Upland Cotton Cultivars Research Articles

ESTIMATION OF SOME GENETIC PARAMETERS AND PATH COEFFICIENT ANALYSIS IN ( GOSSYPIUM HIRSUTUM ) BY USING PLANT DENSITY

A field Experiment was Conducted at the farm of Agriculture collee , University Of Anbar, the alternative location (Abu – Gharib) during the season of 2016 to study the effect of planting density (66666, 55555, and 47619) on the yield of the seed cotton and its components for eight cultivars of Upland cotton (CA22, IK347, Lachata, Aleppo 33, Montana, Coker 310, Sp 8886, Iranian 16). Split plot design within R.C.B.D with three replication was used. The varieties as a main plots, while the three siding rates as sub plots with three replication. Genotypic, phenotypic variances and coefficient of variability broad since heritability percentage of fiber index for all planting density (D1, D2 and D3) were high (91.8, 86.9 and 90.5) respectively. Path coefficient analysis that number of bolls and fiber ratios for plant density (D1 and D2) gave highly effect direct (0.92 and 0.94) respectively, while weight of bolls gave high indirect effect from (D3) (0.99).

Diallel analysis and inbreeding depression in agronomic and technological traits of cotton genotypes

ABSTRACT Cotton provides about 90% of the world textile fiber, and is one of the crops of greater industrial relevance. The objectives of this study were to estimate the inbreeding depressionand the genetic effects involved in the control of the agronomic andfiber quality traits in F1 and F2 generations and to identify promising hybrids for obtaining superior cotton genotypes. Two cultivars of upland cotton and two moco (Brazilian endemic) cotton were crossed using a half-diallel scheme. The following traits were evaluated: percentage of fibers and weight of one boll, fiber length, fiber uniformity, short fiber index, fiber strength, and micronaire index. The additive genetic effects are predominant in the evaluated agronomic and fiber quality traits. Cultivar FM 966 is the most suitable parent to compose crossing blocks for the improvement of cotton agronomic and fiber quality traits. The hybrids FM 966 × CNPA 7MH and FM 966 × BRS 286 are the most promising for obtaining segregating populations aiming to select superior genotypes. Inbreeding depression is more pronounced in the agronomic traits than in the fiber quality traits.

Fibras de algodoeiro herbáceo sob déficit hídrico

A região semiárida brasileira caracteriza-se por apresentar baixa disponibilidade hídrica devido a persistentes períodos de seca, com isso há necessidade de melhor uso da água na irrigação das culturas. Assim, objetivou-se avaliar o efeito do déficit hidrico, imposto nas distintas fases fenológicas, sobre a produtividade de algodão em pluma, a percentagem e a qualidade das fibras das cultivares BRS 286 e BRS 336 de algodoeiro herbáceo. O delineamento experimental foi blocos casualizados em parcelas subdivididas, com os seis regimes de déficits hídricos, aplicados em diferentes fases fenológicas do algodoeiro, formando as parcelas e, as duas cultivares de algodoeiro herbáceo, as subparcelas, em 4 repetições. As variáveis analisadas foram rendimento e percentagem de algodão em pluma e algumas características tecnológicas da fibra, as quais foram Comprimento, Uniformidade, Índice de fibras curtas, Resistência, Alongamento à ruptura, Índice micronaire e Maturidade. O déficit hídrico foi mais relevante nas fases de botão, flor e maça. As fases mais tolerantes ao déficit foram crescimento inicial e capulho. As características tecnológicas das fibras como comprimento, uniformidade, índice micronaire e maturidade, inerentes a cada cultivar, se apresentaram dentro do padrão varietal requerido pela indústria têxtil. As duas cultivares mostraram bom potencial de cultivo para o semiárido, considerando as características distintas, mas a escolha é de acordo com o interesse do produtor.

Evaluation of a multi-parent advanced generation inter-cross (MAGIC) introgressed line population for Verticillium wilt resistance in Upland cotton

Verticillium wilt (VW, caused by Verticillium dahliae Kleb) is a destructive fungal soil-borne disease in Upland cotton (Gossypium hirsutum L.). High levels of VW resistance can be transferred into Upland from Pima cotton (G. barbadense L.) through interspecific introgression breeding. In this greenhouse study, VW resistance was evaluated in a multi-parent advanced generation inter-cross (MAGIC) introgressed line (IL) population, derived from a random mated Barbadense Upland population with five generations of intermating (called RMBUP-C4) between three Upland cotton cultivars and 18 CS-B Upland lines each carrying a pair of G. barbadense chromosome or arm in the TM-1 background. The objectives of this study were to, (1) evaluate VW resistance of 530 MAGIC ILs in the greenhouse; and (2) to identify lines with VW resistance in the MAGIC population based on a total of three replicated greenhouse tests. Approximately 8 plants for each line in each replicate were grown and screened for VW resistance using three parameters i.e., disease leaf severity rating, percentage defoliated leaves, and percentage infected plants, with a total of ~ 25,190 plants evaluated. A correlation analysis indicated that the three parameters were significantly and positively correlated with one another in each test. The disease leaf severity rating was the best parameter to assess VW resistance due to its relatively low coefficient of variation and its higher resolution to differentiate resistant genotypes from susceptible ones. Of the 530 genotypes, 5 showed resistance to VW, namely, NMIL348, NMIL518, NMIL405, NMIL290, NMIL307 and had higher levels of resistance to VW with mean disease leaf severity ratings, percentage of defoliated leaves, and percentage of infected plants across three tests ranging from 0.58–1.46, 9.46–26.74, and 25–95%, respectively. These lines can be used as parental lines to improve VW resistance in cotton breeding programs.

Comparative transcriptome study provides insights into acquisition of embryogenic ability in upland cotton during somatic embryogenesis

BackgroundThe conversion from non-embryogenic callus (NEC) to embryogenic callus (EC) is the key bottleneck step in regeneration of upland cotton (Gossypium hirsutum), and hinders the transgenic breeding of upland cotton. To investigate molecular mechanisms underlying acquisition of embryogenic potential during this process, comparation analysis of transcriptome dynamics between two upland cotton cultivars with different somatic embryogenesis abilities was conducted.ResultsDifferentially expressed genes involved in the transformation from NEC to EC were detected in the two different cultivars. Principal component analysis based on DEGs showed that the NEC tissues of the two cultivars were highly heterogeneous, whereas the derived EC tissues were similar, which suggested the homogeneousness of EC between different lines. In the highly embryogenic cultivar CCRI 24, more of these genes were down-regulated, whereas, in the recalcitrant cultivar CCRI 12, more were up-regulated. Bioinformatics analysis on these DEGs showed that the vast majority of differentially expressed genes were enriched in metabolism and secondary metabolites biosynthesis pathways. Flavonoid biosynthesis and phenylpropanoid biosynthesis pathways were enriched in both cultivars, and the associated genes were down-regulated more in CCRI 24 than in CCRI 12. We deduced that vigorous secondary metabolism in CCRI 12 may hinder primary metabolism, resulting in tardiness of cell differentiation. Interestingly, genes involved in the plant hormone signal transduction pathway were enriched in the recalcitrant cultivar CCRI 12, but not in CCRI 24, suggesting more radical regulation of hormone signal transduction in the recalcitrant cultivar. Signal transduction rather than biosynthesis of plant hormones is more likely to be the determining factor triggering NEC to EC transition in recalcitrant cotton lines. Transcription factor encoding genes showed differential regulation between two cultivars.ConclusionsOur study provides valuable information about the molecular mechanism of conversion from NEC to EC in cotton and allows for identification of novel genes involved. By comparing transcriptome changes in transformation from NEC to EC between the two cultivars, we identified 46 transcripts that may contribute to initiating embryogenic shift.

Auxin homeostasis and signaling alterations result in the aberrant phenotype in scl mutant of cotton (Gossypium hirsutum L.)

Leaves are the most important organs for photosynthesis. Many cotton leaf mutants (Gossypium spp.) have been reported and broadened the insights of leaf development. A natural occurring small, crinkled leaf (scl) mutant of upland cotton (Gossypium hirsutum L.) occurs in SY321 (wild type, WT), a high-yield upland cotton cultivar that is widely planted in China. The scl has a small and crinkled leaf phenotype. The shoot apical meristem (SAM) of scl did not form the essential typical layered structure, and the cell layers were arranged in a disordered manner. The free IAA concentration of shoot tips was significantly reduced in the scl according to ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis. Gene expression profiles showed that 432 genes were differentially expressed between scl and WT. The top 20 enriched pathways were analyzed using the Kyoto encyclopedia of genes and genomes (KEGG) database and four pathways, including flavonoid biosynthesis, photosynthesis, RNA transport, and carbon fixation in photosynthetic organisms, were considered as significantly enriched pathways. Furthermore, a number of differentially expressed genes related to auxin activity, including flavonoids biosynthesis, auxin perception and signal transduction pathway, auxin transport, and ubiquitin-mediated proteolysis pathways, were identified, and the altered expressions of these genes might be responsible for the aberrant phenotype of the scl.

Evaluation of commercial Upland (Gossypium hirsutum) and Pima (G. barbadense) cotton cultivars, advanced breeding lines and glandless cotton for resistance to Alternaria leaf spot (Alternaria alternata) under field conditions

Alternaria leaf spot (ALS, caused by Alternaria spp.) is one of the most common foliar diseases in cotton (Gossypium spp.) that occurs in most cotton-growing regions of the world including the United States. In New Mexico, ALS caused by A. alternata (Nees:Fr.) Keissler is becoming prevalent due to favorable weather conditions in the late cropping season; however, there is limited information on screening cotton for ALS resistance. In this study, a total of 125 Upland cotton (G. hirsutum L.) genotypes were separated into 5 trials each with 32 entries and 3–4 replications, together with one trial including 8 Pima cotton (G. barbadense L.) cultivars and lines with 4 replications in 2016. Three additional field trials each with 32 or 34 genotypes and 4 replications were conducted in 2017. Based on the high disease incidence (99.9% with a range of 90–100% in 2016 and 100% in 2017) and high disease severity index (DSI, 26.7–92.0 with a mean of 62.4 in 2016 and 42.0–89.0 with a mean of 66.7 in 2017) of foliar symptoms in the late growing season in both years, no cotton genotype was immune to ALS (A. alternata) under the natural infection field conditions. The analysis of variance showed that there were significant genotypic variations in six of the nine replicated trials, and the broad-sense heritability estimates for DSI ranged from 0.489 to 0.702 with an average of 0.566. No significant genotypic difference was detected among Pima cotton cultivars and lines in both years. An orthogonal contrast detected no overall significant difference between Upland and Pima cotton in both years, while 15 Upland glandless lines as a group, had a significantly lower DSI than the glanded group with 17 Upland lines in one replicated test. Glandless NuMex COT 15 GLS, NM 13P1117 and NM 12Y1002, and glanded commercial transgenic FM 2484 B2F, PHY 444 WRF and NG 4545 B2XF were consistently resistant to ALS in two or more tests. The results provide useful information for breeding cotton for ALS resistance.

Cultivares de algodoeiro herbáceo sob déficit hídrico aplicado em fases fenológicas

Para o uso do recurso água na agricultura procura-se uma maior eficiência devido á escassez em determinadas regiões. Objetivou-se avaliar o efeito do déficit hídrico, aplicado em diferentes fases fenológicas, sobre o crescimento, fisiologia e produção das cultivares BRS 286 e BRS 336 de algodoeiro herbáceo. O delineamento experimental foi blocos casualizados em parcelas subdivididas, com os seis regimes de déficits hídricos, aplicados em diferentes fases fenológicas do algodoeiro, formando as parcelas e, as duas cultivares de algodoeiro herbáceo, as subparcelas, em 4 repetições. Foram avaliadas as variáveis de crescimento, fisiológicas e produtividade de algodão em caroço do algodoeiro herbáceo. O déficit hídrico restringiu o crescimento de ambas as cultivares de algodoeiro herbáceo, com as fases mais sensíveis sendo as de crescimento inicial, de botão floral e de flor. O déficit de 14 dias, aplicados nas diferentes fases fenológicas, não influenciou a fotossíntese das plantas de ambas as cultivares, mas alterou a condutâncias estomática e a transpiração das mesmas. As fases fenológicas de flor e de maçã foram as mais sensíveis ao déficit hídrico por apresentarem menor produção. Os tratamentos sem déficit em todo o ciclo e com déficit nas fases de crescimento inicial e de capulho, de ambas as cultivares de algodoeiro herbáceo, permitiram produtividade satisfatória em relação à média nacional.

Effect of water deficiency on relationships between metabolism, physiology, biomass, and yield of upland cotton (Gossypium hirsutum L.)

Drought is a common abiotic stress that considerably limits crop production. The objective of this study is to explore the influence of water deficiency on the yield, physiologic and metabolomic attributes in upland cotton cultivars (Gossypium hirsutum L). Cotton cultivars, 'Ishonch' and 'Tashkent-6' were selected to study the relationships among their physiologic, metabolomic and yield attributes during water deficiency. Deficit irrigation was designed by modifying the traditional watering protocol to reduce water use. Results indicate that cotton cultivars respond differently to water deficit stress. Water deficit significantly influenced plant height, the number of internodes, and sympodial branches in both cultivars. However, yield components such as the number of bolls, boll seed, lint mass, and individual plant yield were significantly reduced only in 'Tashkent-6'. The leaf area decreased and the specific leaf weight increased in 'Ishonch' under deficit irrigation conditions. However, 'Tashkent-6' demonstrated significant water loss compared to 'Ishonch', and both cultivars showed reduced transpiration rates. Untargeted metabolite profiles of leaves showed clear separation in 'Ishonch', but not in 'Tashkent-6' under deficit irrigation compared to full irrigation. The individual metabolites such as proline and galactinol showed strong association with yield under water deficit stress. Moreover, this study indicates that leaf area and transpiration intensity influence yield during water deficiency. In summary, the correlation among morpho-physiologic, metabolic, and yield components significantly varied between the two cultivars under water deficiency. The flowering stage was sensitive to water stress for both cultivars. The direct relationship between physiology, metabolism, and yield may be a useful selection criterion for determining candidate parents for cotton drought tolerance breeding.

Effects of Cadmium Stress on Physiological and Biochemical Characteristics and Agronomic Traits of Three Upland Cotton Cultivars

Effects of Cadmium Stress on Physiological and Biochemical Characteristics and Agronomic Traits of Three Upland Cotton Cultivars

Genetic Map Construction and Fiber Quality QTL Mapping Using the CottonSNP80K Array in Upland Cotton.

Cotton fiber quality traits are controlled by multiple quantitative trait loci (QTL), and the improvement of these traits requires extensive germplasm. Herein, an Upland cotton cultivar from America, Acala Maxxa, was crossed with a local high fiber quality cultivar, Yumian 1, and 180 recombinant inbred lines (RILs) were obtained. In order to dissect the genetic basis of fiber quality differences between these parents, a genetic map containing 12116 SNP markers was constructed using the CottonSNP80K assay, which covered 3741.81 cM with an average distance of 0.31 cM between markers. Based on the genetic map and growouts in three environments, we detected a total of 104 QTL controlling fiber quality traits. Among these QTL, 25 were detected in all three environments and 35 in two environments. Meanwhile, 19 QTL clusters were also identified, and nine contained at least one stable QTL (detected in three environments for a given trait). These stable QTL or QTL clusters are priorities for fine mapping, identifying candidate genes, elaborating molecular mechanisms of fiber development, and application in cotton breeding programs by marker-assisted selection (MAS).

The Elusive Search for Reniform Nematode Resistance in Cotton.

The reniform nematode (Rotylenchulus reniformis Linford and Oliveira) has emerged as the most important plant-parasitic nematode of cotton in the United States cotton belt. Success in the development of reniform nematode-resistant upland cotton cultivars (Gossypium hirsutum L.) has not been realized despite over three decades of breeding efforts. Research approaches ranging from conventional breeding to triple species hybrids to marker-assisted selection have been employed to introgress reniform nematode resistance from other species of cotton into upland cultivars. Reniform nematode-resistant breeding lines derived from G. longicalyx were developed in 2007. However, these breeding lines displayed stunting symptoms and a hypersensitive response to reniform nematode infection. Subsequent breeding efforts focused on G. barbadense, G. aridum, G. armoreanum, and other species that have a high level of resistance to reniform nematode. Marker-assisted selection has greatly improved screening of reniform nematode-resistant lines. The use of advanced molecular techniques such as CRISPER-Cas9 systems and alternative ways such as delivery of suitable "cry" proteins and specific double-stranded RNA to nematodes will assist in developing resistant cultivars of cotton. In spite of the efforts of cotton breeders and nematologists, successes are limited only to the development of reniform nematode-resistant breeding lines. In this article, we provide an overview of the approaches employed to develop reniform nematode-resistant upland cotton cultivars in the past, progress to date, major obstacles, and some promising future research activity.

Introducción y desarrollo de variedades de algodón Upland en el sistema productivo colombiano: Una revisión

El propósito de esta revisión es ofrecer un documento comprensivo de los cultivares de algodón Upland introducidos en los sistemas de producción colombianos. En el caso de las variedades nacionales, toda la información referida a genealogía y características se encuentra dispersa en documentos de literatura gris, lo cual limita su hallazgo, acceso y evaluación. En este contexto, los objetivos de esta revisión fueron: i) describir las características y genealogía de las variedades de algodón Upland desarrolladas por los programas de mejoramiento en Colombia y ii) describir las variedades de algodón Upland introducidas desde otros países en el sistema productivo colombiano. La información aquí descrita es parte de un proceso de consolidación de datos dispersos en entidades públicas y privadas del cultivo de algodón desarrollado con fines de análisis de metadata. En el futuro, este documento puede ser usado como guía descriptiva para programas de mejoramiento genético, incorporación de nuevas variedades o evaluación del impacto del desarrollo e introducción de variedades sobre las brechas de rendimiento y productividad; adicionalmente, incorpora una serie de recomendaciones para nuevas variedades, basados en el actual escenario que enfrenta el sector algodonero.

Evaluating Within‐Plant Variability of Cotton Fiber Length and Maturity

Core Ideas Cultivars showed differences for the within‐plant fiber length and maturity.Some cultivars exhibited relatively stable within‐plant fiber length and maturity.Genetic component plays a significant role for the differences among the cultivars. Previous studies have indicated differences in fiber quality parameters including fiber length and maturity within the canopy of cotton (Gossypium hirsutum L) plants. A 3‐yr study was conducted to investigate the impact of within‐plant variability on fiber length and maturity of upland cotton cultivars widely grown on the High Plains of Texas. Twelve upland cotton cultivars were grown in a randomized complete block design with three field replications, in Lubbock, TX, during the 2012, 2013, and 2014 growing seasons. A box‐picking harvesting method was used to individualize samples so that the within‐plant variability of cotton fiber quality could be studied. Bolls harvested from different positions on the plants were ginned with a tabletop roller gin to minimize fiber damage. The lint from each fruiting position was blended with a supple needles laboratory blender to reduce within‐sample variability while minimizing fiber breakage. Each sample collected from a different fruiting position on the plant was tested on the Advanced Fiber Information System (AFIS) with three replications of 3000 fibers. The results indicated that cultivars such as FM 9170 B2F, NG 4111 RF, PHY 499 WRF, and FM 2484 B2F showed lower within‐plant variability, while DP 1044 B2RF, PHY 367 WRF, and ST 5458 B2F showed relatively high within‐plant variability for AFIS fiber length and fiber maturity. In conclusion, variations in within‐plant fiber length and maturity among upland cotton cultivars could be a potential source of variability for breeding programs aimed at improving fiber quality.

History and Progress in Cotton Breeding, Genetics, and Genomics in New Mexico

The New Mexico Cotton Breeding Program was established in 1926 and has been led by five generations of breeders. The program has released 37 Acala 1517 and one short-staple Upland cotton (Gossypium hirsutum L.) cultivars and numerous germplasm lines. Two Sea-Island G. barbadense L. cultivars have been released for production in the Mesilla Valley, NM. New Mexico germplasm has contributed to the development of 45% of the commercial cotton cultivars including almost all Acala cultivars in California, and has contributed to the improvement in fiber length and strength in U.S. cottons. Many Acala 1517 cultivars are tolerant or resistant to Verticillium wilt and bacterial blight. The recent releases include three transgenic Acala 1517 cultivars, one conventional and two glandless cultivars. The current research program focuses on fiber and seed quality (glandless) to develop elite germplasm with high yields and superior fiber quality and with resistance to Verticillium and Fusarium wilt, thrips, bacterial blight, leaf spot, cotton rust, and tolerance to drought and salinity. Upland × Pima introgression and development of the hybrid seed production system based on cytoplasmic male sterility and the haploid-producing system based on semigamy are also important aspects of the program. Extensive applications of genomic tools and approaches in the program include DNA marker and population development, linkage map construction, and quantitative trait locus mapping. In recent years, reduction in funding and lack of institutional support has hampered the program in delivering solutions to challenging issues such as Fusarium wilt race 4 faced by the cotton farmer.

BRS 368RF: A glyphosate tolerant, midseason upland cotton cultivar for Northeast and North Brazilian cerrado

BRS 368RF: A glyphosate tolerant, midseason upland cotton cultivar for Northeast and North Brazilian cerrado

Registration of ‘Tamcot G11’ Upland Cotton Cultivar

‘Tamcot G11’ upland cotton (Gossypium hirsutum L.) cultivar (Reg. No. CV‐135, PI 682743) was developed by Texas A&M AgriLife Research and released in 2017 as part of an ongoing effort to create cultivars and germplasm with combinations of improved fiber quality parameters, especially upper half mean length (UHML) and fiber bundle strength. Tamcot G11 is a conventional cultivar that is competitive in lint yield potential with current upland cultivars available for production in central and south Texas. Tamcot G11 exhibited significantly longer UHML, measured by high volume instrument (HVI), than the average of all comparison cultivars in 16 of 17 performance trials across central and south Texas during 2013 through 2016. Micronaire of Tamcot G11 was within the premium range in 12 of the 17 performance trials, while the control cultivars averaged the premium range in only 3 or the 17 trials. Strength of Tamcot G11 and the mean of all controls were equal in all except two trials, whereas Tamcot G11 tended to have lower fiber elongation at break. Lint yield of Tamcot G11 was equal to or greater than the average of all control cultivars in 16 of the 17 trials. Lint percentage of Tamcot G11 was acceptable yet below that of most current upland cultivars. Tamcot G11 provides producers with a competitive, high‐quality conventional cultivar with UHML sufficient to reduce the probability of discounts based on fiber length.

Correlations between Cotton Characteristics in Greek Multi-environments

Correlations of data provided by AFIS and HVI were performed under a multi-location evaluation of cotton fiber characteristics in the Greek environment. Four main cotton-production Greek regions were selected and the five most cultivated commercial upland cotton (Gossypium hirsutum L.) cultivars were used for evaluation of fiber length and short fiber characteristics by AFIS and HVI instruments. Each cultivar was sown in 16 fields and 80 fields in total were used for all cultivars. Both HVI and AFIS gave reliable data concerning fiber length and short fiber estimations. High positive and statistically significant correlations between the two instruments were found indicating the similarity of final measurements. Fiber length estimations can be performed with higher accuracy than short fiber estimations, because CV values were lower for both instruments. HVI and AFIS showed different advantages in estimating fiber length and short fiber characteristics. Measurements of AFIS on fiber length had a smaller range between maximum and minimum values, but HVI showed lower CV% which is more useful for breeders, since it may indicate gene fixation that ensures easier breeding procedure. For short fibers, AFIS also showed a smaller range between maximum and minimum values and HVI showed lower CV%. Graphical comparisons between HVI and AFIS measurements for fiber length and short fibers showed that HVI had a more pattern with lower fluctuations than AFIS.

Genome-wide assessment of genetic diversity and fiber quality traits characterization in Gossypium hirsutum races

Gossypium hirsutum races are believed to be potential reservoirs of desirable traits, which can play crucial roles to overcome the existing narrow genetic base of modern Upland cotton cultivars. However, prior to utilizing the races in cotton improvement programs, understanding their genetic constitutions is needed. Thus, this study used molecular and morphological techniques to characterize 110 G. hirsutum germplasm including 109 semi-wild accessions and one Upland cotton cultivar, CRI12. In the study, 104 SSR markers detected 795 alleles, with an average of 7.64 alleles per marker, ranging from 3 to 14, and average polymorphism information content (PIC) value of 0.71. And 96 of the markers were found to be highly informative, with PIC value≥0.50. Pairwise genetic similarity coefficient across the accessions ranged from 0.19 to 1.00, with an average value of 0.46. Morphological characterization was done using fiber length, fiber strength, micronaire, fiber uniformity index, and fiber elongation. Pairwise taxonomic distance within the accessions ranged from 0.17 to 3.41, with a mean of 1.33. The SSR and fiber quality traits data set based unweighted pair group method of arithmetic mean (UPGMA) analysis grouped the accessions into 7 and 12 distinct clusters, respectively, that corresponds well with the results of principal component analysis (PCA). Our study revealed the existence of vast molecular and morphological diversities within the accessions and provided valuable information on each semi-wild accession for quick and better informed germplasm utilization in cotton breeding programs.

Transcriptome Analysis Suggests That Chromosome Introgression Fragments from Sea Island Cotton (Gossypium barbadense) Increase Fiber Strength in Upland Cotton (Gossypium hirsutum)

As high-strength cotton fibers are critical components of high quality cotton, developing cotton cultivars with high-strength fibers as well as high yield is a top priority for cotton development. Recently, chromosome segment substitution lines (CSSLs) have been developed from high-yield Upland cotton (Gossypium hirsutum) crossed with high-quality Sea Island cotton (G. barbadense). Here, we constructed a CSSL population by crossing CCRI45, a high-yield Upland cotton cultivar, with Hai1, a Sea Island cotton cultivar with superior fiber quality. We then selected two CSSLs with significantly higher fiber strength than CCRI45 (MBI7747 and MBI7561), and one CSSL with lower fiber strength than CCRI45 (MBI7285), for further analysis. We sequenced all four transcriptomes at four different time points postanthesis, and clustered the 44,678 identified genes by function. We identified 2200 common differentially-expressed genes (DEGs): those that were found in both high quality CSSLs (MBI7747 and MBI7561), but not in the low quality CSSL (MBI7285). Many of these genes were associated with various metabolic pathways that affect fiber strength. Upregulated DEGs were associated with polysaccharide metabolic regulation, single-organism localization, cell wall organization, and biogenesis, while the downregulated DEGs were associated with microtubule regulation, the cellular response to stress, and the cell cycle. Further analyses indicated that three genes, XLOC_036333 [mannosyl-oligosaccharide-α-mannosidase (MNS1)], XLOC_029945 (FLA8), and XLOC_075372 (snakin-1), were potentially important for the regulation of cotton fiber strength. Our results suggest that these genes may be good candidates for future investigation of the molecular mechanisms of fiber strength formation and for the improvement of cotton fiber quality through molecular breeding.