Crop Science Illumina
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Published online 1 March 2007
Published in Crop Sci 47:561-570 (2007)
© 2007 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Jenkins, J. N.
Right arrow Articles by Stelly, D. M.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Jenkins, J. N.
Right arrow Articles by Stelly, D. M.
Agricola
Right arrow Articles by Jenkins, J. N.
Right arrow Articles by Stelly, D. M.
Related Collections
Right arrow Cotton
Right arrow Plant Genetic Resources
Right arrow Crop Genetics

CROP BREEDING & GENETICS

Genetic Effects of Thirteen Gossypium barbadense L. Chromosome Substitution Lines in Topcrosses with Upland Cotton Cultivars: II. Fiber Quality Traits

Johnie N. Jenkinsa,*, Jack C. McCartya, Jixiang Wub, Sukumar Sahaa, Osman Gutierrezb, Russell Hayesa and David M. Stellyc

a USDA-ARS Crop Science Research Lab., Mississippi State, MS 39762
b Dep. of Plant and Soil Sciences, Mississippi State Univ., Mississippi State, MS 39762
c Dep. of Soil and Crop Sciences, Texas A&M Univ., College Station, TX 77843-2474. Mention of trade names or commercial products in this manuscript does not imply recommendation or endorsement by the USDA. Joint contribution of USDA-ARS and Mississippi State University. Journal paper No. J 10974 of Mississippi Agricultural and Forestry Experiment Station

* Corresponding author (jnjenkins{at}ars.usda.gov).


   ABSTRACT
TOP
 NOTES
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Thirteen chromosome substitution lines (CS-B) lines with individual 3-79 Gossypium barbadense L. chromosome or arms substituted into TM-1, G. hirsutum L., were crossed with five Upland cultivars and additive and dominance effects for fiber micronaire, elongation, length, and strength were measured over four environments. Additive genetic effects were considerably larger than dominance or environmental interaction effects. Fiber strength of 3-79 and FM966 were 282 and 240 kN m kg–1, respectively. FM966 had greater additive effects for fiber length (1.13 mm) and strength (12.90 kN m kg–1) than any CS-B line; however, CS-B25 had the greatest additive effects (8.97 kN m kg–1) for strength among CS-B lines. The greatest negative additive effect for fiber length was –1.29 mm (CS-B22sh). Although several CS-B lines had negative additive effects on strength, none was more negative than TM-1 (–5.31 kN m kg–1). CS-B02 and CS-B25 had additive effects on strength of 2.36 and 8.97 kN m kg–1. SG747 had the greatest negative additive effect (–12.13 kN m kg–1) for strength among cultivars and CS-B lines. CS-B07 and CS-B18 had negative additive effects for fiber strength but had significant and positive dominance effects with FM966. When individual CS-B lines were crossed with elite cultivars beneficial alleles for fiber properties were uncovered on specific chromosomes or chromosome arms that should aid introgression of alleles from 3-79 into Upland.

Abbreviations: CS-B, chromosome substitution line from G. barbadense • GCA, general combining ability • QTL, quantitative trait locus • SCA, specific combining ability.


   INTRODUCTION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
THERE ARE two cultivated tetraploid species of cotton, Gossypium hirsutum (Upland) and G. barbadense. Each species is derived from a common A-D allotetraploid event (2n = 52) about 1 to 2 million years ago. Upland cotton is the most widely cultivated cotton species on a worldwide basis. In most environments, Upland cotton cultivars have a higher yield potential than G. barbadense cultivars; however, the fiber quality of G. barbadense cultivars is generally superior. These cultivars have longer, stronger, and finer fibers than Upland cultivars. Fiber quality of Upland cultivars needs to be improved to meet the demands of the marketplace and modern spinning machinery. Since these two species are derived from a recent polyploidy event, it would seem logical to introgress fiber quality genes from G. barbadense into Upland. There have been many attempts and some success regarding interspecific hybridization and selection. A higher level of fiber quality has been achieved in selected Upland cultivars; however, no Upland cultivar has the fiber quality of modern G. barbadense cultivars. Additionally, interspecific crosses between these two species have generally resulted in difficulties such as infertility, cytological abnormalities, and distorted segregation in the F2 generations and beyond, (Beasley and Brown, 1942).

Lacape et al. (2005) conducted an extensive quantitative trait locus (QTL) study from an interspecific cross of ‘Guazuncho 2’ (G. hirsutum) and ‘VH8-4602’ (G. barbadense) followed by two backcrosses to Guazuncho 2. They reported that fiber length, strength, fineness, and color were influenced by 15, 12, 21, and 16 QTLs, respectively. They also report the contributions of the parents was such that the majority of the favorable alleles for fiber length, strength, and fineness came from G. barbadense; whereas, the G. hirsutum parent contributed positive alleles for fiber color. The QTL alleles from G. barbadense for fiber length, strength, or fineness mapped to 15 different chromosomes. Percy et al. (2006) have developed recombinant inbred lines from a cross of a stable line NM24016, a stable G. hirsutum line with significant introgression from G. barbadense, and TM-1 and used these lines to investigate genetic variation and heritability of agronomic and fiber traits. They reported significant broad sense heritability for most traits except fiber elongation. They identified transgressive segregation for most traits.

Chromosome substitution has been an indispensable method for intraspecific germplasm introgression into bread wheat (Triticum aestivum L., 2n = 42) and has been useful for genetic analysis and breeding (Al-Quadhy et al., 1988; Berke et al., 1992a, 1992b; Campbell et al., 2003, 2004; Kaeppler, 1997; Law, 1966; Mansur et al., 1990; Shah et al., 1999; Yen and Baenziger, 1992; Yen et al., 1997; Zemetra and Morris, 1988; Zemetra et al., 1986). Methods for development of interspecific chromosome substitution in G. hirsutum were outlined by Endrizzi (1963), and several of the initially discovered G. hirsutum monosomics were used to substitute G. barbadense chromosomes into G. hirsutum (Endrizzi, 1963; Kohel et al., 1977; Ma and Kohel, 1983). We have recently developed 17 disomic, alien, chromosome substitution (CS-B) lines through hypoaneuploid-based backcross chromosome substitution (Stelly et al., 2005). In each CS-B line, a pair of chromosomes (or chromosome arms) of G. hirsutum inbred TM-1 was replaced by the respective pair from G. barbadense doubled-haploid 3-79 lines (Stelly et al., 2005). These substitution lines are near-isogenic to the recurrent parent TM-1 for 25 chromosome pairs and are near-isogenic to one another for 24 chromosome pairs. These CS-B lines provide an opportunity to associate important traits with specific chromosomes or chromosome arms. Saha et al. (2006) utilized F2 progeny (TM-1 x CS-B lines) to measure additive and dominance effects. CS-B25 had additive effects for increasing fiber strength and length. Study of several previously developed CS-B lines (Kohel et al., 1977; Ma and Kohel, 1983) indicated that chromosome 6 was associated with higher lint percentage, finer fiber, and later flowering; whereas, chromosome 17 was associated with short fiber length. Using 178 families from the cross of a substitution line for chromosome 16 and TM-1, QTLs for boll size, lint percentage, fiber length, and fiber elongation were mapped to chromosome 16 (Ren et al., 2002). Recent analyses of an expanded set of new and resynthesized CS-B lines, per se, showed that chromosomes 16 and 18 from 3-79 were associated with reductions in yield and chromosome 25 of 3-79 was associated with reduced micronaire and increased fiber length and strength compared to TM-1 (Saha et al., 2004a, 2004b, 2006). Substituted chromosome arms 22sh and 22Lo from 3-79 had greater additive effects for lint percentage and lint yield than homologous chromosome arms from TM-1 (Jenkins et al., 2006). Three hybrids DP90 x CS-B15sh, ST474 x CS-B17, and FM966 x CS-B02 had positive dominance effects for lint yield significantly greater than homologous chromosomes in TM-1. Alleles for yield components were found on specific 3-79 chromosomes that interacted positively with alleles in elite G. hirsutum cultivars (Jenkins et al., 2006).

These studies indicate the complexity of the genetics of yield and fiber traits. These results suggest specific chromosomes in G. barbadense as the probable locations of genes that significantly affect fiber quality traits and other important quantitative traits.

We crossed 13 CS-B lines, the recurrent parent TM-1, and the donor parent 3-79 with five elite cultivars. The 75 F2 hybrids and 20 parents were evaluated in four environments for fiber quality traits. The objectives were to estimate variance components and genetic effects to determine combining ability of specific CS-B lines for improving cotton fiber quality in breeding programs. In a previous manuscript (Jenkins et al., 2006), we focused on yield and yield components, whereas fiber quality traits are addressed in this manuscript. In both studies we bridge across genetic interest to plant breeding interest as we determine the genetic effects of specific 3-79 chromosome or chromosome arm and the homologous chromosome or arm in crosses with elite cultivars.


   MATERIALS AND METHODS
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Development of Plant Materials
Five elite cultivars, ‘Deltapine 90’ (DP90); ‘Sure-Grow 747’ (SG747); ‘Phytogen 355’ (PSC355); ‘Stoneville 474’ (ST474); and ‘FiberMax 966’ (FM966), representing germplasm of the major cotton seed breeding companies in the USA, were crossed as females with 13 CS-B lines (Stelly et al., 2005), TM-1, and G. barbadense line 3-79. The chromosome substitution lines include five subgenome A and eight subgenome D chromosomes or chromosome arms from 3-79 substituted into TM-1.

Field Design and Procedures
The 75 top crosses were made at Mississippi State, MS, in the summer of 2002. The F1 seeds were sent to a winter nursery in Tecoman, Mexico, to produce the F2 seeds. The resulting 75 F2 hybrids, five cultivars, 13 CS-B lines, and TM-1 and 3-79 parents were evaluated over four environments in 2003 and 2004 at the Plant Science Research Center at Mississippi State, MS (33°4‘ N, 88°8’ W). These are the same crosses and field plots used in our previous study on yield and yield components and details are shown in Jenkins et al. (2006). A 25-boll sample was hand-harvested from first position bolls near the middle nodes of plants in each plot. This sample was weighed and ginned on a laboratory 10-saw gin, after which, the lint samples were sent to STARLAB, Inc., in Knoxville, TN, for determination of micronaire, elongation, 2.5% span length, and fiber strength.

Data Analyses
Analysis of Phenotypic Data
Data for four fiber traits were subjected to analysis of variance using SAS procedures (SAS Institute, 2001). Means were separated using Fisher's protected least significant difference (LSD) at the 0.05 level. Parents and F2 were analyzed separately. Mean squares for genotype effects were considerably greater than mean squares for genotype x environment interactions (data not shown), thus we report parent and F2 data as means across environments.

Genetic Analysis
An additive-dominance (AD) genetic model, with genotype x environment interaction was used for data analysis (Tang et al., 1996; Wu et al., 1995; Zhu, 1993, 1994). This is the same genetic model used for yield and yield components in our previous report (Jenkins et al., 2006).

In this study, some coefficients for genetic effects were fractions rather than 0 and 1, thus, ANOVA and general linear model methods were not appropriate. Genetic variances and genetic effects for each genetic component were calculated. The phenotypic variance was partitioned into components for additive (VA), dominance (VD), additive by environment (VAE), dominance by environment (VDE), and residual (Ve) and expressed as proportions of the total phenotypic variance (Tang et al., 1996). A mixed linear model approach, minimum norm quadratic unbiased estimation with an initial value of 1.0 called MINQUE1, was used to estimate the variance components (Zhu, 1998). Genetic effects were predicted by the adjusted unbiased prediction approach (Zhu, 1993). Standard errors of variance components and genetic effects were estimated by jackknife resampling over one replication within each environment. An approximate one-tailed t test (df = 15) was used to detect the significance of variance components and a two-tailed t test was used to detect the significance of genetic effects (Miller, 1974).

The predicted genetic effects were deviations from the respective population grand mean µ, not from TM-1. A t test was utilized to detect the significance of genetic effects from zero. For the CS-B parents these are measures of the additive or homozygous dominance effects of the entire genome of the CS-B parent (25 chromosomes from TM-1 and one chromosome or chromosome arm from 3-79). In addition, a significant difference in additive or homozygous dominance effects between a specific CS-B line and TM-1 is considered to be a significant additive or homozygous dominance chromosome effect attributed to the specific substituted chromosome or chromosome arm from 3-79.

The difference between the heterozygous dominance effects for TM-1 and a CS-B line, when crossed with the same cultivar, can be considered as due to the allelic interaction between the substituted G. barbadense chromosome in the CS-B line and the homologous chromosome in the cultivar. Mathematically if we define Di1 as the heterozygous dominance effects between the female parent i and the male parent TM-1, and Dij as the heterozygous dominant effect between the female parent i and a CS-B line j, then a significant difference of Dij minus Di1 can be considered as the interaction effect (heterozygous dominance effect) due to the specific substituted chromosome or arm from 3-79 and the homologous chromosome or arm in female cultivar parent i. This is essentially a probe of the effect of the specific combination between the substituted chromosome in the CS-B line and the homologous chromosome in the cultivar.

The significance of the difference between the genetic effects for a CS-B line and TM-1 was detected by the method of Paterson (1939) using the standard error of the difference between two effects.


   RESULTS AND DISCUSSION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
Mean Comparisons among Parents
Micronaire is a measurement that relates to both fiber fineness and fiber maturity. As expected, 3-79 had the lowest micronaire and longest and strongest fibers among all parents (Table 1). Among the five commercial cultivars, FM966 and DP90 had micronaire values less than 5.0. Values above 5.0 are in the discount price range. Nine CS-B parents had micronaire values less than 5.0 and CS-B17 and CS-B25 values were less than 4.5. Cultivars SG747, PSC355, and ST474, had higher micronaire than TM-1; whereas, DP90 and FM966 were not significantly different than TM-1. CS-B02, CS-B18, and CS-B22sh, and CS-B22Lo had higher micronaire than TM-1 while CS-B17 and CS-B25 had lower micronaire than TM-1.


View this table:
[in this window]
[in a new window]

  		Table 1. Mean fiber quality values for micronaire (MIC), elongation (E1), 2.5% span length (SL 2.5), and strength (T1) for parents over four environments.

 
Fiber elongation is a measure of the amount of stretch a fiber bundle undergoes before breakage. SG747, PSC355, and ST474 had greater fiber elongation than DP90 and FM966 (Table 1). SG747 and PSC355 had greater fiber elongation than TM-1. CS-B04, CS-B17, and CS-B15sh had greater fiber elongation than TM-1; whereas, CS-B02, CS-B25, CS-B22sh, and CS-B22Lo had less elongation than TM-1. Parent 3-79 and TM-1 did not differ in elongation.

Fiber 2.5% span length is a measure of the length of the longest 2.5% of the fibers in a fiber sample array when scanned. Cultivars ranged from 28.4 to 30.6 mm in fiber length (Table 1). FM966, CS-B25, CS-B14sh, CS-B15sh, and 3-79 had significantly longer fibers than TM-1. Substitution lines CS-B18, CS-B22sh, and CS-B22Lo had shorter fibers than TM-1.

Fiber strength is a measure of breaking strength of a bundle of fibers when gripped between the jaws of a stelometer set 3.175 mm apart. Fiber strength among cultivars ranged from 182 to 240 kN m kg–1 and from 188 to 218 kN m kg–1 among CS-B lines (Table 1). Strength of TM-1 and 3-79 was 195 and 282, respectively. FM966 had the strongest fibers (240 kN m kg–1) among five cultivars. FM966 and DP90 had stronger fibers than SG747, PSC355, ST474, and TM-1. CS-B02, CS-B25, CS-B14, and CS-B15 had stronger fibers than TM-1. No CS-B lines showed weaker fibers than TM-1. Based on mean values for each substitution line, CS-B25 displayed the most comparable trait values to the best commercial cultivar for micronaire, length, and strength.

Mean Comparisons among F2 Hybrids
The mean of hybrids and midparents were similar for micronaire, elongation, 2.5% span length, and strength, indicating that additive effects are major factors in control of these fiber traits (Tables 2–5GoGoGo). Ranges among CS-B hybrids were 4.25 to 5.23 for micronaire, 6.5 to 9.8% for elongation, 27.6 to 30.9 mm for 2.5% fiber span length, and 183 to 229 kN m kg–1 for fiber strength (Tables 2–5GoGoGo).


View this table:
[in this window]
[in a new window]

  		Table 2. Micronaire of F2 hybrid from crosses of five cultivars with CS-B lines, TM-1, and 3-79.{dagger}

 

View this table:
[in this window]
[in a new window]

  		Table 3. Elongation (percentage) of F2 hybrid from crosses of five cultivars with CS-B lines, TM-1, and 3-79.{dagger}

 

View this table:
[in this window]
[in a new window]

  		Table 4. Fiber 2.5% span length (mm) of F2 hybrid from crosses of five cultivars with CS-B lines, TM-1, and 3-79.{dagger}

 

View this table:
[in this window]
[in a new window]

  		Table 5. Fiber strength (kN m kg–1) of F2 hybrid from crosses of five cultivars with CS-B lines, TM-1, and 3-79.{dagger}

 
Hybrids with DP90 had lower micronaire than hybrids with the other four cultivars on average (Table 2). The means of hybrids with SG747, PSC355, and ST474 did not differ but had higher micronaire values than hybrids with FM966 and DP90. Among the 75 hybrids micronaire ranged from 3.66 to 5.23. The mean micronaire values for hybrids across cultivars were higher for eight hybrids than for hybrids with TM-1. Hybrids with 3-79 had the lowest micronaire and only hybrids with 3-79 and CS-B25 had micronaire values lower than hybrids with TM-1.

Elongation values among hybrids ranged from 6.5 to 9.8%. When averaged by cultivar, the greatest elongation values were for hybrids with SG747 and PSC355, whereas hybrids with FM966 were the lowest. When averaged across cultivars, no hybrids were higher in elongation than hybrids with TM-1, and seven hybrids were lower in elongation than hybrids with TM-1 (Table 3).

Fiber 2.5% span length ranged from 27.7 to 33.2 mm among the 75 hybrids. Hybrids with FM966 had significantly longer fibers and those with ST474 had significantly shorter fibers than hybrids with the other cultivars. Fibers of hybrids with CS-B25, CS-B14sh, CS-B15sh, and 3-79 were significantly longer and hybrids with CS-B16 and CS-B17 were significantly shorter than hybrids with TM-1 (Table 4).

Fiber strength of the 75 hybrids ranged from 183 to 259 kN m kg–1. The fiber strength of the hybrids was strongest with parents FM966, DP90, PSC355, ST474, and SG747, respectively. Among male parents, hybrids with 3-79 were significantly stronger than any other hybrids (Table 5). On average, hybrids with CS-B02, CS-B18, CS-B25, CS-B14sh, and CS-B15sh, and 3-79 had stronger fibers than the hybrids with TM-1. Hybrids with CS-B25 had higher fiber strength than the hybrids with TM-1 or any other CS-B lines.

Variance Components
When chromosome substitution lines are crossed with elite cultivars the phenotypic complexity is expected to be reduced when compared to interspecific lineages with the same elite cultivars (Jenkins et al., 2006). We expect this should improve variance component estimates. The variance components were expressed as a proportion of the phenotypic variance and are summarized in Table 6. Additive effects contributed the most to all fiber traits (micronaire 48.0%, elongation 37.4%, span length 53.1%, and strength 60.2%). Dominance effects also made significant contributions to the phenotypic variance (micronaire 12.7%, elongation 13.6%, span length 13.5%, and strength 8.9%). The genotype x environment interaction variance contributed less than 10% to the phenotypic variances for fiber elongation span length and strength and accounted for only 12.7% of the phenotypic variance for micronaire.


View this table:
[in this window]
[in a new window]

  		Table 6. Variance components and standard errors expressed as proportions of the phenotypic variances for fiber traits.{dagger}

 
In the additive dominance model, the larger proportion of the phenotypic variance attributed to additive effects, implies that these effects can be utilized in breeding programs designed to improve fiber quality of cultivars. The significant heterozygous dominance components indicate that specific CS-B lines may be useful for developing cotton hybrids with improved fiber quality.

Additive Effects
In the additive dominance model, the additive effects measure the general combining ability (GCA) of parents and we report these as deviations from the population grand mean (Table 7). We calculated the difference in additive effect between hybrids with a CS-B parent and hybrids with the TM-1 parent and consider this as the additive effect of the specific chromosome or chromosome arm from 3-79 that is substituted into the CS-B parent.


View this table:
[in this window]
[in a new window]

  		Table 7. Additive effects and standard errors for fiber traits expressed as deviations from population grand mean.

 
Micronaire
Three cultivars and seven CS-B lines contributed positive additive effects while DP90, 3-79, and two CS-B lines contributed negative additive effects for micronaire (Table 7). Cultivars SG747, PSC355, ST474, FM966, and CS-B02, CS-B04, CS-B07, CS-B16, CS-B18, CS-B05sh, CS-B22sh, and CS-B22Lo had positive additive effects greater than TM-1 for micronaire; while CSB25 and 3-79 had negative additive effects greater than TM-1. The results suggested that substituted chromosomes or arms 2, 4, 7, 16, 18, 5sh, 22sh, and 22Lo from 3-79 would increase micronaire significantly more than the corresponding arm from TM-1; whereas, substituted chromosome 25 would decrease micronaire (a favorable response) significantly more than the homologous chromosome 25 from TM-1.

Elongation
SG747, PSC355, TM-1, CS-B04, CS-B17, CS-B15sh, and 3-79 had positive additive effects on fiber elongation, while DP90, FM966, CS-B02, CS-B14sh, and CS-B22Lo had negative additive effects on fiber elongation. DP90, FM966, CS-B02, CS-B18, CS-B25, CS-B14sh, CS-B22sh, and CS-B22Lo had negative additive effects on elongation that were significantly different than TM-1, while SG747 and CS-B04 had higher additive effects than TM-1. This suggests that only chromosome 4 from 3-79 increases fiber elongation more than the homologous chromosome from TM-1.

2.5% Fiber Length
Only FM966, CS-B25, CS-B15sh, and 3-79 had positive additive effects on 2.5% fiber span length, whereas SG747, ST474, CS-B02, CS-B16, CS-B17, CS-B18, CS-B05sh, CS-B22sh, and CS-B22Lo had negative additive effects on fiber length. Only FM966, CS-B04, CSB25, CS-B14sh, CS-B15sh, and 3-79 had positive additive effects greater than TM-1 for 2.5% fiber length, whereas ST474, CS-B16, CS-B05sh, CS-B22sh, and CS-B22Lo had greater negative additive effects than TM-1. This suggest that chromosomes 4, 25, 14sh, and 15sh from 3-79 should increase fiber length significantly more than the homologous chromosomes in TM-1.

Fiber Strength
Only FM966, CS-B02, CS-B25, and 3-79 had significant and positive additive effects on fiber strength, whereas SG747, TM-1, CS-B04, CS-B06, CS-B07, CS-B16, CS-B17, CS-B05sh, CS-B22sh, and CS-B22Lo had negative additive effects. CS-B02, CS-B25, CS-B15sh, and 3-79 had significantly greater additive effects than TM-1. CS-B14sh had negative additive effects, but less negative than TM-1. This suggest that chromosomes 2, 25, and 15sh, from 3-79 increase fiber strength more than homologous chromosomes in TM-1 and CS-B14sh was less negative than TM-1.

These data indicate that by using chromosome substitution lines in crosses with elite cultivars we have discovered alleles on several chromosomes that are masked in whole genome crosses. Significant additive variance effects demonstrate that CS-B lines can be used to improve fiber properties of Upland cultivars. Alleles in CS-B25 decrease fiber micronaire, increase span length, and increase strength, all of which improve fiber quality. Alleles on CS-B02 increase fiber strength. CS-B02 and CS-B25 were shown to have no significant effect on lint yield in our previous study (Jenkins et al., 2006). However, we have also identified several chromosome substitution lines that have detrimental effects on fiber quality parameters of length and strength.

Dominance Effects
In the additive dominance model, heterozygous dominance effects measure the specific combining ability (SCA) of parents in specific hybrid combinations. We estimated both homozygous (Dii) and heterozygous (Dij) dominance effects. A negative homozygous dominance effect for a parent will result in inbreeding depression in generations following the use of this parent in a cross. High heterozygous dominance effects between two parents should result in high heterosis in the F1 or F2 hybrid.

Homozygous Dominance Effects
Homozygous dominance effects are summarized in Table 8. CS-B04, CS-B07, CS-B17, and CS-B05sh showed significant negative homozygous dominance effects for micronaire; whereas 3-79 showed significant positive homozygous dominance effect. The genetic effects for these four CS-B lines were also significantly different from the effects of the homologous chromosomes or chromosome arms in TM-1.


View this table:
[in this window]
[in a new window]

  		Table 8. Homozygous dominance effects and standard errors for fiber traits expressed as deviations from population grand mean.

 
PSC355, FM966, CS-B04, CS-B16, CS-B17, and CS-B15sh had positive homozygous dominance effects and only 3-79 had negative homozygous dominance effect for fiber elongation. SG747, PSC355, FM966, CS-B04, CS-B07, CS-B16, CS-B17, CS-B18, CS-B05sh, CS-B14sh, and CS-B15sh had greater homozygous dominance effects than TM-1 for fiber elongation.

Only 3-79 had positive homozygous dominance effects on fiber length. PSC355, FM966, TM-1, CS-B04, CS-B06, CS-B17, and CS-B15sh had negative homozygous dominance effects. CS-B25 CS-B05sh, CS-B22sh, and 3-79 differed from TM-1 in homozygous dominance effects for 2.5% span length.

DP90, FM966, CS-B06, and CS-B22sh had significant positive homozygous dominance effects for fiber strength with DP90 and FM966 having greater homozygous dominance effect than TM-1.

Heterozygous Dominance Effects
When heterozygous dominance effects of a specific chromosome substitution line crossed with a cultivar are significantly different from the effects of TM-1 crossed with the same cultivar, these can be viewed as chromosome specific heterozygous dominance effects. This is essentially a probe of the heterozygous dominance effects between the specific chromosome in the CS-B line and the homologous chromosome in the cultivar. Because the CS-B lines each have a common TM-1 background, we can calculate these effects. The heterozygous dominance effects are shown in Tables 9–12GoGoGo. The main interest in these CS-B lines are those where the CS-B line effects are significantly different from those of TM-1, otherwise the hybrid could be made using TM-1 as one parent. Thus, the heterozygous dominance data are shown with test for significance differences from TM-1.


View this table:
[in this window]
[in a new window]

  		Table 9. Heterozygous dominance effects and standard errors for fiber micronaire expressed as deviations from population mean.

 

View this table:
[in this window]
[in a new window]

  		Table 10. Heterozygous effects and standard errors for fiber elongation expressed as deviations from population grand mean.

 

View this table:
[in this window]
[in a new window]

  		Table 11. Heterozygous dominance effects and standard errors for fiber 2.5% span length (mm) expressed as deviations from the population grand mean.

 

View this table:
[in this window]
[in a new window]

  		Table 12. Heterozygous dominance effects and standard errors for fiber strength (kN m kg–1) expressed as deviations from population grand mean.

 
Micronaire
Heterozygous dominance effects significantly different from TM-1 were found as follows: DP90 hybrids with CS-B06; SG747 hybrids with CS-B07, CS-B17, and CS-B15sh; PSC355 hybrids with CS-B04, CS-B18, CS-B05sh, and CS-B22Lo; ST474 hybrids with CS-B02 and CS-B25; and FM966 hybrids with CS-B02, CS-B04, CS-B06, CS-B05sh, and CS-B22sh. All effects were positive excluding one hybrid with PSC355 and two hybrids with ST474. Effects of 3-79 whole genome hybrids were significantly different than TM-1 whole genome hybrids with all cultivars except SG747. The specific effect for TM-1 hybrids was negative with three cultivars and positive with two cultivars (Table 9).

Elongation
Heterozygous dominance effects for DP90 hybrids with CS-B02, CS-B06, CS-B16, and CS-B25; for SG747 hybrids with CS-B02, CS-B04, and CS-B06; for PSC355 hybrids with CS-B04 and CS-B16; for ST474 hybrids with CS-B06 and CS-B17; and for FM966 hybrids with CS-B02, CS-B04, CS-B16, CS-B17, CS-B18, CS-B25, CS-B22sh, and CS-B22Lo, were significantly different than the respective cultivar by TM-1 heterozygous dominance effects (Table 10). The four DP90 hybrids increased elongation which is a positive effect; whereas, the CS-B hybrids with the other four cultivars reduced fiber elongation compared to TM-1.

2.5% Span Length of Fiber
No CS-B hybrid with DP90 had heterozygous dominance effects greater than the TM-1 hybrid. One hybrid with SG747, six with PSC355, and one with FM966 had negative heterozygous dominance effects, but none had positive heterozygous dominance effects greater than the respective cultivar hybrids with TM-1. Hybrids of ST474 with CS-B04, CS-B06, CS-B25, and CS-B05sh showed positive and significantly greater effects than the TM-1 x ST474 hybrid (Table 11).

Fiber Strength
In hybrids with SG747, PSC355, and ST474 there were several CS-B hybrids with a significantly greater effect than TM-1 hybrids; however, the effects were negative on fiber strength (Table 12). Positive heterozygous dominance effects for several CS-B hybrids with DP90 and FM966 were greater than TM-1 hybrids. These two cultivars have the highest strength among cultivars and it is significant that hybrids of DP90 with CS-B07, CS-B16, and CS-B25 and hybrids of FM966 with CS-B02, CS-B04, CS-B07, CS-B18, CS-B25, and CS-B22Lo have significantly greater positive effects on fiber strength than respective TM-1 hybrids. The three CS-B hybrids with DP90 contributed lower effects than 3-79; however, in the FM966 hybrids, five were as good as 3-79 and the CS-B18 hybrid was better.


   CONCLUSIONS
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
In the additive dominance model, additive effects can be considered as representing GCA effects and heterozygous dominance effects as SCA effects. The additive proportion of total variance was considerably larger than the dominance variance for each fiber trait. This is similar to what we found for the yield components with these same crosses (Jenkins et al., 2006). Considering yield components (Jenkins et al., 2006) and fiber traits in this manuscript, some chromosomes or chromosome arms from 3-79 exhibited beneficial additive effects significantly greater than the homologous chromosome from TM-1 (Table 13). For example, we found that several chromosomes had significant positive or negative GCA or SCA effects for the trait lint percentage. Since this is a trait affected by many other traits such as boll weight, seed size, number of seed per lock, etc. this was not an unexpected result. However, other traits such as fiber strength or length were affected positively by fewer chromosomes. A summary of the significant positive and negative genetic effects for yield and yield components (Jenkins et al., 2006) and fiber traits are shown in Table 13.


View this table:
[in this window]
[in a new window]

  		Table 13. A summary of general combining ability (GCA) and specific combining ability (SCA) genetic effects by chromosome that are significantly greater or significantly less than genetic effects for TM-1.{dagger}

 
These combined data show that these 13 CS-B lines harbor beneficial alleles providing GCA effects for improving yield and fiber properties for cultivar development, as well as, SCA effects that would offer improved yield and fiber properties for hybrids. Fiber properties of the G. barbadense line 3-79 are superior in fiber micronaire, length, and strength compared to the elite cultivars; however, entire genome crosses between 3 and 79 and these Upland cultivars would be plagued with the common hybrid breakdown problems of interspecific hybridization in cotton (Beasley and Brown, 1942). These include partial sterility, poor seed viability, and other disruptions which are either due to specific yield and fiber related genes or from the disruption of regulatory genes determining fertility and viability. These chromosome substitution lines are good candidates for introgressing specific chromosomal regions harboring fiber strength genes from G. barbadense into Upland cotton. Because they offer opportunities to utilize alleles on single G. barbadense chromosomes or chromosome arms in crosses, their use should overcome some of the problems with whole genome crosses between these two species. Although no CS-B line had as great GCA or SCA effects for fiber length and strength as the cultivar FM966, selected CS-B lines may carry different alleles than the cultivars. For example, CS-B25 provided alleles for improving fiber length, strength, and micronaire.

The results in this manuscript and the companion manuscript (Jenkins et al., 2006) provide guidance for use of the chromosome substitution lines with five elite cultivars from diverse commercial breeding programs and should provide guidance on which specific lines can be used with specific germplasm families for introgression of yield and fiber quality genes from G. barbadense into Upland cotton. These results show that genetic background is very important when using CS-B lines. We have measured additive and dominance effects of specific G. barbadense chromosomes. Future research should consider epistasis as this could be an important consideration for the use of these CS-B lines in breeding programs. The epistatic effects can be detected if the data sets include parents, F1, and F2 or parents, F2, and F3 data (Wu et al., 2006a).

The analyses we have developed and utilized in this work and our prior work (Jenkins et al., 2006) provide a partitioning of the additive and dominance effects which could be used with other crops where chromosome substitution lines are available. On the other hand, because each CS-B lines was in a common TM-1 background and TM-1 was used along with the CS-B parental lines in crosses with the elite cultivars, we were able to separate the genetic effects of the CS-B line genome from the genetic effects of the specific G. barbadense chromosome substituted into the CS-B line. This approach should be of great value to both molecular geneticists and plant breeders. The value of having all the chromosome substitution lines in a common background greatly extends the utility of chromosome substitution lines.

The recently developed additive dominance chromosome model (Wu et al., 2006b), can be used to analyze data sets composed of a CS-B line, its recurrent parent, and F1 or F2 hybrids resulting from crosses of the CS-B line and recurrent parent with several inbreds or cultivars. Analysis using this model will predict the additive and dominance effects attributed to the substituted alien chromosome in the CS-B line, as well as, the overall genetic effects of the nonsubstituted chromosomes. It will also predict the effects of the chromosome that is homologous to the substituted chromosome in individual inbreds or cultivars. Thus, the new chromosome model (Wu et al., 2006b), along with the model used to analyze the data in this manuscript, should be of great value to geneticists and plant breeders of other crops. Our results suggest different cultivars may have different alleles of QTLs on different chromosomes for improving specific traits. Accordingly these CS-B lines can be used as tester stocks to reveal different sources of beneficial QTLs in different cultivars; thereby, providing a tool to identify parents to use in plant breeding or molecular genetics research.

Our research should also facilitate molecular genomic studies in cotton as it has targeted desirable alleles for traits of interest to specific chromosomal segments. These chromosome substitution lines provide an ideal opportunity to identify associations of important fiber and agronomic traits with individual chromosomes or chromosome arms in cotton. Being able to associate important traits with chromosomes or chromosome arms should allow molecular geneticists to concentrate on these functional regions of the genome without having to sort through the entire genome for alleles affecting traits of interest.


   NOTES
TOP
 NOTES
ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Received for publication June 15, 2006.


   REFERENCES
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 





This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Jenkins, J. N.
Right arrow Articles by Stelly, D. M.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Jenkins, J. N.
Right arrow Articles by Stelly, D. M.
Agricola
Right arrow Articles by Jenkins, J. N.
Right arrow Articles by Stelly, D. M.
Related Collections
Right arrow Cotton
Right arrow Plant Genetic Resources
Right arrow Crop Genetics

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
The SCI Journals Agronomy Journal Vadose Zone Journal
Journal of Natural Resources
and Life Sciences Education		 Soil Science Society of America Journal
Journal of Plant Registrations Journal of
Environmental Quality		 The Plant Genome