QTL mapping in A-genome diploid Asiatic cotton and their congruence analysis with AD-genome tetraploid cotton in genus Gossypium

Asiatic cotton(Gossypium arboreum L.) is an Old World cultivated cotton species.The sinense race was planted extensively in China.Due to the advances in spinning technology during the last century,the species was replaced by the New World allotetraploid cotton G.hirsutum L.Gossypium arboreum is still grown in India and Pakistan and also used as an elite in current cotton breeding programs.In addition,G.arboreum serves as a model for genomic research in Gossypium.In the present study,we generated an A-genome diploid cotton intraspecific genetic map including 264 SSR loci with three morphological markers mapped to 1 3 linkage groups.The map spans 2,508.71 cM with an average distance of 9.4 cM between adjacent loci.A population containing 1 76 F2:3 families was used to perform quantitative trait loci(QTL)mapping for 17 phenotypes using Multiple QTL Model(MQM)of MapQTL ver 5.0.Overall,108 QTLs were detected on 13 chromosomes.Thirty-one QTLs for yield and its components were detected in the F2 population.Forty-one QTLs for yield and its components were detected in the F2:3 families with a total of 43 QTLs for fiber qualities.Two QTLs for seed cotton weight/plant and lint index and three QTLs for seed index were consistently detected both in F2 and F2:3.Most QTLs for fiber qualities and yields were located at the same interval or neighboring intervals.These results indicated that the negative correlation between fiber qualities and yield traits may result from either pleiotropic effect of one gene or linkage effects of multiple closely linked genes.     

Introgression of cotton leaf curl virus-resistant genes from Asiatic cotton (Gossypium arboreum) into upland cotton (G. hirsutum)

Cotton is under the constant threat of leaf curl virus, which is a major constraint for successful production of cotton in the Pakistan. A total of 3338 cotton genotypes belonging to different research stations were screened, but none were found to be resistant against the Burewala strain of cotton leaf curl virus (CLCuV). We explored the possibility of transferring virus-resistant genes from Gossypium arboreum (2n = 26) into G. hirsutum (2n = 52) through conventional breeding techniques. Hybridization was done manually between an artificial autotetraploid of G. arboreum and an allotetraploid G. hirsutum, under field conditions. Boll shedding was controlled by application of exogenous hormones, 50 mg/L gibberellic acid and 100 mg/L naphthalene acetic acid. Percentage pollen viability in F(1) hybrids was 1.90% in 2(G. arboreum) x G. hirsutum and 2.38% in G. hirsutum x G. arboreum. Cytological studies of young buds taken from the F(1) hybrids confirmed that they all were sterile. Resistance against CLCuV in the F(1) hybrids was assessed through grafting, using the hybrid plant as the scion; the stock was a virus susceptible cotton plant, tested under field and greenhouse conditions. All F(1) cotton hybrids showed resistance against CLCuV, indicating that it is possible to transfer resistant genes from the autotetraploid of the diploid donor specie G. arboreum into allotetraploid G. hirsutum through conventional breeding, and durable resistance against CLCuV can then be deployed in the field.     

Nucleolar size at early stages of cotton fiber development in relation to final fiber dimension

Changes in nucleolar size and nucleolar vacuolation at early stages of fiber development and final fiber dimensions were determined for cotton of different species: Gossypium hirsutum L. cv. B49, Gossypium barbadense L. cv. Menoufi and Gossypium arboreum L. cv. Virnar. Size of the nucleolus in combination with its vacuolation at an early stage of development was found to be clearly associated with the final result of fiber development.     

Protein markers for identification of different species and varieties of cotton

Reference electrophoretic spectra that allow compiling electrophoretic formulas of certain cotton species and varieties were obtained on the basis of analysis of the electrophoretic spectrum of water-soluble and barely soluble proteins of seeds of diploid cotton species of genomic group A (Gossypium arboretum var. indicum, G. arboreum ssp. obtusifolum, G. herbaceum ssp. africanum, and G. herbaceum Harga), group C (G. australe, G. bickii, G. nelsone, and G. sturtianum), group D (G. davidsonii. G. harknessii. G. klotzschianum, G. raimondii, G. thurberi, and G. trilobum), and amphidiploid species of group AD (G. mustelinum, G. hirsutum ssp. palmeri, G. tricuspidatum Bagota, G. tricuspidatum Mari Galanta, G. barbadense L., and G. hirsutum L.).     

Genetic Diversity of Landraces in Gossypium arboreum L. Race sinense Assessed with Simple Sequence Repeat Markers

Asiatic cotton (Gossypium arboreum L.) is an "Old World" cultivated cotton species, the sinense race of which is planted extensively in China. This species is still used in the current tetraploid cotton breeding program as an elite germplasm line, and is also used as a model for genomic research in Gossypium. In the present study, 60 cotton microsatellite markers, averaging 4.6 markers for each A-genome chromosome,were chosen to assess the genetic diversity of 109 accessions. These included 106 G. arboreum landraces,collected from 18 provinces throughout four Asiatic cotton-growing regions in China. A total of 128 alleles were detected, with an average of 2.13 alleles per locus. The largest number of alleles, as well as the maximum number of polymorphic loci, was detected in the A03 linkage group. No polymorphic alleles were detected on chromosome 10. The polymorphism information content for the 22 polymorphic microsatellite loci varied from 0.52 to 0.98, with an average of 0.89. Genetic diversity analysis revealed that the landraces in the Southern region had more genetic variability than those from the other two regions, and no significant difference was detected between landraces in the Yangtze and the Yellow River Valley regions. These findings are consistent with the history of sinense introduction, with the Southern region being the presumed center of origin for Chinese Asiatic cotton, and with subsequent northeastward extension to the Yangtze and Yellow River Valleys. Cluster analysis, based on simple sequence repeat data for 60 microsatellite loci, clearly differentiated Vietnamese and G. herbaceum landraces from the sinense landrace. No relationship between inter-variety similarity and geographical ecological region was observed. The present findings indicate that the Southern region landraces may have been directly introduced into the provinces in the middle and lower Yangtze River Valley, where Asiatic cotton was most extensively grown, and further race sinense crops were subsequently produced.     

利用SSR标记技术研究棉属A、D染色体组的进化

利用SSR分子标记技术,对棉属A、D染色体二倍体及四倍体代表棉种进行了遗传多样性分析。供试的10个二倍体代表棉种间遗传多态性丰富,分子聚类结果与Fryxell棉属分类结果相同。分子水平上进一步揭示出属于D染色体组的拟似棉与其他D染色体组棉种的相似系数最低,A,D染色体组间相似系数很高,该结果支持拟全民族似棉是D染色体组最原始棉种,棉属不同染色体组是共同起源,单元进化的理论,利用栽培的异源四倍体棉种不太适于研究棉属A、D染色体组的进化。     

Analysis of xyloglucan endotransglycosylase/hydrolase (XTH) genes from allotetraploid (Gossypium hirsutum) cotton and its diploid progenitors expressed during fiber elongation

Multiple cellular pathways have been shown to be involved during fiber initiation and elongation stages in the cultivated allotetraploid cotton (Gossypium hirsutum). The cell wall enzymes xyloglucan endotransglycosylase/hydrolases (XTH) have been reported to be associated with the biosynthesis of the cell wall and the growth of cotton fibers, probably regulating the plasticity of the primary cell wall. Among various cotton fiber cDNAs found to be preferentially expressed in cotton fibers, a xyloglucan endotransglycosylase (XTH) cDNA was significantly up-regulated during the elongation stage of cotton fiber development. In the present study, we isolated and characterized genomic clones encoding cotton XTH from cultivated cotton (Gossypium hirsutum) and its diploid progenitors (Gossypium arboreum and Gossypium raimondii), designated GhXTH1-1, GhXTH1-2, GaXTH1 and GrXTH, respectively. In addition, we isolated and characterized, by in silico methods, the putative promoter of XTH1 from Gossypium hirsutum. Sequence analysis revealed more than 50% homology to XTH's at the protein level. DNA gel blot hybridization indicated that at least two copies of GhXTH1 are present in Gossypium hirsutum whereas the diploid progenitor species Gossypium arboreum and Gossypium raimondii has only a single copy. Quantitative real-time PCR and high-resolution melting experiments indicated that in Gossypium hirsutum cultivars, in cotton fibers during early stages of fiber elongation specifically expressing only the GhXTH1-1 gene and expression levels of GhXTH1-1 in fibers varies among cultivars differing in fiber percentage and fiber length.     

Completely distinguishing individual A-genome chromosomes and their karyotyping analysis by multiple bacterial artificial chromosome - fluorescence in situ hybridization

Twenty bacterial artificial chromosome (BAC) clones that could produce bright signals and no or very low fluorescence in situ hybridization (FISH) background were identified from Gossypium arboreum cv. JLZM, and G. hirsutum accession (acc.) TM-1 and 0-613-2R. Combining with 45S and 5S rDNA, a 22-probe cocktail that could identify all 13 G. arboreum chromosomes simultaneously was developed. According to their homology with tetraploid cotton, the G. arboreum chromosomes were designated as A1-A13, and a standard karyotype analysis of G. arboreum was presented. These results demonstrated an application for multiple BAC-FISH in cotton cytogenetic studies and a technique to overcome the problem of simultaneous chromosome recognition in mitotic cotton cells.     

Genetic diversity evaluation of some elite cotton varieties by RAPD analysis

Random amplified polymorphic DNA (RAPD) analysis was used to evaluate the genetic diversity of elite commercial cotton varieties. Twenty two varieties belonging to Gossypium hirsutum L. and one to G. arboreum L. were analyzed with 50 random decamer primers using the polymerase chain reaction (PCR). Forty nine primers detected polymorphism in all 23 cotton varieties, while one produced monomorphic amplification profiles. A total of 349 bands were amplified, 89.1% of which were polymorphic. Cluster analysis by the unweighted pair group method of arithmetic means (UPGMA) showed that 17 varieties can be placed in two groups with a similarity ranging from 81.51% to 93.41%. G. hirsutum L. varieties S-12, V3 and MNH-93 showed a similarity of 78.12, 74.46 and 69.56% respectively with rest of the varieties. One variety, CIM-1100, showed 57.02% similarity and was quite distinct. The diploid cotton G. arboreum L. var. Ravi was also very distinct from rest of its tetraploid counterparts and showed only 55.7% similarity. The analysis revealed that the intervarietal genetic relationships of several varieties is related to their center of origin. As expected, most of the varieties have a narrow genetic base. The results obtained can be used for the selection of possible parents to generate a mapping population. The results also reveal the genetic relationship of elite commercial cotton varieties with some standard “Coker” varieties and the diploid G. arboreum L. var. Ravi (old world cotton). Received: 12 July 1996 / Accepted: 26 July 1996     

不同棉蚜种群对棉花和黄瓜的适合度分化

通过室内转接试验,研究来源于越冬寄主花椒、木槿、石榴和夏寄主棉花、黄瓜共5个棉蚜Aphids gossypii Glover种群对棉花和黄瓜的适合度。结果表明:花椒棉蚜、木槿棉蚜、棉花棉蚜转接到棉花上的成虫留居率和种群繁殖率均明显地高于黄瓜;黄瓜棉蚜转接到棉花上的成虫留居率和种群繁殖率均显著地低于黄瓜;石榴棉蚜转接到棉花上的种群繁殖率显著低于黄瓜,但成虫留居率在2种寄主之间没有明显差异。     

Genetic and epigenetic status of triple exotic consanguinity cotton introgression lines

Introgression lines are some of the most important germplasm for breeding applications and other research conducted on cotton crops. The DNA methylation level among 10 introgression lines of cotton (Gossypium hirsutum) and three exotic parental species (G. arboreum, G. thurberi and G. barbadense) were assessed by methylation-sensitive amplified polymorphism (MSAP) technology. The methylation level in the introgression lines ranged from 33.3 to 51.5%. However, the lines PD0111 and PD0113 had the lowest methylation level (34.6 and 33.3%, respectively) due to demethylation of most non-coding sequences. Amplified fragment length polymorphism (AFLP) was used to evaluate the genetic polymorphism in the cotton introgression lines. A high degree of polymorphism was observed in all introgression lines (mean 47.2%) based on AFLP and MSAP analyses. This confirmed the effects of genetic improvement on cotton introgression lines. The low methylation varieties, PD0111 and PD0113 (introgression lines), clustered outside of the introgression lines based on MSAP data, which was incongruent with an AFLP-based dendrogram. This phenomenon could be caused by environmental changes or introgression of exotic DNA fragments.     

Genome-Wide Analysis of the Sus Gene Family in Cotton

Sucrose synthase (Sus) is a key enzyme in plant sucrose metabolism. In cotton, Sus (EC 2.4.1.13) is the main enzyme that degrades sucrose imported into cotton fibers from the phloem of the seed coat. This study demonstrated that the genomes of Gossypium arboreum L., G. raimondii Ulbr., and G. hirsutum L., contained 8, 8, and 15 Sus genes, respectively. Their structural organizations, phylogenetic relationships, and expression profiles were characterized. Comparisons of genomic and coding sequences identified multiple introns, the number and positions of which were highly conserved between diploid and allotetraploid cotton species. Most of the phylogenetic clades contained sequences from all three species, suggesting that the Sus genes of tetraploid G. hirsutum derived from those of its diploid ancestors. One Sus group (Sus I) underwent expansion during cotton evolution. Expression analyses indicated that most Sus genes were differentially expressed in various tissues and had development-dependent expression profiles in cotton fiber cells. Members of the same orthologous group had very similar expression patterns in all three species. These results provide new insights into the evolution of the cotton Sus gene family, and insight into its members' physiological functions during fiber growth and development.     

Chromosome structural changes in diploid and tetraploid A genomes of Gossypium.

The genus Gossypium, which comprises a divergent group of diploid species and several recently formed allotetraploids, offers an excellent opportunity to study polyploid genome evolution. In this study, chromosome structural variation among the A, At, and D genomes of Gossypium was evaluated by comparative genetic linkage mapping. We constructed a fully resolved RFLP linkage map for the diploid A genome consisting of 275 loci using an F2 interspecific Gossypium arboreum x Gossypium herbaceum family. The 13 chromosomes of the A genome are represented by 12 large linkage groups in our map, reflecting an expected interchromosomal translocation between G. arboreum and G. herbaceum. The A-genome chromosomes are largely collinear with the D genomes, save for a few small inversions. Although the 2 diploid mapping parents represent the closest living relatives of the allotetraploid At-genome progenitor, 2 translocations and 7 inversions were observed between the A and At genomes. The recombination rates are similar between the 2 diploid genomes; however, the At genome shows a 93% increase in recombination relative to its diploid progenitors. Elevated recombination in the Dt genome was reported previously. These data on the At genome thus indicate that elevated recombination was a general property of allotetraploidy in cotton.     

四个栽培棉种间的杂种F1细胞遗传学与亲缘关系研究

以棉属四个栽培棉种进行种间杂交,产生(亚洲棉×草棉)和(陆地棉×海岛棉)2个二元杂种F1及其[(亚洲棉×草棉)×(陆地棉×海岛棉)]四元杂种F1,观察和测定4个栽培棉种及其2个二元杂种F1和四元杂种F1的花粉母细胞(PMC)减数分裂的染色体行为及其花粉生活力,以研究4个栽培棉种间的亲缘关系和进化关系。结果表明,二元杂种(亚洲棉×草棉)F1的PMC减数分裂中期Ⅰ出现一个四体环,其余为二价体,染色体构型为2n=26=11Ⅱ 1Ⅳ;花粉生活力的测定表明,(亚洲棉×草棉)F1可育型花粉为50.71%,表现为典型的配子半不育特性,说明两个二倍体棉种间发生一次染色体易位。(陆地棉×海岛棉)F1以26个二价体细胞为主,但有少量的单价体、三价体以及四价体,染色体构型为2n=52=0.78Ⅰ 22.24Ⅱ 0.94Ⅲ 0.98Ⅳ。花粉生活力的测定表明,(陆地棉×海岛棉)F1可育型花粉为54.84%,可见2个四倍体棉种间亲缘关系较近,二者之间仅发生了染色体的易位或倒位。而由4个栽培种合成的四元杂种F1,其减数分裂异常,染色体丢失现象普遍,部分染色体不能联会配对,以单价体的形式存在,并出现三价体、四价体、五价体等多价体,染色体构型为2n=52=5.45Ⅰ 14.41Ⅱ 2.44Ⅲ 1.59Ⅳ 0.63Ⅴ 0.15Ⅵ,其可育花粉为6.87%。研究结果表明了4种栽培棉种之间的亲缘关系相对较近,可以通过遗传重组产生综合有4个栽培棉种性状的新种质。