Genetic association of yield with its component traits in a recombinant inbred line population of cotton

Lint yield of upland cotton (Gossypium hirsutum L.) is determined by its component traits, boll number, boll weight, and lint percentage. Selecting high yielding lines is based on the ability to manipulate component traits. In this study, 188 recombinant inbred lines and two parental lines were grown in 1999 and 2000 at Mississippi State University. Lint yield and its three component traits were measured and analyzed by an extended conditional mixed linear model approach. Boll number unit-area^–1 made the largest contribution to genotypic and genotype × environment (G × E) variations for lint yield. Both boll number and lint percentage, and boll number and boll weight jointly accounted for more than 70% of the genotypic and G × E variations in lint yield. Ninety-nine percent of the genetic and phenotypic variation in lint yield could be explained by the three component traits, indicating that lint yield was mainly dependent on its three component traits. Small phenotypic variation in lint yield could be accounted for by effects of genotype, G × E interactions of boll number or boll number combined with other component trait(s) (Table 5). For boll number unit-area^–1 a wider distribution of genotypic contribution effects was detected than for lint percentage and boll weight in this study. Boll number and boll weight interacted to affect lint yield, indicating that balanced selection for boll weight and boll number is needed in high-yielding line development. Comparative results with other approaches were also discussed in this study.The U.S. Governments right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged     

Germplasm for genetic improvement of lint yield in Upland cotton: genetic analysis of lint yield with yield components

Determination of genetic effects for lint yield and yield components in cotton (Gossypium hirsutum L.) germplasm is critical for its utilization in breeding programs. This study was designed to apply the conditional approach and an additive and dominant model to analyze genetic effects for lint yield and yield components. Forty-eight F₂ populations derived from crosses between four existent Upland cotton cultivars as female parents and 12 germplasm lines as male parents were evaluated at two locations in 2008 and 2009. Conditional and unconditional variance components were estimated by the mixed linear model based conditional approach. Lint yield and yield components were mainly controlled by genotypic effects, i.e., additive variance and dominance variance (≥66 % of total phenotypic variation). Lint percentage and lint index had the highest proportions of additive variance component to the total phenotypic variances. SP156 and SP205 had positive additive effects for lint yield and yield components, and were also parents of the most hybrids with positive predicted dominant effects. Therefore, these two lines are good combiners for development of both pure lines and hybrids. Positive additive contribution effects to lint yield from lint percentage, boll number, boll weight, and seed index were detected in different parents. Adding seed index to boll number and lint percentage increased additive contribution effects to lint yield from these two components relative to the contribution effects from either boll number or lint percentage alone. Results in this study suggest that boll number, lint percentage, and seed index should be balanced in pure line development.     

Genetic variance components and genetic effects among eleven diverse upland cotton lines and their F2 hybrids

Selecting high yielding upland cotton, Gossypium hirsutum L. lines with improved fiber quality is a primary breeding goal. A diverse set of ten cultivars and one breeding line were crossed in a half diallel. Parents and F₂ hybrids were grown in three environments at Mississippi State, MS. Ten agronomic and fiber traits were analyzed by a mixed linear model approach based on the additive-dominance genetic model. Variance component, genetic effects and genetic correlations were calculated. ‘Acala Ultima’ was a desirable general combiner for fiber length, uniformity, strength, micronaire, lint percentage, and boll weight. ‘FiberMax 966’ was a desirable general combiner for fiber length, uniformity, strength, and all agronomic traits. ‘Tamcot Pyramid’ and M240 were poor general combiners for both fiber and agronomic traits. ‘Coker 315’ was a good general combiner for fiber length, uniformity, micronaire, boll weight, boll number, and yield. Heterozygous dominance effects were associated with several crosses, which suggest their use as hybrids.     

Evaluation of genetic variances, heritabilities, and correlations for yield and fiber traits among cotton F2 hybrid populations

Summary F₂ hybrid cultivars continue to occupy a small portion of the cotton (Gossypium hirsutum L.) production are in the United States, but occupy a larger proportion of the production area in some other countries. Sixty-four F₂ hybrids resulting from crosses of four commercial cultivars and 16 pest-resistant germplasm lines were evaluated for five fiber and four yield traits in four environments at Mississippi State, MS. An additive-dominance genetic model was employed for these traits. The minimum norm quadratic unbiased estimation (MINQUE) method was used with a mixed model approach for estimating genetic variance and covariance components and for predicting genetic correlations. This study investigated genetic variances, heritabilities, and genetic and phenotypic correlations between agronomic and fiber traits among these 64 F₂ hybrid populations and discussed the usefulness of these populations for use as hybrids or for selections for pure lines.Dominance variance accounted for the major proportion of the phenotypic variances for lint yield, lint percentage, and boll size indicating that hybrids should have an advantage for these traits compared to pure lines. A low proportion of additive variance for fiber traits and the significant additive x environment variance components indicated a lack of substantial useful additive genetic variability for fiber traits. This suggests that selections for pure lines within these F₂ populations would have limited success in improving fiber traits. Genetic and phenotypic correlation coefficients were of comparable magnitude for most pairs of characters. Fiber strength showed a positive additive genetic correlation with boll weight. Dominance genetic correlations of fiber strength with elongation and 2.5% span length were also significant and positive; however, the additive genetic correlation of length and strength was zero.Contribution of the USDA-ARS in cooperation with the Mississippi Agric. and Forestry Exp. Stn.     

Heterosis,combining ability and genetic effect,and relationship with genetic distance based on a diallel of hybrids from five diverse <Emphasis Type="Italic">Gossypium barbadense</Emphasis> cotton genotypes

The cultivated tetraploid Gossypium barbadense L. cotton produces superior natural fibers for the textile industry in the world. However, the possibility in utilization of heterosis to further increase its lint yield has not been extensively explored. In this study, two commercial US Pima cotton cultivars and three exotic G. barbadense lines, together with all of their possible hybrids in F₁ and F₂ progeny without reciprocals, were tested for lint yield, yield components, and fiber quality traits in four environments in 2005–2007. With a few exceptions, genotype (G), environment (E), and G × E were all significant or highly significant for all the traits studied. General combining ability (GCA) variances for all the traits in both F₁ and F₂ were also significant, while specific combining ability (SCA) variances were detected only for lint yield, fiber length, and micronaire in both generations and boll weight in F₁. GCA × E was also detected for lint percent, seed index, and fiber length in both F₁ and F₂, and boll weight in F₁, but none of the traits had significant SCA × E. As a group, F₁ and F₂ out-yielded the parent group by 20–40% and 6–10%, respectively. Mid-parent heterosis (MPH) for lint yield in F₁ was generally positive, ranging from ?4.7 to 116.4% with an average of 21.2–48.7%, while lint yield MPH in F₂ ranged from ?23.3 to 69.4% with an average of 6.4–12.4%. However, useful heterosis in lint yield was only detected in the hybrid between the two US commercial cultivars Pima S-7 and DP 340. MPH for other traits was low or not detected. MPH in F₂ was lower than that in F₁ but they were generally positively correlated. The genetic distances (GD) of the parents (based on 467 polymorphic RAPD and AFLP markers) between the five parents was not consistently correlated with MPH and SCA of their hybrids and dominant effects for lint yield and other traits. However, significant and positive correlations between GD of parents and the performance of their hybrids were detected for lint yield, lint percentage, and lint index in both F₁ and F₂ in most of the tests. GD of parents was also correlated with their GCA and additive effects in lint yield, lint percent, lint index, micronaire, plant height, and elongation. The results suggest that the close correlation between GD and hybrid performance per se was mainly due to the existence of GCA and additive effects from parents.     

陆地棉配合力与杂种优势、遗传距离的相关性分析

 用10个陆地棉亲本进行不完全双列杂交,共配置了45个组合,计算亲本的一般配合力（GCA）、特殊配合力(SCA)、杂种优势,并结合SSR标记研究了陆地棉亲本配合力与杂种优势、遗传距离之间的相关关系。配合力分析发现,10个亲本的一般配合力和特殊配合力存在显著或极显著差异。分析亲本配合力、杂种优势和遗传距离的相关性发现,子棉产量、皮棉产量、衣分的一般配合力和杂种优势呈显著或极显著相关,纤维长度、比强度、麦克隆值、株高、果枝数、单株铃数、铃重、子棉产量、皮棉产量、衣分的特殊配合力和杂种优势均呈极显著正相关,而与遗传距离相关均不显著。单株铃数、铃重、子棉产量、皮棉产量、衣分的杂种优势与遗传距离均为正向显著或极显著相关。在育种实践中这些显著或极显著相关的性状可能具有较高的改良潜力。     

持续高温干旱年份陆地棉农艺和产量性状的遗传效应分析

本文采用NCⅡ交配设计方法,以9个陆地棉品种(系)配置16个杂交组合,利用加性—显性与环境互作的遗传模型(ADE模型),分析亲本和F1在2013年持续高温干旱条件下望江、九江2个环境下的农艺和产量性状,估算了各项遗传方差分量,分析了性状间各项遗传效应的相关性和各性状的杂种优势。结果表明,农艺和产量性状易受环境条件影响,子棉产量、皮棉产量、单株铃数和铃重的遗传主要受显性效应控制,衣分同时受加性和显性效应控制,子指主要受加性效应控制。遗传相关分析表明,子棉产量和皮棉产量与铃重和衣分呈显性正相关;铃重与衣分呈显性正相关,衣分与子指的加性和显性均为负相关。杂种优势分析表明,中棉所63的铃重、衣分、子指、子棉产量和皮棉产量的群体平均优势达极显著水平,其皮棉产量的杂种优势可以利用至F3。     

光子陆地棉种质资源主要性状的遗传评价

以102份光子陆地棉材料为母本,分别与遗传标准系TM-1杂交,获得102个F₁群体。采用随机区组设计,设置3个重复,对光子陆地棉材料主要性状进行遗传评价。结果表明,调查的11个性状表型差异均较大,材料间产量性状(株高、果枝数、铃数、铃重、衣分和子指)差异大于纤维品质性状(纤维长度、纤维强度、马克隆值、整齐度和伸长率),特别是衣分、铃数等性状差异更明显; 除果枝数、马克隆值、伸长率以外,光子亲本群体其他性状的平均值都小于F₁群体。而亲本群体所有性状的变异系数均大于F₁,不同光子材料的杂种优势有很大差别,中亲优势和超亲优势也有很大的差别,有些种质某些性状的中亲、超亲优势为负值,其后代性状表现劣势; 纤维品质性状的中亲、超亲优势与毛子程度均呈负相关,而产量性状的中亲、超亲优势与毛子程度均呈正相关,说明可利用光子材料杂种优势改良纤维品质,而其后代产量性状的杂种优势利用受到限制; SSR分子标记遗传相似系数与各个性状的中亲、超亲优势的相关都不显著,说明在光子材料的育种中,杂种优势是不能通过亲本之间的遗传背景相似程度来预测的。     

Identification of QTLs for salt tolerance at germination and seedling stage of Sorghum bicolor L. Moench

Upland cotton (Gossypium hirsutum L.) hybrids display commercially useful levels of heterosis for lint yield. Cotton lint yield is primarily a multiplicative product of boll number and lint per boll, both of which can be further dissected into sub-components. Relationships among the yield components are complex where they further interact with the environment. To identify different yield components of hybrid cotton lint yield and their relationship with environment, three cotton varieties, DP51, STV474 and LA887 and, their respective hybrids were evaluated for lint yield components across five environments. Heterosis was observed for lint yield as well as yield components. The relationship between heterosis and mean environmental yield was negative for two hybrid combinations, whereas one hybrid showed increased heterosis from low to high yielding environments. Boll number was the major yield component contributing to lint yield. However, yield components contributing to the change in heterosis from low to high yielding environments were different for the three hybrids. The change in lint yield heterosis across environments was correlated with lint per boll and lint per seed for DP51 × STV474 and LA887 × DP51. Whereas, bolls number and boll retention were the main yield components contributing to higher lint yield heterosis of STV474 × LA887 in low yielding environments. Results also reveal effects of parental entries on lint yield as well as relationship of heterosis and environment.     

Combining ability estimates for yield and fibre quality traits in 4 × 13 line × tester crosses of Gossypium hirsutum

The aim of this study was to estimate the general combining ability of the parents and specific combining ability of hybrids considered for the development of high yielding and better quality cultivars. Seventeen genotypes and 52 F₁ hybrids obtained by crossing 4 lines and 13 testers in line × tester mating system during 2003 were sown in randomized complete block design in 2004. Line × Tester analysis revealed significant GCA and SCA effects for all the traits except fibre elongation. Preponderance of non-additive gene action was obtained for seed cotton yield per␣plant and majority of its component traits including fibre traits. Among the parents: PIL-8 for days to 50% flowering, CCH-526612 for boll weight, CITH-77 for number of open bolls per plant and CNH-36 for seed cotton yield per plant were detected with higher general combining ability. Parent, CCH-526612 for 2.5% span length, fibre strength and fibre elongation and AKH-9618 for micronaire value, fibre strength and fibre elongation were good combiners for fibre quality traits. The F₁s achieved high seed cotton yield by producing more number of open bolls. The high yielding hybrids with acceptable fibre quality traits were: CISV-24 × LH-1995, H-1242 × PIL-8 and RS-2283 × SGNR-2 deducted with significant SCA effects for seed cotton yield and fibre characteristics; 2.5% span length and fibre strength. These cross combinations involved at least one parent with high or average GCA effect for a particular trait.     

Genetic association of within‐boll yield components and boll morphological traits with fibre properties in upland cotton (Gossypium hirsutum L.)

Knowledge of genetic relationships between within‐boll yield components and fibre quality is essential for simultaneous improvement of lint yield and fibre quality in upland cotton (Gossypium hirsutum L.). Nine parents and their F₁ progeny with reciprocals from a 3 × 6 factorial mating design were grown in 2008 and 2009. Seven within‐boll yield components and two boll morphological traits and the three fibre quality parameters were analysed based on a conditional additive/dominance (AD) genetic model. Results showed that boll length contributed to the largest proportion of phenotypic, additive and dominance variances for UHM length; seed index contributed to the largest proportion of phenotypic and additive variances for fibre strength; boll width made the largest contribution to phenotypic and additive variances and the second largest contribution to dominance‐by‐environment interaction variance for micronaire, indicating that they played an important role than the other traits for fibre length, strength and fineness/maturity, respectively. It is worthy of note that those correlations between boll shape and fibre quality apply only to the nine parents and the resultant hybrids in this study and do not imply a cause and effect relationship.     

陆地棉核不育系杂交组合F1经济性状杂种优势及遗传分析

为探究利用陆地棉核不育系配制杂交种在经济性状方面的优势及遗传特点,采用3个陆地棉核不育亲本与4个陆地棉可育亲本不完全双列杂交设计,对12个F1杂交组合及对照经济性状进行表型方差分析,利用加性-显性（AD）模型,对其亲本及12个F1组合进行配合力分析,同时对经济性状进行遗传方差及相关性分析。结果表明,经济性状方面,F1组合竞争优势不明显。不育系2、可育亲本48784特殊配合力和一般配合力均较高,可选作优良杂交亲本;经济性状的加性方差占表型方差比值较大,单铃重、衣分的狭义遗传率在70%以上,早代选择有效;籽棉产量、皮棉产量、霜前皮棉产量的狭义遗传率在25%以上、显性方差占表现总方差的比值达到极显著水平,这3个性状宜在偏晚世代选择,并且有较好的杂种优势利用潜力;除衣分与籽棉产量加性遗传相关不显著、单铃重与衣分加性遗传负向极显著相关外,其他成对性状加性遗传相关均达到了正向显著水平以上;籽棉产量、皮棉产量、霜前皮棉产量之间及单铃重与衣分的显性相关都达到了极显著水平。不育系在棉花杂种优势利用方面具有较大的利用前景。     

Dissection of genetic effects of quantitative trait loci (QTL) in transgenic cotton

When alien DNA inserts into the cotton genome in a multicopy manner, several quantitative trait loci (QTLs) in the cotton genome are disrupted; these are called dQTL in this study. A transgenic mutant line is near-isogenic to its recipient, which is divergent for the dQTL from the remaining QTLs. Therefore, a set of data from a transgenic QTL line mutated by Agrobacterium-mediated transformation (30074), its recipient and their F1 hybrids, and three elite lines were analyzed under a modified additive-dominance model with genotype × environment interactions in three different environments to separate the genetic effects due to dQTL from whole-genome effects. Our result showed that dQTL had significant additive effects on lint percentage, boll weight, and boll number per square meter, while it had little genetic association with fiber traits, seed cotton yield, and lint yield. The dQTL in 30074 significantly increased lint percentage and boll number, while significantly decreasing boll weight, having little effect on fibre traits, while those from the recipient and three elite lines showed significant genetic effects on lint percentage. In addition, the remaining QTL other than dQTL had significant additive effects on seed cotton yield, fruiting branch number, uniformity index, micronaire, and short fibre index, and significant dominance effects on seed cotton yield, lint yield, and boll number per square meter. The additive and dominance effects under homozygous and heterozygous conditions for each line are also predicted in this study.     

棉花不同铃重类型种质主要纤维性状遗传及其变异

以中棉所48的母本S9708与不同铃重大小的父本杂交,配置6个F2群体,采用SAS 8.0软件对各组合亲本、F1和F2的铃重和衣分及纤维品质等数量性状进行统计分析。结果表明:在所有F2群体中纤维性状都有极显著差异。铃重和麦克隆值的变异系数较大,其次是衣分和纤维强度,而纤维长度、伸长率和整齐度变异系数较小。在杂交早代群体中,仍然表现亲本的铃大、衣分高、纤维长、强度高、整齐度好等优良特性。这表明,在杂种优势利用选择亲本时,选择大铃、高衣分、优质纤维材料仍较为重要。     

陆地棉芽黄品系在棉花杂种优势上的利用研究

我室以陆地棉芽黄突变品系作为指示性状，对品种间Ｆ＿１杂种优势利用效应的研究已连续进行了三轮四次试验，都表明芽黄品系与常规品种间的杂种Ｆ＿１具有明显的杂种优势。Ｆ＿１的产量结构和常规品种的相类似，铃数、铃重和衣分等三个主要产量构成因素中，铃数对产量的直接贡献最大，其次是衣分和铃重。７月１５日～８月１０日间的棉铃脱落率对产量和产量构成因素有一定影响。配合力效应分析表明，特殊配合力高的杂交组合有较高的杂种优势，而特殊配合力效应伍与一般配合力有密切相关关系，即双亲一般配合力高的，杂种Ｆ１优势也高。试验结果证明，陆地棉芽黄品系在杂种优势利用中有一定增产作用，并有其标记基因效应。     

Commonality analysis and selection of parents for within-boll yield components in upland cotton

Relationships between lint yield and within-boll yield components are important for genetic improvement of lint yield in cotton (Gossypium hirsutum L.) cultivars. F₂ plants derived from crosses between germplasm lines and high yielding cultivars were analyzed to determine the contributions of within-boll yield components to lint yield and to select parents with desirable combining ability for multiple within-boll yield components. Forty-five F₂ hybrids were planted at two field sites in 2010 and 2011 with 4 and 3 replicates, respectively. There were a total of six yield components analyzed including lint percentage (LP), seed number per boll, lint weight per seed (LW_S), seed surface area per seed, lint weight per unit seed surface area (LW_SA), and lint number per unit seed surface area (LN_SA). The contributions of these yield components to lint yield were analyzed by commonality analysis that separated the contributions to lint yield into the unique contributions of single yield components and the common contributions of the single yield components with one or more other yield components. The unique contributions of the six yield components to lint yield ranged from 1.6 to 21 % of total variation for lint yield in the 2-year experiments. The greatest common contributions to lint yield among all combinations of the six yield components were identified for a combination of four components, LP, LW_S, LW_SA, and LN_SA with 67 and 44 % of the total variation of lint yield in 2010 and 2011, respectively. Results suggest that all four of these yield components should be considered simultaneously in breeding for genetic improvement of lint yield. The germplasm line SP225 was detected as a good combiner with positive general combining ability (GCA) for LP (1.4 %), LW_SA (0.03 mg mm^?2), and LN_SA (14.3 no mm^?2), and favorable GCA for fineness (?3.1 mg km^?1).     

陆地棉品种与陆地棉族系种质系间杂种优势及其组成分析

采用ＮＣⅡ遗传交配设计,选用３个陆地棉常规品种和５个陆地棉族系种质系材料杂交,杂种Ｆ１代产量和纤维品质优势表现明显。通径分析结果表明,提高铃重,单株铃数的中亲优势,适当降低单铃种子数和株高的优势。在其它性状适宜的情况下,可以显著地提高皮棉产量的中亲优势。各个优势组合在产量优势来源上有差异。种质系材料在杂种优势利用上具有很大潜力。     

Genetic effects and heterosis of within-boll yield components in upland cotton (Gossypium hirsutum L.)

Within-boll yield components are the most basic contributors to lint and seed yield of cotton (Gossypium hirsutum L.), which is a major source of natural fiber and edible oil throughout the world. Little information is available on genetic effects and heterosis of these traits in cotton. Three cotton cultivars and six breeding lines differing in within-boll yield components were used for this study. Parents and their F₁ progeny with reciprocals from a 3×6 factorial mating design were grown at Jiangxi Agricultural University experimental farm in 2008 and 2009. Seven within-boll yield components and two boll bur characters were analyzed under an additive-dominance genetic model with genotype and environment interaction. Additive effects were significant for all traits and dominance effects were significant for all traits except seed mass per seed. Genetic variances for lint mass per seed, SM/S and boll bur weight were primarily additive variances ranging from 39.6 to 58.9 %. Lint mass per boll and seed number per boll variances were primarily due to dominance genetic effects ranging from 36.4 to 48.8 %. Dominance and additive effects were equally important for boll weight, seed mass per boll and boll bur percentage. Additive and additive × environment effects were more important than other effects for lint percentage. A802-1 had the best mean performance and additive effects increasing BW, SM/B, S/B and SM/S, but reduced LP and LM/S. A9-1 and Lu40534 had additive effects associated with increasing LP. The two crosses A9-1×Lu40534 and Tezsh×33B were detected with favorable heterozygous dominant effects and heterosis over best parent for BW, LP, LM/B, SM/B and S/B. Favorable genotypic and phenotypic correlations were identified between within-boll lint yield components (LM/B, LM/S) and within-boll seed yield components (SM/B, S/B, SM/S). These results indicate that simultaneous genetic improvement of multiple within-boll yield components can be expected in breeding populations derived from these cotton cultivars and breeding lines.     

Comparative seed yield performance of high-by-high and low-by-high crosses in flax *

Successful identification of a desirable segregant depends partly on the parents chosen to make the crosses. This experiment was conducted to compare performance and genetic variability for seed yield, yield components, agronomic traits and harvest index of lines derived from low- and high-yielding flax (Linum usitatissimum L.) crosses, and to identify important yield components for flax seed yield improvement. The lines chosen as high yielding parents for this experiment were‘Linott’and 'Summit; and the low yielding parents were‘Grant’and Ci2395. The high-yielding lines produced significantly more seeds per boll and had a higher harvest index than the low-yielding lines. Evaluation of 161 F_2:6 lines from four crosses among these lines showed that the greatest genetic variability, highest cross average, and highest F₆ line seed yield occurred in the low x high cross,‘Grant’x‘Linott’. All low X high crosses exhibited higher genetic variances for seed yield than the high x high crosses. The high x high cross 'Summit’x‘Linott’had low genetic variance for seed yield. Number of bolls per area was determined by linear regression, path coefficient analysis, and stepwise multiple regression analysis to be the most important component of seed yield. This study showed that hybridization of low and high-yielding flax lines may be useful to increase genetic variability and obtain high-yielding flax lines.