Excellent Fiber Quality Research Articles

Efficiency of navmutant lines in the creation of cotton (g. hirsutum l.) varieties

According to the article, new promising families and lines of cotton that are resistant to unfavorable climatic conditions have been created. The cotton is fruitful, quick-growing, and has high fiber quality. The study was based on the variability and heredity of the main morphoeconomic characters in the hybrid generations obtained between cotton varieties with promising lines of cotton. We investigated the L-203 K line, SML-3882, SML-5531, SML-4042 mutant variety lines, the Bukhara-6 cotton variety, and the connections between the L-203 K line and mutant variety lines in our research. In reciprocal hybrids, the inheritance and variability of features were examined. In the breeding procedure, the maternal form's fully grown flower buds were taken out and the maternal flowers got fertilized the following day after the male pollen grains had reached maturity. The system developed by S. Wright and published in the publications of G. V. Beil and others was employed to determine the degree of character dominance in hybrids of the first syllable. Heritability and variability of traits were studied by comparison with parental samples in the reciprocal hybrids obtained through cross-breeding, including plant height, height of the first harvest branch, time from sowing to flowering, ripening speed, fiber yield, fiber length, cotton weight per boll, number of bolls per plant, etc. Many new families and ridges that were well suited to the soil and climate of the Bukhara region were separated. These families and ridges had high yields, excellent fiber quality, and yields. After extensive breeding over many years, a new cotton variety called "Zhondor Qudrati 1" was produced.

A novel eco–friendly solid–state degumming method for extraction of hemp fibers

Hemp represents a valuable resource of natural fibers on account of its environment favorable characteristics and excellent fiber quality. To fabricate hemp fibers, the traditional alkaline boiling degumming is used in the industry, which consumes a lot of water and generates a substantial amount of wastewater. In the present study, a novel eco–friendly solid–state degumming method was developed by using ethanolamine (ETA). The ETA degumming exhibited a high lignin removal rate (87.5%) at a high solid loading (30%), decreasing water consumption by 33.3%. Moreover, the ETA solution was readily reused up to five times without purification. The degummed hemp fibers possessed commendable fitness (4.2 dtex) and breaking strength (3.75 cN/dtex) without change of the crystalline cellulose structure. Besides, the lignin in wastewater was confirmed to be aminated, which is beneficial to the potential valorization of the by–product. Thus, the solid–state ETA degumming method holds significant potential for the fabrication of hemp fibers.

Registration of Arkot 1112, Arkot 1114, and Arkot 1115 cotton germplasm lines

AbstractArkot 1112 (Reg. no. GP‐1139, PI 702559), Arkot 1114 (Reg. no. GP‐1140, PI 702560), and Arkot 1115 (Reg. no. GP‐1141, PI 702561) are conventional cotton (Gossypium hirsutum L.) germplasm lines released by the Arkansas Agricultural Experiment Station in November, 2022. The three lines share Arkot 0306 (PI 671966) as a common parent. The second parents for Arkot 1112, Arkot 1114, and Arkot 1115 were ‘UA222’ (US patent no. 8,859,862), Arkot 0309 (PI 669969), and Arkot 0316 (PI 669970), respectively. The three lines were compared with ‘UA48’ and UA222 in replicated field tests at four Arkansas sites over 5 years. Over these tests, each of the three lines produced about 11 and 25% higher lint yields than UA48 and UA222, respectively. Lint yields of Arkot 1115 exceeded those of Arkot 1112 and Arkot 1114. Over 10 locations of the 2019 Regional Breeders Testing Network test, lint yields of Arkot 1112, Arkot 1114, and Arkot 1115 were equal to each other and ranked third, fourth, and fifth, respectively, out of 22 genotypes, indicating that the lines have wide adaptation. Leaf pubescence, stem pubescence, and bract trichome density of the lines were higher than UA48 and similar to UA222. All three lines displayed high resistance to bacterial blight. The lines were more resistant to tarnished plant bug than UA48 but were more susceptible to tarnished plant bug than UA222. Fiber quality of Arkot 1115 approached that of UA48 (excellent fiber quality), whereas Arkot 1112 and Arkot 1114 was similar to UA222 (good fiber quality).

A Systematic Review on the Improvement of Cd Stress Tolerance in Ramie Crop, Limitations and Future Prospective

Cadmium (Cd) is a non-essential, highly phytotoxic metal and damages ramie plant growth and development even at low concentrations. Ramie is one of the most significant crops in China, with excellent fiber quality and immense industrial importance. Planting Cd-tolerant ramie cultivars can prevent yield loss on contaminated soil. Previously, significant efforts have been made to develop Cd tolerance in ramie. However, the Cd tolerance mechanism is still not fully understood; hence, breeding industrial crops is critical to tackling the ongoing challenges. Cd tolerance is a complex genetic mechanism requiring high-level molecular studies to clarify the genes network. Genetic studies have identified several Cd-tolerant genes in ramie, which led to the development of several ramie cultivars suitable to grow on toxic soils; however, due to the continuous rise in Cd toxicity, potent molecular tools are critical in modern-day breeding programs. Genetic engineering, and transcriptome analysis have been used to develop abiotic stress tolerance in ramie, but QTL mapping and clustered regularly interspaced short palindromic repeats (CRISPR) are rarely studied. However, studies are still limited in addressing this issue. This review critically elaborated on using QTL mapping, transcriptomes, transcription factors, CRISPR/Cas9, and genetic engineering to enhance Cd tolerance in ramie. These genes/QTL should be transferred or edited into sensitive cultivars using genetic engineering or CRISPR/Cas9. CRISPR/Cas9 is highly recommended because it provides targeted gene editing in ramie, its use is limited and can address the research gaps, and it would revolutionize the field of agriculture. Limitations, gaps, and future potential are briefly discussed. This review paper presents new clues to help future researchers comprehensively understand Cd tolerance in ramie and develop tolerant cultivars for industrial purposes.

Identification of Candidate Genes for Lint Percentage and Fiber Quality Through QTL Mapping and Transcriptome Analysis in an Allotetraploid Interspecific Cotton CSSLs Population.

Upland cotton (Gossypium hirsutum) has long been an important fiber crop, but the narrow genetic diversity of modern G. hirsutum limits the potential for simultaneous improvement of yield and fiber quality. It is an effective approach to broaden the genetic base of G. hirsutum through introgression of novel alleles from G. barbadense with excellent fiber quality. In the present study, an interspecific chromosome segment substitution lines (CSSLs) population was established using G. barbadense cultivar Pima S-7 as the donor parent and G. hirsutum cultivar CCRI35 as the recipient parent. A total of 105 quantitative trait loci (QTL), including 85 QTL for fiber quality and 20 QTL for lint percentage (LP), were identified based on phenotypic data collected from four environments. Among these QTL, 25 stable QTL were detected in two or more environments, including four for LP, eleven for fiber length (FL), three for fiber strength (FS), six for fiber micronaire (FM), and one for fiber elongation (FE). Eleven QTL clusters were observed on nine chromosomes, of which seven QTL clusters harbored stable QTL. Moreover, eleven major QTL for fiber quality were verified through analysis of introgressed segments of the eight superior lines with the best comprehensive phenotypes. A total of 586 putative candidate genes were identified for 25 stable QTL associated with lint percentage and fiber quality through transcriptome analysis. Furthermore, three candidate genes for FL, GH_A08G1681 (GhSCPL40), GH_A12G2328 (GhPBL19), and GH_D02G0370 (GhHSP22.7), and one candidate gene for FM, GH_D05G1346 (GhAPG), were identified through RNA-Seq and qRT-PCR analysis. These results lay the foundation for understanding the molecular regulatory mechanism of fiber development and provide valuable information for marker-assisted selection (MAS) in cotton breeding.

Boron application influenced growth, yield and fiber quality of upland cotton (Gossipium hirsutum L.) under different irrigation regimes

Cotton is a major imperative cash crop crop globally including Pakistan. Among abiotic stresses, drought stress is critical that suppress plant growth, reduce crop production, low fiber quality and poor earnings for farmers. Nutrient deficiency is major factor resulting in poor crop production. Sufficient nutrient application has better capability to increase yield because it helps to plants to stand against adverse climatic conditions within the growing areas. Therefore, present study was conducted on evaluation of cultivars performance applying numerous irrigation systems and use of boron through different methods. Cultivar CIM-678 had maximum growth traits, allometry parameters and fiber quality attributes than CIM-602 which had minimum growth, allometry and fiber quality traits. Foliar application of boron and field capacity (75%) also increased plant growth, allometry and fiber traits. The interactive effects of cultivars, boron use and field capacity were improved the plant growth, yield, allometry parameter and fiber quality traits. Conclusively, CIM-678, boron foliar spray and field capacity (75%) improved the cotton crop production with excellent fiber quality traits. Keywords: BCR; Drought stress; Field capacity; Foliar spray http://dx.doi.org/10.19045/bspab.2021.100139

Comparative transcriptome analysis of fiber and nonfiber tissues to identify the genes preferentially expressed in fiber development in Gossypium hirsutum

Cotton is an important natural fiber crop and economic crop worldwide. The quality of cotton fiber directly determines the quality of cotton textiles. Identifying cotton fiber development-related genes and exploring their biological functions will not only help to better understand the elongation and development mechanisms of cotton fibers but also provide a theoretical basis for the cultivation of new cotton varieties with excellent fiber quality. In this study, RNA sequencing technology was used to construct transcriptome databases for different nonfiber tissues (root, leaf, anther and stigma) and fiber developmental stages (7 days post-anthesis (DPA), 14 DPA, and 26 DPA) of upland cotton Coker 312. The sizes of the seven transcriptome databases constructed ranged from 4.43 to 5.20 Gb, corresponding to approximately twice the genome size of Gossypium hirsutum (2.5 Gb). Among the obtained clean reads, 83.32% to 88.22% could be compared to the upland cotton TM-1 reference genome. By analyzing the differential gene expression profiles of the transcriptome libraries of fiber and nonfiber tissues, we obtained 1205, 1135 and 937 genes with significantly upregulated expression at 7 DPA, 14 DPA and 26 DPA, respectively, and 124, 179 and 213 genes with significantly downregulated expression. Subsequently, Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analyses were performed, which revealed that these genes were mainly involved in catalytic activity, carbohydrate metabolism, the cell membrane and organelles, signal transduction and other functions and metabolic pathways. Through gene annotation analysis, many transcription factors and genes related to fiber development were screened. Thirty-six genes were randomly selected from the significantly upregulated genes in fiber, and expression profile analysis was performed using qRT-PCR. The results were highly consistent with the gene expression profile analyzed by RNA-seq, and all of the genes were specifically or predominantly expressed in fiber. Therefore, our RNA sequencing-based comparative transcriptome analysis will lay a foundation for future research to provide new genetic resources for the genetic engineering of improved cotton fiber quality and for cultivating new transgenic cotton germplasms for fiber quality improvement.

Registration of two Arkot 0912 sister cotton germplasm lines

AbstractArkot 0912‐18 (Reg. no. GP‐1098, PI 697032) and Arkot 0912‐41 (Reg. no. GP‐1097, PI 697031) are conventional cotton (Gossypium hirsutum L.) germplasm lines released by the Arkansas Agricultural Experiment Station in December 2020. Both lines were derived from crossing ‘UA48’ and ‘UA222’. They produced higher lint yields than their parents over 5 yr and at four test sites in Arkansas. Both produced similar lint yields at each test site. Over test sites, the lines produced about 13 and 24% higher lint yields than UA222 and UA48, respectively. Arkot 0912‐18 produced the highest lint yield of all entries evaluated in the 2017 Regional Breeders Network Test. Over all locations of the 2017 Regional High Quality Test, lint yields of Arkot 0912‐41 ranked fourth out of 20 genotypes (second‐highest of 11 conventional genotypes) and equaled the lint yields of DP 1646 B2XF (U.S. patent no. 9,961,845) and PHY 444 WRF. Both lines produced higher lint percentage and lint index and were taller than either parent. Leaf pubescence, stem pubescence, and bract trichome density of each line exceeded both parents. Visual ratings of Verticillium wilt for Arkot 0912‐18 exceeded those of UA48. Both lines displayed high resistance to bacterial blight and were similar to UA222 and UA48 in their response to other diseases. The lines were more resistant to tarnished plant bug than UA48 but were more susceptible to tarnished plant bugs than UA222. Measurements of fiber quality for the two lines were intermediate between that of UA48 (excellent fiber quality) and UA222 (good fiber quality).

Registration of PD 20170048, PD 20170049, PD 20170050, PD 20170053, and PD 20170054 germplasm lines of cotton

AbstractPD 20170048 (Reg. no. GP‐1092, PI 698606), PD 20170049 (Reg. no. GP‐1093, PI 698607), PD 20170050 (Reg. no. GP‐1094, PI 698608), PD 20170053 (Reg. no GP‐1095, PI 698609), and PD 20170054 (Reg. no. GP‐1096, PI 698610) are noncommercial breeding lines of upland cotton (Gossypium hirsutum L.) jointly released by the USDA–ARS, the Clemson University Experiment Station, and Cotton Incorporated in 2020. PD 20170048, PD 20170049, PD 20170050, PD 20170053, and PD 20170054 are breeding lines selected from a cross between an elite cultivar or germplasm line and an exotic landrace accession from Asia, Africa, or South America. Each breeding line possesses 50% exotic landrace parentage, excellent fiber quality, and excellent yield performance—significantly better than several commercial cultivars. PD 20170048, PD 20170049, PD 20170050, PD 20170053, and PD 20170054 display good adaptation in three distinct regions of the U.S. upland cotton production region and provide valuable sources of new genetic diversity to cultivar development programs.

Genome-wide quantitative trait loci mapping on Verticillium wilt resistance in 300 chromosome segment substitution lines from Gossypium hirsutum × Gossypium barbadense.

Cotton Verticillium wilt (VW) is a devastating disease seriously affecting fiber yield and quality, and the most effective and economical prevention measure at present is selection and extension of Gossypium varieties harboring high resistance to VW. However, multiple attempts to improve the VW resistance of the most widely cultivated upland cottons have made little significant progress. The introduction of chromosome segment substitution lines (CSSLs) provide the practical solutions for merging the superior genes related with high yield and wide adaptation from Gossypium hirsutum and VW resistance and the excellent fiber quality from Gossypium barbadense. In this study, 300 CSSLs were chosen from the developed BC5F3:5 CSSLs constructed from CCRI36 (G. hirsutum) and Hai1 (G. barbadense) to conduct quantitative trait locus (QTL) mapping of VW resistance, and a total of 40 QTL relevant to VW disease index (DI) were identified. Phenotypic data were obtained from a 2-year investigation in two fields with two replications per year. All the QTL were distributed on 21 chromosomes, with phenotypic variation of 1.05%–10.52%, and 21 stable QTL were consistent in at least two environments. Based on a meta-analysis, 34 novel QTL were identified, while 6 loci were consistent with previously identified QTL. Meanwhile, 70 QTL hotspot regions were detected, including 44 novel regions. This study concentrates on QTL identification and screening for hotspot regions related with VW in the 300 CSSLs, and the results lay a solid foundation not only for revealing the genetic and molecular mechanisms of VW resistance but also for further fine mapping, gene cloning and molecular designing in breeding programs for resistant cotton varieties.

Multi-responses of O-methyltransferase genes to salt stress and fiber development of Gossypium species

BackgroundO-methyltransferases (OMTs) are an important group of enzymes that catalyze the transfer of a methyl group from S-adenosyl-L-methionine to their acceptor substrates. OMTs are divided into several groups according to their structural features. In Gossypium species, they are involved in phenolics and flavonoid pathways. Phenolics defend the cellulose fiber from dreadful external conditions of biotic and abiotic stresses, promoting strength and growth of plant cell wall.ResultsAn OMT gene family, containing a total of 192 members, has been identified and characterized in three main Gossypium species, G. hirsutum, G. arboreum and G. raimondii. Cis-regulatory elements analysis suggested important roles of OMT genes in growth, development, and defense against stresses. Transcriptome data of different fiber developmental stages in Chromosome Substitution Segment Lines (CSSLs), Recombination Inbred Lines (RILs) with excellent fiber quality, and standard genetic cotton cultivar TM-1 demonstrate that up-regulation of OMT genes at different fiber developmental stages, and abiotic stress treatments have some significant correlations with fiber quality formation, and with salt stress response. Quantitative RT-PCR results revealed that GhOMT10_Dt and GhOMT70_At genes had a specific expression in response to salt stress while GhOMT49_At, GhOMT49_Dt, and GhOMT48_At in fiber elongation and secondary cell wall stages.ConclusionsOur results indicate that O-methyltransferase genes have multi-responses to salt stress and fiber development in Gossypium species and that they may contribute to salt tolerance or fiber quality formation in Gossypium.

Genetic Variability of Morphological, Flowering, and Biomass Quality Traits in Hemp (Cannabis sativa L.).

Hemp (Cannabis sativa L.) is a bast-fiber crop well-known for the great potential to produce sustainable fibers. Nevertheless, hemp fiber quality is a complex trait, and little is known about the phenotypic variability and heritability of fiber quality traits in hemp. The aim of this study is to gain insights into the variability in fiber quality within the hemp germplasm and to estimate the genetic components, environmental components, and genotype-by-environment (G×E) interactions on fiber quality traits in hemp. To investigate these parameters, a panel of 123 hemp accessions was phenotyped for 28 traits relevant to fiber quality at three locations in Europe, corresponding to climates of northern, central, and southern Europe. In general, hemp cultivated in northern latitudes showed a larger plant vigor while earlier flowering was characteristic of plants cultivated in southern latitudes. Extensive variability between accessions was observed for all traits. Most cell wall components (contents of monosaccharides derived from cellulose and hemicellulose; and lignin content), bast fiber content, and flowering traits revealed large genetic components with low G×E interactions and high broad-sense heritability values, making these traits suitable to maximize the genetic gains of fiber quality. In contrast, contents of pectin-related monosaccharides, most agronomic traits, and several fiber traits (fineness and decortication efficiency) showed low genetic components with large G×E interactions affecting the rankings across locations. These results suggest that pectin, agronomic traits, and fiber traits are unsuitable targets in breeding programs of hemp, as their large G×E interactions might lead to unexpected phenotypes in untested locations. Furthermore, all environmental effects on the 28 traits were statistically significant, suggesting a strong adaptive behavior of fiber quality in hemp to specific environments. The high variability in fiber quality observed in the hemp panel, the broad range in heritability, and adaptability among all traits prescribe positive prospects for the development of new hemp cultivars of excellent fiber quality.

RNA-seq reveals hormone-regulated synthesis of non-cellulose polysaccharides associated with fiber strength in a single-chromosomal-fragment-substituted upland cotton line

Cotton fibers are the main raw materials of the textile industry. Exogenous superior fiber genes have been introduced into upland cotton to develop high-yield cultivars with excellent fiber quality. We used a single chromosomal segment on the chromosome A07 substitution line SL7, with high fiber strength, to investigate the molecular mechanism underlying its fiber quality. RNA-seq and KEGG analysis showed that 70 differentially expressed genes were enriched in plant hormone transduction pathways, including auxin, ethylene and abscisic acid, in fibers at 10 days post-anthesis (DPA). Among these, fiber-development related transcription factors MYB and NAC, including Gh_A11G0981 (MYB108), Gh_A03G0887 (NAC029), and Gh_A08G1691 (NAC021), were significantly upregulated in SL7, as were numerous cellulose synthase-like (CSL) genes involved in non-cellulose polysaccharide and cell wall synthesis. The hemicellulose content of SL7 was significantly higher than that of L22, an upland cotton cultivar. These results suggest that key genes in the introgressed chromosomal segment of SL7 regulate the expression of transcription-factor genes via hormone-transduction pathways, thereby inducing the expression of genes involved in secondary wall synthesis and ultimately improving fiber quality. This study has shed light on the molecular mechanism of fiber development and will contribute to the improvement of fiber quality of upland cotton by molecular breeding.

QTL mapping and genetic effect of chromosome segment substitution lines with excellent fiber quality from Gossypium hirsutum \xd7 Gossypium barbadense

Chromosome segment substitution lines (CSSLs) are ideal materials for identifying genetic effects. In this study, CSSL MBI7561 with excellent fiber quality that was selected from BC4F3:5 of CCRI45 (Gossypium hirsutum) × Hai1 (Gossypium barbadense) was used to construct 3 secondary segregating populations with 2 generations (BC5F2 and BC5F2:3). Eighty-one polymorphic markers related to 33 chromosome introgressive segments on 18 chromosomes were finally screened using 2292 SSR markers which covered the whole tetraploid cotton genome. A total of 129 quantitative trait loci (QTL) associated with fiber quality (103) and yield-related traits (26) were detected on 17 chromosomes, explaining 0.85–30.35% of the phenotypic variation; 39 were stable (30.2%), 53 were common (41.1%), 76 were new (58.9%), and 86 had favorable effects on the related traits. More QTL were distributed in the Dt subgenome than in the At subgenome. Twenty-five stable QTL clusters (with stable or common QTL) were detected on 22 chromosome introgressed segments. Finally, the 6 important chromosome introgressed segments (Seg-A02-1, Seg-A06-1, Seg-A07-2, Seg-A07-3, Seg-D07-3, and Seg-D06-2) were identified as candidate chromosome regions for fiber quality, which should be given more attention in future QTL fine mapping, gene cloning, and marker-assisted selection (MAS) breeding.

Genetic improvement of naked-tufted seed mutants in upland cotton (Gossypium hirsutum L.)

This research evaluated the potential for using sexual crosses for genetic improvement of fiber yield, lint percent, AFIS fiber quality, and fiber initiation of two naked-tufted mutants of cotton (Gossypium hirsutum L.). The naked tufted lines were crossed with ten fuzzy breeding lines to generate 10 F2 populations. The F2 distributions were tested with Chi Square for Goodness of Fit to two monogenic and two digenetic segregation ratios. Five of the six F2 populations made with Atlas-NS-129 segregated as either a single dominant gene (3 Naked-tufted: 1 fuzzy) or as two dominant genes (9 Naked-tufted: 7 fuzzy). Three of the four F2 populations made with SC 9023-ns-57 segregated as either a single recessive gene (3 Fuzzy: 1 naked-tufted) or as duplicate recessive genes (9 Fuzzy: 7 naked-tufted). However, the F2 populations when crossed with the Fuzzy line of Tejas 48 showed a reversal of dominance. The F2 population of Atlas-NS-129 X Tejas 48 fit a 9 Fuzzy: 7 naked tufted ratio expected of two recessive genes. The F2 population of the cross of SC 9023-ns X Tejas 48 fit a 3 Naked-tufted: 1 fuzzy ratio expected of a single dominant gene. Additional studies will be necessary to fully determine the number of gene(s) and the expected phenotypic ratios of individual naked-tufted mutants in crosses with fuzzy seeded breeding lines. Eight of the F2 and F3 populations were also evaluated for lint yield, lint percent and AFIS fiber quality traits. The F2 and F3 populations of the cross of Atlas-NS-129 X Holland 338 produced the highest average lint yields (1089 kg ha−1) as well as excellent fiber quality. These data indicate that it may be possible to develop relatively high yielding naked tufted cultivars by crossing these mutant lines with elite higher yielding breeding lines.

Irrigation\u2019s effect and applied selection on the fiber quality of Ethyl MethaneSulfonate (EMS) treated upland cotton (Gossypium hirsutum L.)

BackgroundProducing rainfed cotton (Gossypium hirsutum L.) with high fiber quality has been challenging in the Texas High Plains because of extended periods of insufficient rainfall during sensitive boll developmental stages. Genetic variation created by Ethyl MethaneSulfonate (EMS) mutagen has successfully improved fiber quality of cotton. However, little is known about the effect of water deficit environments on fiber quality. Three EMS treated populations were advanced from the first to the fourth generation (M1 to M4) as bulk harvested populations. In 2014, single-plant divergent selection was applied based on perceived morphological and agronomic differences seen during and at the end of the season.ResultsAnalyses from these selections in 2014–2016 showed significant (P < 0.05) improvement between and within populations for fiber traits (micronaire, length, strength, uniformity, and elongation) when compared with the original non-treated EMS source; some selections were found to have excellent fiber quality under diverse irrigation-regimes.ConclusionsSome of these selections are being considered for germplasm release and could be useful for improving the fiber quality of cotton under water limited conditions, thereby helping to ensure the long-term survival of the cotton industry on the Texas High Plains.

Multi-Locus Genome-Wide Association Studies of Fiber-Quality Related Traits in Chinese Early-Maturity Upland Cotton.

Early-maturity varieties of upland cotton are becoming increasingly important for farmers to improve their economic benefits through double cropping practices and mechanical harvesting production in China. However, fiber qualities of early-maturing varieties are relatively poor compared with those of middle- and late- maturing ones. Therefore, it is crucial for researchers to elucidate the genetic bases controlling fiber-quality related traits in early-maturity cultivars, and to improve synergistically cotton earliness and fiber quality. Here, multi-locus genome-wide association studies (ML-GWAS) were conducted in a panel consisting of 160 early-maturing cotton accessions. Each accession was genotyped by 72,792 high-quality single nucleotide polymorphisms (SNPs) using specific-locus amplified fragment sequencing (SLAF-seq) approach, and fiber quality-related traits under four environmental conditions were measured. Applying at least three ML-GWAS methods, a total of 70 significant quantitative trait nucleotides (QTNs) were identified to be associated with five objective traits, including fiber length (FL), fiber strength (FS), fiber micronaire (FM), fiber uniformity (FU) and fiber elongation (FE). Among these QTNs, D11_21619830, A05_28352019 and D03_34920546 were found to be significantly associated with FL, FS, and FM, respectively, across at least two environments. Among 96 genes located in the three target genomic regions (A05: 27.95 28.75, D03: 34.52 35.32, and D11: 21.22 22.02 Mbp), six genes (Gh_A05G2325, Gh_A05G2329, Gh_A05G2334, Gh_D11G1853, Gh_D11G1876, and Gh_D11G1879) were detected to be highly expressed in fibers relative to other eight tissues by transcriptome sequencing method in 12 cotton tissues. Together, multiple favorable QTN alleles and six candidate key genes were characterized to regulate fiber development in early-maturity cotton. This will lay a solid foundation for breeding novel cotton varieties with earliness and excellent fiber-quality in the future.

Genetic and phenotypic effects of chromosome segments introgressed from Gossypium barbadense into Gossypium hirsutum.

MBI9915 is an introgression cotton line with excellent fiber quality. It was obtained by advanced backcrossing and continuous inbreeding from an interspecific cross between the upland cotton (Gossypium hirsutum) cultivar CCRI36 as the recurrent parent and the sea island cotton (G. barbadense) cultivar Hai1, as the donor parent. To study the genetic effects of the introgressed chromosome segments in G. hirsutum, an F2 secondary segregating population of 1537 individuals was created by crossing MBI9915 and CCRI36, and an F2:3 population was created by randomly selecting 347 individuals from the F2 generation. Quantitative trait locus (QTL) mapping and interaction for fiber length and strength were identified using IciMapping software. The genotype analysis showed that the recovery rate for MBI9915 was 97.9%, with a total 6 heterozygous segments and 13 homozygous segments. A total of 18 QTLs for fiber quality and 6 QTLs for yield related traits were detected using the two segregating generations. These QTLs were distributed across 7 chromosomes and collectively explained 0.81%–9.51% of the observed phenotypic variations. Six QTLs were consistently detected in two generations and 6 QTLs were identified in previous studies. A total of 13 pairs of interaction for fiber length and 13 pairs of interaction for fiber strength were identified in two generations. Among them, 3 pairs of interaction for fiber length and 3 pairs of interaction for fiber strength could be identified in all generations; 4 pairs of interactions affected fiber length and fiber strength simultaneously. The results clearly showed that 5 chromosome segments (Seg-5-1, Seg-7-1, Seg-8-1, Seg-20-2 and Seg-20-3) have important effects on fiber yield and quality. This study provides the useful information for gene cloning and marker-assisted breeding for excellent fiber related quality.

Construction of a High‐Density Genetic Map and Its Application to QTL Identification for Fiber Strength in Upland Cotton

Cotton (Gossypium sp.) is an important worldwide cash crop that provides a competitive renewable natural fiber supply for the demands of textile industry. The development of new textile technologies and the improvement of living standards increase the demands for both fiber quantity and fiber quality. ‘0–153’ is an upland cotton cultivar with excellent fiber quality derived from Asiatic cotton sources, especially with regards to fiber strength. To identify quantitative trait loci (QTLs) for fiber strength in this line, a recombinant inbred line population consisting of 196 lines was developed from a cross between it and ‘sGK9708’. A genetic linkage map consisting of 2393 loci was constructed using this recombinant inbred line population, with single nucleotide polymorphism (SNP) markers from the IntlCottonSNPConsortium_70k chip. Quantitative trait loci for fiber strength were detected across 11 environments using both single‐environment and combined multiple‐environment models. A total of 63 QTLs controlling fiber strength were detected by the single‐environment model. Sixteen QTLs were identified by the combined multiple‐environment model. These QTLs could make a contribution to the improvement of fiber quality via marker‐assisted selection and provide useful information for QTL fine mapping and functional gene research activities as well.

Identification of Chromosome Segment Substitution Lines of Gossypium barbadense Introgressed in G. hirsutum and Quantitative Trait Locus Mapping for Fiber Quality and Yield Traits.

Chromosome segment substitution lines MBI9804, MBI9855, MBI9752, and MBI9134, which were obtained by advanced backcrossing and continuously inbreeding from an interspecific cross between CCRI36, a cultivar of upland cotton (Gossypium hirsutum) as the recurrent parent, and Hai1, a cultivar of sea island cotton (G. barbadense) as the donor parent, were used to construct a multiple parent population of (MBI9804×MBI9855)×(MBI9752×MBI9134). The segregating generations of double-crossed F1 and F2 and F2:3 were used to map the quantitative trait locus (QTL) for fiber quality and yield-related traits. The recovery rate of the recurrent parent CCRI36 in the four parental lines was from 94.3%–96.9%. Each of the parental lines harbored 12–20 introgressed segments from Hai1across 21 chromosomes. The number of introgressed segments ranged from 1 to 27 for the individuals in the three generations, mostly from 9 to 18, which represented a genetic length of between 126 cM and 246 cM. A total of 24 QTLs controlling fiber quality and 11 QTLs controlling yield traits were detected using the three segregating generations. These QTLs were distributed across 11 chromosomes and could collectively explain 1.78%–20.27% of the observed phenotypic variations. Sixteen QTLs were consistently detected in two or more generations, four of them were for fiber yield traits and 12 were for fiber quality traits. One introgressed segment could significantly reduce both lint percentage and fiber micronaire. This study provides useful information for gene cloning and marker-assisted breeding for excellent fiber quality.