL and qTBN-2 shared the same region, indicating a possible pleiotropic effect. An F2:3 population was developed to further verify QTLs in the F2 population. Finally, qTBN-5, qTW-2 and qCSL_N-10 were detected reproducibly. To help screen potential candidate genes, we chose 12 genes within the regions of qTBN-5, qML-6, qCSL_N-7 and qTW-2 and that were possibly involved in tassel morphogenesis according to Gene Ontology (GO) annotation analysis and performed quantitative real-time polymerase chain reaction (qRT-PCR). The expression of eight of the 12 genes was significantly (P < 0.05) or extremely significantly different (P < 0.01) between parents of the F2 population during the young tassel development stage, suggesting that those eight were possible candidate genes. These results provide insights into the genetic mechanisms controlling tassel architecture and will benefit both tassel-related QTL fine mapping and causal gene cloning in maize. [ABSTRACT FROM AUTHOR]