Seed coat fragments (SCF) are portions of cottonseed that have broken off from mature or immature seeds and might or might not have attached cotton fibers. SCF are created during cotton harvesting or ginning processes. Additional factors that contribute to SCF include genetics (cultivar), environmental issues, weathering events, and cultural practices. SCF are the second most common impurity in textile products. Neps, which are entanglements of fibers, are the most common impurity and make up most imperfections found in yarn. SCF reduce processing efficiency by causing ends-down during spinning and lead to defects in fabrics. This article presents past research and current unpublished research that has been conducted on SCF. Discussions include: chemical and physical properties of the seed coat leading to SCF; ability to use genetic information to select for genotypes with low SCF potential; opportunities in variety development and G x E interactions; modifications of mechanical processing to reduce SCF; and textile mill impacts of SCF. Based on findings from these studies, future strategies to combat SCF include better understanding of the physiology of SCF components and how formation is impacted by the environment, modeling to predict favorable harvest and ginning conditions, and modifying ginning and textile machinery to reduce the formation and increase the removal of SCF in U.S. cotton.

HighlightsRelationships between seed coat fragments and other seed and fiber properties were examined among cotton genotypes.Genotypes in the study had a broad range of properties that were significantly different among genotypes.Seed coat fragment levels were significantly correlated with cottonseed fragility, fiber-seed attachment force, and ginning energy.Longer, stronger cottons tended to have higher seed coat fragment levels.Abstract. Seed coat fragments (SCF) are difficult to remove from ginned lint. Cotton genotypes vary in SCF levels, but details are lacking regarding the cause of SCF. This study examined ten genotypes with highly variable levels of SCF to find relationships between SCF and cottonseed rupture force, fiber-seed attachment force, and net gin stand energy. Results showed that the attachment force of the fiber to the seed increased significantly with SCF levels, and net gin stand energy consumption increased with SCF levels, suggesting fibers more strongly attached to seed were prone to SCF formation. Cottonseed rupture force was measured, but only one genotype with very low seed rupture force had increased SCF; otherwise, SCF increased with cottonseed rupture force. Unexpectedly, fiber length, strength, and micronaire were significantly correlated with SCF levels, indicating that the longer, stronger, cottons with lower micronaire in the premium range tended to have higher SCF levels. These results show that multiple, otherwise desirable factors may contribute to cotton containing high SCF levels. Keywords: Seed coat fragments, Cottonseed fragility, Cotton attachment force, Gin stand energy, Fiber quality.

Nine diverse Upland cotton cultivars and germplasm lines differing in seed size were planted at two locations at Stoneville, MS in 2015, 2016, and 2017. ‘AR 9317-26’ and ‘DP 555 BG/RR’ were classified as small with a seed index (SI) < 10 g. ‘FM 832’, ‘FM 966’, and ‘MD 15’ had SI ranging from 10 to 12 g and were classified as intermediate seed size. ‘TAM 182-34 ELS’ and three other breeding lines: ‘201-2’, ‘107-1’, and ‘152-1’ had large seeds with SI > 12 g. The seeds were planted in three replications at two sites at Stoneville, MS. Data were collected on ginning energy requirement (Wh kg-1 lint), ginning rate (g lint s-1), and other agronomic and quality traits. The objectives of the test were to determine the effect of seed size on the above parameters. Statistical analyses were performed using Proc GLM. Simple Pearson’s correlation tests and regression analyses were conducted to test the relationships between SI and these traits. Covariance estimates were calculated using Proc GLIMMIX to determine the direction of linear relationships. Differences in SI were highly significant among cultivars. SI was positively and significantly correlated with ginning rate but significantly and negatively correlated with ginning energy requirement. Significant and negative relationships were observed between SI and fiber uniformity, lint yield, lint turnout, and number of seeds per kg. Significant and positive relationships were observed between SI and fiber strength, fuzz percentage, and seed surface area. Relationships among SI and micronaire, fineness, and fiber length were minor.

Previously we identified a major cotton fiber strength QTL (qFS-c7-1) on chromosome A07 using a multi-parent advanced generation intercross (MAGIC) population. To assess the stability and transferability of this QTL and its utility in cotton breeding, we made ten new populations. These populations were developed from crosses between MAGIC recombinant inbred lines, or between cotton cultivars that are different from the MAGIC parents. A total of 2801 F2 plants were grown and their fiber quality traits were measured. We also selected a subset of F3 seeds from two populations, and grew F3 progeny plots to further evaluate the stability of this QTL. Our results showed that the peak of qFS-c7-1 is at 70–72 Mb region. This QTL had a major effect on fiber strength explaining 21.9% phenotypic variance. Its effect on other fiber quality attributes such as micronaire, short fiber content, length and uniformity varied between populations, and no effect on fiber elongation was observed. The QTL effects were stable in the populations analyzed, and in different generations of the same population. The SSR and SNP markers near and within the QTL peak reported herein will assist selecting superior fiber quality traits in breeding, with a recommendation that the parental cotton lines should be analyzed using the seven DNA markers within the QTL peak before fully implementing marker assisted selection in a cotton breeding program.

Cotton fiber mutants are valuable resources for studying functions of altered genes and their roles in fiber development. The n4t is a recessive tufted-fuzzless seed mutant created through chemical mutagenesis with ethyl methanesulfonate. Genetic analysis indicated that the tufted-fuzzless phenotype is controlled by a single recessive locus. In this study, we developed an F2 population of 602 progeny plants and sequenced the genomes of the parents and two DNA bulks from F2 progenies showing the mutant phenotype. We identified DNA sequence variants between the tufted-fuzzless mutant and wild type by aligning the sequence reads to the reference TM-1 genome and designed subgenome-specific SNP markers. We mapped the n4t locus on chromosome D04 within a genomic interval of about 411 kb. In this region, seven genes showed significant differential expression between the tufted-fuzzless mutant and wild type. Possible candidate genes are discussed in this study. The utilization of the n4t mutant along with other fiber mutants will facilitate our understanding of the molecular mechanisms of cotton fiber cell growth and development.

Six mutant lines of cotton (Gosspium hirsutum L.) with superior fiber quality were developed by the Department of Plant and Soil Science at Texas Tech University at Lubbock, TX, and released in 2019. Additional evaluations were conducted at Texas A&M University, College Station, TX, and at the USDA-ARS, Crop Genetics Research Unit, Stoneville, MS. Three of the lines, TTU 1-817 (Reg. no. GP-1076, PI 691517), TTU 1-1051 (Reg. no. GP-1077, PI 691518), and TTU 1-1283 (Reg. no. GP-1078, PI 691519), were selected from a mutant population of 'Acala 1517-99'. Another three lines, TTU 2-411 (Reg. no. GP-1079, PI 691520), TTU 2-475 (Reg. no. GP-1080, PI 691521), and TTU 2-1073 (Reg. no. GP-1081, PI 691522), were selected from a mutant population derived from TAM 94L-25. Imbibed seeds of Acala 1517-99 and TAM 94L-25 were treated with 3.0% v/v of ethyl methane sulfonate (EMS). In 2002 (M-2), 2003 (M-3), and 2004 (M-4), generations of the mutant populations were advanced by harvesting a single boll from each plant and hulking the seeds to generate the next generation. In 2005, seed cotton samples were hand harvested from a total of 3,122 individual M-2:5 plants and evaluated for fiber quality. In 2012, 2013, 2014, and 2015, 33 of these M-5 lines selected from the TAM 94-L25 mutant population and 30 M-5 lines from the Acala 1517-99 mutant population were evaluated. Six M-5 lines were selected and released for their longer, stronger fibers and lower micronaire.

Previous analyses of relationships of neppiness traits with lint yield and other fiber properties in upland cotton (Gossypium hirsutum L.) were mainly based on phenotypes. The potential of genetic improvement in neppiness traits as well as their genetic relationships with lint yield and other fiber properties in breeding selections is unknown. In this study, realized heritability of neppiness traits, correlated selection responses (CRs), realized genetic correlations (GRs) between neppiness traits and lint yield, and other fiber properties were analyzed in two breeding populations-FiberMax832 x SP205 and MD15 x JJ1145ne-in F-3, F-4, and F-5 generations. The realized heritability was identified as low to moderate for fiber nep size, fiber nep count, seed coat nep (SCN) size, and SCN count ranging from 0.00 to 0.52 and from 0.12 to 0.58 at selection intensities of 10 and 20%, respectively. The realized heritability of fiber nep count was higher, ranging from 0.44 to 0.52 and from 0.20 to 0.58 at selection intensities of 10 and 20%, respectively. At the 20% selection intensity, there were no unfavorable CRs between lint yield and neppiness traits. Selections for fewer fiber nep count consistently increased fineness values (unfavorable) and decreased immature fiber content (IFC) values (favorable) in the two populations. Realized GR between fiber nep count and fineness was high, 0.80-0.84 in the two populations. The GR between fiber nep count and IFC was moderate, 0.50-0.64 in the two populations. The results in this study suggest the possibility of simultaneous genetic improvement of fiber nep count with lint yield and IFC as well as the difficulty of simultaneous genetic improvement for fiber nep count and fineness.

Cotton fiber mutants are useful tools for understanding the genetics and physiology of cotton fiber development. Currently, there are two naturally occurring, dominant lintless mutant lines, Ligon-lintless-1 (Li1) and Ligon-lintless-2 (Li2), and one man-made mutant line, Ligon-lintless-x (Lix), that exhibit extremely short lint fibers. Here we report a new lintless mutant that is the result of artificial chemical mutagenesis. In 2008, the cotton line MD 15 (PI 642769) was mutagenized with 3.2% v/v ethyl methane sulfonate (EMS). In 2010, a single Ligon-lintless-type plant was identified among the 2,000 M2 mutant progeny plants and was designated liy. This plant was crossed with the wild-type MD 15 with the objective of determining the genetic control of the lintless trait. Unlike Li1, Li2, and Lix, which are controlled by a single dominant gene, this new lintless trait is controlled by a monogenic recessive gene designated as liy. The liy plant is short and stunted and has an okra-leaf phenotype. The liy gene is not allelic to either Li1 or Li2. The genetic loci controlling these four Ligon-lintless mutations are located on four different chromosomes. This new lintless mutant will be useful in further investigating fiber elongation in cotton.

Determination of an efficient number of testing locations in multiple-location tests for cotton (Gossypium hirsutum L.) fiber quality can allow removal of unnecessary locations while maintaining the statistical power in detection of genotype (g) by environment (e) interactions. Fiber quality data from Regional High-Quality (RHQ) tests from 2011 to 2016 were used to determine an efficient number of locations in the tests for fiber quality and relationships among locations for their representativeness and ability to discriminate among genotypes. Covariance parameters of g, location (l), and gl in the original RHQ tests were estimated in a random model. The simulating data with varying number of locations omitted from the original tests were created by performing 100 unique simulations. When locations were reduced to five, the standard deviations (std) of gl increased from 18 to 37% compared to the original tests. Further reduction of locations to four or less increased std of gl from 30 to 217% compared to the original tests. Therefore, five locations were determined to be an efficient number of locations in tests for fiber quality. The discriminating ability and representativeness of the eight locations for fiber properties were calculated as their distances to an "ideal environment", which was designed as a center in GGE biplot graphs for representativeness and discriminating ability. The relationships among locations were different across years. However, by averaging the distances across testing years, the locations of Stoneville, MS; Keiser, AR; Lubbock, TX; and College Station, TX were identified as the most representative testing sites for fiber properties.

The objective of this study was to identify mutants of upland cottonseed (Gossypium hirsutum L.) with reduced levels of palmitic acid (C16:0) in the seed. The five parental populations that had been exposed to Ethyl MethaneSulfonate in 1997 or 2002 were initially screened for either herbicide tolerance or divergent fiber quality. Fatty acid composition were determined for five seed bulks from 140 M5 mutant lines in 2009 and 100 M6 partial seeds in 2010. Mutants with reduced levels of palmitic acid levels were isolated from TAM 94L-25 (PI 631440), Acala 1517-99 (Reg. No. CV-115, PI 612326) and TTU SCM3-7-3 (Reg. No.GS-4, PI 657942). Thirteen M6 single seeds with reduced levels of palmitic acid (17.9–19.6%) were intercrossed in the greenhouse. Ten of the single seed selections were designated as potential male parents and randomly crossed to three potential female parents to generate F1 plants and 21 F2 populations for allele testing. Based on these tests, five F2 populations with reduced levels of low palmitic acid, were selected for further evaluation. The development of mutant lines with reduced levels of palmitic acid in upland cotton was submitted for proprietary protection under U.S. Patent No. 20160222399.

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.

The EMS-induced threonine/isoleucine substitution in a tetratricopeptide repeat-like superfamily protein encoded by gene Ghir_A12G008870 is responsible for the Ligon-lintless-y (liy) short fiber phenotype in cotton. A short fiber mutant Ligon-lintless-y was created through treating the seeds of the cotton line MD15 with ethyl methanesulfonate. Genetic analysis indicated that the short fiber phenotype is controlled by a single recessive locus designated liy. From F2 populations derived from crosses between the mutant and its wild type (WT), we selected 132 short fiber progeny (liy/liy) and made two DNA bulks. We sequenced these DNA bulks along with the two parents of the population. The liy locus was located on chromosome A12. Using multiple F2 populations and F3 progeny plants, we mapped the liy locus within a genomic region of 1.18 Mb. In this region, there is only one gene, i.e., Ghir_A12G008870 encoding a tetratricopeptide repeat-like superfamily protein that has a non-synonymous mutation between the liy mutant and its WT. Analysis of a SNP marker representing this gene in the F2 and F3 progeny plants demonstrated its complete linkage with the liy short fiber phenotype. We further analyzed this SNP marker in a panel of 384 cotton varieties. The mutant allele is absent in all varieties analyzed. RNAseq and RT-qPCR analysis of the gene Ghir_A12G008870 during fiber development showed a significant expression difference between the liy mutant and its WT in developing fiber cells beginning at 12 days post-anthesis. Virus-induced gene silencing of the gene Ghir_A12G008870 significantly reduced the fiber length of the WT cotton line MD15. Taken together, our results suggest that the gene Ghir_A12G008870 is involved in the cotton fiber cell elongation process and is a promising candidate gene responsible for the liy short fiber phenotype.

Cotton breeders have focused mainly on selecting for high yield and early maturity under the impact of the boll weevil (Anthonomus grandis Boh.) in the last century. Selection for high fiber quality was once a less important objective in cotton breeding. With the transition of the U.S. cotton industry from a domestic consumer to a major exporter of raw fibers into the global market and the technology advancements in the textile industry since the 1990s, the need for high fiber quality in cotton cultivars has increased. In recent years, genetic improvement in cultivars for insect resistance, disease resistance, and abiotic stress tolerance has become important for maintaining cotton yield. Under strong competition from other major crops, increasing profit in cotton production has become an urgent task for cotton breeders and increasing economic potential in cottonseed and other economic traits can help promote profits for cotton growers. In this paper, the major research projects related to cotton breeding at the USDA-ARS at Stoneville, MS since the 1960s are reviewed. These research projects reflect the changing needs in cotton production during the period and focus on broadening the genetic base of Upland cotton for improving agronomic traits and fiber quality in cotton cultivars by a group of scientists with different scientific disciplines. A comprehensive review of this research can help develop strategies and identify research fields to strengthen to meet challenges in future.

Upland cotton (Gossypium hirsutum L.) germplasm USDA MD 16‐1 (Reg. No. CV‐138, PI 682133), and USDA MD 16‐2 (Reg. No. CV‐139, PI 682134) have enhanced yield and good fiber quality. These germplasm lines were developed by the USDA‐ARS, Stoneville, MS, and released on 27 June 2017. Two crosses, MD 25‐51 × MD 10‐9‐1 and MD 25‐51 × MD 10‐9‐10 were made at the Jamie Whitten Delta State Research Center, USDA‐ARS, Stoneville, in 2010. The F1 population was grown at the winter nursery in Mexico in 2010. The F2 populations were planted at Stoneville in 2011. One boll per plant was bulked, and the F3 population was grown in 2012. This process was repeated during 2013 (F4). In 2014, individual plants (F5) were selected for progeny rows. In 2015 (F6) and 2016 (F7) selected progeny rows were tested for yield and fiber quality, and one progeny row from MD 25‐51 × MD 10‐9‐1 (named USDA MD 16‐1) and another progeny row from MD 25‐51 × MD 10‐9‐10 (named USDA MD 16‐2) were identified for their superior lint yield and fiber quality. During 2015 and 2016, the two germplasm were planted along with the check cultivars in randomized complete designs at Stoneville and were evaluated at the 2016 Regional Breeders’ Testing Network (RBTN) test across 13 locations spanning across all cotton growing regions. Data were collected on lint yield and quality parameters. Data at Stoneville indicated that both USDA MD 16‐1 and USDA MD 16‐2 had 9 to 16% and 6 to 14% higher lint yield than the two check cultivars, MD 25 and MD 10‐5, respectively In the 2016 RBTN across 13 locations, USDA MD 16‐1 was the top yielder (1710 kg ha−1), and USDA MD 16‐2 had the strongest fiber (355 kN m kg−1).

In this work we describe a chemically-induced short fiber mutant cotton line, Ligon-lintless-y (liy), which is controlled by a single recessive locus and affects multiple traits, including height of the plant, and length and maturity of fiber. An RNAseq analysis was used to evaluate global transcriptional changes during cotton fiber development at 3, 8 and 16days post anthesis. We found that 613, 2629 and 3397 genes were significantly down-regulated, while 2700, 477 and 3260 were significantly up-regulated in liy at 3, 8 and 16 DPA. Gene set enrichment analysis revealed that many metabolic pathways, including carbohydrate, cell wall, hormone metabolism and transport were substantially altered in liy developing fibers. We discuss perturbed expression of genes involved in signal transduction and biosynthesis of phytohormones, such as auxin, abscisic acid, gibberellin and ethylene. The results of this study provide new insights into transcriptional regulation of cotton fiber development.

Fiber properties measured by high volume instrument (HVI) and advanced fiber information system (AFIS) are currently being used in Upland cotton (Gossypium hirsutum L.) breeding. It would be interesting to know if it is equally efficient in selection for parameters measured by the two instrumental systems and how are the correlated selection responses of the parameters between the two systems. A study was designed to determine the correlated selection responses between fiber properties measured by the two systems in F3, F4, and F5 generations of two crosses, FM 832 × SP 205 and MD 52ne × JJ 1145ne. Selections for HVI-fiber length, HVI-short fiber content, and HVI-maturity were made in the F3 generation and the correlated responses of AFIS-fiber properties to the selections were estimated in the subsequent F4 and F5 generations. Selections for AFIS-fiber length, AFIS-short fiber content, and AFIS-maturity were made in the F4 generation and the correlated responses of HVI-fiber properties to the selections were estimated in the F5 generation. Moderate to high realized heritability was identified for both HVI- and AFIS-fiber properties. Significant correlated selection responses of fiber length and maturity between the HVI and AFIS methods were consistently observed in both crosses, suggesting similar genetic basis for fiber length and maturity measured by HVI and AFIS. Therefore, equal effectiveness is expected of the selection for both traits by the two instrumental systems. Correlated selection responses of short fiber content parameters between the HVI and AFIS methods were not consistent, suggesting a possible different genetic basis or differential variations of measurement quality between the two systems.

Appropriate crossing systems for genetic improvement of quantitative traits are critical in cotton breeding. Determination of genetic variance for lint yield and fiber quality in three different crossing schemes (single cross [SC], three‐way cross [TWC], and double cross [DC]) of upland cotton (Gossypium histutum L.) will help breeders decide which crossing scheme to use in hybrid production and pure‐line development. This study was designed to compare agronomic performance and fiber quality among SCs, TWCs, and DCs and determine genetic variance for evaluated traits in the three crossing systems. A balanced set of 10 F2 hybrid populations from each crossing system was planted with their five parents in 2013, 2014, and 2015. There were no significant differences for lint yield and fiber properties between SC and the other two crossing systems. When genetic variance components were expressed as proportions of the total phenotypic variances (VP), there were mainly dominance (VD) and environmental variances (VE) for lint yield in F2 hybrids of all three crossing systems. The predominance of VD for lint yield suggests that selection would be more successful in later generations than in early generations among lines derived from SCs, TWCs, and DCs. The proportion of dominance (VD/VP) and additive genetic variances (VA/VP) for yield components was greater in TWCs and DCs than in SCs. Midparent heterosis (MPH) of lint yield in TWCs increased compared with SCs. Results indicate that TWCs may be used to enhance heterosis in hybrids, and TWCs and DCs may be used in pure‐line development to increase yield potential of upland cotton cultivars.

Mutant germplasm lines MD 15‐Mut 13 (Reg. No. GP‐1025, PI 681706), MD 15‐Mut 31 (Reg. No. GP‐1026, PI 681707), MD 15‐Mut 61 (Reg. No. GP‐1027, PI 681708), MD 15‐Mut 89 (Reg. No. GP‐1028, PI 681709), and MD 15‐Mut 138 (Reg. No. GP‐1029, PI 681710) are unique genotypes of upland cotton (Gossypium hirsutum L.). These germplasm lines were developed by the USDA‐ARS, Stoneville, MS, and released on 18 Apr. 2017. In 2008, about 5000 seeds of the germplasm line MD 15 were chemically mutagenized with 3.2% (v/v) of ethyl methane sulfonate. The treated seeds were hand planted in the field in 2008 to produce the M0 generation. One boll was hand‐picked from each of 2000 surviving plants, and this bulk was planted in 2009 to produce the M1. In 2010, 2011, and 2012, the same procedure was followed to produce the M2, M3, and M4 generations, respectively. Individual progeny rows of the best fiber quality mutants, along with the check genotypes, were tested in replicated trials at Stoneville during 2013 to 2016. These tests identified five mutants designated as MD 15‐Mut 13, MD 15‐Mut 31, MD 15‐Mut 61, MD 15‐Mut 89 and MD 15‐Mut 138 with outstanding fiber length, strength, and uniformity. These mutants have long to extra‐long, very strong, and highly uniform fibers.

Cotton cultivars with reduced fiber-seed attachment force have the potential to be ginned faster with less energy. The objective of this study was to identify quantitative trait loci (QTL) for net ginning energy requirement (NGE), and its relationship with other fiber quality traits in upland cotton. Two cotton lines, TAM 182-34 ELS and AR 9317-26, with significant differences in NGE and fiber-seed attachment force, were crossed and 285 F-2 plants derived from a single F-1 plant were planted in the field and leaf samples collected for DNA marker analysis (Population A). Individual F-3 plants and the two parents were planted in replicated progeny rows. The cotton was ginned on a 10-saw laboratory gin stand. Electrical power used by the gin was measured and recorded with a Yokogawa CW121 power meter. Fiber quality attributes were measured using a high volume instrument. A total of 455 SSR marker loci were used to construct a linkage map. Two QTLs were identified for NGE on chromosomes 12 and 20, associated with markers CIR148 and DPL0600, explaining 14 and 8.8% of the phenotypic variation, respectively. NGE shared the same genomic region with fuzz percent on chromosome 12. Population B, consisting of 260 F-2 progeny from the reciprocal cross AR 9317-26 X TAM 182-34 ELS, was used to confirm these QTLs by analyzing SSR markers mapped on Chrs 12 and 20. TheseQTLs (qNGE-c12 and qNGE-c20) were confirmed and appeared stable. Further validation of significantly associated markers on different populations is necessary prior to implementation in marker-assisted selection.

Combining ability describes the breeding value of parental lines to produce hybrids. The objectives of this study were to estimate specific (SCA) and general combining ability (GCA) for ginning rate and net ginning energy requirement in a set of upland cotton (Gossypium hirsutum L.) germplasm. Ginning efficiency was based on measurements of ginning energy (watt hour [Wh] kg−1 lint) and ginning rate (g lint s−1). There is little information in the scientific literature on this topic. Crosses were made in a 5 × 8 factorial design between five female and eight male diverse cotton genotypes. The experiment was conducted in a randomized complete plot design. Analysis of variance was performed using a mixed model of the GLM procedures. Even though the study indicated the presence of both additive (GCA) and nonadditive (SCA) genes controlling these traits, a preponderance of the GCA effects was evident. The cotton genotype MD 25 had the highest GCA effect for ginning rate, and AR 9317‐26 had the highest significant negative GCA effect for net ginning energy. For lowering fuzz percentage, any of the seminaked seed lines (AR 9317‐26, Tejas NS, SC 9023 NS) can be exploited. This study and other previous studies showed significant positive correlation of fuzz percentage with net ginning energy. For cultivar development, cross JJ 1145ne × SC 9023 NS may be used for improving ginning rate, crosses FM 832 × Tejas NS and JJ 1145ne × SG 747 can be used for reducing fuzz percentage, and the hybrid Phytogen 72 × TAM 98‐99ne can be exploited for improving all three traits.