Using molecular markers and field performance data to characterize the Pee Dee cotton germplasm resources

Knowledge of genetic relationships in crop breeding programs provides valuable information that can be used by plant breeders as a parental line selection tool. In Upland cotton (Gossypium hirsutum L.), the Pee Dee germplasm program represents one of the most historically significant Upland cotton breeding programs and is known as a key source of fiber quality genes for commercial cultivars. The foundation of the Pee Dee germplasm is known to represent an array of genetic diversity involving the hybridization of G. hirsutum L., G. barbadense L., and triple hybrid strains (G. arboreum L. × G. thurberi Todaro × G. hirsutum L.). In this study, we characterized genetic relationships within the Pee Dee germplasm collection using molecular marker and field performance data. Molecular marker and field performance data showed the Pee Dee germplasm collection still maintains useful amounts of genetic diversity. The methods described provide plant breeders of cotton and other crops a strategy to develop a parental line selection tool based on genotypic and phenotypic information. Cotton breeders can directly use the information provided to select specific Pee Dee germplasm parental line combinations based on genotypic (molecular marker) and phenotypic (field performance) information rather than relying on pedigree and phenotypic information alone.     

Genetic diversity for agronomic and fiber traits in day-neutral accessions derived from primitive cotton germplasm

Upland cotton (Gossypium hirsutumL) is an important crop that is cultivated in warm climates through-out the world. Agronomic performance and fiber quality must continually be improved if cotton is to maintain economic viability. Primitive ancestors of cotton contain diversity for trait improvement; however, many of these accessions have a short-day flowering response (photoperiodic) and are not readily useable in breeding programs. In this study, 114 day-neutral derived primitive germplasm lines were evaluated in field trials for two years. Agronomic and fiber trait data were collected and analyzed. Variance components, genotypic values, and genotypic correlations were calculated. Genotypic effects for all traits studied made significant contributions to the phenotypic variation indicating genetic diversity among these lines. The predicted genotypic values showed a wide range of variation for agronomic and fiber traits. Weak genotypic correlations were found between yield and 2.5% span length and fiber strength, two important fiber traits. Although these day-neutral derived accessions had lower lint percentage, they had improved fiber length, strength, micronaire, and comparable yields with two commercial cultivars. Thus, these day-neutral derived accessions are sources of genetic variation that when used in breeding programs offer the potential to improve important traits and expand genetic diversity.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.     

Genetic Diversity and Association Analysis of Fiber Quality Traits with SSR Markers in Germplasm Resources of Early Maturity Upland Cotton in Xinjiang

[Objective] We explored the genetic diversity of early maturity upland cotton germplasm resources in Xinjiang, China. We discovered specific germplasm resources and elite allelic variation related to fiber quality. [Method] We used 219 early maturity upland cotton accessions in our experiments and investigated 15 agronomic traits in three environments. We used a total of 128 pairs of simple sequence repeat (SSR) primers to scan for polymorphism. We then used NTsys-pc2.1 software to analyze genetic diversity, and Structure2.3.1 and Tassle5.0 software to perform association analysis of fiber quality traits based on phenotypic effect values to identify elite allele variation and conventional materials. [Result] A total of 244 loci were amplified by 128 marker pairs in 219 samples with an average of 1.91 loci per marker. The polymorphic information content ranged from 0.13 to 0.86 with an average of 0.63. The distribution range of the genetic similarity coefficient between materials in this population was 0.42-0.99 with an average of 0.61. The genetic similarity coefficient was between 0.5 and 0.7 and accounted for 90.19%. Through association analysis, we detected 11 markers that were significantly (P<0.01) associated with fiber quality traits, and discovered seven typical materials with specific allele. [Conclusion] In total, 219 Xinjiang early-maturing upland cotton germplasm resources have low genetic diversity. Based on SSR association analysis, we discovered some specific allele variations and conventional materials related to fiber quality traits.     

Performance and combining ability in cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) populations with diverse parents

Improving fiber quality properties of cotton is important for increasing the efficiency of manufacturing textiles, including enhancing yarn quality and spinning performance. This study was conducted to determine if we could identify valuable cotton cultivars to use as parents in breeding programs with the goal of improving fiber properties. Seven parents were combined in a diallel design and selfed to obtain 21 F₂ populations. Positive general and specific combining ability effects were observed for all traits. General combining ability tended to be larger than specific combining ability, indicating these traits are controlled primarily by additive genetic effects. Correlations among traits were generally positive except for lint yield correlations with fiber strength and length. For improving the fiber quality measures of strength and length, line 7235 shows excellent general combining ability effects. SG125 would provide elite germplasm to increase agronomic measures of lint yield and lint percent. The MD51 genotype has the highest potential among the genotypes tested here to provide germplasm combining both improved yield and fiber strength. These parents, or their selected progeny, should be useful in a breeding program to generate variability from which selection can be used to identify lines with improved fiber and/or agronomic properties.     

AFLP marker associations with agronomic and fiber traits in cotton

DNA markers linked with major QTL contributing to traits of importance will be a useful tool for cotton (Gossypium spp.) genetics and breeding. We crossed four photoperiod-sensitive accessions of cotton, G. hirsutum L., with a cultivar, selected day-neutral plants and backcrossed four times to each of the four photoperiod-sensitive accessions, selecting day-neutral plants at each generation. The day-neutral plants from the first cross and the four backcross generations were advanced to the F₆. These 20 day-neutral lines and four cultivars were grown in two environments at Mississippi State, MS and scored for seven agronomic and fiber quality traits. They were also scored for AFLP markers using a bulk sample of leaves from each of 24 lines. More than 50 AFLP markers were associated with the seven traits with fewer markers associated with fiber than agronomic traits. However, one to four markers were associated with 22–93% of the phenotypic variability of each of the seven traits. The results suggest that selected markers could be used in marker assisted selection (MAS) in crosses designed to use alleles from exotic accessions or cultivars to develop elite breeding lines for cotton improvement.     

EPSPS外源基因对陆地棉农艺性状和纤维品质的影响

以G6-1至G6-19等19个转基因抗草甘膦除草剂棉花种质为材料,以其非转基因背景亲本中棉所49为对照,研究EPSPS外源基因导入对陆地棉农艺性状和纤维品质的影响,结果表明外源基因的导入对棉花纤维上半部平均长度、马克隆值、断裂伸长率和断裂比强度等品质性状有显著影响;对于棉花衣分和铃重等农艺性状亦有显著的影响,衣分变异范围为30.5%~42.7%,T1和T2相关性分析表明衣分的变异为可遗传性变异,铃重最高为6.5 g,最低为4.6 g,两者相差40%。因此,转基因棉花育种研究不仅要注重目标性状的转育,还要注重非目标性状的筛选。     

Genetic effects and genetic values of fiber properties in F2 and F3 hybrids between germplasm lines and high yield cultivars

Utilization of cotton (Gossypium hirsutum L.) germplasm for genetic improvement of fiber properties requires determination of genetic effects in the germplasm lines. A study was designed to analyze genetic populations derived from multiple crosses between nine germplasm lines as male parents and five cultivars and elite breeding lines as female parents to determine genetic values of fiber properties. Parents and F₂ populations were planted at 2 field sites in 2010 and 2011 with 4 and 3 replicates, respectively, and parents and F₃ populations were planted at 2 field sites in 2011 with 3 replicates. Lint yield and seven fiber properties were analyzed by an additive and dominant model with genotype by environment interaction effects. Significant additive and dominant effects were identified for both lint yield and fiber properties. Germplasm lines JC60, JC65, JC186, and SP205 were good general combiners for micronaire, elongation, strength, 50 % span length, short fiber content, and fineness. Six to fifteen crosses were detected with favorable heterozygous dominant effects for lint yield and diverse fiber traits, which suggest useful heterosis of these hybrids. Favorable additive correlations were identified between fiber properties such as micronaire versus 50 % span length (?0.57), micronaire versus fineness (0.82), strength versus 50 % span length (0.54), strength versus short fiber content (?0.69), and 50 % span length versus short fiber content (?0.78) while unfavorable additive correlations were not identified among fiber properties. These results indicated potential of simultaneous genetic improvement for these multiple properties in breeding populations derived from these germplasm lines.     

陆地棉高品质纤维种质基因库的拓建

采用远缘杂交,开展了棉属野生种的高强纤维潜力基因向陆地棉品种转育研究,以构建高纤维品质的种质基因库.在适宜的自然条件和人工条件下,陆地棉分别与异常棉(Gossypium anomalum)、辣根棉(G.armourianum)、雷蒙德氏棉(G.raimondii)等杂交,克服杂交不可交配性、杂种一代的高度不育性等,通过多年的回交选择和纤维品质测定筛选,     

利用黄褐棉染色体片段导入系定位产量和纤维品质性状QTL

陆地棉的遗传基础狭窄,阻碍了棉花的遗传改良进程。为有效拓宽陆地棉的遗传基础,本试验利用野生种黄褐棉(AD4)为供体亲本,以综合性状优良的B0011品系为受体亲本(国审棉华杂棉H318的亲本之一),构建了含71个株系的导入系BC5S5群体。基于SLAF-seq的基因分型和多年多点田间试验的综合分析表明,该导入系在产量和纤维性状方面具有很大的变异,共检测到48个QTL,其中包含19个产量和29个纤维构成因素相关的QTL。在At亚组检测到9个性状的32个QTL,在Dt亚组为16个。进一步对QTL加性效应方向分析显示,其中有30个QTL的加性效应为正,18个QTL的加性效应为负。本研究结果为利用黄褐棉重要农艺性状有利等位基因改良陆地棉产量和品质奠定了基础。     

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.     

Adaptation of tropical maize germplasm to temperate environments

Maize (Zea mays L.) is one of few crops that can offer significant genetic gains with the utilization of genetic diversity. Genetically broad-based germplasm has the potential to contribute useful and unique alleles to U.S. Corn Belt breeding programs not present in current U.S. genome sequences (e.g. B73, NAM, etc.). Our objectives were to determine if unique tropical genetic materials have been effectively adapted to temperate environments and how their agronomic performance was relative to adapted populations. An important long-term objective of the Iowa and North Dakota maize breeding programs has been, in addition to the typical elite by elite line pedigree selection cultivar development process, to adapt exotic and unique germplasm, maximize their genetic improvement, and develop unique products for breeding and commercial uses. Stratified mass selection methodology for earliness has been utilized for the adaptation of tropical and temperate populations to Iowa and North Dakota environments. This method has allowed screening of up to 25,000 genotypes per population cycle at a rate of one cycle per year. In addition, the estimated cost per year our programs had for the adaptation of each population was less than $2,000 which could successfully be applied in any breeding program across the globe. This cost has been less than 1 % of the total cost for finding minor genes on the same trait. Our results showed the successful adaptation of exotic populations was independent from genetic background. We can speculate there are a few major genes responsible for most of flowering date expression. We encourage the use of technology to target traits according to their genetic complexity. Stratified mass selection at the phenotypic level has been successful. Each of the populations with either 25 of 100 % tropical germplasm are available for anyone who may desire to expand the germplasm base of their breeding programs with tropical germplasm adapted to temperate mid- and short-season U.S. Corn Belt environments.     

具有野生棉外源基因的陆地棉特异种质创造与利用进展

总结了优质纤维、自然抗虫、抗病、高衣分等具有野生棉外源基因的陆地棉种质的创造,及其在棉花常规育种、杂种优势利用、分子生物学等方面的研究进展,并分析了该类种质资源的利用前景,以期促进该类种质在棉花育种改良中发挥更大的作用。     

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 association of cotton yield with its component traits in derived primitive accessions crossed by elite upland cultivars using the conditional ADAA genetic model

Boll number, lint percentage, and boll weight are three component traits for lint yield of upland cotton, Gossypium hirsutum L. Selecting high yielding lines or hybrids depends on the ability to dissect the genetic relationship of lint yield with these component traits. In this study, 14 day-neutral lines with desirable fiber quality derived from primitive accessions were top crossed with five commercial cultivars. The F₂ populations and parents were grown in one location in 1998 and two locations in 1999 at Mississippi State, MS. The F₃ populations and parents were grown in two locations in 2000. Lint yield and three component traits were measured and analyzed by the ADAA genetic model with the mixed model based conditional approach. Results showed that boll number or boll number with lint percentage or boll weight contributed to the majority of the phenotypic variance and variance components for lint yield. Boll number was more important than the other two component traits in terms of various genetic effects. The results also showed that the combination of boll number and boll weight greatly increased the contribution to lint yield even though boll weight itself had no significant contribution to lint yield compared to boll number alone. The genetic contribution effects were also predicted due to single component traits or their combinations for parents and crosses. The results revealed that the balanced selection of boll weight and boll number should be considered to obtain high yielding hybrids or pure lines. 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.     

机采棉杂交后代主要株型性状与产量和品质的关系

【目的】从株型、产量及品质众多复杂因素中找出影响机械化生产较大的因素并进行遗传改良,选育适宜机械化生产的高产优质品种,提高棉花育种的效率。【方法】以陆地棉Z571与中棉所49杂交的F2:3群体为研究对象,应用统计软件SAS V8等分析其农艺性状的变异、方差和相关性。【结果】F2:3群体株系材料间农艺性状发生了显著分离,且后代中出现了许多超亲个体,在田间进行选择时要注意农艺性状之间复杂的关系;株高、单株果枝数与单位面积籽棉产量呈极显著正相关;单株果枝数与纤维上半部平均长度、断裂比强度呈极显著负相关,与马克隆值呈现正相关;单株营养枝数与纤维上半部平均长度、断裂比强度呈极显著正相关,与马克隆值呈现显著负相关;产量构成因素中的单位面积铃数与纤维上半部平均长度、断裂比强度呈极显著正相关,与马克隆值呈极显著负相关,铃重和品质性状的相关性与单位面积铃数相反。【结论】株型性状与产量和品质之间均存在显著或极显著的遗传相关;高产高品质的株型特征为单株营养枝数较多;选育高产优质的棉花新品种时要选择铃数较多、铃重较小的材料。     

Genetic Dissection of Allelic Loci Associated with Economic Traits of Upland Cottons in Xinjiang

[Objective] We completed anassociation analysis of economic traits for upland cotton using simple sequence repeat (SSR) markers. We then explored the allelic variation sites to analyze the genetic basis of economically important traits, studied the genetic mechanism of Xinjiang upland cotton, and aimed to accelerate efficient breeding of upland cotton. [Method] We carried out polymorphic scanning on 156 upland cotton varieties in Xinjiang by screening 73 pairs of SSR markers encompassing the whole cotton genome. We constructed boxplot maps using R statistical computing software and graphics language and used TASSEL software to correlate yield or fiber quality traits with significant allelic variation loci. [Results] We obtained 10 allelic variation loci related to yield traits using the correlation analysis of Xinjiang upland cotton varieties from six different environments. The interpretation rate of phenotypic variation ranged from 6.69% to 9.88% with an average of 8.43%. Twenty-three allelic variation loci associated with fiber quality traits and phenotypic variation interpretation rates ranged from 3.73% to 13.22% with an average of 7.52%. The 22 detected quantitative trait loci were reported in previous studies and 10 showed the same associated traits as previously reported. [Conclusion] The population genetic structure of Xinjiang upland cotton varieties is simple, the linkage disequilibrium level is low, and the phenotypic traits show a stable trend under six environments. Using association analysis, we discovered unique allelic variation genes related to yield and fiber quality and diverse allele loci.     

陆地棉主要农艺与纤维品质性状的双列杂交分 析简

 本文利用加性-显性与环境互作的遗传模型（ADE模型）,分析8个陆地棉亲本及其F1在不同环境下的农艺和纤维品质性状,在估算遗传方差分量、遗传效应的基础上,分析各类性状间的遗传相关性,并预测F1和F2的杂种优势,为棉花杂种优势利用和新品种选育提供了较有价值的信息。研究表明,农艺与纤维品质性状的遗传主要受加性、显性和加性与环境互作效应控制。遗传相关分析表明,皮棉产量与纤维品质性状的显性相关系数值较大,利用杂种优势在早期世代可以得到协同改良,纤维品质性状间易实现协同改良。杂种优势分析表明,F₁和F₂的皮棉产量均具有显著的超亲优势,纤维品质性状的杂种优势不明显。     

Exotic barley germplasm: variation and effects on agronomic traits in complex crosses

Summary Utilization of exotic germplasm offers an approach to broaden genetic variability in breeding populations. This study was conducted in order to 1) compare germplasm of exotic origin with adapted Swedish barleys with respect to genetic differences and 2) to evaluate how exotic material affected agronomic performance in complex crosses. Allozyme studies showed the following Nei's gene diversities among parents: 0.13 (adapted parents), 0.16 (landraces) and 0.25 (H. spontaneum). Cluster analysis indicated that parental groups were genetically divergent. Earliness, straw length, number of ears per plant and thousand kernel weight (TKW) were studied. Variation in agronomic traits showed the following pattern: landraces > H. spontaneum > adapted lines. The best sources for earliness were adapted parents and landraces. Mean straw length was greatest in H. spontaneum lines. Number of ears per plant was quite similar in all groups. The highest TKW was among landraces and adapted parents. Hybrids from the complex crossing programme exceeded parents in earliness and TKW. An index composed from the four traits showed the most favorable frequency distributions for adapted parents and hybrids. Both genetic and agronomic studies indicate that new valuable variation from exotic germplasm may be introduced into barley breeding material.     

Testcross performance and diversity analysis of white maize lines derived from backcrosses containing exotic germplasm

Introgression from exotic maize (Zea mays L.) into adapted breeding pools can broaden and diversify the genetic base of adapted germplasm. The first objective of this study was to determine the agronomic performance of white maize lines derived from adapted × exotic backcrosses in tropical environments. Six exotic white maize inbred lines were crossed to an adapted white line (1368) and the F₁s were backcrossed to 1368. Forty-one BC₁F₄ lines derived from these backcrosses and the recurrent parent were crossed with a common inbred tester (9071) and the progeny were evaluated at eight environments in Nigeria. The testcrosses × environment interaction mean square was not significant for all agronomic traits. The BC-derived lines containing exotic germplasm contributed significantly to the variation in testcross mean grain yields and other agronomic traits. Among the 41 testcrosses, only 5 yielded significantly less than 1368 × 9071, with the 7 best testcrosses producing between 304 and 867 kg ha⁻¹ more grain than 1368 × 9071. The second objective of this study was to assess the genetic divergence of the BC-derived white lines from their adapted recurrent parent. Thirty-nine BC-derived white lines along with 1368 and 9071 were genotyped with ten AFLP primer pairs that generated 506 polymorphic fragments. The average allelic diversity of the lines was 31 ± 0.07. The genetic distance (GD) estimates of each BC-derived line from 1368 varied from 0.76 to 0.84, with a mean of 0.80 ± 0.003. The average GD for all pairs of the BC-derived lines was 0.63 ± 0.005, varying from 0.31 to 0.89. The observed significant amount of variation among the BC-derived white lines suggests that they can contribute new alleles for expanding the genetic base of tropical maize and for developing high-yielding hybrids.     

Creation of a New Resistant Germplasm to Verticillium Wilt by Distant Hybridization in Upland Cotton

To create new germplasm lines resistant to Verticillium wilt in upland cotton, 65 distant hybridization germplasm lines (DHGLs) in upland cotton genetic background were cultivated by interspecific hybridization between Gossypium hirsutum and wild species including G. anomalum, G. armourianum, G. aridum, G. raimondii, G. mustelinum, interspecific F₁ backcrossing with G. hirsutum for four generations, and selfing for four generations, followed by a conventional breeding program. The results of agronomic trait identification during 2011-2012 indicated that average plant heights of DHGLs were closely similar to commercial cultivars of upland cotton, while average fruit branches, fruit nodes, bolls of DHGLs individual plant were lower than those in commercial cultivars of upland cotton. Average single boll weight and lint percentage of DHGLs were lower than commercial cultivars of upland cotton. Fiber length, strength, fineness and maturity of DHGLs were reasonably collocated. Fiber of most lines was suitable for spinning extra high count yarn, but the main fiber quality indices of commercial cultivars of upland cotton were not well coordinated. Identification of resistance to Verticillium wilt in defoliation disease nursery during 2012-2013 indicated that five DHGLs resistant to Verticillium wilt . Suyuan 040, Suyuan 045 and Suyuan 061 were highly resistant to Verticillium wilt with a disease index of 8.33, 4.35 and 7.79, respectively. Suyuan 030 and Suyuan 034 were resistant to Verticillium wilt with a disease index of 12.35 and 13.70, respectively. The genetic relationship of new germplasm lines resistant to Verticillium wilt were traced and showed that Suyuan 040 and Suyuan 045 were DHGLs of G. raimondii, Suyuan 061 was DHGL of G.mustelinum, Suyuan 030 and Suyuan 034 were DHGLs of G. aridum.