With the development of cotton genomics and transcriptomics, cotton genetics and breeding would be enhanced by the identification of differentially expressed genes and the development of molecular makers based on candidate genes. The salt-tolerant cotton variety Miscott 7913-83 and salt-sensitive variety Su 12 were used as experimental materials in this study. RNA samples prepared from the roots and leaves of the two cultivars were pooled for transcriptome sequencing. Variations in gene expression were then examined after exposing the plants to 200 mmol·L^－1 NaCl for 12 and 72 h. A total of 3232 differentially expressed genes were then examined between Miscott 7913-83 and Su 12, and functional molecular markers such as EST-SSR and EST-InDel were designed by informatics tools according to differentially expressed gene sequences. Some SSR and InDel primers were randomly selected and further confirmed the accuracy. This research provides efficient methods for the rapid development of polymorphic markers in cotton. By focusing on functional molecular markers associated with salt tolerance, this should aid the improvement of salt tolerance by marker-assisted selection in upland cotton.

The expression changes of transcriptome of tender leaves of Z12/Z12YW were analyzed by RNA-Seq to reveal the molecular mechanism of gland formation. Z12/Z12YW are cotton near-isogenic lines with a common genetic background but contrasting a gland phenotype. A total of 306 differentially expressed genes were uncovered, of which 282 were down-regulated and 24 were up-regulated in the glandless material Z12YW. Gene Ontology functional annotation showed that the cell part, the extracellular matrix part and the cell killing played important roles in the process of gland development. Clustering of Orthologous groups and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that the upstream key genes of the mevalonate pathway had a great influence on the biosynthesis of gossypol and other terpene compounds. In addition, we screened 13 transcription factors with different expression levels, which might display key function in gland formation and gossypol biosynthesis.

Twenty-three Xincaimian cotton cultivars as authorized until 2012 were used as materials in the construction of DNA fingerprinting and analysis of genetic diversity with simple sequence repeat(SSR) markers. Fifty-two primer pairs with high polymorphism, good repeatability, and even distribution on the 26 chromosomes were screened out from 5000 pairs of SSR primers to genotype the 23 cultivars. A total of 47 SSR primer pairs were polymorphic and generated 162 polymorphic loci among the 23 cultivars; each marker detected 2-7 polymorphic loci with an average of 3.45; the polymorphism information content ranged from 0.4537 to 0.8686, with an average of 0.7096. The results showed that there 14 cultivars could be differentiated by specific or characteristic primer, the rest 9 cultivars could be identified by primer combinations. In the end, 18 specific or characteristic and primer combinations could completely differentiate the 23 Xincaimian cotton cultivars from each other. DNA fingerprinting of Xincaimian 1 to Xincaimian 23 were constructed with 18 pairs of SSR markers. NTSYSpc v2.10 software was used to analyze genetic diversity of the 23 cultivars; the results indicated that genetic similarity coefficient of the 23 cultivars ranged from 0.3781 to 0.9298 with an average of 0.5511, which showed that there was abundant genetic diversity in Xincaimian cotton varieties.

Cotton whole genome SNP (Single nucleotide polymorphism) markers were evaluated and screened across representative cotton materials, with the aim of obtaining an appropriate set of core SNP markers suitable for high-throughput identification of cotton hybrid purity based on KASP (Kompetitive allele specific PCR) technology. 5474 and 1850 single-copy SNP markers were screened out of a 63K SNP array with reference to two TM-1 genome versions (Institute of Cotton Research of the Chinese Academy of Agricultural Sciences version; Nanjing Agriculture University version), respectively. A set of 26 pairs of core SNP markers (one marker per chromosome) was achieved in view of polymorphism, genotyping quality, and homozygous and heterozygosis rates. The set of core SNP loci were then converted to KASP markers using Kraken^TM software. Genotyping assays of the KASP markers set were then performed on the SNPline platform. High-throughput genotyping assays of large numbers of samples were achieved, especially for the rapid purity tests.

The TCP gene family encodes a specific type of plant transcription factors that are involved extensively in plant growth, development, and the signal transduction pathways of many physiological and biochemical responses. However, limited information is available about cotton TCP genes. Thirty-seven TCP genes were identified from the diploid cotton Gossypium arboreum (A2) and G. raimondii (D5) genome databases. According to the conserved motifs defined in Arabidopsis thaliana L., the protein structure and conserved sequences of each TCP motif were analyzed. We also analyzed the phylogenetic relationship and subcellular localization of the identified gene sequences. Structural analysis revealed that most TCP genes had simple structures and did not contain introns. The putative proteins of these genes contained highly conserved TCP structural domains and shared similar motifs. These proteins could be classified into two subfamilies according to their structure and phylogenic relationships. These results provide a basis for the further study of cotton TCP transcription factors.

The Zinc finger-homeodomain (ZF-HD) protein family of homeobox genes plays a vital role during the development processes of plants and animals. The number, subcellular localization, chromosome distribution, motif, evolutionary relationships and tissue-expression patterns of the ZF-HD protein family were studied in the genome of Gossypium hirsutum L. acc. 'TM-1' using bioinformatics methods. In total, 35 GhZHD genes were identified in the 'TM-1' genome, and a majority of the members are located in nucleus. The family members were distributed on 20 chromosomes and two scaffolds, and 11 pairs were orthologous genes. The family could be divided into six groups based on the phylogenetic analysis, and there were similar motif types and arrangements in each group. Most GhZHD genes were expressed in ovules and fibers, some were expressed in roots, stems, buds and flowers, and a fraction were expressed in leaves and calli.

[Objective] The glycosylphosphatidylinositol-anchored lipid transfer protein (LTPG) genes were identified from the whole genome of Gossypium hirsutum to provide support for subsequent research. [Method] Bioinformatics methods were used to screen and identify the LTPG gene family from the TM-1 genome, and the physicochemical properties of proteins, phylogenetic relationship, gene duplication, gene structure, and cis-acting elements in the promoter region were predicted and analyzed. Transcriptome data and real-time quantitative polymerase chain reaction (qRT-PCR) were used to analyze their expression pattern in different tissues and organs and under different abiotic stresses. The subcellular localization of the target proteins was identified by transient transformation in tobacco leaves. [Result] Ninety-five GhLTPG genes were identified in the G. hirsutum genome, which were clustered into 5 categories by phylogenetic tree analysis. Segment duplication is the main reason for the expansion of the GhLTPG gene family. K_a/K_s analysis indicated that GhLTPG underwent strong purification selection. Transcriptome data analysis showed that some GhLTPG responded to low temperature, high temperature, salt, or drought stress. The results of qRT-PCR analysis showed that GhLTPG11/14/52/62 responded to low temperature, high temperature, salt and drought stress, and GhLTPG24/56 responded to low temperature, salt, or drought stress. Subcellular localization experiments showed that both GhLTPG24 and GhLTPG62 were localized in the cell membrane. [Conclusion] Ninety-five GhLTPG genes were identified in the whole genome of G. hirsutum. Some GhLTPG genes responded to abiotic stresses such as low temperature, high temperature, salt and drought, which laid a foundation for in-depth analysis of the function of specific GhLTPG gene.

[Objective] The purpose of this study was to evaluate the selection and pyramiding effects of quantitative trait loci (QTL) related to fiber length and fiber strength through molecular marker-assisted selections using populations of chromosome segment substitution lines (CSSLs) from Gossypium hirsutum × G. barbadense. [Method] In this study, CSSL MBI7561 with excellent fiber quality selected from BC₄F_3:5 of CCRI 45 (G. hirsutum) × Hai 1 (G. barbadense) was used to construct the secondary segregating populations of two generations BC₅F₂ and BC₅F_2:3. Then two populations (BC₆F₂ and BC₆F_2:3) were obtained through backcrossing with the recurrent parents and selfing. Four simple sequence repeat markers, CGR6894a, PGML02608, NAU5408 and NAU3594, linked to three major QTL for fiber length (qFL-16-1, qFL-16-4, qFL-16-5) and three major QTL for fiber strength (qFS-16-1, qFS-16-4 and qFS-16-5) on chromosome 16, were used to screen individuals of BC₆F₂ and BC₆F_2:3. [Result] Four markers related to qFL-16-1, qFL-16-4, qFL-16-5, qFS-16-1, qFS-16-4 and qFS-16-5 indicated obvious and significant single marker selection effect and pairwise marker pyramiding effect for fiber length and fiber strength in the two populations of BC₆F₂ and BC₆F_2:3. Furthermore, the excellent individual which contain more than two QTL was screened. [Conclusion] The analyzed QTL related to fiber length and fiber strength on chromosome 16 had significant genetic effects in different generations of the CSSLs, and the fiber length and fiber strength of individuals were significantly increased by pyramiding two QTL. This study laid an important foundation for molecular marker to assist the pyramiding selection of fiber length and strength.

Crop maturity is the comprehensive performance reflection of crop growth, development and maturation. It is usually expressed by the growth period or life cycle from seedling emergence to harvest. It is also a critical indicator of crop ecological adaptability. The selection of cotton varieties with appropriate maturity is an important prerequisite to ensure normal maturity, high yield, superior fiber quality, and timely harvest. Accurate evaluation of cotton crop maturity is an important basis for cotton cultivation management and genetic improvement. Due to the indeterminate growth characteristic of cotton, the evaluation of cotton crop maturity is complicated, and there are still controversies so far. This manuscript clarifies the concept of cotton crop maturity, and discusses its main influencing factors (genetic factors, environmental factors, and cultivation measures), and reviews predictors and methods used for cotton crop maturity evaluation based on growth characteristics (the first fruit branch node, fruit branch occurrence speed and flowering time interval, pre-frost seed cotton rate, etc.), growth process (growth period, physiological termination period, the number of fruit branches above cracked boll, early maturity index, etc.) and the comprehensive index. In the end, the following suggestions have been given: enhancing the innovation of evaluation predictors for cotton crop maturity, establishment of the evaluation system for cotton crop maturity, and creation of an innovative information collection system, which will provide theoretical and technical support for cotton simplified and mechanized production.

[Objective] The purpose of this study is to study the influence of cotton-wheat cropping modes on yield and cotton maturity in the Yellow River Basin, to provide technical support for the whole-process mechanization management under the machine-harvested cotton mode. [Method] The experiments were carried out in Anyang, Henan in 2017/2018 and 2018/2019 seasons including 6 treatments with 2 cotton varieties (ZM50, ZM79) and 3 cropping modes, W6C2 (6 rows wheat and 2 rows cotton), W3C1 (3 rows wheat and 1 row cotton) and W2C1 (2 rows wheat and 1 row cotton) under the machine-harvested cotton row space (76 cm) cultivation. Some key indexes such as the wheat yield and side effects, and cotton biomass accumulation, the time distribution of cotton bolls, percentage of seed-cotton yield before frost, and fiber quality were compared and analyzed. [Result] The wheat yield was significantly higher in the mode W3C1 than the mode W2C1 and W6C2 by 16.2%-43.3% and 28.4%-52.3% respectively; the number of effective panicles significantly increased by 29.2%-47.5% and 34.9%-53.6%, respectively; however, the indexes such as wheat yield(2019) and effective panicles per hectare(2018) of W3C1 were significantly lower than W6C2. No significant differences in fiber length, breaking tenacity, and micronaire were found among different cropping modes. There was no significant difference in the seed cotton yield and harvest index(HI) of ZM50 under different modes，while the seed cotton yield and HI of ZM79 in the mode W3C1 in 2018 was lower than that in W6C2 and W2C1. Under W3C1 mode, short season cotton ZM50, compared with ZM79, showed an earlier maturity performance, such as a lower node/branch ratio, and faster reproductive growth, higher ratio of the middle season bolls between July 16 and August 15, lower cotton boll shell ratio, and higher percentage of seed-cotton yield before frost by 38.7%-54.2%; moreover, land equivalent ratio (LER) of this mode is over 1.689-1.697, significantly higher than other modes. [Conclusion] It is suggested that under the machine-harvested cotton row space in the Yellow River Basin, adopting the short-season cotton ZM50 and mode W3C1 can obtain a higher LER and percentage of seed-cotton yield before frost, and is conducive to increasing crop uniformity and yield of wheat. So, taking this configuration for wheat-cotton cropping in the Yellow River Basin is helpful to improve the mechanized management level of the crops and the planting benefit.

In this study, F₂ populations from two chromosome segment substitution lines MBI7455 and MBI7358, were quantified using SSR to evaluate the parents' genotype and detect QTL related to fiber quality plus yield traits of cotton. Results show that the recurrent parent (CCRI45) hosted 96.70% and 95.60% of chromosome segment substitution in MBI7455 with 12 chromosome segments and in MBI7358 with 16 chromosome substitution segments of Gossypium barbadense, respectively. In the F₂ population, the average rate of chromosome substitution of the recurrent parent (CCRI45) was 96.44%, and the average segments of chromosome substitution of Gossypium barbadense was 13.42, with an average segments of homozygous donor chromosome value of 3.90. Analysis showed 19 fiber quality-related QTL with a phenotypic variance of between 2.52%-13.11% and seven yield traits-related QTL with a range of 2.93%-11.40% phenotypic variance, resulting in a total of 26 QTL. The CSSLs could be used to detect QTL for fiber yield and quality traits, which offer an important foundation for the cotton molecular-assisted breeding.

[Objective] This study aims to investigate the regulatory effect of "fertigation adjusted water management" on the physiology and the growth of drip-irrigated cotton in alleviating drought stress, and to enhance cotton yield under limited water resource. [Methods] Using Zhongmian 619 as the test material, two types of irrigation quotas for deficient irrigation (W1: 45 mm) and full irrigation (W2: 54 mm) in combination of three nitrogen input doses, including low nitrogen (F1: 150 kg·hm^-2), medium nitrogen (F2: 225 kg·hm^-2), and high nitrogen (F3: 300 kg·hm^-2) were set. The effects of different irrigation quotas and nitrogen doses on cotton physiological growth indicators and seed cotton yield were analyzed. [Results] The results indicated that increased irrigation quotas promoted cotton growth, enhanced two-year average leaf area index (LAI), relative chlorophyll content (soil and plant analyzer development, SPAD value), and net photosynthetic rate (P_n), while redued the activities of cotton superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and malondialdehyde (MDA) content. With the increase of nitrogen application, LAI, SPAD, P_n, and antioxidant enzyme activity were increased, MDA content was decreased on average, and the influence of water deficiency on cotton development was alleviated. Under W1 treatment, increased nitrogen application improved cotton yield, while under W2 treatment, cotton yield showed the trend of increasing first and then decreasing with the increase of nitrogen application. Under water-nitrogen interaction, the highest two-year average seed cotton yield (6 821.86 kg·hm^-2) was recorded under W2F2 treatment followed by W1F3 treatment (6 717.72 kg·hm^-2). In the technique for order preference by similarity to ideal solution(TOPSIS) analysis, the comprehensive scores of W1F3 and W2F2 were 0.57 and 0.56, respectively, and the differences between the two-year yield of W1F3 and W2F2 treatments were not significant. [Conclusion] Increased nitrogen application under deficit irrigation effectively alleviates the adverse effects of drought on the physiological characteristics and yield in cotton. It is recommended to use 45 mm irrigation quota combined with 300 kg·hm^-2 nitrogen application as the fertigation strategy for the filmless drip-irrigated cotton in southern Xinjiang, to effectively ensure cotton yield under limited water resource.

Cotton Verticillium wilt caused by Verticillium dahliae Kleb. has become one of the main impediments to cotton sustainable production in China in recent years．This disease is a soil-borne and seed-borne vascular disease and difficult to control. The host range of V. dahliae is unusually wide as a plant pathogen．This paper summarized the latest research progresses of the pathogenicity differentiation, genome sequence, pathogenesis mechanism, microsclerotial development and germination mechanism of V. dahliae, molecular mechanism of disease resistance in cotton as well as the control methods of cotton Verticillium wilt．

[Objective] Screening the drought- or salt-resistant lines and measurement of key physiological and biochemical indexes for a set of monosomic alien addition lines (MAALs) derived from Gossypium anomalum in G. hirsutum background would provide the theory and material basis for drought and salt resistance breeding in cotton. [Method] The genotypes of all the MAALs were confirmed by chromosome-specific simple sequence repeat (SSR) markers of G. anomalum. The MAALs with drought or salt resistance potential was screened based on the phenotypic observation and related indexes measurement, and physiological and biochemical indexes were determined, including the content of hydrogen peroxide(H₂O₂), malondialdehyde (MDA), proline(PRO) and chlorophyll(SPAD value) and the activity of peroxidase(POD), catalase(CAT) and superoxide dismutase(SOD). [Result] The transmission rate of MAALs ranged from 34.66% to 51.50%. MAAL_1B, MAAL_5B, MAAL_7B, MAAL_8B, MAAL_11B, and MAAL_12B had drought resistance potential, while MAAL_4B, MAAL_6B, MAAL_8B, MAAL_9B, and MAAL_10B showed salt resistance potential. Under drought or salt stress, the content of MDA, H₂O₂ and PRO of all the tested plants increased compared with the control conditions, and the content of MDA and H₂O₂ of the recurrent parent G. hirsutum Su8289 was higher than that of MAALs with drought or salt resistance potential. The CAT and SOD activity in MAAL_1B, the CAT, SOD activity and PRO content in MAAL_5B, the SOD activity in MAAL_7B, the POD, CAT, SOD activity and SPAD value in MAAL_8B, the POD and CAT activity in MAAL_11B, and the CAT activity and SPAD value in MAAL_12B were significantly or extremely significantly higher than that in Su8289 at 10 days after drought treatment. Three days after 350 mmol·L^-1 NaCl treatment, the POD, SOD activity and SPAD value in MAAL_6B, the CAT activity in MAAL_8B, the POD and SOD activity in MAAL_9B, and the SOD activity and SPAD value in MAAL_10B were significantly or extremely significantly higher than that in Su8289. [Conclusion] Some MAALs had drought or salt resistance potential, and may respond to drought or salt stress through different physiological and biochemical process.

Cotton has obvious heterosis, which is manifested in traits including yield, fiber quality, and resistance to diseases and insects. Hybrid seed production is a very important step in the utilization of cotton heterosis. Recently, as the cost of manual pollination in seed production increases year by year, the simplified, efficient, and low-cost seed production techniques have become an inevitable trend for future hybrid cotton development. The field practice shows that the use of cytoplasmic male sterile lines not only simplify the procedure of seed production but also save labor costs, so it has become a research hotspot in the utilization of crop heterosis. However, the sterile cytoplasm does have certain impacts on cotton morphogenesis, anther development, yield formation, fiber development, and have negative effects on cotton growth and development, thereby limiting the further promotion and utilization of “three-line (male sterile line, maintainer line, and restoring line)” hybrid cotton. In this paper, the effects of male sterile cytoplasm on the main traits of cotton and the molecular basis for its negative effects were systematically reviewed. And the potential ways to overcome the negative effects of male sterile cytoplasm in cotton were preliminarily discussed, which would provide new ideas for breeding and improvement of cotton cytoplasmic male sterile restorer lines and excellent “three-line” hybrids in the future.

[Objective] This study aimed to map the fuzzless mutant (i.e., naked seed) gene n₂ in XZ142w cotton plants. [Method] An F₂ population of upland cotton (Gossypium hirsutum L.) was generated from a cross between XZ142 and the lintless-fuzzless mutant XZ142w. First, 108 simple sequence repeat (SSR) markers were used for mapping. High resolution melting (HRM) technology was then applied to screen 50 single nucleotide polymorphism (SNP) primer pairs designed based on a comparative transcriptomic analysis of the two parents. The SNP markers were used for genotyping. [Results] The n₂ gene was first mapped to a 20.2-cM region on chromosome 26 based on 108 SSR markers. Nine pairs of SNP markers from the HRM screening were used to genotype the F₂ progeny. Using the linkage map based on SSR markers, the genetic interval of n₂ was finally narrowed to a 19.5-cM region. At a genetic distance of 5.5 cM, the closest marker was Cricaas20158 (an SNP marker). The linkage map was mostly consistent with an in silico physical map based on a sequenced upland cotton genome. [Conclusion] The application of HRM technology is useful for detecting cotton SNPs and mapping the n₂ gene.

[Objective] The aim of this study was to clarify the role of host plant volatiles in the chemical communication of Lygus pratensis adults, and the effects of rapeseed (Brassica campestris L.) as a trap plant on the trapping and control in cotton fields, so as to provide basic informations for the development and ecological regulation of plant-derived attractors for the insect. [Method] Solid phase microextraction (SPME) and gas-mass spectrometry (GC-MS) were used to analyze and identify the volatiles of host plants. The electroantennography (EAG) and four-arm olfactory instrument were used to measure the EAG response and tendency behavior response of L. pratensis adult to selected volatiles. At the same time, cotton fields were planted with rapeseed attractor zone, and the populations of L. pratensis in the attractor zone and its adjacent cotton fields and control fields (without rapeseed cultivation) were investigated and analyzed. [Result] A total of 25 volatile compounds were identified in 5 species of host plants of L. pratensis, including 9 compounds were identified in Brassica napus, 9 in Chenopodium glaucum, 11 in Gossypium hirsutum L., 10 in Solanum nigrum and 6 in Portulaca oleracea. The EAG response of female L. pratensis to phenylacetaldehyde was the highest, and the attraction of phenylacetaldehyde and S-butyl isothiocyanate to female L. pratensis reached an extremely significant and significant level, respectively. The direct assay showed that rapeseed was more attractive to L. pratensis than other host plants. The rapeseed trapping zone in cotton field had a good trapping effect on L. pratensis, and the occurrence of L. pratensis in cotton field was significantly reduced. [Conclusion] The attraction of phenylacetaldehyde and S-butyl isothiocyanate to the female L. pratensis reached an extremely significant or significant level, which could be used as potential attractant candidates. The rapeseed trapping belt planted in cotton field has a good trapping effect on L. pratensis, which is an ideal trapping plant for L. pratensis.

To develop an expression system to study the function of the GhVP gene in cotton (Gossypium hirsutum), we successfully cloned GhVP and used it to construct a pBI121-GhVP∷GFP fluorescence expression vector. We transformed the vector into onion (Allium cepa) epidermal cells using gene gun technology and found that the GhVP protein was located on the cytomembrane. The pBI121-GhVP∷GFP vector was then transformed into cotton pollen. Detection of green fluorescence in the pollen indicated that the gene was successfully expressed from the pBI121-GhVP∷GFP vector. These results lay the foundation for the study of GhVP in cotton and the development of salt tolerance breeding.

【Objective] In this study, we examined the effect of row spacing and planting density on canopy structure and yield. [Method] Hybrid cotton Lumianyan 24 and conventional cotton Xinluzao 60 were used as materials for field experiments. Our experimental design consisted of three arrangements: a film of three lines with equal row spacing (76 cm+76 cm+76 cm) under low planting density, a film of six lines with wide-narrow row spacing (66 cm +10 cm) under high density, and a film of three lines with equal row spacing (76 cm+76 cm+76 cm) under high density. [Result] Cotton growth in a film of three lines with equal row spacing under low planting density was vigorous, with LAI and R_LI increasing rapidly and peaking at the early growth stage. Under this arrangement, the decrease intensity of LAI and R_LI were 10.4%-13.6% and 3.7%-4.2% lower than the other two treatments, respectively; this arrangement of hybrid cotton also exhibited the highest dry matter accumulation at the late growth stage and gave the highest yield at harvest. [Conclusion] Compared with the other two arrangements, hybrid cotton planted in equally spaced rows under low planting density conditions had the greatest dry matter accumulation in the late growth stage and gave the highest yields because LAI, R_LI and dry matter accumulation increased rapidly in the early growth stage, with photosynthetic efficiency accordingly increased by high LAI and R_LI.

A FT-like homolog was isolated from Gossypium hirsutum L. CV. Xinluzao 33 through RT-PCR and RACE, which was named GhFTL1 gene (accession number: HM631972). The 525-bp open reading frame encoded a putative protein of 174 amino acids with high similarity to FT proteins of different plants which contains two critical residues and conserved motif, both of which identified as diagnostic of true FT. GhFTL1 gene showed constitutive expression in root, stem, flower, leaf, fiber, and ovule. The levels of transcript in leaf and ovule were higher than that in other tissues. Phylogenetic analysis at the amino acid level confirmed that the isolated sequence is FT-like, and also showed that GhFTL1 had shorter genetic distance with MdFT1 compared with other 18 FT homologs confirmed to inducing early flowering from 13 different plants. Over-expression of GhFTL1 in Arabidopsis using the CaMV 35S promoter resulted in significant accelerated flowering compared with wild-type plants. Based on our results, we concluded that GhFTL1 was responsible for inducing flowering and may be one of important components for the flowering pathway in cotton.

[Objective] The unmanned aerial vehicle (UAV) multi-spectral remote sensing technology was used to monitor the severity of cotton Verticillium wilt, which will provide theoretical guidance for the precise prevention and control of cotton Verticillium wilt. [Method] By analyzing the spectral characteristics of canopy in cotton field affected by Verticillium wilt, the best vegetation index, the best wavelength combination and the best time phase for multi-spectral identification of Verticillium wilt by UAV were selected. The images of cotton fields differing in the severity of Verticillium wilt were established based on the optimal time phase. Parallelepiped method, maximum likelihood method and support vector machine radial basis function classification method were used to classify and evaluate the accuracy of the images. [Result] The results showed that the canopy spectral reflectance of cotton plants differing with occurrence of Verticillium wilt increased obviously with the increase of wavelength at 710-760 nm, the spectral reflectance of cotton canopy decreased obviously with the aggravation of Verticillium wilt at the wavelength of 760-950 nm. With the aggravation of Verticillium wilt, the chlorophyll content of leaves, fresh mass of aerial tissue per plant, dry mass of aerial tissue per plant, plant water content and leaf area index of cotton plants were all decreased. The best vegetation index and best band combination for UAV multi-spectral remote sensing to identify cotton Verticillium wilt were difference vegetation index (DVI) and B_3-5-8 (the corresponding wavelengths are 550 nm, 656 nm and 800 nm). Mid to late August was the best time to identify the occurrence degree of cotton Verticillium wilt by UAV multi-spectral remote sensing. Support vector machine radial basis function classification method, best band combination B_3-5-8 and DVI integrated image had the highest classification accuracy for Verticillium wilt in cotton field (classification accuracy was 96.64%, and Kappa coefficient was 95.61%). The classification results of Verticillium wilt severity in cotton fields corresponded to the changes in canopy spectral reflectance and agronomic parameters of cotton plants, and were consistent with the field investigation results. [Conclusion] It is feasible to classify the severity of Verticillium wilt in cotton field by using support vector machine radial basis function classification method, optimal band combination B_3-5-8 and DVI integrated images. The results can provide theoretical ground for monitoring similar crop pests and diseases by remote sensing technology.

Salinity stress is one of the major abiotic factors affecting the growth and productivity of cotton(Gossypium hirsutum L.). To further understand the possible mechanism of salt tolerance, an experiment was conducted to investigate the effect of salt stress on growth and K⁺/Na⁺ homeostasis of cotton seedlings using three cultivars(CCRI 49, CCRI 35 and Zhong 51504). We found that 150 mmol·L^－1 NaCl treatment significantly decreased biomass accumulation, photosynthesis rate(P_n), photochemical quenching(qP), photochemical quantum yield of photosystem (Φ_PSII) and electron transport rate(ETR), but significantly increased non-photochemical quenching coefficients(qN) in PSII. The biomass accumulation of Zhong 51504 was less affected by salt stress than CCRI 49 or CCRI 35, and Zhong 51504 also retained higher P_n, ΦP_SII, ETR and qN but lower ETR/P_n under saline conditions. Compared with the control, the salinity treatment caused a significant rise in Na⁺ concentration and decreased K⁺ concentration. The limited negative impact in Zhong 51504 derived from the lower content of Na⁺ and higher K⁺ in the tissues under salt stress. As expected, Zhong 51504 also retained a higher Na⁺/K⁺ ratio than other cultivars under salt treatment. Experiments of salt shock and long exposure to salt tested by the non-invasive ion flux measuring technique also revealed that Zhong 51504 not only had higher Na⁺ exclusion but also showed better K⁺ retention. Our results indicated that maintaining the K^+/Na⁺ homeostasis can contribute to genotypic differences in salinity tolerance under conditions of high salinity.

[Objective] Cadmium (Cd) is one of the serious environmental pollutants, and Cd stress affects seed germination. Melatonin (MT), as an antioxidant, and can promotes seed germination. In this study, the effects of MT on cotton seed germination, antioxidant activity, and osmotic adjustment content under Cd stress were analyzed to clarify the regulatory effect of MT on cotton seed germination under Cd stress. [Method] Seeds of the transgenic insect-resistant cotton variety Nongdamian 601 were used as material, Cd concentration and MT concentration were screened. And four treatments, CK (control, water), MT (melatonin treatment, 50 μmol·L^-1), Cd (cadmium stress 100 μmol·L^-1 treatment), CM (cadmium + melatonin treatment) were set. The germination potential, germination rate, seedling biomass, antioxidant enzyme activity, and osmotic adjustment content of cotton seed under different treatments were studied. [Result] Cd stress of 100 μmol·L^-1 significantly decreased the germination potential, the germination rate, the length of radicle and plumule, the fresh and dry mass of radicle, but had no significant effect on the fresh or dry mass of plumule. Under the stress of Cd, the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and soluble protein content of cotton seed were decreased. The content of proline, soluble sugar and malondialdehyde (MDA) were increased. Application of MT (50 μmol·L^-1) increased the germination potential and germination rate of cotton seed under Cd stress, the activity of SOD, POD and CAT, the content of soluble protein, soluble sugar and proline, while decreased the content of MDA, significantly increased the length of radicle and plumule, and significantly increased radicle biomass. [Conclusion] Exogenous MT (50 μmol·L^-1) could effectively alleviate the inhibitory effeet of Cd stress (100 μmol·L^-1) on cotton seed germination.

[Objective] This study aims to characterize the GhROP6 and study its roles of resistance to Verticillium wiltin upland cotton (Gossypium hirsutum L.). [Method] The bioinformatics analysis was used to identify Rho-related guanosine triphosphatase from plants (ROP) genes in upland cotton. The chromosome distributions, expression pattern analysis of GhROP genes were investigated. The function of GhROP6 gene was studied by quantitative real-time polymerase chain reaction (qRT-PCR), virus-induced gene silencing (VIGS), plant genetic transformation and metabolism analysis. [Result] Totally, 28 ROP genes were identified in upland cotton. And the corresponding amino acid sequence contained the ROP protein specific structures, including four GTP/GDP binding domains, effector domain binding to downstream target proteins and variable C-terminal regions. Chromosomal mapping analysis showed that 24 ROP genes were symmetrically distributed in subgenome A and subgenome D, and 3 genes specifically distributed in subgenome D. qRT-PCR analysis showed that the transcript levels of GhROP6 varied in different organs, and showed higher expression level in petals, stigma, fiber of 10 days post anthesis. Meanwhile, the transcript level of GhROP6 was upregulated in cotton by methyl jasmonate (MeJA). Knock-down of GhROP6 through VIGS weakened the cotton resistance to Verticillium wilt, and reduced the expression of GhLOX1, GhOPR3-1, GhOPR3-3, GhAOC1, GhAOS involved in jasmonic acid (JA) synthesis, and the expression of GhMYC2 involved in JA signaling pathway, and the expression of GhCCR-1, GhF5H-1, GhCCoAOMT-2, and GhCCoAOMT-3 genes involved in lignin synthesis. However, constitutively activated GhROP6 in Arabidopsis enhanced the plants resistantce to V. dahliae. Further analysis showed that the contents of JA-isoleucine and lignin in transgenic Arabidopsis were higher than those of wild type. [Conclusion] GhROP6 may involve in the resistance of cotton to Verticillium wilt through JA synthesis and signaling pathway and lignin synthesis.

Transcription factors play important regulatory roles in various stages of cotton fiber development, beginning with initiation and continuing through secondary cell wall synthesis and maturity. In recent years, many transcription factors related to cotton fiber development have been reported, including MYB, HD-ZIP, MADS, and TCP families. Among them, MYB transcription factors have been identified as essential proteins involved in this process. Arabidopsis trichome development, which has been well characterized at the molecular level, is regulated by a MYB-bHLH-WD40 protein complex. As several studies using cotton fiber-related genes have demonstrated a close relationship between cotton seed fibers and Arabidopsis leaf trichomes, cotton fiber development and Arabidopsis leaf trichome differentiation likely share similar regulatory mechanisms. MIXTA-like MYB genes such as GhMYB25 and GhMYB25-like also have significant regulatory roles in cotton fiber development. GL1-like MYB genes and MIXTA-like MYB genes most likely control cotton fiber development through different regulatory networks. Extensive research on transcription factors related to cotton fiber cells has provided insights into the molecular mechanisms of fiber cell differentiation and development. This paper discusses some achievements in this field.

[Objective] This study aimed to explore the optimal boll-setting period of summer direct seeding mode and suitable cultivars in the Yangtze River Valley by studying the relationship between the boll temporal distribution and yield of different cotton cultivars, so as to provide a theoretical basis for the promotion of this mode. [Method] The experiment was conducted in the farm of Huazhong Agricultural University in 2019 and 2020. A random block design was used with 3 cotton cultivars (JH116, ZD2040 and HM3097) from Southern region and 2 cultivars (Z425 and Z619) from Northern region. Plant-mapping was used to investigate boll temporal distribution; cotton growth stages, dry matter accumulation, yield and its components were also investigated. [Result] Under the summer direct seeding mode, the cotton growth period was about 90 in 2019. The peak squaring period is about 44-63 d after emergence, the peak boll-setting period is about 63-82 d after emergence, and the peak boll-opening period is about 92-118 d after emergence. In 2020, due to the high precipitation and the low temperature, cotton growth period was extended by 23-40 d, and the start time of rapid growth period of the number of buds, flowers and open bolls was delayed by 19 d, 17 d, and 34 d, respectively; seed cotton yield and lint yield decreased obviously. On average of the two years, the sink biomass and plant biomass of cultivar HM3097 at the plant removal stage were 9.6%-43.0% and 14.7%-54.3% higher than other cultivars, respectively, and its lint yield was 12.5%-22.6% higher than other cultivars. Correlation analysis showed that lint yield was significantly positively correlated with the initial time and the duration of rapid accumulation period of cotton boll number and sink dry matter accumulation. [Conclusion] Under summer direct seeding mode, the proportion of late summer bolls is the largest, followed by early autumn bolls. Cultivar HM3097 from Southern region is more suitable for cultivating in the Yangtze River Valley due to its better yield performance under different weather conditions.

[Objective] This study aims to monitor the chlorophyll content of cotton leaves by utilizing unmanned aerial vehicle (UAV)-based multispectral technology. [Methods] This study utilized multispectral images of cotton canopies obtained by UAV in southern Xinjiang and employed seven different machine learning methods to estimate the canopy chlorophyll content during the flowering and boll-setting stage which is the critical growth period of cotton. The seven methods include linear regression (LR)-based methods, i.e., simple linear regression, partial least squares regression (PLSR), ridge regression (RR), least absolute shrinkage and selection operator (LASSO) regression, support vector regression (SVR), K-nearest neighbors regression (KNNR), and random forest regression (RFR). [Results] The results showed that compared with the LR method, the RFR, SVR and KNNR can improve the accuracy of prediction model of chlorophyll content in cotton canopies, especially the RFR algorithm, which had the coefficient of determination of 0.742, root mean square error of 1.158 mg·L^-1, residual predictive deviation of 1.969 with the validation dataset. [Conclusion] The use of UAV-based multispectral images with the RFR machine learning method, exhibits the most outstanding performance to estimate the chlorophyll content of cotton leaves and provide essential technical support for precision management in cotton field.

[Objective] The study aims to examine the rhizosphere soil enzyme activity and bacterial community response to foliar application of 1,1-dimethyl-piperidinium chloride (DPC) and sodium nitroprusside (SNP) at the cotton seedling stage, and to screen rhizoshpere events potentially involved in cotton seedling growth. [Method] An upland cotton line A201 was grown in nursery trays under a controlled environment. The treatment with DPC of 50 mg·L^-1 and SNP of 500 μmol·L^-1, respectively, was foliar-applied at the one-leaf-one-heart stage, and the treatment with deionized water application was selected as the control. The rhizosphere soil was sampled to quantify the activities of sucrase, urease, catalase, and alkaline phosphate at the three-leaf-one-heart stage. The rhizosphere bacteria composition examined by 16S rRNA sequence analysis. [Result] The root growth, stem diameter, and dry mass of whole cotton plant were significantly increased by the DPC and SNP treatments. The activities of urease and sucrase were significantly improved by the DPC treatment. SNP application significantly enhanced sucrase activity but significantly decreased urease activity, while DPC treatment and SNP treatment had no significant effect on the activities of catalase and alkaline phosphatase. DPC application increased the relative abundance of Patescibacteria and Simpson's diversity index of soil bacterial community, but reduced the relative abundances of Chloroflexi and Acidobacteriota and Shannon Wiener’s diversity index of soil bacterial community. The results of redundancy analysis on family and genus level showed that the abundances of Saccharimonadaceae and TM7a were higher in the DPC treatment; the abundance of Cellvibrionaceae was greater in the SNP treatment; the abundance of Rhizobiaceae was greater in the DPC and SNP treatments. The control exhibited greater Nitrospiraceae and Nitrospira abundances compared with the DPC and SNP treatments. Urease activity was positively correlated with Saccharimonadaceae and TM7a relative abundances. [Conclusion] DPC and SNP could promote the growth of cotton roots and aerial parts, and influence the soil enzyme activity and bacterial community composition in the rhizosphere.

[Objective] A model for estimating the quantity of seedlings in drip-irrigated cotton using color characteristics and morphological characteristics of unmanned aerial vehicle (UAV) image data was constructed to provide a theoretical basis for accurate management in cotton field. [Methods] The experiment was carried out in 2020-2021 and the cultivar Lumianyan 24 was used in the experiment. Three different planting densities were set as follow: low density (D1, 6.9 × 10⁴ plant·hm^-2), medium density (D2, 13.8 × 10⁴ plant·hm^-2) and high density (D3, 24 × 10⁴ plant·hm^-2). The UAV images were obtained on the 25 days old cotton seedlings, and the vegetation indices (VIs) of red, green, and blue (RGB) and target morphological features were extracted from the acquired UAV images. Based on the selected independent variable according to the correlation analysis, the model to estimate the quantity of cotton seedlings was constructed using stepwise multiple regression, followed by the model validation. [Results] (1) Comparing the segmentation effects of extracting cotton targets by triangular greenness index (TGI), excess greenness index (ExG), and green-blue difference + modified excess greenness index (GBDI + MExG), all these three VIs had relatively good segmentation effects, while TGI showed the highest precision of segmentation of cotton targets. (2) Comparing the two cotton plant quantity estimation models constructed with the two feature parameters, the estimation model based on the target morphological features for cotton seedling (R²=0.935 5) is better than the estimation model based on the VI of RGB (R²=0.903 6). (3) The estimation accuracy of the VIs-based seedling quantity estimation model were 96.77%, 99.55%, and 95.95% at D1, D2 and D3 densities respectively, and the overall estimation accuracy was 98.47%; the estimation accuracy of the plant estimation model based on the target morphological features at D1, D2 and D3 densities were 99.98%, 99.21%, and 97.92% respectively, and the overall estimation accuracy was 99.21%. The accuracy of the plant number estimation model based on the target morphological characteristics was slightly higher than that of the plant number estimation model based on VIs, but both models had good estimation outcome under different planting densities. [Conclusion] Using the UAV based low-altitude remote sensing platform with the integration of high-resolution sensors, the quantity estimation models for the drip-irrigated cotton seedlings were constructed by color vegetation indices and morphological features of target plants. Both models can effectively and accurately identify and quantify the drip-irrigated cotton plants under mulching, providing technical support for subsequent precision management in cotton fields.

During the long process of evolution, plants have adapted to their environments through the biosynthesis of secondary metabolites (SM) using the acetate-malonate pathway, mevalonic acids pathway, or shikimic acid pathway, leading to resistance to different pests. As a major cash crop, cotton can produce many secondary metabolites with insecticidal activity, and show self-defense mechanisms under biotic stress conditions. These characteristics of cotton ensure reduced pest incidence and maintenance of ecological balance. This paper discusses the types of SMs, their synthesis, and insect resistance of cotton secondary metabolites in relation to their defense function. We propose possible pest-control strategies using secondary metabolites in cotton.

This research used the ASD Field Spec Pro VNIR 2500 high spectrometer at different growth stages for cotton canopy hyperspectral remote sensing data, and spectroscopic analysis of cotton canopy structure and the relationship between the spectral data were analysed, respectively. The results showed that obvious differences existed in cotton canopy reflectance among different species, densities, configurations and growing conditions of cotton.  Cotton canopy reflectance is closely related with chlorophyll content, leaf area, biomass and growth stage, the health conditions and factors such as phenology. Hyperspectral remote sensing technology is a fast, effective, non-contact, non-disruptive access to the information on the interpretation of the cotton canopy, cotton groups predict and the ideal designing of great significance.

Based on the dataset of planting area of individual cotton varieties released by National Extension and Service Center of Agricultural Technology in the past 40 years, the varieties with planting area ranking the first in the main cotton producing regions in one year, or with more than 0.33 million hm² planting area and ranking the top three in one or more years were defined as mega varieties. The cumulative planting area, the maximum annual area, the number of years with area ranking in top three, and the planting area percentage of the mega varieties were analyzed. Around forty-four cotton mega varieties were selected in the main cotton production regions (i.e. the Yellow River basin, the Yangtze River basin and the Northwest inland cotton production region) in the past 40 years, among of which the cultivar Lumianyan 15 was found to be a mega cultivar both in the Yellow River basin and the Yangtze River basin cotton production regions. The total number of cotton varieties applied in production every year was generally on the rise during 1981-2020. The increase step of variety number was slow during 1981-2000, but speeded up during 2001-2020. Meanwhile, the proportion of mega varieties planting area to the total area of main cotton producing regions in each year showed significant historical characteristics. The proportion was relatively stable during 1981-1995, with a proportion of around 61%, 36%, and 83% in the Yellow River basin, the Yangtze River basin and the Northwest inland cotton production regions respectively. After then, the area proportion of mega varieties suffered a sharp decline to about 20% on average during 1996-2006, and followed by a slow drop period to around 15% on average till 2020. Cotton mega varieties contributed greatly indeed to the stability and development of cotton production in the history. However, the cotton breeding target at current and also in the future will be more functional and regional oriented to meet the versatile needs of seed industry and market development.

Salinity is the major environmental factor limiting cotton germination and growth during the seedling period. To evaluate the potential of the phytotoxin coronatine (COR) for alleviating salt stress on cotton germination and seedling growth, hydroponic culture experiments were carried out using transgenic insect-resistant cotton(Gossypium hirsutum L, cv. CCRI 45) treated with NaCl and COR. We found that cotton germination and seedling growth were limited under high level salt stress (150 mmol·L^-1 NaCl), which increased the root/shoot ratio. The reduction in cotton biomass was alleviated by the application of COR (0.01 μmol·L^-1). An in situ histochemistry assay indicated that COR at low concentrations decreased H₂O₂ accumulation under induced salt stress. COR appears to have potential as a positive regulator for improving the salt tolerance of cotton.

[Objective] This research aimed to clarify the effect of farmland landscape patterns on the population dynamics of Lygus pratensis in cotton field, so as to provide a theoretical basis for the ecological control of L. pratensis. [Method] A total of 20 cotton fields in Aral Reclamation Area of Xinjiang were selected as experimental sites from 2019 to 2021. The methods of net trapping and sex attracter combined with yellow plate trapping were used to investigate the population dynamics of L. pratensis adults, and the land use status around the cotton field within a radius of 2 000 m was also investigated. A linear mixed model was fitted to the landscape parameters of farmland landscape patterns at 500 m, 1 000 m, 1 500 m and 2 000 m scales and the population number of the L. pratensis adults of the second- and third-generation. [Result] L. pratensis had 4 generations in Aral Reclamation Area every year, and the second and third generations were the main populations in cotton fields. At the four scales, host crop habitat (Host) accounted for the highest area (64.14%-69.85%), followed by single crop (Cotton) habitat (51.21%-55.26%), while the area ratio of forest belt and desolate sands habitat (FBDS), shrub habitat (Shrub), building land habitat (Building), other crop habitat (Other crops) and water habitat (Water) were relatively low. The results of model fitting showed that the control effect of landscape variables on the population number of the second-generation adults in the cotton field gradually weakened with the increase of the scale. There were extremely significant or significant positive correlation between the population number of the second-generation adults and the area ratio of Building (500 m scale) and FBDS (1 500 m scale), and a strong and extremely significant negative correlation between the population number of the second-generation adults and the area ratio of Host (1 000 m scale). There was a strong and extremely significant positive correlation between the population number of the third-generation adults of L. pratensis and the area ratio of Building (500 m scale). The population number of the third-generation adults was negatively correlated with the area ratio of Host (1 000 m), Other crops (1 000 m, P < 0.01) and Water (1 000 km, P < 0.05), and positively correlated with the perimeter area ratio (1 500 m, P < 0.05; 2 000 m, P < 0.01). [Conclusion] The farmland landscape pattern had an obvious regulatory effect on the population number of L. pratensis adults in cotton field. The increase of the area ratio of Host, Other crops and Water in farmland landscape had a certain control effect on the population number of L. pratensis in cotton field. The increase of the area ratio of FBDS and Building promoted the occurrence of L. pratensis in cotton fields.

[Objective] Field experiment was carried out to study the effect of different planting systems on lint yield, economic benefit, and nitrogen efficiency of cotton (Gossypium hirsutum L.) in the Yangtze River valley and to provide theoretical support for high yield and efficiency production of cotton. [Method] A split-plot experiment was conducted to explore the biomass accumulation and allocation characteristics, lint yield, economic benefit and nitrogen efficiency of cotton in response to different planting patterns (transplanting and field-seeded), varieties (early-maturing and medium-maturing) and nitrogen applications(no nitrogen and optimum nitrogen). [Result] The growing process fasted especially for the seedling stage under field-seeded pattern compared with that under transplanting pattern. The biomass and nitrogen accumulation at the medium-late stage of cotton under field-seeded pattern were higher than those under transplanting pattern, and the economic coefficients of early-maturing variety were higher than those of medium-maturing variety. The lint yield of the early-maturing variety under field-seeded pattern and the medium-maturity variety under transplanting pattern were higher under nitrogen application, and the difference between them was not significant. Under nitrogen application, the output value of seed cotton under transplanting pattern was 1.0-1.2 times of that under field-seeded pattern, but the cost of the former was 1.8-2.0 times of that of the latter, and the benefit of the former was only 23.0%-43.1% of the latter. The effects of planting pattern on the nitrogen agronomic efficiency (NAE) and nitrogen apparent recovery efficiency (NARE) were greater than those of variety and nitrogen application, and the NAE and NARE under field-seeded pattern were 40.0% and 76.4% (2017) higher than those under transplanting pattern. The effects of variety on nitrogen production efficiency (NPE) were greater than those of planting pattern and nitrogen application, and the NPE of early-maturing variety was 45.3% higher than medium-maturing variety in 2017. [Conclusion] The early-maturing variety with optimum nitrogen application under field-seeded pattern was conducive to higher yield, lower cost and higher benefit, and has higher NAE, NARE and NPE, which is the high yield and efficiency planting system for cotton after wheat in the Yangtze River valley.

In order to study the effect of the plant growth rugulators on Bt protein expression and nitrogen metabolism of the bolls, GA3 and DPC were used to spray bolls of the two Bt cotton cultivars (Sikang 1 was conventional, Siza 3 was hybrid). The results showed that DPC increased Bt protein contents of bolls at 10 days post anthesis (DPA) and 30 DPA; GA₃ decreased the Bt protein contents of the boll shell and the seeds at 10 DPA, but enhanced the contents at 30 DPA. Bolls with DPC treatment had higher total nitrogen, free amino acid and soluble content, greater in NR, GPT and GOT activity. Bolls with spraying GA₃ had an opposite effect at 10 DPA. There were similar results for the two Bt cultivars with different genotypes. There were significant positive correlation between the Bt toxin content and the activity of the NR, GPT and GOT. The correlation coefficients were 0.8776^**, 0.7172^** and 0.7028^**. The results suggest that spraying DPC and GA3 during boll nutrient filling may enhance nitrogen metabolism intensity, promote the expression of the Bt protein and increase the ability of the insect resistance.

[Objective] This study aims to screen the suitable nitrogen (N) concentration and investigate its effects on the growth, macronutrients uptake and N use efficiency of cotton at seedling stage. [Methods] HM3097 was used and cultured with nutrient solution for 21 d of six N concentrations with 0, 0.04, 0.4, 1, 4, 8 mmol·L^-1 Ca(NO₃)₂, named N0, N0.04, N0.4, N1, N4, N8, respectively. The root and shoot morphology, biomass, absorption and distribution of macronutrients, photosynthetic capacity, N uptake efficiency (NUpE) and N utilization efficiency (NUtE) of cotton seedlings were determined. [Results] With the increase of N concentration, the growth (include root and shoot), biomass, macronutrients accumulation and photosynthetic capacity of cotton seedlings increased first and then decreased, and 4 mmol·L^-1 Ca(NO₃)₂ was the most appropriate N concentration for cotton at seedling stage, at which the cotton growth was the most vigorous. The maximum accumulations of N, P, K, and Ca of cotton seedlings were 34.4 mg, 6.3 mg, 41.6 mg, and 16.5 mg per plant, respectively, with the ratio of 1∶0.2∶1.2∶0.5. NUpE and NUtE were positively correlated with root-shoot ratio, and the change trend were also consistent with the root biomass distribution proportion, root average diameter, and the root macronutrients distribution proportion, which decreased with the increase of N concentration. In the range of 0-4 mmol·L^-1 Ca(NO₃)₂, the contents of N, K, and Ca, leaf biomass and the shoot macronutrients distribution proportion all increased with the increase of N concentration. [Conclusion] 4 mmol·L^-1 Ca(NO₃)₂ was the most appropriate N concentration for cotton at seedling stage, which could significantly promote the absorption of N, P, K, and Ca of cotton seedlings. 1 mmol·L^-1 Ca(NO₃)₂ could increase the root macronutrients distribution proportion, promote root elongation and proliferation, and improve NUpE and NUtE.

[Objective] This study aims to analyze the effects of chemical topping on cotton dry matter accumulation and distribution. [Method] Three upland cotton varieties (Xinluzhong 37, Xinluzao 77, and Xinluzhong 82) were selected as the experimental materials. A two-factor split plot design was adopted, taking four topping treatment (75, 105, 135 g·hm^-2 mepiquat chloride, and manual topping) in the main plot, three cotton varieties in the secondary plot, to study the effects of the chemical topping on dry matter accumulation and distribution of cotton in the arid area of Southern Xinjiang. [Result] The 75 g·hm^-2 mepiquat chloride treated plants had the lowest total dry weight of vegetative organs at 7-28 days after the treatment, which was 2.91%-31.12% lower than that of 105 g·hm^-2, 135 g·hm^-2 treatment and manual topping. The dry matter accumulation of reproductive organs of 75 g·hm^-2 and 105 g·hm^-2 chemical topping treatments were 9.18% and 13.93% higher than that of manual topping at 42 days after treatment, respectively. Under 75 g·hm^-2 treatment, the yield of Xinluzhong 37, Xinluzao 77, and Xinluzhong 82 was 8.64%, 4.54% and 18.56% higher than that of manual topping, respectively. [Conclusion] Applying of 75 g·hm^-2 mepiquat chloride had more obvious inhibition effect on dry matter mass of vegetative organs and could effectively increase cotton yield. There was significant or extremely significant interaction between chemical topping dosage and cotton varieties on dry matter accumulation in cotton vegetative organs.