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PubMed2001

Chemical composition of components comprising bast tissue in flax.

Components from the bast region of flax (Linum usitatissium) were removed by hand from seed flax and fiber flax and analyzed by gas chromatography and mass spectrometry. Stems soaked in water were separated by hand into an outer layer, which consisted of epidermis with cuticle and parenchyma cells, and fiber bundles. Each of the two fractions were evaluated for chemical markers that could be used to predict the degree of retting and possibly fiber quality. The outer layer was subsequently treated with a mixed enzyme preparation to remove the carbohydrate portion, thus providing another fraction consisting primarily of cuticle. Four main constituent groups were investigated: dihydroxy fatty acids, long-chain fatty acids and alcohols, sterols, and aromatics. Long-chain fatty acids and alcohols located in the outer layer accounted for 80-92% of the total found in both fractions. Aromatics and sterols in the outer layer accounted for 29--72 and 27--67%, respectively, of the total and do not appear to be a reliable marker for the degree of retting. The best markers for retting were the dihydroxy fatty acids, of which 98--99% were accounted for in the outer layer. The main dihydroxy fatty acids were a mixture of 8,16- and 9,16-dihydroxyhexadecanoic acids and represented 87--89% of the total dihydroxy fatty acids measured. As a constituent of cuticle, this compound may serve as an excellent marker for indicating the degree of retting as well as a possible marker for fiber quality because this compound is almost always exclusively associated with the outer layer and not the fiber.

Alcohols↗

PubMed2004

Chromosomal assignment of RFLP linkage groups harboring important QTLs on an intraspecific cotton (Gossypium hirsutum L.) Joinmap.

Chromosome identities were assigned to 15 linkage groups of the RFLP joinmap developed from four intraspecific cotton (Gossypium hirsutum L.) populations with different genetic backgrounds (Acala, Delta, and Texas Plains). The linkage groups were assigned to chromosomes by deficiency analysis of probes in the previously published joinmap, based on genomic DNA from hypoaneuploid chromosome substitution lines. These findings were integrated with QTL identification for multiple fiber and yield traits. Overall results revealed the presence of 63 QTLs on five different chromosomes of the A subgenome (chromosomes-03, -07, -09, -10, and -12) and 29 QTLs on the three different D subgenome (chromosomes-14 Lo, -20, and the long arm of -26). Linkage group-1 (chromosome-03) harbored 26 QTLs, covering 117 cM with 54 RFLP loci. Linkage group-2, (the long arm of chromosome-26) harbored 19 QTLs, covering 77.6 cM with 27 RFLP loci. Approximately 49% of the putative 92 QTLs for agronomic and fiber quality traits were placed on the above two major joinmap linkage groups, which correspond to just two different chromosomes, indicating that cotton chromosomes may have islands of high and low meiotic recombination like some other eukaryotic organisms. In addition, it reveals highly recombined and putative gene abundant regions in the cotton genome. QTLs for fiber quality traits in certain regions are located between two RFLP markers with an average of less than one cM (approximately 0.4-0.6 Mb) and possibly represent targets for map-based cloning. Identification of chromosomal location of RFLP markers common to different intra- and interspecific-populations will facilitate development of portable framework markers, as well as genetic and physical mapping of the cotton genome.

Agriculture↗

PubMed1998

Polyploid formation created unique avenues for response to selection in Gossypium (cotton).

A detailed restriction fragment length polymorphism map was used to determine the chromosomal locations and subgenomic distributions of quantitative trait loci (QTLs) segregating in a cross between cultivars of allotetraploid (AADD) Gossypium hirsutum ("Upland" cotton) and Gossypium barbadense ("Sea Island," "Pima," or "Egyptian" cotton) that differ markedly in the quality and quantity of seed epidermal fibers. Most QTLs influencing fiber quality and yield are located on the "D" subgenome, derived from an ancestor that does not produce spinnable fibers. D subgenome QTLs may partly account for the fact that domestication and breeding of tetraploid cottons has resulted in fiber yield and quality levels superior to those achieved by parallel improvement of "A" genome diploid cottons. The merger of two genomes with different evolutionary histories in a common nucleus appears to offer unique avenues for phenotypic response to selection. This may partly compensate for reduction in quantitative variation associated with polyploid formation and be one basis for the prominence of polyploids among extant angiosperms. These findings impel molecular dissection of the roles of divergent subgenomes in quantitative inheritance in many other polyploids and further exploration of both "synthetic" polyploids and exotic diploid genotypes for agriculturally useful variation.

Journal Article↗

PubMed1988

Relationships between nutritive quality and fiber components of cool season and warm season forages: a retrospective study.

Feeding trials were conducted with 428 forages in three forage classes (C3 grasses, legumes, C4 grasses) fed ad libitum to sheep and with 170 forages fed to cattle over a 20-yr period. Of this total, 153 forages were fed concurrently to sheep and cattle. Where the same forages were fed, mean dry matter digestibility (DMD) and dry matter intake (DMI) were lower (P less than .01) for sheep than for cattle, with significant effects of forage class. With the main population of forages, the regression of DMI on DMD was positive and curvilinear (P less than .01) for sheep, with no effect of forage class, and positive and linear (P less than .0001) for cattle, with a significant effect of class. For all forages, correlations between DMI and neutral detergent fiber (NDF) concentration were -.57 for sheep and -.41 for cattle; regressions differed (P less than .05) with class and animal species. Correlations of DMD with NDF and acid detergent fiber (ADF) concentrations were -.45 and -.59 (P less than .01), respectively, for sheep, and -.32 and -.39 (P less than .01) for cattle; again, regressions differed significantly with class and animal species. Within forage class, regressions of DMD and DMI on fiber components generally were linear. Intake of NDF (NDFI) was related to NDF percentage for all forages by a quadratic regression, with significant differences due to animal species and forage class. Results indicate that relationships between DMD, DMI and fiber fractions differ between forage classes and animal species, that C4 grasses are consumed at levels higher than would be expected from their DMD and fiber concentrations and that ruminants increase NDFI in response to higher NDF concentrations in the forage.

Animal Feed↗

PubMed2026

3D chromatin remodeling during domestication defines novel targets for crop improvement.

Three-dimensional (3D) genome folding shapes gene regulation, yet the genetic underpinnings linking 3D genome evolution to phenotypic innovation during domestication remain elusive. Using population-scale Hi-C profiling of 34 semi-wild and 267 cultivated allotetraploid cottons, we generated a pan-3D genome atlas capturing extensive diversity in topologically associating domains (TADs) and chromatin loops. Chromatin interactome-wide association studies identified 105 TAD reconfigurations and 58 loop rewirings that were established as the 3D chromatin basis of fiber quality, boosting heritability estimates for fiber strength by 16% and fiber length by 20%. We reveal that domestication selection within sequence-defined sweeps fixed 57% of 3D conformation signatures, thereby decoupling sequence-level from chromatin-level selection and shifting the subgenome expression balance of 39 homoeologs in cultivated cotton. Sequence-based modeling and mutational analyses identified the C2H2 zinc-finger protein YY1 as a conserved mediator of 3D genome organization. This study provides a resource for redefining precision-breeding paradigms by harnessing cryptic 3D chromatin targets.

3D genome↗

PubMed2005

Quantitative trait loci mapping for meat quality and muscle fiber traits in a Japanese wild boar x Large White intercross.

Three generations of a swine family produced by crossing a Japanese wild boar and three Large White female pigs were used to map QTL for various production traits. Here we report the results of QTL analyses for skeletal muscle fiber composition and meat quality traits based on phenotypic data of 353 F(2) animals and genotypic data of 225 markers covering almost the entire pig genome for all of the F(2) animals as well as their F(1) parents and F(0) grandparents. The results of a genome scan using least squares regression interval mapping provided evidence that QTL (<1% genome-wise error rate) affected the proportion of the number of type IIA muscle fibers on SSC2, the number of type IIB on SSC14, the relative area (RA) of type I on SSCX, the RA of type IIA on SSC6, the RA of type IIB on SSC6 and SSC14, the Minolta a* values of loin on SSC4 and SSC6, the Minolta b* value of loin on SSC15, and the hematin content of the LM on SSC6. Quantitative trait loci (<5% genome-wise error rate) were found for the number of type I on SSC1, SSC14, and SSCX, for the number of type IIA on SSC14, for the number of type IIB on SSC2, for the RA of type IIA on SSC2, for the Minolta b* value of loin on SSC3, for the pH of loin on SSC15, and for the i.m. fat content on SSC15. Twenty-four QTL were detected for 11 traits at the 5% genome-wise level. Some traits were associated with each other, so the 24 QTL were located on 11 genomic regions. In five QTL located on SSC2, SSC6, and SSC14, each wild boar allele had the effect of increasing types I and IIA muscle fibers and decreasing type IIB muscle fibers. These effects are expected to improve meat quality.

Animals↗

PubMed2003

The effects of A-fiber pressure block on perception and neurophysiological correlates of brief non-painful and painful CO2 laser stimuli in humans.

This study examined the relative capacity of Adelta- and C-fibers to encode non-painful and painful brief CO(2) laser stimuli by comparing the effects of Adelta/C-fiber activation versus C-fiber activation alone. In nine normal subjects, brief CO(2) laser pulses of four different intensities (range 5.8-10.6mJ/mm(2)) were delivered at random on the first intermetacarpal zone of the dorsum of the hand. A-fiber pressure block of the superficial radial nerve was performed to fully isolate the activity of C-fibers. Quality and intensity (VAS) of percepts, reaction time (RT) and laser-evoked potentials (LEPs) were examined in baseline and A-fiber block conditions. During A-fiber block, absolute detection threshold increased dramatically from 4.8+/-1.8 to 10.9+/-4.8mJ/mm(2), proportion of detected stimuli decreased from 87% to 47% and proportion of pain reports from 39% to 10%. The quality of sensations became mainly 'light touch' and the 'pricking' sensation almost vanished. The stimulus-VAS curve shifted to the right and the slope was reduced. Signal Detection Theory analysis revealed that discrimination performance (P(A)) was significantly depressed and that response bias (B) evolved from a neutral towards a stoical attitude. Median RT increased from 492 to 1355ms. The late LEPs, attributed to the activation of Adelta-fibers, disappeared and ultra-late LEPs were recorded at Cz with a positivity peaking around 800ms. Collectively, these observations lead to the conclusion that Adelta-fibers are the main peripheral mediators for the perception of brief CO(2) laser stimuli and that they provide more sensory information than C-fibers.

Adult↗

PubMed2006

Cotton genome mapping with new microsatellites from Acala 'Maxxa' BAC-ends.

Fine mapping and positional cloning will eventually improve with the anchoring of additional markers derived from genomic clones such as BACs. From 2,603 new BAC-end genomic sequences from Gossypium hirsutum Acala 'Maxxa', 1,316 PCR primer pairs (designated as MUSB) were designed to flank microsatellite or simple sequence repeat motif sequences. Most (1164 or 88%) MUSB primer pairs successfully amplified DNA from three species of cotton with an average of three amplicons per marker and 365 markers (21%) were polymorphic between G. hirsutum and G. barbadense. An interspecific RIL population developed from the above two entries was used to map 433 marker loci and 46 linkage groups with a genetic distance of 2,126.3 cM covering approximately 45% of the cotton genome and an average distance between two loci of 4.9 cM. Based on genome-specific chromosomes identified in G. hirsutum tetraploid (A and D), 56.9% of the coverage was located on the A subgenome while 39.7% was assigned to the D subgenome in the genetic map, suggesting that the A subgenome may be more polymorphic and recombinationally active than originally thought. The linkage groups were assigned to 23 of the 26 chromosomes. This is the first genetic map in which the linkage groups A01 and A02/D03 have been assigned to specific chromosomes. In addition the MUSB-derived markers from BAC-end sequences markers allows fine genetic and QTL mapping of important traits and for the first time provides reconciliation of the genetic and physical maps. Limited QTL analyses suggested that loci on chromosomes 2, 3, 12, 15 and 18 may affect variation in fiber quality traits. The original BAC clones containing the newly mapped MUSB that tag the QTLs provide critical DNA regions for the discovery of gene sequences involved in biological processes such as fiber development and pest resistance in cotton.

Chromosomes, Artificial, Bacterial↗

PubMed2003

Application of partial least-squares regression to near-infrared reflectance spectroscopic determination of shive content in flax.

Shive, the nonfiberous core portion of the stem, in flax fiber after retting is related to fiber quality. The objective of this study is to develop a standard calibration model for determining shive content in retted flax by using near-infrared reflectance spectroscopy. Calibration samples were prepared by manually mixing pure, ground shive and pure, ground fiber from flax retted by three different methods (water, dew, and enzyme retting) to provide a wide range of shive content from 0 to 100%. Partial least-squares (PLS) regression was used to generate a calibration model, and spectral data were processed using various pretreatments such as a multiplicative scatter correction (MSC), normalization, derivatives, and Martens' Uncertainty option to improve the calibration model. The calibration model developed with a single sample set resulted in a standard error of 1.8% with one factor. The best algorithm was produced from first-derivative processing of the spectral data. MSC was not effective processing for this model. However, a big bias was observed when independent sample sets were applied to this calibration model to predict shive content in flax fiber. The calibration model developed using a combination sample set showed a slightly higher standard error and number of factors compared to the model for a single sample set, but this model was sufficiently accurate to apply to each sample set. The best algorithm for the combination sample set was generated from second derivatives followed by MSC processing of spectral data and from Martens' Uncertainty option; it resulted in a standard error of 2.3% with 2 factors. The value of the digital second derivative centered at 1674 nm for these spectral data was highly correlated to shive content of flax and could form the basis for a simple, low-cost sensor for the shive or fiber content in retted flax.

Algorithms↗

PubMed2005

Molecular marker assisted selection and pyramiding of two QTLs for fiber strength in upland cotton.

Based on two major QTLs that control high fiber strength which originated from an elite fiber germ-plasm line 7235 (Gossypium hiusutum L.), the efficiency of molecular marker-assisted selection (MAS) was investigated using two populations from pedigree selection and modified backcrossing pyramiding developed for the breeding purpose. Simian 3 (SM3), a widely planted variety in the Yangtze River Valley, and 7235 were used as parents to develop the two populations. In the two major QTLs for fiber strength from 7235, QTLfs-1 could explain more than 30% of the phenotypic variation (PV) in the (7235 x TM-1) F2 population. QTLfs-2 was at first identified in another super quality fiber line HS427-10 from (HS427-10 x TM-1) F2 population with 12.5% of PV explanation,which was further also identified in 7235 line but was non-allelic with QTLfs-1. The result of molecular marker-assisted selection for fiber strength showed that the genetic effect of the QTLfs-1 was stable under different environmental conditions, and its molecular marker-assisted selection showed significant selective efficiency among breeding populations with different genetic backgrounds. QTLfs-2 also showed high selective efficiency in advanced generation populations though its effect was a little lower than the former. When QTLfs-1 was selected simultaneously with 2 molecular markers with known genetic distance, the selection efficiency for the fiber strength was greatly increased. The pyramiding for two QTLs that control high fiber strength by MAS greatly improved the selection efficiency for cotton fiber strength. This report provides a successful example of MAS pyramiding for QTL for favorable traits in breeding programs.

Cotton Fiber↗

PubMed2006

Single muscle fiber size and contractility after spinal cord injury in rats.

Spinal cord injury (SCI) results in muscle weakness but the degree of impairment at the level of single fibers is not known. The purpose of this study was to examine the effects of T9-level SCI on single muscle fibers from the tibialis anterior of rats. Significant decreases in cross-sectional area (CSA), maximal force (Po), and specific force (SF = Po/CSA) were noted at 2 weeks. Atrophy and force-generating capacity were reversed at 4 weeks, but SF remained impaired. Maximum shortening velocity (Vo) did not change after injury. SCI thus appears to affect various contractile properties of single muscle fibers differently. Normal cage activity may partially restore function but new interventions are needed to restore muscle fiber quality.

Analysis of Variance↗

PubMed2004

The study of devitrification processes in heavy-metal fluoride glasses.

Heavy-metal fluoride glasses are very promising optical fiber materials because of their predicted ultralow loss and long transparency range. Although conventional silica fibers have attained their theoretical minimum loss of 0.15 dB/km, fluoride glasses have the potential to yield losses of only 0.001 dB/km. Fluoride glasses also exhibit transparency into mid-IR frequencies, a region inaccessible to silica fibers. However, this group of glasses is very unstable to devitrification during both bulk glass synthesis and fiber-drawing. This instability has limited their commercial exploitation to a small niche market in the laser industry. The ZBLAN glass (53ZrF(4)-20BaF(2)-4LaF(3)-3AlF(3)-20NaF) is the most promising of these materials since its fiber-drawing region lies on the edge, or possibly just outside its crystallization region. It is believed that additional research into understanding the nucleation mechanics involved in the devitrification of fluoride glasses will lead to the development of technology to suppress such nucleation, or at least minimize the associated crystallization temperature region, allowing high optical quality fibers to be produced. It has recently been demonstrated that a microgravity environment can suppress devitrification in ZBLAN glass preform preparation, and that devitrification may be reduced when preparing ZBLAN terrestrially in a containerless facility. It is believed that the role of viscosity is critical in the devitrification mechanism of ZBLAN glass and in determining the optimum fiber-drawing temperature. Unfortunately, viscosity data for fluoride glasses are only available above the melting point and around the glass transition. A piezoelectric viscometer has been developed and is being used to determine the missing viscosity data in the fiber-drawing and crystallization temperature regions. Shear thinning of the glasses and/or the application of hydrostatic pressure on the glasses have been recently proposed to be responsible for devitrification during fiber-drawing at 1 g and in reduced gravity. The study we report here is to explore the extent to which such a proposal is realistic.

Chemical Phenomena↗

PubMed2006

Sex differences in single muscle fiber power in older adults.

PURPOSE: This study was conducted to determine whether differences in power at the single muscle fiber level contribute to sex differences in whole muscle power production in the elderly. METHODS: A total of 16 sedentary older persons (10 women, 6 men), mean age 72 yr, had percutaneous needle biopsy of musculus vastus lateralis. Chemically skinned single muscle fibers were activated with Ca for maximal isometric force measurement (Po). The slack test was performed to determine maximal unloaded shortening velocity (Vo). Force-velocity and power curves were generated via a series of isotonic contractions, allowing measurement of peak power and specific power. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to determine myosin heavy chain composition of single muscle fibers. Whole muscle strength, velocity, and power were measured for knee extension and double leg press. RESULTS: Men had greater whole muscle strength, power, and velocity compared with women. Studied were 274 type I and 33 type IIa single fibers. No significant sex differences were found for fiber size, Po, specific force, Vo, power, or specific power in type I or IIa fibers. CONCLUSIONS: Single muscle fiber quality in older women is equivalent to that in older men and can not explain the differences seen in whole muscle strength, power, or function.

Aged↗

PubMed2002

RFLP genetic linkage maps from four F(2.3) populations and a joinmap of Gossypium hirsutum L.

An RFLP genetic linkage joinmap was constructed from four different mapping populations of cotton ( Gossypium hirsutum L.). Genetic maps from two of the four populations have been previously reported. The third genetic map was constructed from 199 bulk-sampled plots of an F(2.3) (HQ95-6x'MD51ne') population. The map comprises 83 loci mapped to 24 linkage groups with an average distance between markers of 10.0 centiMorgan (cM), covering 830.1 cM or approximately 18% of the genome. The fourth genetic map was developed from 155 bulk-sampled plots of an F(2.3) (119- 5 sub-okrax'MD51ne') population. This map comprises 56 loci mapped to 16 linkage groups with an average distance between markers of 9.3 cM, covering 520.4 cM or approximately 11% of the cotton genome. A core of 104 cDNA probes was shared between populations, yielding 111 RFLP loci. The constructed genetic linkage joinmap from the above four populations comprises 284 loci mapped to 47 linkage groups with the average distance between markers of 5.3 cM, covering 1,502.6 cM or approximately 31% of the total recombinational length of the cotton genome. The linkage groups contained from 2 to 54 loci each and ranged in distance from 1.0 to 142.6 cM. The joinmap provided further knowledge of competitive chromosome arrangement, parental relationships, gene order, and increased the potential to map genes for the improvement of the cotton crop. This is the first genetic linkage joinmap assembled in G. hirsutum with a core of RFLP markers assayed on different genetic backgrounds of cotton populations (Acala, Delta, and Texas plain). Research is ongoing for the identification of quantitative trait loci for agronomic, physiological and fiber quality traits on these maps, and the identification of RFLP loci lineage for G. hirsutum from its diploid progenitors (the A and D genomes).

Journal Article↗

PubMed2002

A beta-tubulin-like cDNA expressed specifically in elongating cotton fibers induces longitudinal growth of fission yeast.

Using cDNA Representational Difference Analysis (RDA) techniques, we isolated a cDNA that was expressed specifically in cotton fibers but not in the ovules of a fuzzless-lintless mutant (fl). We designated it as Gh-BTubL for it shares high sequence identity with known plant and yeast beta-tubulins. RT-PCR and robotic cDNA dot blot analyses indicated that the expression of Gh-BTubL was correlated with the elongation pattern of cotton fibers. In situ hybridization results verified that there was no Gh-BTubL mRNA in fl ovules while it was easily detected in the elongating wild type cotton fiber cells. Overexpression of Gh-BTubL in fission yeast induced longitudinal growth of the host cells by 1.74-fold, with no apparent effect on other aspects of the host cells. We suggest that Gh-BTubL plays an important role in cotton fiber elongation and we believe that elucidation of the control mechanisms for expression of tubulin-like proteins may help improve fiber quality and productivity.

Amino Acid Sequence↗

PubMed2001

Development and commercial use of Bollgard cotton in the USA--early promises versus today's reality.

Bollgard cotton is the trademark given to a number of varieties of cotton bio-engineered to produce an insecticidal protein from Bacillus thuringiensis (Bt). When produced by the modified cotton plants, this protein controls certain lepidopterous cotton insect pests. Commercially available since 1996, these cotton varieties are purchased under a license agreement in which the growers pay a fee and agree to abide by the terms, which include a 1-year license to use the technology and agreement to participate in an insect resistance management program. Today, Bollgard cotton is grown on more than one-third of all cotton acreage in the USA. This product has reduced cotton production costs and insecticide use by providing an effective alternative to chemical insecticides for the control of tobacco budworm, Heliothis virescens; cotton bollworm, Helicoverpa zea; and pink bollworm, Pectinophora gossypiella. The specificity and safety profile of the Bt protein produced in planta in cotton was maintained. It has retained its selectivity for lepidopterous insects and lacks the characteristics found in potential allergenic proteins. Fiber quality, the agronomic characteristics of the plant and seed composition remain unchanged. New cotton technology is being developed to provide improved insect control and a wider spectrum of activity. These future products could further reduce insecticide use in the production of cotton, while maintaining the high level of safety and reliability that has been demonstrated by five seasons of Bollgard cotton use.

Agriculture↗

PubMed2001

Treatment thresholds for stink bugs (Hemiptera: Pentatomidae) in cotton.

The green stink bug, Acrosternum hilare (Say), the southern green stink bug, Nezara viridula (L), and the brown stink bug, Euschistus servus (Say), were predominant phytophagous Pentatomidae detected during 1995-1997 in cotton in South Carolina. These species occurred in similar numbers in conventional and transgenic cotton 'NuCOTN33B', containing the gene for expression of CryIA(c) delta-endotoxin of Bacillus thuringiensis Berliner variety kurstaki. Adult stink bugs moved into cotton from wild and cultivated alternate hosts during July, and reproducing populations usually were detected in cotton from late July into September. Applications of either methyl parathion (0.56 kg [AI]/ha) directed for stink bugs or lambda-cyhalothrin (0.037 kg [AI]/ha) or cyfluthrin (0.056 kg [AI]/ha) for control of cotton bollworm, Helicoverpa zea (Boddie), provided effective control of pentatomids in NuCOTN33B or conventional 'DP5415' and increased yields compared with untreated plots. Fiber quality did not differ among treated or untreated plots of NuCOTN33B. The ground-cloth technique was used to estimate populations of stink bugs, and data indicated that treatment at one bug per 2 m of row adequately protected cotton from yield loss due to stink bug damage. Observations on boll damage indicated that treatment might be necessary if >20-25% reveal internal symptoms of feeding injury during mid- to late season. More detailed damage thresholds should be developed to complement an approach based on population monitoring. This study validated current recommendations for management of pentatomids in cotton, demonstrated the necessity of threshold use for stink bugs in transgenic cultivars expressing endotoxin from B. thuringiensis, and provided insight into further development of management options for pentatomids in the crop.

Animals↗

PubMed2001

[Genetic diversity detected by DNA markers and phenotypes in Upland cotton].

Genetic diversity of Upland cotton (Gossypium hirsutum L.) cultivars was evaluated by SSR, ISSR, and RAPD. The genomic DNAs of 36 domestic and exotic cultivars were amplified with 81 SSR primer pairs; 7 ISSR primers and 53 RAPD primers, which yielded 282 polymorphic bands. The range of pair similarity coefficient (Nei, M. And W. Li 1979) between cultivars is from 0.5745 to 0.9291. The result indicated that although the present cultivars have genetic variation to a certain extent, the genetic basis of them is relatively narrow, and it is essential to find some new germplasm for the development of new cultivars. As expected, the classification of the cotton cultivars using the Unweighted Pair-group Method with Arithmetic Average based on the pair similarity coefficients is mostly consistent with known pedigree information and breeding experience. The 36 cotton cultivars have been mainly classed into exotic cultivar group, Chinese Xinjiang ecological region cultivar group, early-mature domestic cutivar group and mediate-mature domestic cultivar group. Carmen and Colorado cultivars from Spain have the lowest similarity with other cultivars, while TM-1 (genetic standard line), MD5lne and PD9364 cultivars from American have higher similarity with domestic cultivars. The reason may be that the parents of the domestic cultivars were mainly introduced from America. However, clusters of domestic cultivars are not all in accordance with their ecological regions, which may result from the pedigree complexity of the cultivars. Meanwhile the genetic diversity of 36 cultivars was investigated at phenotypic level with agronomic and fiber quality traits in the field experiments in 1999 and 2000, and was measured by Euclidean distance on the genotypes. Although grouping result of cluster analysis based on the Euclidean distance is similar than that of molecular data with a significant negative correlation of -0.3350 between the pair similarity coefficients and the Euclidean distance, the subgroup classification of the two methods gives different result. The molecular markers can be effectively applied in classifying cultivars within the group. The study provides useful information for the selection of parents in the development of cotton cultivars and hybrids as well.

Cluster Analysis↗