GhWDL3 is involved in the formation and development of fiber cell morphology in upland cotton(Gossypium hirsutum L.)

Background Cotton fiber is a model tissue for studying microtubule-associated proteins(MAPs).The Xklp2(TPX2)proteins that belong to the novel MAPs member mainly participate in the formation and development of microtubule(MT).However,there is a lack of studies concerning the systematic characterization of the TPX2 genes family in cotton.Therefore,the identification and portrayal of G.hirsutum TPX2 genes can provide key targets for molecular manipula-tion in the breeding of cotton fiber improvement.Result In this study,TPX2 family genes were classified into two distinct subclasses TPXLs and MAP genes WAVE DAMP-ENED2-LIKE(WDLs)and quite conservative in quantity.GhWDL3 was significantly up-regulated in 15 days post anthe-sis fibers of ZRI-015(an upland cotton with longer and stronger fiber).GhWDL3 promotes all stem hairs to become straight when overexpressed in Arabidopsis,which may indirectly regulate cotton fiber cell morphology during fiber development.Virus induced gene silencing(VIGS)results showed that GhWDL3 inhibited fiber cell elongation at fiber development periods through regulating the expression of cell wall related genes.Conclusion These results reveal that GhWDL3 regulated cotton fiber cell elongation and provide crucial information for the further investigation in the regulatory mechanisms/networks of cotton fiber length.

Genetics of biochemical attributes regulating morpho-physiology of upland cotton under high temperature conditions

Background Cotton is a strategically important fibre crop for global textile industry.It profoundly impacts several countries’industrial and agricultural sectors.Sustainable cotton production is continuously threatened by the unpre-dictable changes in climate,specifically high temperatures.Breeding heat-tolerant,high-yielding cotton cultivars with wide adaptability to be grown in the regions with rising temperatures is one of the primary objectives of modern cotton breeding programmes.Therefore,the main objective of the current study is to figure out the effective breed-ing approach to imparting heat tolerance as well as the judicious utilization of commercially significant and stress-tolerant attributes in cotton breeding.Initially,the two most notable heat-susceptible(FH-115 and NIAB Kiran)and tolerant(IUB-13 and GH-Mubarak)cotton cultivars were spotted to develop filial and backcross populations to accom-plish the preceding study objectives.The heat tolerant cultivars were screened on the basis of various morphological(seed cotton yield per plant,ginning turnout percentage),physiological(pollen viability,cell membrane thermostabil-ity)and biochemical(peroxidase activity,proline content,hydrogen peroxide content)parameters.Results The results clearly exhibited that heat stress consequently had a detrimental impact on every studied plant trait,as revealed by the ability of crossing and their backcross populations to tolerate high temperatures.However,when considering overall yield,biochemical,and physiological traits,the IUB-13×FH-115 cross went over particularly well at both normal and high temperature conditions.Moreover,overall seed cotton yield per plant exhibited a posi-tive correlation with both pollen viability and antioxidant levels(POD activity and proline content).Conclusions Selection from segregation population and criteria involving pollen viability and antioxidant levels concluded to be an effective strategy for the screening of heat-tolerant cotton germplasms.Therefore,understanding acquired from this study can assist breeders identifying traits that should be prioritized in order to develop climate resilient cotton cultivars.

Genetic variability predicting breeding potential of upland cotton(Gossypium hirsutum L.)for high temperature tolerance

Background High temperature stress at peak flowering stage of cotton is a major hindrance for crop potential.This study aimed to increase genetic divergence regarding heat tolerance in newly developed cultivars and hybrids.Fifty cotton genotypes and 40 F1(hybrids)were tested under field conditions following the treatments,viz.,high temperature stress and control at peak flowering stage in August and October under April and June sowing,respectively.Results The mean squares revealed significant differences among genotypes,treatments,genotype×treatment for relative cell injury,chlorophyll contents,canopy temperature,boll retention and seed cotton yield per plant.The genetic diversity among 50 genotypes was analyzed through cluster analysis and heat susceptibility index(HSI).The heat tolerant genotypes including FH-Noor,NIAB-545,FH-466,FH-Lalazar,FH-458,NIAB-878,IR-NIBGE-8,Weal-AGShahkar,and heat sensitive,i.e.,CIM-602,Silky-3,FH-326,SLH-12 and FH-442 were hybridized in line×tester fashion to produce F1 populations.The breeding materials’populations(40 F1)revealed higher specific combining ability variances along with dominance variances,decided the non-additive type gene action for all the traits.The best general combining ability effects for most of the traits were displayed by the lines,i.e.,FH-Lalazar,NIAB-878 along with testers FH-326 and Silky-3.Specific combining ability effects and better-parent heterosis were showed by the crosses,viz.,FH-Lalazar×Silky-3,FH-Lalazar×FH-326,NIAB-878×Silky-3,and NIAB-878×FH-326 for seed cotton yield and yield contributing traits under high temperature stress.Conclusion Heterosis breeding should be carried out in the presence of non-additive type gene action for all the studied traits.The best combiner parents with better-parent heterosis may be used in crossing program to develop high yielding cultivars,and hybrids for high temperature stress tolerance.

A bZIP transcription factor GhVIP1 increased drought tolerance in upland cotton

Background Cotton is extremely affected by severe natural stresses.Drought is one of the most serious abiotic stress that adversely influences cotton growth,productivity,and fiber quality.Previous studies indicate that basic leucinezipper(bZIP)transcription factors are involved in the response of plants to various stresses.However,the molecular function and regulatory mechanism of GhVIP1 in response to drought stress are still unknown.Results In this research,GhVIP1 was cloned from a drought-tolerant variety.Expression of GhVIP1 was up-regulated in response to multiple abiotic stresses,especially under drought stress.And GhVIP1 was highly expressed in the root,stem,and 10 days post-anthesis ovule.Inhibiting the expression of GhVIP1 in cotton using the virus-induced gene silencing method resulted in higher electrical conductivity in leaves,but lower water content under drought stress compared with the WT plant.Overexpression of GhVIP1 in Arabidopsis enhanced plant drought tolerance through increasing the seed germination rate and improving the development of root.The exogenous expression of GhVIP1 up-regulated the transcription of genes associated with drought response and proline biosynthesis during drought stress in Arabidopsis.Conclusion In summary,these results indicated that GhVIP1 played a positive role in plants’response to drought stress.The use of GhVIP1 via modern biotechnology might facilitate the improvement of drought tolerance in cotton cultivars.

Association mapping of lignin response to Verticillium wilt through an eight-way MAGIC population in Upland cotton

Lignin metabolism plays a pivotal role in plant defense against pathogens and is always positively correlated as a response to pathogen infection. Thus, understanding resistance genes against plant pathogens depends on a genetic analysis of the lignin response. This study used eight Upland cotton lines to construct a multi-parent advanced generation intercross(MAGIC) population(n=280), which exhibited peculiar characteristics from the convergence of various alleles coding for advantageous traits. In order to measure the lignin response to Verticillium wilt(LRVW), the artificial disease nursery(ADN) and rotation nursery(RN) were prepared for MAGIC population planting in four environments. The stem lignin contents were collected, and the LRVW was measured with the lignin value of ADN/RN in each environment, which showed significant variations. We employed 9 323 high-quality single-nucleotide polymorphism(SNP) markers obtained from the Cotton-SNP63K array for genotyping the MAGIC population. The SNPs were distributed through the whole genome with 4.78 SNP/Mb density, ranging from 1.14(ChrA06) to 10.08(ChrD08). In addition, a genome-wide association study was performed using a Mixed Linear Model(MLM) for LRVW. Three stable quantitative trait loci(QTLs), qLRVW-A04, qLRVW-A10, and qLRVW-D05, were identified in more than two environments. Two key candidate genes, Ghi_D05G01046 and Ghi_D05G01221, were selected within the QTLs through the combination of variations in the coding sequence, induced expression patterns, and function annotations. Both genes presented nonsynonymous mutations in coding regions and were strongly induced by Verticillium dahliae. Ghi_D05G01046 encodes a leucine-rich extensin(LRx) protein involved in Arabidopsis cell wall biosynthesis and organization. Ghi_D05G01221 encodes a transcriptional co-repressor novel interactor of novel interactor of jasmonic acid ZIM-domain(JAZ–NINJA), which functions in the jasmonic acid(JA) signaling pathway. In summary, the study creates valuable genetic resources for breeding and QTL mapping and opens up a new perspective to uncover the genetic basis of VW resistance in Upland cotton.

Growth,leaf anatomy,and photosynthesis of cotton(Gossypium hirsutum L.)seedlings in response to four light-emitting diodes and high pressure sodium lamp

Background Light is a critical factor in plant growth and development,particularly in controlled environments.Light-emitting diodes(LEDs)have become a reliable alternative to conventional high pressure sodium(HSP)lamps because they are more efficient and versatile in light sources.In contrast to well-known specialized LED light spectra for vegetables,the appropriate LED lights for crops such as cotton remain unknown.Results In this growth chamber study,we selected and compared four LED lights with varying percentages(26.44%–68.68%)of red light(R,600–700 nm),combined with other lights,for their effects on growth,leaf anatomy,and photosynthesis of cotton seedlings,using HSP lamp as a control.The total photosynthetic photon flux density(PPFD)was(215±2)μmol·m-2·s-1 for all LEDs and HSP lamp.The results showed significant differences in all tested parameters among lights,and the percentage of far red(FR,701–780 nm)within the range of 3.03%–11.86%was positively correlated with plant growth(characterized by leaf number and area,plant height,stem diameter,and total biomass),palisade layer thickness,photosynthesis rate(Pn),and stomatal conductance(Gs).The ratio of R/FR(4.445–11.497)negatively influenced the growth of cotton seedlings,and blue light(B)suppressed stem elongation but increased palisade cell length,chlorophyll content,and Pn.Conclusion The LED 2 was superior to other LED lights and HSP lamp.It had the highest ratio of FR within the total PPFD(11.86%)and the lowest ratio of R/FR(4.445).LED 2 may therefore be used to replace HPS lamp under controlled environments for the study of cotton at the seedling stage.

Genome-wide identification and analysis of the CNGC gene family in upland cotton under multiple stress conditions

Background The cyclic nucleotide-gated channel(CNGC)gene family plays a significant role in the uptake of both essential and toxic cations,and has a role in enhancing tolerance to various forms of abiotic stresses as well as the modulation of the heavy metal toxicity to plant through the absorption of heavy metals.Results A complete genome-wide identification and functional characterization of the cotton CNGC genes was carried out,in which 55,28,and 29 CNGC genes were identified in Gossypium hirsutum,G.raimondii,and G.arboreum,respectively.The protein encoded by the CNGC genes exhibited GRAVY value below zero,indicating their hydrophilic property.CNGC genes were unevenly distributed in 19 out of 26 chromosomes,in which the highest density were observed on Ah05,with 8 genes.High gene coverage was observed among the diploid cotton species,with CNGC genes mapped on all A chromosomes and on 11 out of 13 of D chromosomes.The majority of CNGC proteins were localized in the endoplasmic reticulum,nucleus,and plasma membrane.Gene expression analysis revealed the up-regulation of Gh_A01G0520(CNGC4)and Gh_D13G1974(CNGC5)across various forms of abiotic stresses.Moreover,down-regulation of Gh_A01G0520(CNGC4)and Gh_D13G1974(CNGC5)in CNGCs silenced plants caused the significantly reduced ability to tolerate drought and salt stresses.All CNGCs silenced plants were recorded to have significantly low content of antioxidants but relatively higher content of oxidant,including MDA and H_(2)O_(2).Furthermore,SPAD,CMS(cell membrane stability),ELWL(excised leaf water loss),SDW(shoot dry matter weight),and RDW(root dry matter weight)were all lower in CNGCs silenced plants compared with the wild type plants.Conclusion Significant reduction in antioxidant content and negative effects of physiological and morphological characters in CNGCs silenced plants has revealed the novel role of CNGC genes in enhancing cell integrity under abiotic stress conditions.These results provide vital information that will expand our understanding of the CNGC gene family in cotton and other plants,thus promoting the integration of these genes in the development of the environmental resilient plants.

The ABA synthesis enzyme allele OsNCED2^(T)promotes dryland adaptation in upland rice

Upland rice shows dryland adaptation in the form of a deeper and denser root system and greater drought resistance than its counterpart,irrigated rice.Our previous study revealed a difference in the frequency of the OsNCED2 gene between upland and irrigated populations.A nonsynonymous mutation(C to T,from irrigated to upland rice)may have led to functional variation fixed by artificial selection,but the exact biological function in dryland adaptation is unclear.In this study,transgenic and association analysis indicated that the domesticated fixed mutation caused functional variation in OsNCED2,increasing ABA levels,root development,and drought tolerance in upland rice under dryland conditions.OsNCED2-overexpressing rice showed increased reactive oxygen species-scavenging abilities and transcription levels of many genes functioning in stress response and development that may regulate root development and drought tolerance.OsNCED2^(T)-NILs showed a denser root system and drought resistance,promoting the yield of rice under dryland conditions.OsNCED2^(T)may confer dryland adaptation in upland rice and may find use in breeding dryland-adapted,water-saving rice.

Artificial selection of the Green Revolution gene Semidwarf 1 is implicated in upland rice breeding

Semidwarf breeding has boosted crop production and is a well-known outcome from the first Green Revolution. The Green Revolution gene Semidwarf 1(SD1), which modulates gibberellic acid(GA) biosynthesis, plays a principal role in determining rice plant height. Mutations in SD1 reduce rice plant height and promote lodging resistance and fertilizer tolerance to increase grain production. The plant height mediated by SD1 also favors grain yield under certain conditions. However, it is not yet known whether the function of SD1 in upland rice promotes adaptation and grain production. In this study, the plant height and grain yield of irrigated and upland rice were comparatively analyzed under paddy and dryland conditions. In response to dryland environments, rice requires a reduction in plant height to cope with water deficits. Upland rice accessions had greater plant heights than their irrigated counterparts under both paddy and dryland conditions, and appropriately reducing plant height could improve adaptability to dryland environments and maintain high grain yield formation. Moreover, upland rice cultivars with thicker stem diameters had stronger lodging resistance, which addresses the lodging problem. Knockout of SD1 in the upland rice cultivar IRAT104 reduced the plant height and grain yield, demonstrating that the adjustment of plant height mediated by SD1 could increase grain production in dryland fields. In addition, an SD1 genetic diversity analysis verified that haplotype variation causes phenotypic variation in plant height. During the breeding history of rice, SD1 allelic mutations were selected from landraces to improve the grain yield of irrigated rice cultivars, and this selection was accompanied by a reduction in plant height. Thus, five known mutant alleles were analyzed to verify that functional SD1 is required for upland rice production. All these results suggest that SD1 might have undergone artificial positive selection in upland rice, which provides further insights concerning greater plant height in upland rice breeding.

Journal of Cotton Research Annual Awards

Hangdling Editor of the Year 2023.Journal of Cotton Research editorial office launches the award of Handling editors of the year to recognize handling editors with the most processed manuscripts in Journal of Cotton Research.Here are the Top 4 Handling editors of 2023:DONG Hezhong,Institute of Industrial Crops,Shandong Academy of Agricultural Sciences,China YANG Guozheng,College of Plant Science&Technology,Huazhong Agricultural University,China ZHANG Lizhen,College of Resources and Environmental Sciences,China Agricultural University,China ZHOU Zhiguo,College of Agriculture,Nanjing Agricultural University,China.

Alternate cotton-peanut intercropping:a new approach to increasing productivity and minimizing environmental impact

Recent publications have highlighted the development of an alternate cotton-peanut intercropping as a novel strat-egy to enhance agricultural productivity.In this article,we provide an overview of the progress made in the alternate cotton-peanut intercropping,specifically focusing on its yield benefits,environmental impacts,and the underlying mechanisms.In addition,we advocate for future investigations into the selection or development of appropriate crop varieties and agricultural equipment,pest management options,and the mechanisms of root-canopy interactions.This review is intended to provide a valuable reference for understanding and adopting an alternate intercropping system for sustainable cotton production.

Barley chitinase genes expression revamp resistance against whitefly (Bemisia Tabaci) in transgenic cotton (Gossypium hirsutum L.)

Background Chitinase is an enzyme that hydrolyzes chitin,a major component of the exoskeleton of insects,including plant pests like whiteflies.The present study aimed to investigate the expression of chemically synthesized barley ch1 and chi2 genes in cotton(Gossypium hirsutum)through Agrobacterium-mediated transformation.Fifty-five putative transgenic cotton plants were obtained,out of which fifteen plants successfully survived and were shifted to the field.Using gene-specific primers,amplification of 447 bp and 401 bp fragments confirmed the presence of the ch1 and chi2 genes in five transgenic cotton plants of the T0 generation.These five plants were further evalu-ated for their mRNA expression levels.The T0 transgenic cotton plants with the highest mRNA expression level and better yield performance in field,were selected to raise their subsequent progenies.Results The T1 cotton plants showed the highest mRNA expression levels of 3.5-fold in P10(2)for the ch1 gene and 3.7-fold in P2(1)for the chi2 gene.Fluorescent in situ hybridization(FISH)confirmed a single copy number of ch1 and chi2(hemizygous)on chromosome no.6.Furthermore,the efficacy of transgenes on whitefly was evaluated through an insect bioassay,where after 96 h of infestation,mortality rates of whitefly were calculated to be 78%–80%in transgenic cotton plants.The number of eggs on transgenic cotton plants were calculated to be 0.1%–0.12 per plant compared with the non-transgenic plants where egg number was calculated to be 0.90–1.00 per plant.Conclusion Based on these findings,it can be concluded that the chemically synthesized barley chitinase genes(ch1 and chi2)have the potential to be effective against insects with chitin exoskeletons,including whiteflies.The transgenic cotton plants expressing these genes showed increased resistance to whiteflies,resulting in reduced egg numbers and higher mortality rates.

Comparative analysis of SIMILAR to RCD ONE(SRO)family from tetraploid cotton species and their diploid progenitors depict their significance in cotton growth and development

Background SRO(Similar to RCD1)genes family is largely recognized for their importance in the growth,develop-ment,and in responding to environmental stresses.However,genome-wide identification and functional characteri-zation of SRO genes from cotton species have not been reported so far.Results A total of 36 SRO genes were identified from four cotton species.Phylogenetic analysis divided these genes into three groups with distinct structure.Syntenic and chromosomal distribution analysis indicated uneven distribu-tion of GaSRO,GrSRO,GhSRO,and GbSRO genes on A2,D5 genomes,Gh-At,Gh-Dt,Gb-At,and Gb-Dt subgenomes,respectively.Gene duplication analysis revealed the presence of six duplicated gene pairs among GhSRO genes.In promoter analysis,several elements responsive to the growth,development and hormones were found in GhSRO genes,implying gene induction during cotton growth and development.Several miRNAs responsive to plant growth and abiotic stress were predicted to target 12 GhSRO genes.Organ-specific expression profiling demonstrated the roles of GhSRO genes in one or more tissues.In addition,specific expression pattern of some GhSRO genes dur-ing ovule development depicted their involvement in these developmental processes.Conclusion The data presented in this report laid a foundation for understanding the classification and functions of SRO genes in cotton.

Laboratory evaluation of toxicity of selected insecticides against egg and larval stages of cotton pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

Background The cryptic nature of pink bollworm Pectinophora gossypiella(Saunders)larvae enables its reduced vul-nerability to insecticidal control.Further,the development of resistance against Bacillus thuringiensis(Bt)toxins posed a serious threat to transgenic cotton cultivation.This necessitated determining the critical timing of spray applications on the control effectiveness.This study assessed the influence of egg age(freshly laid vs.three-day-old)and the loca-tion of larvae(directly exposed to the insecticide residues on the boll rind vs.burrowed inside the bolls)on insecticide control efficacy.Results The results revealed a significant decrease in the ovicidal activity of tested insecticides with an increase in the age of eggs from one day old to three days old(paired t-test,P<0.05).The larvae directly exposed to the insec-ticide residues on the boll rind were more susceptible(>80%mortality)than the larvae exposed after they had bur-rowed inside the bolls(<49%mortality).The inhibitory effects of tested insecticides on developmental biology were more pronounced in the experiment on pre-larval release insecticide treatment compared with insecticide treatment given post-larval release and entry inside the bolls.Conclusion Egg age influences the insecticide susceptibility,as does the larval location,directly exposed vs bur-rowed inside the bolls.Older eggs and the larvae that had burrowed inside the green bolls of cotton were relatively less susceptible to the insecticide treatments.The toxic effects of insecticides on egg and larval stages were primar-ily ephemeral.These findings are significant for devising a comprehensive strategy for pink bollworm management on a sustainable basis.

Surface Morphology and Thermo-Electrical Energy Analysis of Polyaniline (PANI) Incorporated Cotton Fabric

With the exponential development in wearable electronics,a significant paradigm shift is observed from rigid electronics to flexible wearable devices.Polyaniline(PANI)is considered as a dominant material in this sector,as it is endowed with the optical properties of both metal and semiconductors.However,its widespread application got delineated because of its irregular rigid form,level of conductivity,and precise choice of solvents.Incorporating PANI in textile materials can generate promising functionality for wearable applications.This research work employed a straightforward in-situ chemical oxidative polymerization to synthesize PANI on Cotton fabric surfaces with varying dopant(HCl)concentrations.Pre-treatment using NaOH is implemented to improve the conductivity of the fabric surface by increasing the monomer absorption.This research explores the morphological and structural analysis employing SEM,FTIR and EDX.The surface resistivity was measured using a digital multimeter,and thermal stability is measured using TGA.Upon successful polymerization,a homogenous coating layer is observed.It is revealed that the simple pre-treatment technique significantly reduces the surface resistivity of Cotton fabric to 1.27 kΩ/cm with increasing acid concentration and thermal stability.The electro-thermal energy can also reach up to 38.2°C within 50 s with a deployed voltage of 15 V.The modified fabric is anticipated to be used in thermal regulation,supercapacitor,sensor,UV shielding,antimicrobial and other prospective functional applications.

The BEL1-like transcription factor GhBLH5-A05 participates in cotton response to drought stress

Drought stress impairs crop growth and development.BEL1-like family transcription factors may be involved in plant response to drought stress,but little is known of the molecular mechanism by which these proteins regulate plant response and defense to drought stress.Here we show that the BEL1-like transcription factor GhBLH5-A05 functions in cotton(Gossypium hirsutum)response and defense to drought stress.Expression of GhBLH5-A05 in cotton was induced by drought stress.Overexpression of GhBLH5-A05 in both Arabidopsis and cotton increased drought tolerance,whereas silencing GhBLH5-A05 in cotton resulted in elevated sensitivity to drought stress.GhBLH5-A05 binds to cis elements in the promoters of GhRD20-A09 and GhDREB2C-D05 to activate the expression of these genes.GhBLH5-A05 interacted with the KNOX transcription factor GhKNAT6-A03.Co-expression of GhBLH5-A05 and GhKNAT6-A03 increased the transcription of GhRD20-A09 and GhDREB2C-D05.We conclude that GhBLH5-A05 acts as a regulatory factor with GhKNAT6-A03 functioning in cotton response to drought stress by activating the expression of the drought-responsive genes GhRD20-A09 and GhDREB2C-D05.

Development of a core set of SNP markers for the identifi cation of upland cotton cultivars in China

Considering the advantages of single nucleotide polymorphisms（SNP） in genotyping and variety identification, the first set public SNP markers at Cotton Marker Database（http：//www.cottonmarker.org/） were validated and screened across standard varieties of cotton distinctness, uniformity and stability（DUS） test, aiming to obtain an appropriate set of core SNP markers suitable for upland cotton cultivars in China. A total of 399 out of 1 005 SNPs from 270 loci including 170 insertions-deletions（In Dels） were evaluated for their polymorphisms among 30 standard varieties using Sanger sequencing. As a result, 147 loci were sequenced successfully, 377 SNPs and 49 In Dels markers were obtained. Among the 377 SNP markers, 333 markers（88.3%） were polymorphic between Gossypium hirsutum and G. barbadense, while 164 markers（43.5%） were polymorphic within upland cotton. As for In Del markers, the polymorphic rate is relatively lower than that of SNP both between species and within species. The homozygous DNA locus ratio of 121 SNPs was higher than 86.2% while that of other 43 SNPs was less than 70%. Only 64 SNPs displayed completely homozygous genotypes among all of the detected upland cotton varieties with 100% homozygous DNA locus ratio. At last, a set of 23 pairs of core SNPs were achieved in view of avoidance of linkage, with polymorphism information content（PIC） values varying from 0.21 to 0.38 with an average of 0.28. Genotype characteristics and genetic diversity were analyzed based on the set of core markers, while 40 pairs of core simple-sequence repeats（SSR） primers comprised of 10 sets of four multiplex PCR combinations were also used for analysis based on fluorescence detection system. Comparison results indicated that the genetic diversity level was almost equal, while various varieties were significantly different from each other. Genetic relationship revealed by SSR markers is related to geographic source to a certain extent. Meanwhile clustering results analyzed by SNP markers are more consistent with kinship, which demonstrated that the screen strategy for core SNP marker is effective.

Major Gene Identification and Quantitative Trait Locus Mapping for YieldRelated Traits in Upland Cotton(Gossypium hirsutum L.)

Segregation analysis of the mixed genetic model of major gene plus polygene was used to identify the major genes for cotton yield-related traits using six generations P1, P2, F1, B1, B2, and F2 generated from the cross of Baimian 1 x TM-1. In addition to boll size and seed index, the major genes for the other five traits were detected： one each for seed yield, lint percentage, boll number, lint index; and two for lint yield. Quantitative trait locus/loci （QTL） mapping was performed in the F2 and F2：3 populations of above cross through molecular marker technology, and a total of 50 QTL （26 suggestive and 24 significant） for yield-related traits were detected. Four common QTL were discovered： qLP-3b（F2）/qLP-3（F2：3） and qLP-19b （F2）/qLP-19（F2：3） for lint percentage, qBN-17（F2）/qBN-17（F2：3） for boll number, and qBS-26b（F2）/qBS-26（F2：3） for boll size. Especially, qLP- 3b（Fz）/qLP-3（F2：3）, not only had LOD scores 〉3 but also exceeded the permutation threshold （5.13 and 5.29, respectively）, correspondingly explaining 23.47 and 29.55% of phenotypic variation. This QTL should be considered preferentially in marker assisted selection （MAS）. Segregation analysis and QTL mapping could mutually complement and verify, which provides a theoretical basis for genetic improvement of cotton yield-related traits by using major genes （QTL）.

Characterization of Gh SERK2 and its expression associated with somatic embryogenesis and hormones level in Upland cotton

Somatic embryogenesis （SE） is one of the most important steps during regeneration of cotton, but the molecular mechanism of SE remains unclear. SOMATIC EMBRYOGENSIS RECEPTOR KINASE （SERK） gene is known to function in SE. A homolog GhSERK2 （accession number： JF430801） was cloned from Upland cotton and characterized for its functions in SE. GhSERK2 expressed in different tissues and showed higher expression level in floral organs than vegetative ones with the highest levels in ovule and anther. GhSERK2 expressed during SE with a high level at globular embryos stage. Upon treatment with indole-3-butytic acid （IBA）, the transcription level of GhSERK2 was induced and promoted SE subsequently. A 2-day treatment of 2,4-dichlorophenoxyacetic acid （2,4-D） induced the expression of GhSERK2, but treatments of 2,4-D for longer periods sharply inhibited the GhSERK2 transcription level of embryogenic callus （EC）. The levels of hormones, including 3-indoleacetic acid （IAA）, abscisic acid （ABA）, and brassinosteroid （BR）, were increased in the initial calli induced from the over-expression of GhSERK2 cotton. Our results indicated that GhSERK2 expression was associated with induction of SE and closely related to hormone levels during tissue culture in Upland cotton, and the gene might play an important role in regeneration of cotton.

Improvement of copper tolerance of Arabidopsis by transgenic expression of an allene oxide cyclase gene,GhA OC1, in upland cotton(Gossypium hirsutum L.)

Allene oxide cyclase(AOC, E 5.3.99.6) is an essential enzyme in the jasmonic acid(JA)biosynthetic pathway and mediates a wide range of adaptive responses. In this report, five AOC genes(Gh AOC1–Gh AOC5) were cloned from upland cotton(Gossypium hirsutum L.),sequenced, and characterized. Real-time PCR analysis indicated that the transcripts of Gh AOCs were abundantly expressed in roots and less in fibers, and regulated in cotton plants under methyl jasmonate(Me JA) and Cu Cl2 stresses. To investigate the role of Gh AOC under copper stress, transgenic Arabidopsis plants overexpressing cotton Gh AOC1 under control of the Cauliflower mosaic virus 35S(Ca MV 35S) promoter were generated. Compared to untransformed plants, Gh AOC1-overexpressing Arabidopsis thaliana plants exhibited markedly higher survival rate, shoot fresh weight, shoot dry weight, and photosynthetic efficiency, and reduced cell membrane damage and lipid peroxidation under copper stress.This study provides the first evidence that Gh AOC1 plays an important role in copper stress tolerance.