Background: Gossypium hirsutum(upland cotton) is one of the principal fiber crops in the world. Cotton yield is highly affected by abiotic stresses, among which salt stress is considered as a major problem around the globe. Transgenic approach is efficient to improve cotton salt tolerance but depending on the availability of salt tolerance genes.Results: In this study we evaluated salt tolerance candidate gene ST7 from Thellungiella halophila, encoding a homolog of Arabidopsis aluminum-induced protein, in cotton. Our results showed that ThST7 overexpression in cotton improved germination under NaCl stress as well as seedling growth. Our field trials also showed that ThST7 transgenic cotton lines produced higher yield under salt stress conditions. The improved salt tolerance of the transgenic cotton lines was partially contributed by enhanced antioxidation as shown by diaminobenzidine(DAB) and nitrotetrazolium blue chloride(NBT) staining. Moreover, transcriptomic analysis of ThST7 overexpression lines showed a significant upregulation of the genes involved in ion homeostasis and antioxidation, consistent with the salt tolerance phenotype of the transgenic cotton.Conclusions: Our results demonstrate that ThST7 has the ability to improve salt tolerance in cotton. The ThST7 transgenic cotton may be used in cotton breeding for salt tolerance cultivars.

Background: Nucleobase–ascorbate transporters(NAT), synonymously called nucleobase–cation symporter 2(NCS2) proteins, were earlier reported to be involved in plant growth, development and resistance to stress. Previous studies concluded that s a polymorphic SNP associated with NAT12 was significant di erent between salt-tolerant and salt-sensitive materials of upland cotton. In current study, a comprehensive analysis of NAT family genes was conducted for the first time in cotton.Results: In this study, we discovered 32, 32, 18, and 16 NAT genes in Gossypium hirsutum, G. barbadense, G. raimondii and G. arboreum, respectively, which were classified into four groups(groups I–IV) based on the multiple sequence analysis. These GhNAT genes were unevenly distributed on At and Dt sub-genome in G. hirsutum. Most GhNAT members in the same group had similar gene structure characteristics and motif composition. The collinearity analysis revealed segmental duplication as well as tandem duplication contributing to the expansion of the GhNATs. The analysis of cis-acting regulatory elements of GhNATs showed that the function of GhNAT genes in cotton might be related to plant hormone and stress response. Under di erent conditions, the expression levels further suggested the GhNAT family genes were associated with plant response to various abiotic stresses. GhNAT12 was detected in the plasma membrane. And it was validated that the GhNAT12 gene played an important role in regulating cotton resistance to salt and drought stress through the virus-induced gene silencing(VIGS) analysis.Conclusions: A comprehensive analysis of NAT gene family was performed in cotton, including phylogenetic analysis, chromosomal location, collinearity analysis, motifs, gene structure and so on. Our results will further broaden the insight into the evolution and potential functions of NAT genes in cotton. Current findings could make significant contribution towards screening more candidate genes related to biotic and abiotic resistance for the improvement in cotton.

Background:This study aimed to develop a set of perfect simple sequence repeat(SSR) markers with a single copy in the cotton genome,to construct a DNA fingerprint database suitable for authentication of cotton cultivars.We optimized the polymerase chain reaction(PCR) system for multi-platform compatibility and improving detection efficiency.Based on the reference genome of upland cotton and 10× resequencing data of 48 basic cotton germplasm lines,single-copy polymorphic SSR sites were identified and developed as diploidization SSR markers.The SSR markers were detected by denaturing polyacrylamide gel electrophoresis(PAGE) for initial screening,then fluorescence capillary electrophoresis for secondary screening.The final perfect SSR markers were evaluated and verified using 210 lines from different sources among Chinese cotton regional trials.Results:Using bioinformatics techniques,1 246 SSR markers were designed from 26 626 single-copy SSR loci.Adopting a stepwise(primary and secondary) screening strategy,a set of 60 perfect SSR markers was selected with high amplification efficiency and stability,easy interpretation of peak type,multiple allelic variations,high polymorphism information content(PIC) value,uniform chromosome distribution,and single-copy characteristics.A multiplex PCR system was established with ten SSR markers using capillary electrophoresis detection.Conclusions:A set of perfect SSR markers of cotton was developed and a high-throughput SSR marker detection system was established.This study lays a foundation for large-scale and standardized construction of a cotton DNA fingerprint database for authentication of cotton varieties.

Australian cotton production predominantly occurs on Vertisols. The average lint yield of cotton grown in Australia is 2 260–2 700 kg·hm~(-2), which is 2.5 to 3 times the world average. This high productivity per unit of land area requires e cient use of resources such as water and nutrients. However, high yields accelerate the export of nutrients such as phosphorus(P) in seed, depleting the soil reserves of P more than in other countries with lower cotton yields. Recent surveys of cotton industry indicate that P application rates should match seed P export(30～ 40 kg·hm~(-2)), but historical depletion within subsoil is still evident and is continuing. Depletion of soil P is typically more pronounced in the subsoil than in the topsoil(0～ 20 cm) where P fertiliser is applied, as cotton roots rely on these layers as important sources of plant available water and available P. This mismatch between zones of P uptake and resupply may increase stratification of available P in the soil profile. Recent studies showed that cotton responded poorly to banded applications of fertiliser P, while dispersal of fertiliser throughout the plant beds was more successful. Researchers have also observed sporadic cotton responses to applied P fertiliser in soils where available P concentrations were well above the previously determined critical concentrations indicative of fertiliser P responses in Australia. To sustain highyielding cotton production in Australia, a greater understanding of cotton root acquisition of applied P, as well as a re-examination of critical soil P concentrations for each production region are required.

Background The strength of cotton fiber has been extensively studied and significantly improved through selective breeding, but fiber elongation has largely been ignored, even though elongation contributes to determining the energy needed to break fibers. Recent developments to calibrate the high volume instrument (HVI) for elongation has renewed interest in elongation. However, it is not understood how best to utilize yet another fiber property which has the potential to add to the complexity of fiber selection. To explore a practical approach to applying elongation, cotton samples were tested using single fiber methods, the Stelometer, and the HVI. Comparison of strength, elongation, and combined properties such as modulus were explored. Results HVI testing was shown to be sensitive enough to characterize elongation differences but unlike single fiber testing it was unable to capture within-sample variation. Fiber bundle testing, like Stelometer and HVI was shown to reduce bias due to fiber selection. Conclusion The use of secant modulus, an intrinsic material property, allowed for one value to represent both strength and elongation. Secant modulus was shown to contain more useful information than either elongation or work-to-break. Work-to-break was shown to be more influenced by a specific value of breaking force or elongation rather than the intrinsic behavior of the sample being tested. Exploring the influence of genetics and environment on elongation, and its interaction with other fiber properties, requires additional work. Secant modulus, by combining strength and elongation into one value, shows the potential to incorporate elongation values into fiber characterization without increasing the complexity of current fiber selection processes.

Background: Verticillium wilt, caused by the soil-borne fungus of Verticillium dahliae Kleb., is one of the most devastating diseases of cotton. The complex mechanism underlying cotton resistance to Verticillium wilt remains uncharacterized. Identifying an endogenous resistance gene may be helpful to control this disease. Previous studies revealed that succinate dehydrogenase(SDH) is involved in reactive oxygen species(ROS)-induced stress signaling pathway that is likely to be triggered by salicylic acid(SA). Here, through the metabolomics and differential expression analyses in wilt-inoculated cotton(Gossypium hirsutum), we noticed that Gh SDH1–1 gene in cotton may play an important role in the resistance to V. dahlia. Then we reported Gh SDH1–1 gene and its functional analysis in relation to the resistance of cotton to V. dahliae.Results: The Gh SDH1–1 gene in cotton root was significantly up-regulated after V. dahlia inoculation, and its expression level peaked at 12 and 24 h post-infection. SA can also induce the up-regulation of Gh SDH1–1.Additionally, the functional analysis showed that Gh SDH1–1-silenced cotton was more susceptible to V. dahliae than the control because of the significant decrease in abundance of immune-related molecules and severe damage to the SA-signaling pathway. In Arabidopsis thaliana, high expression of Gh SDH1–1 conferred high resistance to V.dahliae. Arabidopsis that overexpressed Gh SDH1–1 had higher resistance to V. dahliae infection compared with the wild-type.Conclusions: Our findings provide new insights into the role of Gh SDH1–1; it positively regulates cotton resistance to Verticillium wilt. The regulatory mechanism of Gh SDH1–1 is closely related to SA-related signaling pathway.

Recent technological advances in cotton(Gossypium hirsutum L.) phenotyping have offered tools to improve the efficiency of data collection and analysis.High-throughput phenotyping(HTP) is a non-destructive and rapid approach of monitoring and measuring multiple phenotypic traits related to the growth,yield,and adaptation to biotic or abiotic stress.Researchers have conducted extensive experiments on HTP and developed techniques including spectral,fluorescence,thermal,and three-dimensional imaging to measure the morphological,physiological,and pathological resistance traits of cotton.In addition,ground-based and aerial-based platforms were also developed to aid in the implementation of these HTP systems.This review paper highlights the techniques and recent developments for HTP in cotton,reviews the potential applications according to morphological and physiological traits of cotton,and compares the advantages and limitations of these HTP systems when used in cotton cropping systems.Overall,the use of HTP has generated many opportunities to accurately and efficiently measure and analyze diverse traits of cotton.However,because of its relative novelty,HTP has some limitations that constrains the ability to take full advantage of what it can offer.These challenges need to be addressed to increase the accuracy and utility of HTP,which can be done by integrating analytical techniques for big data and continuous advances in imaging.

Background: Micronaire is a comprehensive index reflecting the fineness and maturity of cotton fiber. Micronaire is one of the important internal quality indicators of the cotton fiber and is closely related to the value of the cotton fiber. Understanding the genetic basis of micronaire is required for the genetic improvement of the trait. However,the genetic architecture of micronaire at the genomic level is unclear. The present genome-wide association study(GWAS) aimed to identify the genetic mechanism of the micronaire trait in 83 representative upland cotton lines grown in multiple environments.Results: GWAS of micronaire used 83 upland cotton accessions assayed by a Cotton 63 K Illumina Infinium single nucleotide polymorphism(SNP) array. A total of 11 quantitative trait loci(QTLs) for micronaire were detected on 10 chromosomes. These 11 QTLs included 27 identified genes with specific expression patterns. A novel QTL, q FM-A12–1,included 12 significant SNPs, and Gh FLA9 was identified as a candidate gene based on haplotype block analysis and on strong and direct linkage disequilibrium between the significantly related SNPs and gene. Gh FLA9 was expressed at a high level during secondary wall thickening at 20～25 days post-anthesis. The expression level of Gh FLA9 was significantly higher in the low micronaire line(Msco-12) than that in the high micronaire line(Chuangyou-9).Conclusions: This study provides a genetic reference for genetic improvement of cotton fiber micronaire and a foundation for verification of the functions of Gh FLA9.

Background:Aphis gossypii is a worldwide sap-sucking pest with a variety of hosts and a vector of more than 50 plant viruses.The strategy of wing polyphenism,mostly resulting from population density increasing,contributes to the evolutionary success of this pest.However,the related molecular basis remains unclear.Here,we identified the effects of postnatal crowding on wing morph determination in cotton aphid,and examined the transcriptomic differences between wingless and wing morphs.Results:Effect of postnatal crowding on wing determination in A gossypii was evaluated firstly.Under the density of 5 nymphs·cm~(-2),no wing aphids appeared.Proportion of wing morphs rised with the increase of density in a certain extent,and peaked to 56.1% at the density of 20 nymphs·cm~(-2),and reduced afterwards.Then,transcriptomes of wingless and wing morphs were assembled and annotated separately to identify potentially exclusively or differentially expressed transcripts between these two morphs,in which 3 126 and 3 392 unigenes annotated in Nr(Non-redundant protein sequence) database were found in wingless or wing morphs exclusively.Moreover,3 187 up-and 1 880 down-regulated genes were identified in wing versus wingless aphid.Pathways analysis suggested the involvement of differentially expressed genes in multiple cellular signaling pathways involved in wing morphs determination,including lipid catabolic and metabolism,insulin,ecdysone and juvenile hormone biosynthesis.The expression levels of related genes were validated by the reverse transcription quantitative real time polymerase chain reaction(RT-qPCR) soon afterwards.Conclusions:The present study identified the effects of postnatal crowding on wing morphs induction and demonstrated that the critical population density for wing morphs formation in A gossypii was 20 nymphs·cm~(-2).Comparative transcriptome analysis provides transcripts potentially expressed exclusively in wingless or wing morph,respectively.Differentially expressed genes between wingless and wing morphs were identified and several signaling pathways potentially involved in cotton aphid wing differentiation were obtained.

Background: Under abiotic stress conditions, cotton growth is inhibited and yield losses are severe. Identification of calnexin family members and function analysis under abiotic stress laid the foundation for the screening of stressrelated candidate genes.Results: A total of 60 CNX family members have been identified in Gossypium hirsutum, G. barbadense, G. arboreum,and G. raimondii, and they were divided into two categories: CNX and CRT genes. Through the construction of a phylogenetic tree, they were subdivided into three classes. Further analysis of chromosome localization, conserved promoters, gene structure and selection under pressure showed that the family members were highly conserved in the evolution process. Analysis of cis-acting elements in the promoter regions showed that CNX family genes contain regulatory elements for growth and development, anaerobic, drought, defense and stress response, and plant hormones. Using RNA-seq data to study the expression pattern of GhCNX genes under cold, hot, salt stress and Polyethylene glycol, it was observed that the gene expression levels changed by di erent degrees under di erent stress conditions, indicating that GhCNX members were involved in the regulation of multiple biological stresses.Conclusion: This study provides an insight into the members of cotton CNX genes. The results of this study suggested that CNX family members play a role in defense against adversity and provide a foundation for the discovery of stress-related genes.

Background In our previous study, a strain EBS03 with good biocontrol potential was screened out of 48 strains of cotton endophyte Bacillus subtilis by evaluating the controlling effect against cotton Verticillium wilt. However, its mechanism for controlling Verticillium wilt remains unclear. The objective of this study was to further clarify its controlling effect and mechanism against cotton Verticillium wilt. Results The results of confrontation culture test and double buckle culture test showed that the inhibitory effects of EBS03 volatile and nonvolatile metabolite on mycelium growth of Verticillium dahliae were 70.03% and 59.00%, respectively; the inhibitory effects of sporulation and microsclerotia germination were 47.16% and 70.06%, respectively. In the greenhouse test, the EBS03 fermentation broth root irrigation had the highest controlling effect at 87.11% on cotton Verticillium wilt, and significantly promoted the growth of cotton seedlings. In the field experiment, the controlling effect of EBS03 fermentation broth to cotton Verticillium wilt was 42.54% at 60 days after cotton sowing, and the boll number per plant and boll weight in EBS03 fermentation broth seed soaking, root irrigation, and spraying treatments significantly increased by 19.48% and 7.42%, 30.90% and 2.62%, 15.99% and 9.20%, respectively. Furthermore, EBS03 improved the resistance of cotton leaves against the infection of V. dahliae, and induced the outbreak of reactive oxygen species and accumulation of callose. In addition, the results of real time fluorescent quantitative polymerase chain reaction (RT-qPCR) detection showed that EBS03 significantly induced upregulation expression level of defense-related genes PAL, POD, PPO, and PR10 in cotton leaves, enhanced cotton plant resistance to V. dahliae, and inhibited colonization level of this fungal pathogen in cotton. Conclusion Bacillus subtilis EBS03 has a good biological defense capability, which can inhibit the growth and colonization level of V. dahliae, and activate the resistance of cotton to Verticillium wilt, thus increase cotton yield.

Background: Photosynthate partitioning and within-plant boll distribution play an important role in yield formation of cotton; however, if and how they interact to mediate yield remains unclear. The objective of this study was to investigate the genotypic variance in photosynthate partitioning and within-plant boll distribution, with a focus on their interactions with regard to yield and yield components. A field experiment was conducted in the Yellow River region in China in 2017 and 2018 using a randomized complete block design with three replicates. Photosynthate partitioning of three commercial cultivars(DP 99 B, Lumianyan 21 and Jimian 169), varying in yield potential, to different organs(including bolls) at early flowering, peak flowering, and peak boll-setting stages, as well as withinplant boll distribution at harvest, and their effects on yield formation were examined.Results: Lint yield of Jimian 169 was the highest, followed by Lumianyan 21 and DP 99 B. Similar differences were observed in the number of inner bolls and boll weight among the three cultivars. J169 partitioned significantly more photosynthate to the fruit and fiber than Lumianyan 21 and DP 99 B and allocated over 80% of assimilates to the inner bolls. Additionally, Lumianyan 21 allocated a higher proportion of photosynthate to bolls and fiber, with12.5%–17.6% more assimilates observed in the inner bolls, than DP 99 B.Conclusions: Genotypic variance in lint yield can be attributed to differences in the number of inner bolls and boll weight, which are affected by photosynthate partitioning. Therefore, the partitioning of photosynthate to fiber and inner bolls can be used as an important reference for cotton breeding and cultivation.

Background:Manganese(Mn) is an essential microelement in cottonseeds,which is usually determined by the techniques relied on hazardous reagents and complex pretreatment procedures.Therefore a rapid,low-cost,and reagent-free analytical way is demanded to substitute the traditional analytical method.Results:The Mn content in cottonseed meal was investigated by near-infrared spectroscopy(NIRS) and chemometrics techniques.Standard normal variate(SNV) combined with first derivatives(FD) was the optimal spectra pre-treatment method.Monte Carlo uninformative variable elimination(MCUVE) and successive projections algorithm method(SPA)were employed to extract the informative variables from the full NIR spectra.The linear and nonlinear calibration models for cottonseed Mn content were developed.Finally,the optimal model for cottonseed Mn content was obtained by MCUVE-SPA-LSSVM,with root mean squares error of prediction(RMSEP) of 1.994 6,coefficient of determination(R2) of 0.949 3,and the residual predictive deviation(RPD) of 4.370 5,respectively.Conclusions:The MCUVE-SPA-LSSVM model is accuracy enough to measure the Mn content in cottonseed meal,which can be used as an alternative way to substitute for traditional analytical method.

Background:Recently,due to the development of food security strategies,cotton has been planted in inland saline-alkali dry soils or in coastal some saline-alkali soils in China.Under the condition,to comprehensively prevent and control Helicoverpa armigera in cotton fields with saline-alkali soils,it is important to study the larval growth and development of H.armigero and to study adult oviposition selectivity in H.armigera adults that feed on NaCI-stressed cotton plants.Results:In this study,Bt cotton GK19 was used for the experimental group and its nontransgenic parent Simian 3 was used for the control to study the effects of biochemical substances in cotton as well as larval growth and development and adult oviposition selectivity of H.armigera.The experiments were performed by growing cotton indoors under NaCl stress at concentrations of 0 mmol-L~(-1),75 mmol-L~(-1) and 150 mmol-L~(-1),respectively.The results showed that the expression of Bt protein was significantly inhibited for NaCI-stressed Bt cotton.The content of soluble protein and K+ in the leaves of cotton were decreased,while the content of gossypol and Na~+were increased.In addition,the 5~(th) instar H.armigera larvae exhibited shorten the life span in a 13-day trial period.Under enclosure treatments and at different female densities,the adult oviposition of H.armigera decreased on high NaCI-stressed nontransgenic cotton,while the oviposition on Bt cotton tended to first increase but then decrease under low,moderate and high NaCl stress treatments.Conclusions:Under certain content ranges of NaCl stress treatments,larval of H.armigera growth and development,and adult oviposition were no significant difference in the change for a certain period.However,under high NaCl stress,larval growth,development and adult oviposition were affected,which may provide insights for the prevention and control of H.armigero for Bt cotton in saline-alkali soils.

Background: The cotton bollworm(Helicoverpa armigera) is one of cotton's most destructive insect pests in terms of yield and quality. Since 1997, China has grown commercially available transgenic Bacillus thuringiensis(Bt) cotton. We aimed to investigate the variation in resistance of transgenic Bt cotton varieties to cotton bollworm in North China.Methods: Populations of cotton bollworm were monitored from 2008 to 2015 in environments where Bt cotton was planted adjacent to other non-Bt crops. The study included 197 Bt cotton varieties planted in 42 counties/locations in three provinces(Hebei, Shandong and Henan) of North China, which were evaluated through field investigations,bioassays, and enzyme-linked immunosorbent assays(ELISA).Results: The average number of cotton bollworms never exceeded the action threshold(10 larvae per 100 cotton plants), however, their number reached 19.55 per 100 cotton plants in 2011. The ratios of damaged plants to total Bt cotton stem-tips, buds, and bolls was low except in 2010, when the ratios reached 1.82%, 2.09%, and 10.63%,respectively. The results of bioassay showed that the corrected mortality were higher at the second generation cotton bollworm stage than the third and fourth germination stages. Totally, Bt protein content declined sharply at the seedling stage from 2008 to 2015.Conclusions: This study indicated that almost all Bt cotton varieties were capable to effectively control the populations of cotton bollworm in North China.

Background: This study addressed the potential of combining a high biomass rye winter cover crop with predawn leaf water potential(ΨPD) irrigation thresholds to increase agricultural water use efficiency(WUE) in cotton. To this end, a study was conducted near Tifton, Georgia under a manually-controlled, variable-rate lateral irrigation system using a Scholander pressure chamber approach to measure leaf water potential and impose varying irrigation scheduling treatments during the growing season. ΨPDthresholds were-0.4 MPa(T1),-0.5 MPa(T2), and-0.7 MPa(T3). A winter rye cover crop or conventional tillage were utilized for T1-T3 as well.Results: Reductions in irrigation of up to 10% were noted in this study for the driest threshold(-0.7 MPa) with no reduction in lint yield relative to the-0.4 MPa and-0.5 MPa thresholds. Drier conditions during flowering(2014)limited plant growth and node production, hastened cutout, and decreased yield and WUE relative to 2015.Conclusions: We conclude that ΨPDirrigation thresholds between-0.5 MPa and-0.7 MPa appear to be viable for use in a ΨPDscheduling system with adequate yield and WUE for cotton production in the southeastern U.S. Rye cover positively impacted water potential at certain points throughout the growing season but not yield or WUE indicating the potential for rye cover crops to improve water use efficiency should be tested under longer-term production scenarios.

Background: Cotton(Gossypium spp.) is one of the most important economic crops worldwide, and its production plays an important role in the economy of many countries. Genetically modified herbicide-tolerant(GMHT) crops, which were developed to minimize the losses caused by weeds, have gradually become the most widely adopted genetically modified crops in the world due to their economic and environmental benefits. However, the potential ecological and environmental risks of GMHT crops have attracted extensive attention and controversy. Arthropod communities form a prominent part of the biodiversity of agroecosystems and are important indicators of environmental health. Elucidating the e ects of GMHT crops on the diversity of arthropod communities is necessary to ensure the safety of GMHT crops.Result: In this 2-year study, we investigated the potential impact of GMHT crops on arthropod communities. The GMHT cotton variety GGK2 with glyphosate tolerance and its near-isogenic non-GMHT variety K312 were used for the experimental groups. The Shannon diversity index(H), Simpson diversity index(D), Pielou evenness index(J), and principal co-ordinates analysis(PCoA) of the Bray–Curtis distance were used to evaluate the population dynamics and biodiversity of arthropods in cotton fields. No significant di erences were found between GGK2 and K312 in their total abundance of arthropod communities, and biodiversity indexes on most sampling dates. The arthropod composition in the GGK2 and K312 plots was similar. Sampling dates had a significant e ect on biodiversity indexes, whereas no clear tendencies related to cotton variety or cotton variety A revealed high similarity between the arthropod commu× sampling dates interaction were recorded. In addition, PConities in the plots of the GMHT cotton variety GGK2 and its near-isogenic variety K312.Conclusion: There was no obvious di erence in abundance, diversity indexes of arthropod communities between GMHT cotton variety GGK2 and its near-isogenic variety K312 under the small-scale planting regime.

Background Boron (B) deficiency is an important factor for poor seed cotton yield and fiber quality. However, it is often missing in the plant nutrition program, particularly in developing countries. The current study investigated B's effect on growth, yield, and fiber quality of Bt (CIM-663) and non-Bt (Cyto-124) cotton cultivars. The experimental plan consisted of twelve treatments: Control (CK); B at 1 mg·kg⁻¹ soil application (SB1); 2 mg·kg⁻¹ B (SB2); 3 mg·kg⁻¹ B (SB3); 0.2% B foliar spray (FB1); 0.4% B foliar spray (FB2); 1 mg·kg⁻¹ B + 0.2% B foliar spray (SB1 + FB1); 1 mg·kg⁻¹ B + 0.4% B foliar spray (SB1 + FB2); 2 mg·kg−1 B + 0.2% B foliar spray (SB2 + FB1); 2 mg·kg⁻¹ B + 0.4% B foliar spray (SB2 + FB2); 3 mg·kg⁻¹ B + 0.2% B foliar spray (SB3 + FB1); 3 mg·kg⁻¹ B + 0.4% B foliar spray (SB3 + FB2). Each treatment has three replications, one pot having two plants per replication. Results B nutrition at all levels and methods of application significantly (P ≤ 0.05) affected the growth, physiological, yield, and fiber quality characteristics of both cotton cultivars. However, SB2 either alone or in combination with foliar spray showed superiority over others, particularly in the non-Bt cultivar which responded better to B nutrition. Maximum improvement in monopodial branches (345%), sympodial branches (143%), chlorophyll-a (177%), chlorophyll-b (194%), photosynthesis (169%), and ginning out turn (579%) in the non-Bt cultivar was found with SB2 compared with CK. In Bt cultivar, although no consistent trend was found but integrated use of SB3 with foliar spray performed relatively better for improving cotton growth compared with other treatments. Fiber quality characteristics in both cultivars were improved markedly but variably with different B treatments. Conclusion B nutrition with SB2 either alone or in combination with foliar spray was found optimum for improving cotton's growth and yield characteristics.

Cotton(Gossypium spp.) contributes significantly to the economy of cotton-producing countries. Pakistan is the fourth-largest producer of cotton after China, the USA and India. The average yield of cotton is about 570.99 kg.hm~(-2) in Pakistan. Climate change and different biotic stresses are causing reduction in cotton production.Transgenic approaches have unique advantage to tackle all these problems. However, how to confer permanent resistance in cotton against insects through genetic modification, is still a big challenge to address. Development of transgenic cotton has been proven to be effective. But its effectiveness depends upon several factors, including heterogeneity, seed purity, diffusion of varieties, backcrossing and ethical concerns. Cotton biotechnology was initiated in Pakistan in 1992–1993 with a focus on acquiring cotton leaf curl virus(CLCuV)-resistant insect-resistant,and improving fiber quality. This review summarizes the use of molecular markers, QTLs, GWAS, and gene cloning for cotton germplasm improvement, particularly in Pakistan.

Background:Cotton is a valuable economic crop and the main significant source of natural fiber for textile industries globally.The effects of drought and salt stress pose a challenge to strong fiber and large-scale production due to the ever-changing climatic conditions.However,plants have evolved a number of survival strategies,among them is the induction of various stress-responsive genes such as the ribosomal protein large(RPL) gene.The RPL gene families encode critical proteins,which alleviate the effects of drought and salt stress in plants.In this study,comprehensive and functional analysis of the cotton RPL genes was carried out under drought and salt stresses.Results:Based on the genome-wide evaluation,26,8,and 5 proteins containing the RPL14 B domain were identified in Gossypiumhirsutum,G.raimondii,and G.arboreum,respectively.Furthermore,through bioinformatics analysis,key cis-regulatory elements related to RPL 148 genes were discovered.The Myb binding sites(MBS),abscisic acid-responsive element(ABRE),CAAT-box,TATA box,TGACG-motif,and CGTCA-motif responsive to methyl jasmonate,as well as the TCA-motif responsive to salicylic acid,were identified.Expression analysis revealed a key gene,Gh_D01G0234(RPL14B),with significantly higher induction levels was further evaluated through a reverse genetic approach.The knockdown of Gh_D01G0234(RPL14B) significantly affected the performance of cotton seedlings under drought/salt stress conditions,as evidenced by a substantial reduction in various morphological and physiological traits.Moreover,the level of the antioxidant enzyme was significantly reduced in VIGS-plants,while oxidant enzyme levels increased significantly,as demonstrated by the higher malondialdehyde concentration level.Conclusion:The results revealed the potential role of the RPL 148 gene in promoting the induction of antioxidant enzymes,which are key in oxidizing the various oxidants.The key pathways need to be investigated and even as we exploit these genes in the developing of more stress-resilient cotton germplasms.

The nitrogen(N) requirements of cotton are well understood and have been extensively studied since 1887, with practical guides, decision support systems, models and recent reviews providing information on the importance of providing cotton crops with a sufficient supply of nutrients and improving nitrogen use efficiency. Given that the financial return to the grower depends on both the cotton quantity and quality and the growing importance of the latter, this review focusses specifically on information and knowledge about the e ect of nitrogen application level on fibre quality.

Verticillium wilt is one of the most important diseases a ecting cotton production in China. The fungus, Verticillium dahliae, has a wide host range and a high degree of genetic variability. No resistance resources have been found in the available planting resources, thus presenting di culties and challenges for our study. The long-term production practice shows that selection of disease-resistant varieties is the most economical and e ective measure to control Verticillium wilt of cotton to reduce the yield loss and quality decline of cotton. In this paper, we summarized the genetic mapping population, the analysis method of genetic localization, the discovery, mining and cloning of disease-resistant quantitative trait loci/markers, and the analysis of their genetic functions, so as to provide information for the molecular breeding approach of disease-resistant cotton.

Background: Salt stress significantly inhibits the growth, development, and productivity of cotton because of osmotic, ionic, and oxidative stresses. Therefore, the screening and development of salt tolerant cotton cultivars is a key issue towards sustainable agriculture. This study subjected 11 upland cotton genotypes at the seedling growth stage to five different salt concentrations and evaluated their salt tolerance and reliable traits.Results: Several morpho-physiological traits were measured after 10 days of salinity treatment and the salt tolerance performance varied significantly among the tested cotton genotypes. The optimal Na Cl concentration for the evaluation of salt tolerance was 200 mmol·L-1. Membership function value and salt tolerance index were used to identify the most consistent salt tolerance traits. Leaf relative water content and photosynthesis were identified as reliable indicators for salt tolerance at the seedling stage. All considered traits related to salt tolerance indices were significantly and positively correlated with each other except for malondialdehyde. Cluster heat map analysis based on the morpho-physiological salt tolerance-indices clearly discriminated the 11 cotton genotypes into three different salt tolerance clusters. Cluster I represented the salt-tolerant genotypes(Z9807, Z0228, and Z7526) whereas clusters II(Z0710, Z7514, Z1910, and Z7516) and III(Z0102, Z7780, Z9648, and Z9612) represented moderately salttolerant and salt-sensitive genotypes, respectively.Conclusions: A hydroponic screening system was established. Leaf relative water content and photosynthesis were identified as two reliable traits that adequately represented the salt tolerance of cotton genotypes at the seedling growth stage. Furthermore, three salt-tolerant genotypes were identified, which might be used as genetic resources for the salt-tolerance breeding of cotton.

Light attenuation within a row of crops such as cotton is influenced by canopy architecture,which is defined by size,shape and orientation of shoot components.Level of light interception causes an array of morpho-anatomical,physiological and biochemical changes.Physiological determinants of growth include light interception,light use efficiency,dry matter accumulation,duration of growth and dry matter partitioning.Maximum light utilization in cotton production can be attained by adopting cultural practices that yields optimum plant populations as they affect canopy arrangement by modifying the plant canopy components.This paper highlights the extent to which spatial arrangement and density affect light interception in cotton crops.The cotton crop branches tend to grow into the inter-row space to avoid shade.The modification of canopy components suggests a shade avoidance and competition for light.Maximum leaf area index is obtained especially at flowering stage with higher populations which depicts better yields in cotton production.

Background: Salinity is a major abiotic stress to global agriculture which hampers crop growth and development, and eventually reduces yield. Transgenic technology is an e ective and e cient approach to improve crop salt tolerance but depending on the availability of e ective genes. We previously isolated Salt Tolerance5(ThST5) from the halophyte Thellungiella halophila, an ortholog of Arabidopsis SPT4-2 which encodes a transcription elongation factor. However, SPT4-2-confered salt tolerance has not been evaluated in crops yet. Here we report the evaluation of Th ST5-conferred salt tolerance in cotton(Gossypium hirsutum L.).Results: The ThST5 overexpression transgenic cotton plants displayed enhanced tolerance to salt stress during seed germination and seedling stage compared with wild type. Particularly, the transgenic plants showed improved salinity tolerance as well as yield under saline field conditions. Comparative transcriptomic analysis showed that ThST5 improved salt tolerance of transgenic cotton mainly by maintaining ion homeostasis. In addition, ThST5 also orchestrated the expression of genes encoding antioxidants and salt-responsive transcription factors.Conclusion: Our results demonstrate that ThST5 is a promising candidate to improve salt tolerance in cotton.

Background: The worldwide pest Aphis gossypii has three-winged morphs in its life cycle, namely, winged parthenogenetic female(WPF), winged gynopara(GP), and winged male, which are all produced by a wingless parthenogenetic female(WLPF). Most studies on A. gossypii have focused on WPF, while few have investigated GP and male. The shared molecular mechanism underlying the wing differentiation in the three wing morphs of A.gossypii remains unknown. The wing differentiation of WPF was explored in a previous study. Herein, GP and male were induced indoors. The characters of the body, internal genitals, wing veins, and fecundity of GP and male were compared with those of WPF or WLPF. Compared with WLPF, the shared and separate differentially expressed genes(DEGs) were identified in these three-wing morphs.Results: Newly-born nymphs reared in short photoperiod condition(8 L:16 D, 18 °C) exclusively produced gynoparae(GPe) and males in adulthood successively, in which the sex ratio was GP biased. A total of 14 GPe and9 males were produced by one mother aphid. Compared with WLPF, the three-wing morphs exhibited similar morphology and wing vein patterns but were obviously discriminated in the length of fore-and underwings,reproductive system, and fecundity. A total of 37 090 annotated unigenes were obtained from libraries constructed using the four morphs via RNA sequencing(RNA-Seq). In addition, 10 867 and 19 334 DEGs were identified in the pairwise comparison of GP versus WLPF and male versus WLPF, respectively. Compared with WLPF, the winged morphs demonstrated 2 335 shared DEGs(1 658 upregulated and 677 downregulated). The 1 658 shared upregulated DEGs were enriched in multiple signaling pathways, including insulin, FoxO, MAPK, starch and sucrose metabolism, fatty acid biosynthesis, and degradation, suggesting their key roles in the regulation of wing plasticity in the cotton aphid. Forty-four genes that spanned the range of differential expression were chosen to validate statistical analysis based on RNA-Seq through the reverse transcription quantitative real time polymerase chain reaction(RT-qPCR). The comparison concurred with the expression pattern(either up-or downregulated) and supported the accuracy and reliability of RNA-Seq. Finally, the potential roles of DEGs related to the insulin signaling pathway in wing dimorphism were discussed in the cotton aphid.Conclusions: The present study established an efficiently standardized protocol for GP and male induction in cotton aphid by transferring newly-born nymphs to short photoperiod conditions(8 L:16 D, 18 °C). The external morphological characters, especially wing vein patterns, were similar among WPFs, GPe, and males. However, their reproductive organs were strikingly different. Compared with WLPF, shared(2 335) and exclusively(1 470 in WLPF,2 419 in GP, 10 774 male) expressed genes were identified in the three-wing morphs through RNA-Seq, and several signaling pathways that are potentially involved in their wing differentiation were obtained, including insulin signaling, starch and sucrose metabolism.

Background: Cotton(Gossypium hirsutum L.) is often grown in locations characterized by high atmospheric evaporative demand. It has been hypothesized that plants which resist hydraulic flow under this condition will limit water use and conserve soil water. Therefore, in a series of controlled environment experiments ten cotton cultivars were exposed to two di erent temperature and vapor pressure deficit(VPD) conditions(i.e., 38 °C, > 3 kPa and 32 °C,1～1.5 kPa) as well as a progressive soil drying. Then, individual di erences in shoot hydraulic conductance(K_(shoot)) was measured using a hydraulic conductance flow meter(HCFM). Physiological parameters were reported included leaf area, dry leaf weight, stomatal conductance(gs), and water use e ciency coe cient(WUE_k).Results: Di erences were observed in K_(shoot) among cultivars under the 38 °C, > 3 kPa but not the 32 °C, 1～1.5 kPa environment. Under the 38 °C, > 3 kPa environment, correlations were found between K_(shoot), stomatal conductance(g_s), VPD breakpoint, WUE_k, total leaf area, dry leaf weight, fraction transpirable soil water(FTSW) threshold, and slope of TR decline after FTSW threshold.Conclusion: Results show that the ability of some cotton cultivars to restrict water loss under high evaporative demand through early stomatal closure is associated with the cultivars' K_(shoot). The K_(shoot) is influential in the limitation of TR trait under high temperature and VPD.

Background: The photosynthetic parameters of cotton plants may be modified by the timing of film removal during their growing period. This study was undertaken during 2015–2017 in Xinjiang, China, to determine to what extent the film mulching removal time, 1 and 10 days before the first irrigation and 1 day before the second irrigation after seedling emergence, influenced cotton's photosynthetic characteristics. The control group(CK) was film-mulched throughout the growth stages.Results: The results suggested the following:(1) Removing mulching-film within 50 days since seedling emergence had adverse effects on soil temperature and moisture.(2) Film-removal before the first or second irrigation after emergence improved the net photosynthetic rate in cotton's later flowering stage and its transpiration rate in mid and later flowering stages while enhancing the actual electron transport rate(ETR) and maximum electron transfer rate(ETRmax) between cotton photosystems I and II.(3) Film-removal treatment also increased cotton plants' tolerance to high irradiation after emergence, the trend was more pronounced in the early flowering stage in wetter years.(4) Leaf area index(LAI) of cotton was reduced in the film-removal treatment for which the least accumulation of dry matter occurred in a drought year(i.e., 2015).(5) Film removal caused a yield decrease in the dry year(2015), and the earlier the film was removed, the more seriously the yield decreased. Removing mulching film before the second irrigation could increase the yield of XLZ42 in the rainy year(2016) and the normal rainfall year(2017). Early film removal can increase the yield of XLZ45 in the rainy year(2016).Conclusions: Collectively, our study's experimental results indicate that applying mulch film removal at an appropriate,targeted time after seedling emergence had no adverse effects on soil moisture and temperature, and improved the photosynthetic performance of cotton, thus increased cotton yield and fiber quality, but no significant difference was reached.

Background: Cotton is the source of natural fibers globally, fulfilling 90% of the textile industry's requirements. However, fiber development is a complex biological process comprising four stages. Fiber develops from a single cell, and cell elongation is a vital process in fiber development. Therefore, it is pertinent to understand and exploit mechanisms underlying cell elongation during fiber development. A previous report about cell division control protein 42(CDC-42) with its key role in cell elongation in eukaryotes inspired us to explore its homologs Rho GTPases for understanding of cell elongation during cotton fiber development.Result: We classified 2 066 Rho proteins from 8 Gossypium species into 5 and 8 groups within A and D sub-genomes,respectively. Asymmetric evolution of Rho members was observed among five tetraploids. Population fixation statistics between two short and long fiber genotypes identified highly diverged regions encompassing 34 Rho genes in G. hirustum, and 31 of them were retained through further validation by genome wide association analysis(GWAS).Moreover, a weighted gene co-expression network characterized genome-wide expression patteren of Rho genes based on previously published transcriptome data. Twenty Rho genes from five modules were identified as hub genes which were potentially related to fiber development. Interaction networks of 5 Rho genes based on transcriptional abundance and gene ontology(GO) enrichment emphasized the involvement of Rho in cell wall biosynthesis, fatty acid elongation, and other biological processes.Conclusion: Our study characterized the Rho proteins in cotton, provided insights into the cell elongation of cotton fiber and potential application in cotton fiber improvement.

Cotton has enormous economic potential providing high-quality protein, oil, and fibre. A large increase in cotton output is necessary due to the world's changing climate and constantly expanding human population. In the past, conventional breeding techniques were used to introduce genes into superior cotton cultivars to increase production and to improve quality. The disadvantages of traditional breeding techniques are their time-consuming, reliance on genetic differences that are already present, and considerable backcrossing. To accomplish goals in a short amount of time, contemporary plant breeding techniques, in particular modern genome editing technologies (GETs), can be used. Numerous crop improvement initiatives have made use of GETs, such as zinc-finger nucleases, transcription-activator-like effector nucleases, clustered regularly interspaced palindromic repeats (CRISPR), and CRISPR-associated proteins systems (CRISPR/Cas)-based technologies. The CRISPR/Cas system has a lot of potential because it combines three qualities that other GETs lack: simplicity, competence, and adaptability. The CRISPR/Cas mechanism can be used to improve cotton tolerance to biotic and abiotic stresses, alter gene expression, and stack genes for critical features with little possibility of segregation. The transgene clean strategy improves CRISPR acceptability addressing regulatory issues associated with the genetically modified organisms (GMOs). The research opportunities for using the CRISPR/Cas system to address biotic and abiotic stresses, fibre quality, plant architecture and blooming, epigenetic changes, and gene stacking for commercially significant traits are highlighted in this article. Furthermore, challenges to use of CRISPR technology in cotton and its potential for the future are covered in detail.

Oxidative stress occurs when crop plants are exposed to extreme abiotic conditions that lead to the excessive production and accumulation of reactive oxygen species(ROS). Those extreme abiotic conditions or stresses include drought, high temperature, heavy metals, salinity, and ultraviolet radiation, and they cause yield and quality losses in crops. ROS are highly reactive species found in nature that can attack plant organelles, metabolites, and molecules by interrupting various metabolic pathways until cell death occurs. Plants have evolved defense mechanisms for the production of antioxidants to detoxify the ROS and to protect the plant against oxidative damage. Modern researches in crop plants revealed that low levels of ROS act as a signal which induces tolerance to environmental extremes by altering the expression of defensive genes. In this review, we summarized the processes involved in ROS production in response to several types of abiotic stress in cotton plants. Furthermore,we discussed the achievements in the understanding and improving oxidative stress tolerance in cotton in recent years. Researches related to plant oxidative stresses have shown excellent potential for the development of stresstolerant crops.

Cotton is the prime natural fiber with economic significance globally. Cotton farming and breeding have a long history in Pakistan. The development of high yielding upland cotton (Gossypium hirsutum) varieties gradually replaced the cultivation of diploid Gossypium species. Climate change along with emergence of new epidemic diseases caused yield loss in recent years. The biotic stress considerably reduced the performance and yield potential of cotton. Suitable breeding strategies are essential to generate useful genetic variations and to identify desired traits. Conventional breeding has remarkably increased cotton yield and fiber quality, which has cultivated the NIAB-78, S-12, MNH‐786, and FH‐Lalazar like cultivars. However, this phenotypic selection based breeding method has low efficiency to produce stress resilient cotton. The efficiency of traditional breeding has significantly improved by the marker assisted selection technology. Breakthroughs in molecular genetics, bioinformatics analysis, genetic engineering, and genome sequencing have opened new technique routes for cotton breeding. In addition, genetic improvement through quantitative trait loci, transcriptome, and CRISPR/Cas9 mediated genomic editing can provide suitable platform to improve the resistance to stresses induced by bollworms, cotton leaf curl virus, heat, drought, and salt. The approval of transgenic lines harboring triple gene Cry1Ac + Cry2A + GTG are critical for cotton crop. This review has critically discussed the progress and limitations of cotton breeding in Pakistan, and reviewed the utilization of novel genetic variations and selection tools for sustainable cotton production.

Background: Nitrogen(N) is a required macronutrient for cotton growth and productivity. Excessive N fertilizers are applied in agriculture for crop yield maximization, which also generates environmental pollution. Improving crop N use efficiency(NUE) is the most economical and desirable way of reducing fertilizer application and environmental pollution. NUE has been an important issue in cotton. So far there is no report on cotton NUE improvement via transgenic approach. Nin-like proteins(NLP) are transcription factors regulating NUE. We previously demonstrated that At NLP7 improved NUE and biomass when overexpressed in Arabidopsis. However, it is not known whether At NLP7 can be used to improve NUE in crops.Results: To test the feasibility, we expressed At NLP7 in cotton and evaluated NUE and yield of the transgenic cotton in the field. Transgenic cotton showed improved NUE and yield under both low and high N conditions. In addition, plant biomass, amount of absorbed N, N contents, activities of N-assimilating enzymes, and the expression of N-related marker genes were significantly increased in transgenic cotton compared with the wild type control, suggesting that At NLP7 enhances NUE in cotton.Conclusion: Together, our results demonstrate that At NLP7 is a promising candidate to improve NUE and yield in cotton.

Background Cotton seed fibres are long single-celled epidermal trichomes that first appear on the surface of the ovule at anthesis and then elongate rapidly over a period of 15–25 days until a secondary cell wall (SCW) begins to develop through a rapid increase in the deposition of microfibrillar cellulose between the plasma membrane and the primary cell wall that eventually terminates elongation. Quantitative measurements of the different polysaccharide components in both wall types over time and how they influence fibre quality can direct studies involved in enhancing fibre properties for yarn quality through cell wall manipulation or molecular breeding. Results A detailed chemical analysis of cell wall composition by differential solvent fractionation was used to identify the range of polysaccharides present in mature cotton fibres and used to validate a simpler total cell wall monosaccharide linkage analysis protocol for wall compositional analysis. Analysis of fibres from 5 days post-anthesis through maturity for three cultivated species, Gossypium hirsutum, G. barbadense, and G. arboreum, showed the dynamic nature of cell wall polysaccharide composition through fibre development and that it progressed differently for each species. Plants grown in the glasshouse during either autumn to winter or spring to summer and within each species had fibre qualities and temporal aspects of cell wall development that were different for each season. Notably, the timing of the deposition of the SCW was delayed in winter grown plants and appeared to influence key fibre quality properties. Conclusions These results suggest that the temporal aspects of cell wall polysaccharide biogenesis during fibre development influence final fibre quality, and this timing is determined by both genetic and environmental factors. The onset of SCW synthesis appears to be a critical factor coinciding with termination of fibre elongation and specifying the duration of wall thickening that then affects fibre length and other wall-associated quality parameters that ultimately determine yarn quality.

Background: The cotton crop is universally considered as protein and edible oil source besides the major contributor of natural fiber and is grown in tropical and subtropical regions around the world Unpredicted environmental stresses are becoming significant threats to sustainable cotton production, ultimately leading to a substantial irreversible economic loss. Mitogen-activated protein kinase(MAPK) is generally considered essential for recognizing environmental stresses through phosphorylating downstream signal pathways and plays a vital role in numerous biological processes.Results: We have identified 74 MAPK genes across cotton, 41 from G. hirsutum, 19 from G. raimondii, whereas 14 have been identified from G. arboreum. The MAPK gene-proteins have been further studied to determine their physicochemical characteristics and other essential features. In this perspective, characterization, phylogenetic relationship,chromosomal mapping, gene motif, cis-regulatory element, and subcellular localization were carried out. Based on phylogenetic analysis, the MAPK family in cotton is usually categorized as A, B, C, D, and E clade. According to the results of the phylogenic relationship, cotton has more MAPKS genes in Clade A than Clade B. The cis-elements identified were classified into five groups(hormone responsiveness, light responsiveness, stress responsiveness, cellular development, and binding site). The prevalence of such elements across the promoter region of these genes signifies their role in the growth and development of plants. Seven GHMAPK genes(GH＿A07G1527, GH＿D02G1138,GH＿D03G0121, GH＿D03G1517, GH＿D05G1003, GH＿D11G0040, and GH＿D12G2528) were selected, and specific tissue expression and profiling were performed across drought and salt stresses. Results expressed that six genes were upregulated under drought treatment except for GH＿D11G0040 which is downregulated. Whereas all the seven genes have been upregulated at various hours of salt stress treatment.Conclusions: RNA sequence and qPCR results showed that genes as di erentially expressed across both vegetative and reproductive plant parts. Similarly, the qPCR analysis showed that six genes had been upregulated substantially through drought treatment while all the seven genes were upregulated across salt treatments. The results of this study showed that cotton GHMPK3 genes play an important role in improving cotton resistance to drought and salt stresses. MAPKs are thought to play a significant regulatory function in plants' responses to abiotic stresses according to various studies. MAPKs' involvement in abiotic stress signaling and innovation is a key goal for crop species research, especially in crop breeding.

Cotton plants are not only the global crops integrating fiber, oil and protein (Hu et al. 2020; Xiao et al. 2017), but also the medicinal plants with potent application values, which were well described in the most complete and comprehensive medical book such as Compendium of Materia Medica and Chinese Materia Medica. Cotton extract has various activities such as stopping bleeding, relieving pain, removing phlegm, and curing chronic bronchitis. Different types of metabolites or defense compounds are produced in cotton plants, including the sesquiterpene aldehyde gossypol, the flavonoids gossypetin and gossypin, and the trisaccharide gossypose (Patel and Patel 2021; Tanyeli et al. 2020; Tian et al. 2018; Kouakou et al. 2009). These metabolites have a variety of pharmacological activities. For example, gossypol was inhibitive to breast cancer (Xiong et al. 2017), ovarian cancer (Qu and Wang 2017), prostate cancer (Akagunduz et al. 2010), and other, gossypose has immunomodulatory effects (Abdel-Latif et al. 2020), and gossypin has bactericidal activities (Chamundeeswari et al. 2007). However, partly due to the enormous interests as an economical crop for textile fiber, vegetable oil and feedstuff, the medicinal value of cotton metabolites has received much less attention, which holds, however, the hope to open up a new way for comprehensive utilization of cotton products.

Background:Cottonseed oil and protein content as well as germination traits are major indicators of seed quality.However,the responses of these indicators to plant density and mepiquat chloride(MC) are still uncertain.To investigate plant density and MC effects on cottonseed yield and main quality parameters,we conducted a twoyear field experiment including four plant densities(1.35,2.55,3.75 and 4.95 plants-m~(-2)) and two doses of MC(0 and135 g·hm~(-2)) in Dafeng,Jiangsu Province,in 2013 and 2014.Results:The application of MC reduced plant height,fruit branch length and fruiting branch number under different plant densities,resulting in a lower and more compact plant canopy.Cottonseed yield showed a nonlinear increase as plant density increasing and achieved the highest value at 3.75 plants·m-2,regardless of MC application.No significant interactions were found between plant density and MC for cottonseed yield and quality parameters.The 100-seed weight cottonseed oil content and vigor index significantly decreased as plant density increased,while these parameters significantly increased with MC applying under different plant densities.Seed vigor index was positively correlated with 100-seed weight and seed oil content across different plant densities and MC treatments.Conclusions:Thus,application of MC could realize a win-win situation between cottonseed yield and main quality parameters under various densities;and plant density of 3.75 plants-m~(-2) combined with 135 g·hm~(-2) of MC applying is optimal for high cottonseed yield and quality in this cotton production area.

Background: Cotton fibers are single-celled extensions of the seed epidermis, a model tissue for studying cytoskeleton. Tubulin genes play a critical role in synthesizing the microtubules(MT) as a core element of the cytoskeleton. However, there is a lack of studies concerning the systematic characterization of the tubulin gene family in cotton. Therefore, the identification and portrayal of G. hirsutum tubulin genes can provide key targets for molecular manipulation in cotton breeding.Result: In this study, we investigated all tubulin genes from different plant species and identified 98 tubulin genes in G. hirsutum. Phylogenetic analysis showed that tubulin family genes were classified into three subfamilies. The protein motifs and gene structure of α-, β-tubulin genes are more conserved compared with γ-tubulin genes. Most tubulin genes are located at the proximate ends of the chromosomes. Spatiotemporal expression pattern by transcriptome and q RT-PCR analysis revealed that 12 α-tubulin and 7 β-tubulin genes are specifically expressed during different fiber development stages. However, Gh.A03 G027200, Gh.D03 G169300, and Gh.A11 G258900 had differential expression patterns at distinct stages of fiber development in varieties J02508 and ZRI015.Conclusion: In this study, the evolutionary analysis showed that the tubulin genes were divided into three clades.The genetic structures and molecular functions were highly conserved in different plants. Three candidate genes,Gh.A03 G027200, Gh.D03 G169300, and Gh.A11 G258900 may play a key role during fiber development complementing fiber length and strength.

Background: An optimal N rate is one of the basic determinants for high cotton yield. The purpose of this study was to determine the optimal N rate on a new cotton cropping pattern with late-sowing, high density and onetime fertilization at the first flower period in Yangtze River Valley, China. A 2-year experiment was conducted in2015 and 2016 with a randomized complete block design. The cotton growth process, yield, and biomass accumulation were examined.Results: The results showed that N rates had no effect on cotton growing progress or periods. Cotton yield was increased with N rates increasing from 120 to 180 kg·hm~(-2), while the yield was not increased when the N rate was beyond 180 kg·hm~(-2), or even decreased(9~29%). Cotton had the highest biomass at the N rate of 180 kg·hm~(-2) is due to its highest accumulation speed during the fast accumulation period.Conclusions: The result suggests that the N rate for cotton could be reduced further to be 180 kg·hm~(-2) under the new cropping pattern in the Yangtze River Valley, China.

Background: Aphis gossypii Glover(Hemiptera: Aphididae), a worldwide polyphagous phloem-feeding agricultural pest, has three wing morphs(winged parthenogenetic female, gynopara, and male) in the life cycle. The exclusive males could fly from summer hosts to winter hosts, which are essential for gene exchanges of cotton aphid populations from di erent hosts or regions. However, the molecular mechanism of wing di erentiation of male in A. gossypii remains unclear.Results: Morphological observation of male A. gossypii showed that there is no distinct di erence in the external morphologies of the 1st and 2nd instar nymphs. The obvious di erentiation of wing buds started in the 3rd instar nymph and was visible via naked eyes in the 4th instar nymphal stage, then adult male emerged with full wings.According to morphological dynamic changes, the development of wings in males were divided into four stages:preliminary stage(the 1st instar to 2nd instar), prophase(the 3rd instar), metaphase(the 4th instar), anaphase(the 5th instar). Results of feeding behavior monitoring via EPG(electrical penetration graph) technology indicated that although the male cotton aphids had strong desire to feed(longer duration of C 55.24%, F 5.05% and Pd waves 2.56%), its feeding e ciency to summer host cotton was low(shorter E1 3.56% and E2 waves 2.63%). Dynamic transcriptome analysis of male aphid at 5 di erent developmental periods showed that in the 3rd instar nymph, the number of up-regulated DEGs was significant increased, and time-course gene transcriptional pattern analyses results also showed that numerous genes categorized in clusters 3, 5, and 8 had the highest expressed levels, which were consistent with morphological changes of wing buds. These results indicate that the 3rd instar nymph is the critical stage of wing bud di erentiation in males. Furthermore, through pathway enrichment analysis of DEGs and WGCNA,it revealed that the neuroactive ligand-receptor interaction, Ras signaling pathway, dopaminergic synapse, circadian entrainment and the corresponding hub genes of PLK1, BUB1, SMC2, TUBG, ASPM, the kinesin family members(KIF23,KIF20, KIF18-19) and the novel subfamily of serine/threonine(Aurora kinase A and Aurora kinase B) probably played an important role in the critical stage of wing bud di erentiation.Conclusion: This study explored morphological changes and genes transcriptional dynamics males in cotton aphid, revealed the phenomenon of low feeding e ciency of winged males on summer host cotton, and identified key signaling pathways and potential hub genes potentially involved in wing bud di erentiation of male in A. gossypii.