HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by McCarty, J. C. Articles by Jenkins, J. N. Search for Related Content PubMed Articles by McCarty, J. C. Articles by Jenkins, J. N. Agricola Articles by McCarty, J. C. Articles by Jenkins, J. N. Related Collections Germplasm Enhancement Cotton Crop Genetics

CROP BREEDING & GENETICS

Use of Primitive Derived Cotton Accessions for Agronomic and Fiber Traits Improvement

Variance Components and Genetic Effects

^a USDA-ARS, Crop Science Research Lab., P. O. Box 5367, Mississippi State, MS 39762
^b Dep. of Plant and Soil Sciences, Mississippi State Univ., Mississippi State, MS 39762

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

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Upland cotton (Gossypium hirsutum L.) is cultivated in warmer climates throughout the world. The genetic base of modern upland cultivars is narrow. As yield and fiber quality traits are improved, the genetic base should be extended by the incorporation of new germplasm into cultivars. In this study, 114 day-neutral derived primitive accessions were crossed to two cultivars, Stoneville 474 and Sure-Grow 747 (female parents). In a 2-yr study, parents and F₂ hybrids were evaluated in field plots where agronomic and fiber traits were measured. An extended additive-dominance genetic model was used, and the data were analyzed on the basis of the mixed model approach. Dominance effects were the primary genetic effects controlling agronomic and fiber traits, while additive effects were small for most of these traits. Consequently, strong heterosis in some F₁ and F₂ hybrids for most traits would be expected. The genetic resources from the primitive accessions, determined on the basis of cluster analyses, did not show any consistent pattern for collection location or taxonomic classification. Even though dominance effects were the most common for traits measured, results indicate that these day-neutral derived primitive accessions provide genes with significant additive effects for fiber quality traits, while the additive effects for yield improvement was not significantly decreased. Thus, these derived germplasm accessions can provide favorable gene resources for developing high yielding cultivars or hybrids with improved fiber quality.

Abbreviations: AD, additive-dominance • DN, day-neutral • SG747, Sure-Grow 747 • ST474, Stoneville 474

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
CROP CULTIVARS should be developed that maintain a wide genetic base so they will exhibit plasticity to stressful environments and offer trait improvements. In cultivar development, it is important to extend the genetic diversity of crops with new and unrelated sources of germplasm. Upland cotton, an economically important cultivated crop with annual production in the 100 million bale range, is facing the risks associated with a reduced genetic base.

The development and pedigrees of modern upland cotton cultivars has recently been examined. Bowman et al. (1996) reported that the average coefficients of parentage among 260 cultivars released between 1970 and 1990 was 0.07. This estimate would suggest substantial diversity; however, on examining pedigrees, 236 cases of reselection were found in the development of the 260 cultivars (Calhoun et al., 1994, 1997; Bowman et al., 1997). Such a high percentage of reselection in cultivar development could indicate a narrow genetic base, which may limit genetic gain and increase genetic vulnerability.

The primitive accessions of G. hirsutum have been shown to contain useful genetic variability for upland cotton cultivar improvement (Percival, 1987; Meredith, 1990; McCarty and Jenkins, 1992; McCarty and Percy, 2001; McCarty et al., 1995, 1998a, 1998b, 2003; Basal et al., 2003, 2005). The collection, distribution, and evaluation of Gossypium spp. germplasm were initially reviewed by Percival and Kohel (1990), and they reported extensive variability in the collection. However, one undesirable character in many accessions is flowering response to photoperiod. Thus, the use of these accessions in upland cotton breeding programs has been limited because of this undesirable flowering habit. A backcross-breeding program has been used to successfully introduce day-neutral (DN) genes into the primitive accessions (McCarty and Jenkins, 1992, 1993; McCarty et al., 1979, 1995, 1998a, 1998b, 2003, 2004a, 2004b, 2005).

A number of race accessions from different regions and subspecies have been developed with a desirable DN flowering habit. For example, McCarty et al. (1995, 1998a, 1998b) evaluated F₅, BC₁F₅, BC₂F₅, BC₃F₅, and BC₄F₅ progenies of 16 DN germplasm accessions for several agronomic and fiber traits and found useful genetic variability for yield and fiber traits in the DN lines. However, the number of backcrosses with the race accessions was found to be inconsistent with respect to agronomic and fiber traits measured (Swindle, 1993; McCarty et al., 1995, 1998a, 1998b) and at the molecular level (Zhong et al., 2002). This was possibly due to the selection pressure of flowering habit, and genetic factors controlling agronomic and fiber traits were associated with the flowering genes. It is also important to evaluate the potential use of DN converted lines in future breeding programs as hybrids. Because of limited human resources, many researchers have focused on parents and F₂ hybrids rather than parents and F₁ hybrids (Meredith, 1990; Tang et al., 1993a, 1993b, 1996; Cheatham et al., 2003). McCarty et al. (2003) studied the genetic properties of yield and fiber traits in derived primitive accessions in their F₂ and F₃ hybrids, and they reported that, on average, fiber strength of derived primitive accessions exceeded that of commercial cultivars. More than 50 of 70 F₂ or F₃ hybrids had higher fiber strength than the cultivar Deltapine 50, suggesting that the fiber strength was significantly improved in most of these F₂ or F₃ hybrids, while a yield comparable to their parental commercial cultivar was maintained. McCarty et al. (2004a, 2004b) also detected significant additive x additive epistatic effects for fiber strength and most agronomic traits. These studies provided useful information for the development of pure lines or hybrids.

One hundred-fourteen race accessions collected from nine regions, covering 16 countries, were crossed to ‘Deltapine 61’, and plants with the DN flowering habit were selected in the F₂ generation (McCarty et al., 2005). To determine the potential utilization of these derived lines, they were top crossed to the commercial cultivars Stoneville 474 (ST474) and Sure-Grow 747 (SG747), their 228 F₂ hybrids, and 114 DN parents; and the two cultivars were evaluated at Mississippi State, MS, for 2 yr. Because of the large numbers of genotypes and possible systematic errors in a large field, we divided the 344 genotypes into 19 groups, each with two commercial cultivars (female parents), six DN lines (male parents), and their 12 F₂ hybrids. Within each group, these 20 genotypes were randomized in blocks with six replicates and the two commercial cultivars within each group also served as common checks across the experiment. On the basis of our previous 2-yr evaluation for each of the 19 groups, the field conditions within each group were uniform (McCarty et al., 2005). Comparing two commercial cultivars and 114 DN converted lines, we identified many DN lines with improved fiber length and strength and yields comparable to the two commercial cultivars, indicating that direct use of some DN converted lines in field practice was very possible (McCarty et al., 2006).

In the current study, an extended AD (additive-dominance) model including field systematic effects was developed. A mixed model approach was applied in this extended AD model to estimate genetic variance components and to predict genetic effects for the 114 DN accessions and their F₂ hybrids resulting from crosses to two commercial cultivars. Thus, this present manuscript will not only reveal the genetic variations in terms of additive and dominance effects for agronomic and fiber traits but also help breeders to appropriately use these derived DN lines for pure line or hybrid development.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Experimental Materials
The North Carolina Design II was employed for population development. One hundred-fourteen DN lines were crossed as male parents in the F₄ to F₈ generation to cultivars ST474 and SG747 in 2000 (McCarty et al., 2005, 2006). Crosses and subsequent evaluations were conducted at the Plant Science Research Center at Mississippi State, MS (33.4° N, 88.8° W). The F₁ seeds were grown in a winter nursery at Tecoman, Mexico, to produce the F₂ seeds. Seeds from the 228 F₂ hybrids and the 116 parents were grown at one field location each year in 2001 and 2002. Because of the large number of entries, the total F₂ hybrids and their male parents were divided into 19 groups (each with six male and two female parents and their 12 F₂ hybrids). Previous analysis indicated a uniform environment within each group (McCarty et al., 2005). The experimental design for each group was a randomized complete block with six replicates. Plot size was a single row 12 m in length with row spacing of 0.97 m. The planting was a two-planted/one-skip row pattern. The stand density consisted of single plants spaced approximately 10 cm apart. The soil type was a Leeper silty clay loam (Fine, smectitic, nonacid, thermic Vertic Epiaquepts).

A 25-boll hand-harvested sample was collected from the middle portion of the plants for each plot before machine picking. Boll samples were weighed (boll weight determination) and ginned on a laboratory 10-saw gin to determine lint percentages and to provide lint samples for fiber analyses. Lint samples were sent to STARLAB, Inc., at Knoxville, TN, where single instruments were used for the determination of micronaire (MIC), elongation (E1), fiber strength (T1), and 2.5% span length (SL2.5). Plots were harvested with a machine picker and seed cotton weighed. Lint yield was calculated by multiplying lint percentage by seed cotton plot weight.

Genetic Model and Analytical Approach
Given that conditions within each of the 19 groups were relatively uniform (McCarty et al., 2005), an AD with genotype x environment interaction genetic model (Zhu, 1994; Wu et al., 1995; Tang et al., 1996) was extended for our data analysis. The models for F₂ and parent were as follows:

F₂:

[1]

Parent:

[2]

Equations [1] and [2] together can be expressed in forms of vectors and matrices as follows in Model [3],

[3]

where y is the vector for an observed trait; 1 is the vector with all elements 1; X_E is the incidence matrix for environmental effect vector b_E, fixed effects; U_S is the incidence matrix for the vector of field position effects e_S, e_SMVN(0, _S²I); U_B is the incidence matrix for the vector of block effects within each group and environment, e_BMVN(0, _B²I); U_A is the incidence matrix for the vector of additive effects e_A, e_AMVN(0, _A²I); U_D is the incidence matrix for the vector of dominance effects e_D, e_DMVN(0, _D²I); U_AE is the incidence matrix for the vector of additive x environment interaction effects e_AE, e_AEMVN(0, _AE²I); U_DE is the incidence matrix for the vector of dominance x environment interaction effects e_DE, e_DEMVN(0, _DE²I); and e is the vector of random errors with eMVN(0, _e²I).

Variance components were estimated by the minimum norm quadratic unbiased estimation (Rao, 1971) in which all prior values were set as 1.0 and called MINQUE(1) by Zhu (1989). Random effects were predicted by the adjusted unbiased prediction (AUP) method (Zhu, 1993). The phenotypic variance was partitioned into the variance components for additive (V_A = 2_A²), dominance (V_D = _D²), additive x environment (V_AE = 2_AE²), dominance x environment (V_DE = _DE²), field position group or systematic (V_S = _S²), and residual (V_e = _e²). The proportions of variance components to the phenotypic variance for each trait were calculated as well. A resampling (jackknife method) was applied to calculate the standard error (SE) for each parameter by removal of one replicate within each experimental group and environment (Miller, 1974). There were six replications within each of 19 groups (experiments) in each year (degrees of freedom = 227). The t test was used to detect the significance of each parameter. Estimation of variance components and prediction of genetic effects mentioned above were conducted by a program written in C by the authors. Discrimination and cluster analyses for the predicted additive effects and parental genotypic values were conducted utilizing SAS 8.0 (SAS Institute, Inc., 1999).

	RESULTS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Field Ranges of Agronomic and Fiber Traits
Among all traits measured, cotton yield is the trait most likely influenced by the soil and moisture conditions at different field locations. Fiber elongation, micronaire, fiber strength, and boll weight varied considerably across the 19 groups in both years. Lint percentage and 2.5% span length were stable across groups in both years. The results show that agronomic and fiber traits could vary considerably in a large experimental field (McCarty et al., 2005). Thus, the field position (or systematic) factors should be considered when a large number of genotypes are evaluated. Accordingly, in this study, the field position effects (also called systematic effects) were included in the traditional AD genetic model for our data analyses (Eq. [1]–[3]).

Variance Components
Field systematic effects contributed 18.5 and 20.8% of the phenotypic variation for seed cotton yield and lint yield, respectively (Table 1). Field systematic effects contributed 8.9, 9.5, and 10.3% of the phenotypic variations for boll weight, micronaire, and fiber elongation, respectively. The remaining three traits measured were only slightly influenced by field systematic effects. McCarty et al. (2005) reported that systematic effects were significant for all traits measured, but the magnitude for different traits varied. Thus, the results in Table 1 are in agreement with our previous results (McCarty et al., 2005). The results suggested the necessity of considering field systematic effects when a large number of genotypes are planted in a large experimental field.

Additive Effects
Additive effects under an AD model are equivalent to general combining ability effects. Thus, evaluating the additive effects for these derived primitive accessions may help cotton researchers choose appropriate lines for use as good general combiners in cultivar improvement. The predicted additive effects for all yield and fiber traits are listed in Table 2. Seventy-four male parents had greater additive effects than ST474 (–127 kg ha^–1) for seed cotton yield, while only one male parent had lower additive effect than ST474. No male parent had a greater additive effect than SG747 (231 kg ha^–1), while 103 of 114 male parents had lower additive effects than SG747 for seed cotton yield. One hundred-four of 114 males had greater additive effects than ST474 (–101 kg ha^–1) and one male parent greater than SG747 (54 kg ha^–1) with respect to lint yield, respectively. No male had lower additive effect than ST474, while 40 were lower than SG747 for lint yield. Most male parents had greater additive effects than either commercial cultivar for boll weight, lint percentage, 2.5% span length, and elongation. The above results suggested that a wide selection of these derived DN lines can be used as good general combiners with ST474 and SG747 for improving fiber quality while maintaining high yields. For example, derived DN lines DNT-1975, DNT-503, DNT-621, DNT-1410, DNT-179, DNT-147, and DNT-260 had comparable additive effects for yield with significantly improved fiber length and fiber elongation (Table 2).

Simultaneous improvement for yield and fiber quality is an important breeding goal in the use of cotton hybrids. In this study, 59 of 114 F₂ hybrids with ST474 showed negative MP heterosis for both seed cotton yield and fiber strength, while six of 114 F₂ hybrids with ST474 had positive heterosis for both seed cotton yield and fiber strength. Thirty-five of 114 F₂ hybrids with SG747 showed negative MP heterosis for both seed cotton yield and fiber strength, while 12 of 114 F₂ hybrids with SG747 had positive heterosis for both seed cotton yield and fiber strength. Less than 10% of the F₂ hybrids had positive heterosis for these two traits. Thus, in general, selecting a favorable cotton hybrid will require a large number of crosses to be made and evaluated. In this study, we found the hybrid SG747xDNT-282 had desirable MP heterosis for both seed cotton yield (population mean based MP heterosis was 22.6%) and fiber strength (population mean based MP heterosis was 7.3%), indicating that this hybrid may have commercial usefulness. However, additional field tests for this hybrid under more environments should be conducted.

Classification of Male Parents
These 114 primitive DN derived accessions represent accessions collected from different geographic regions and countries worldwide (McCarty et al., 2005). Thus, cotton breeders are interested in determining if any consistent genetic conclusions relative to geography can be made among these accessions. With this in mind, both cluster and discrimination analyses were conducted using both additive effects and genotypic values of the 114 male parents. Discrimination and cluster analysis did not show any solid tendency related to geographic origins for these 114 male parents (data not shown). From results in this study and in a previous study (McCarty et al., 2006), we concluded that derived primitive accessions from various regions may have equal potential to produce high yields comparable to commercial cultivars, while fiber qualities may be significantly improved (McCarty et al., 2003, 2004a, 2004b, 2005). Derived primitive accessions may provide a wide gene resource for improving fiber quality and stress tolerance while expanding the genetic base of cotton.

	DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Collecting, maintaining, and converting a diverse genetic base of upland cotton is useful for developing cultivars with several improved traits. This is currently important because of a lack of genetic diversity among current commercial cultivars (Bowman et al., 1996, 1997; Calhoun et al., 1994, 1997). Such a narrow genetic base will not only limit the expected genetic gain in yield and fiber quality but will also result in reduced tolerance to environmental stress. In the past three decades, many race accessions with photoperiodic flowering habit have been derived with DN genes and are available for current breeding studies (Percival, 1987; Meredith, 1990; McCarty and Jenkins, 1992; McCarty and Percy, 2001; McCarty et al., 1995, 1998a, 1998b, 2003; Basal et al., 2003, 2005). Research work is also ongoing for developing and evaluating additional derived DN lines. Such work will greatly benefit both public and private cotton breeding programs.

In this study, we evaluated 114 derived DN lines from nine regions around the world as well as their 228 F₂ hybrids from crosses with two widely adapted commercial cultivars, Stoneville 474 and Sure-Grow 747. Evaluating such a large number of genotypes including parents and F₂ hybrids is interesting, but it is also practically challenging because of the possible systematic errors in a large experimental field. Thus, we divided these 344 genotypes into 19 groups of 12 hybrids and parents. Our previous study showed that the variability within each group was small (McCarty et al., 2005). In this study, we extended the traditional AD model to include field systematic effects in the genetic model. Then, we applied the mixed model approach to estimate genetic variance components and to predict genetic effects.

Seed cotton yield and lint cotton yield were highly influenced by systematic effects, while other agronomic and fiber traits we measured were only slightly influenced (McCarty et al., 2005; and Table 1, this manuscript). Results showed that dominance effects were the primary genetic effects controlling agronomic and fiber traits, while additive effects were slightly involved with most of these traits. The results suggested a large number of general combiners among these male parents were possible. The results indicated that the diversity between male and female parents likely resulted in large dominance effects. However, the majority of these crosses did not provide favorable dominance effects for traits when these derived DN lines were crossed to two commercial cultivars (Tables 3 and 4). We identified 18 (7.8%) F₂ hybrids with positive MP heterosis for seed cotton yield and fiber strength, while only one cross (SG747xDNT-282) had favorable heterosis for both seed cotton yield and fiber strength. Hybrid cotton seed is currently not being produced and sold in the USA because producers currently rely on inbred cultivars. Even though dominance effects were significant and common in the DN lines, they can still be used in conventional breeding programs; however, selection would be done in later generations.

On the basis of cluster and discrimination analyses, the genetic resources from the primitive accessions showed no consistent effect of collection location or geographic race based on the traits measured in this study. These DN derived primitive accessions provide genes with significant additive effect for fiber qualities, while the additive effects for yield improvement were not significantly decreased.

In this study, two widely adapted commercial cultivars were used as female parents to evaluate the potential utilization of these converted day-neutral lines. In future studies, cotton breeders can use more commercial cultivars as parents to cross with these DN lines to identify useful hybrids for commercial use. On the other hand, predicting genotypic values at different generations (i.e., F₁ and F₂) will be an interesting research task (Zhu, 1993; McCarty et al., 2004b). The genotypic values at different generations without selection pressure have been predicted with the computer program we developed (Wu et al., 2003). The detailed results will be addressed in another manuscript. The results will help breeder's select useful crosses for hybrids or cultivars.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Contribution of the USDA-ARS in cooperation with the Mississippi Agric. and Forestry Exp. Stn. Mention of trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by USDA, ARS and does not imply its approval to the exclusion of other products or vendors that may also be suitable.

Received for publication June 19, 2006.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

• Basal, H., P. Bebeli, C.W. Smith, and P.S. Thaxton. 2003. Root growth parameters of converted race stocks of upland cotton and two BC₂F₂ populations. Crop Sci. 43:1983–1988.[Abstract/Free Full Text]
• Basal, H., C.W. Smith, P.S. Thaxton, and J.K. Hemphill. 2005. Seedling drought tolerance in upland cotton. Crop Sci. 45:766–771.[Abstract/Free Full Text]
• Bowman, D.T., O.L. May, and D.S. Calhoun. 1996. Genetic base of upland cotton cultivars releases between 1970 and 1990. Crop Sci. 36:577–581.[Abstract/Free Full Text]
• Bowman, D.T., O.L. May, and D.S. Calhoun. 1997. Coefficients of parentage for 260 cotton cultivars releases between 1970 and 1990. USDA-ARS Bull. 1852. U.S. Gov. Print. Office, Washington, DC.
• Calhoun, D.S., D.T. Bowman, and O.L. May. 1994. Pedigrees of upland and pima cotton cultivars released between 1970 and 1990. Mississippi Agric. For. Exp. Stn. Bull. 1017.
• Calhoun, D.S., D.T. Bowman, and O.L. May. 1997. Pedigrees of upland and pima cotton cultivars releases between 1970 and 1995. Mississippi Agric. For. Exp. Stn. Bull. 1069.
• Cheatham, C.L., J.N. Jenkins, J.C. McCarty, Jr., C.E. Watson, and J. Wu. 2003. Genetic variance and combining ability of crosses of American cultivars, Australian cultivars, and wild cottons. J. Cotton Sci. 7:16–22.
• McCarty, J.C., Jr., and J.N. Jenkins. 1992. Characteristics of 79-neutral primitive race accessions. Mississippi Agric. For. Exp. Stn. Tech. Bull. 184.
• McCarty, J.C., Jr., and J.N. Jenkins. 1993. Registration of 79 day-neutral primitive cotton germplasm lines. Crop Sci. 33:351.[Free Full Text]
• McCarty, J.C., and R.G. Percy. 2001. Genes from exotic germplasm and their use in cultivar improvement in Gossypium hirsutum L. and G. barbadense L. p. 65–80. In J.N. Jenkins and S. Saha (ed.) Genetic improvement of cotton—Emerging technologies. Science Publishers, Inc., Enfield, NH.
• McCarty, J.C., Jr., J.N. Jenkins, and B. Tang. 1995. Primitive cotton germplasm: Variability of yield and fiber traits. Mississippi Agric. and For. Exp. Stn. Technical Bull. 202.
• McCarty, J.C., Jr., J.N. Jenkins, W.L. Parrott, and R.G. Creech. 1979. The conversion of photoperiodic primitive race stocks of cotton to day-neutral stocks. Mississippi Agric. For. Exp. Stn. Res. Rep. 4(19):4.
• McCarty, J.C., J.N. Jenkins, and J. Wu. 2003. Use of primitive accessions of cotton as sources of genes for improving yield components and fiber properties. Mississippi Agric. For. Exp. Stn. Bull. 1130.
• McCarty, J.C., J.N. Jenkins, and J. Wu. 2004a. Primitive accession germplasm by cultivar crosses as sources for cotton improvement I: Phenotypic values and variance components. Crop Sci. 44:1226–1230.[Abstract/Free Full Text]
• McCarty, J.C., J.N. Jenkins, and J. Wu. 2004b. Primitive accession germplasm by cultivar crosses as sources for cotton improvement II: Genetic effects and genotype values. Crop Sci. 44:1231–1235.[Abstract/Free Full Text]
• McCarty, J.C., J.N. Jenkins, and J. Wu. 2005. The Use of derived primitive accessions of cotton for improvement of agronomic and fiber traits in F₂ hybrids. Mississippi Agric. For. Exp. Stn. Bull. 1141.
• McCarty, J.C., J. Wu, and J.N. Jenkins. 2006. Genetic diversity for agronomic and fiber traits in day-neutral accessions derived from primitive cotton germplasm. Euphytica 148:283–293.[CrossRef]
• McCarty, J.C., Jr., J.N. Jenkins, and J. Zhu. 1998a. Introgression of day-neutral genes in primitive cotton accessions: I. Genetic variances and correlations. Crop Sci. 38:1425–1428.[Abstract/Free Full Text]
• McCarty, J.C., Jr., J.N. Jenkins, and J. Zhu. 1998b. Introgression of day-neutral genes in primitive cotton accessions: I. Predicted genetic effects. Crop Sci. 38:1428–1431.[Abstract/Free Full Text]
• Meredith, W.R., Jr. 1990. Yield and fiber-quality potential for second generation hybrids. Crop Sci. 30:1045–1048.[Abstract/Free Full Text]
• Miller, R.G. 1974. The Jackknife- a review. Biometrika 61:1–15.[Abstract/Free Full Text]
• Percival, A.E. 1987. The national collection of Gossypium germplasm. Southern Cooperative Ser. Bull, 321.
• Percival, A.E., and R.J. Kohel. 1990. Distribution, collection, and evaluation of Gossypium. Adv. Agron. 44:225–256.
• Rao, C.R. 1971. Estimation of variance and covariance components-MINQUE theory. J. Multivariate Anal. 1:257–275.
• SAS Institute, Inc. 1999. SAS software Version 8.0. SAS Institute, Cary, NC.
• Swindle, M.G. 1993. Performance of F2 hybrids in cotton from crosses of exotic germplasm and cultivars. M.S. Thesis, Mississippi State Univ., Mississippi State, MS.
• Tang, B., J.N. Jenkins, J.C. McCarty, and C.E. Watson. 1993a. F₂ hybrids of host plant germplasm and cotton cultivars: I. Heterosis and combining ability for lint yield and yield components. Crop Sci. 33:700–705.[Abstract/Free Full Text]
• Tang, B., J.N. Jenkins, J.C. McCarty, and C.E. Watson. 1993b. F₂ hybrids of host plant germplasm and cotton cultivars: II. Heterosis and combining ability for fiber properties. Crop Sci. 33:700–705.
• Tang, B., J.N. Jenkins, C.E. Watson, J.C. McCarty, and R.G. Creech. 1996. Evaluation of genetic variances, heritabilities, and correlations for yield and fiber traits among cotton F₂ hybrid populations. Euphytica 91:315–322.[CrossRef][ISI]
• Wu, J., J. Zhu, and J.N. Jenkins. 2003. Mixed linear model approaches in quantitative genetic models. In M.S. Kang (ed.) Formulars, software, and techniques for genetics and breeders. The Haworth Reference Press Inc., New York.
• Wu, J., J. Zhu, F.H. Xu, and D.F. Ji. 1995. Analysis of genetic effect by environment interactions for yield traits in upland cotton. Heredita 17(5):1–4.
• Zhong, M., J.C. McCarty, J.N. Jenkins, and S. Saha. 2002. Assessment of day-neutral backcross populations of cotton using AFLP markers. J. Cotton Sci. 6:97–103.
• Zhu, J. 1989. Estimation of genetic variance components in the general mixed model. Ph.D. Dissertation, NC State University, Raleigh (Diss. Abstr. DA8924291).
• Zhu, J. 1993. Methods of predicting genotype value and heterosis for offspring of hybrids. J. Biomath. 8(1):32–40.
• Zhu, J. 1994. General genetic models and new analysis methods for quantitative traits. J. Zhejiang Agric. Univ. 20(6):551–559.
• Zhu, J. 1998. Analytical methods for genetic models. Press of China Agriculture, Beijing, China.

This Article Abstract Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by McCarty, J. C. Articles by Jenkins, J. N. Search for Related Content PubMed Articles by McCarty, J. C. Articles by Jenkins, J. N. Agricola Articles by McCarty, J. C. Articles by Jenkins, J. N. Related Collections Germplasm Enhancement Cotton Crop Genetics