[Objective] This study aimed to screen the single-guide RNA (sgRNA) for gene editing of GhOMT1 (encoding flavonoid 3-O-methyltransferase) and GhPGF (related to gland formation) in cotton, laying the foundation for rapid detection of mutant plants. [Methods] Based on the Cas9-overexpressing cotton Jin668, sgRNAs targeting GhOMT1and GhPGF genes were designed. The editing efficiency and specificity of the sgRNAs were detected by using the cotton leaf crumple virus (CLCrV) vector-mediated gene editing system and high-throughput tracking of mutations (Hi-TOM) technology. [Results] GhOMT1-sgRNA2 and GhPGF-sgRNA induced mutations at the target sites of GhOMT1 and GhPGF, respectively. Hi-TOM sequencing revealed that 12 out of 15 cotton plants transformed with GhOMT1-sgRNA2 exhibited mutations, with a mutation efficiency of 80%. The editing efficiency in single plants ranged from 7.90% to 43.72% for the A subgenome and from 9.60% to 56.32% for the D subgenome. The mutation efficiency of GhPGF-sgRNA was 80%, with an editing efficiency ranging from 10.23% to 30.27%. No off-target effects were observed at the three potential off-target sites of GhOMT1-sgRNA2, and GhPGF-sgRNA had no potential off-target sites in the coding regions of the genome, indicating the high specificity of these sgRNAs. [Conclusion] One sgRNA targeting GhOMT1 and one sgRNA targeting GhPGF were screened using the CLCrV-mediated gene editing system.

[Objective] Accurate identification of cotton species is of great significance for breeding, cultivation management, and pest control. However, the traditional manual identification method is subjective and inefficient. Therefore, this study aims to develop a rapid classification model based on red, green, and blue(RGB) image and random forest (RF) algorithm to realize automatic recognition of cotton species. [Methods] In this study, Gossypium herbaceum, G. arboreum, G. barbadense, and G. hirsutum lines were planted to collect the RGB images of cotton leaves at the squaring stage and the flowering and boll-setting stages, then the color and morphological feature parameters were extracted. Based on the extracted features, three RF models were constructed: one using only leaf features at the squaring stage, another using only leaf features at the flowering and boll-setting stages, and a comprehensive model combined features from both stages. The classification performance of each model was evaluated, and the key features affecting cotton species were identified through feature importance analysis. To assess the superiority of the RF model, the classification effect of the support vector machine(SVM) and K nearest neighbor (KNN) algorithm was conducted for comparison. [Results] The classification model combining the leaf features of the squaring stage and the flowering and boll-setting stages had the highest accuracy, with an overall accuracy of 97.71% and a Kappa coefficient of 0.95, which was superior to the model based only on leaf features from a single growth stage. Feature importance analysis showed that leaf area and roundness played an important role in cotton species recognition. Additionally, the RF model demonstrated better classification performance than SVM and KNN, exhibiting higher stability and accuracy. [Conclusion] The cotton species identification method based on RGB images and the RF algorithm proposed in this study does not require complex image pre-processing and can provide new insights and technical support for crop precision management and the application of machine learning algorithms in agriculture.

[Objective] This study aims to investigate the potential of cotton carbon credits under the CCER (Chinese Certified Emission Reduction) mechanism, quantitatively evaluate the greenhouse gas reduction potential of cotton production that can participate in the CCER mechanism, predict the economic value it can generate, and explore the possibility of additionality certification for cotton carbon credits based on the CCER mechanism. [Methods] First, a counterfactual analysis framework was constructed through scenario division. Based on the existing mature life cycle assessment boundaries of cotton, components meeting the requirements of the CCER mechanism were identified. The development potential, economic value, and future trends of cotton carbon credit in China's three main cotton regions were estimated and predicted. Furthermore, the additionality of cotton carbon credit was demonstrated using the general proof methods required by the CCER mechanism. [Results] The cotton carbon credit in China's three main cotton regions exhibits significant development potential and economic value. Under the best-line scenario, the annual average carbon credit potential and economic value from 2014 to 2023 were 7.932 4 million tons of CO₂ equivalence and 729 million CNY, respectively, with an upward trend. Under the better-line scenario, the respective figures were 2.412 3 million tons of CO₂ equivalence and 222 million CNY. The Northwest Inland Cotton Region is the primary area for cotton carbon credit development, accounting for over 90% and continuing to increase. Promoting and adopting low-carbon agricultural technologies can help cotton carbon credits pass the additionality certification based on the CCER mechanism. The better-line scenario's technological choices provide a more pragmatic approach. [Conclusion] The three main cotton-growing regions in China, especially the Northwest Inland Cotton Region, have great potential for carbon credit development. Considering the practical context of "increased production equating to increased income", efforts should focus on leveraging the scale advantages of the Northwest Inland Cotton Region and exploring collaborative cooperation models between the upstream and downstream ends of the industry chain to promote the practical development of cotton carbon credit.

[Objective] This study aims to explore the effects of applying different amounts of 1,1-dimethyl piperidinium chloride (DPC) through drip irrigation on cotton plant architecture characteristics and yield traits under dry-sowing and wet-emergence planting mode, and to screen the optimal amount of DPC, so as to promote the simplified chemical manipulation of cotton. [Methods] Field experiments were conducted in Shawan City, Xinjiang, from April 2023 to October 2024. The control treatment (CK) was established with foliar application of 315 g·hm^-2 DPC. Four treatments were set up with different drip application rates of DPC: 315 g·hm^-2 (D1), 630 g·hm^-2 (D2), 1 260 g·hm^-2 (D3), and 1 890 g·hm^-2 (D4). The effects of drip-applied DPC on cotton plant height, plant width, stem diameter, and other plant architecture characteristics, as well as leaf area index (LAI), and yield traits were investigated. [Results] In 2023 and 2024, cotton plant height, internode length of main stem, cotyledon node height, plant width, fruiting branch length, number of fruiting branches per plant, height of the first fruiting branch node, and LAI all decreased with the increasing amount of DPC through drip irrigation. There were no significant differences between D2 and CK treatment in plant height, cotyledon node height, plant width, vegetative shoot length, stem diameter, fruiting branch number per plant, first fruiting branch node and its height, plant height-width ratio, fruiting node number-fruiting branch number ratio, and LAI (except for peak boll-setting stage in 2023). There were no significant difference in harvest density and lint percentage among different treatments. Compared with CK treatment, the boll weight of D1-D4 treatment and the boll number per plant of D1 and D2 treatment were no significant difference, and the boll number per plant of D3 and D4 treatment were significantly reduced. The seed cotton yield of D2 treatment showed no significant difference with CK, and it was higher than that of D1 treatment, and significantly increased by 19.7% to 20.0% and 27.1% to 49.6%, respectively compared with D3 and D4 treatments. [Conclusion] The application of 630 g·hm^-2 DPC through drip irrigation under the dry-sowing and wet-emergence planting mode in cotton fields of northern Xinjiang can effectively regulate the plant architecture of cotton, ensuring high cotton yield.

[Objective] With the adjustment of planting structure and the change of planting area of cotton in China, the main diseases and pests are constantly evolving, especially in the case of the sharp fluctuation of cotton planting area in the Yellow River Basin. Clarifying the evolution characteristics of diseases and pests in this area can provide reference for scientific control. [Methods] Based on the relevant data of National Bureau of Statistics and National Plant Protection Statistics released by National Agro-Tech Extension and Service Center, the changing trends of cotton planting area, occurrence and control of disease and pest, and yield loss in the cotton planting region of the Yellow River Basin were analyzed. [Results] From 1998 to 2023, the cotton planting area of the Yellow River Basin and its proportion to the cotton planting area of the whole country increased first and then decreased. The occurrence area, control area, recover loss, and actual loss showed an overall trend of decreasing-increasing-decreasing. The total control area of disease and pest in cotton planting area of the Yellow River Basin is larger than the occurrence area. The occurrence area, control area, recover loss, and actual loss of pest are greater than that of disease. In order of average annual occurrence area from large to small, the major pests and diseases were Helicoverpa armigera, Aphis gossypii, cotton mirid bug, Tetranychus cinnabarinus, seedling disease, boll disease, Bemisia tabaci, Fusarium wilt, cotton thrips, and Ostrinia furnacalis. Over all, the occurrence area ratio of A. gossypii, cotton mirid bug, B. tabaci, cotton thrips, and boll disease showed an increasing trend, while the occurrence area ratio of H. armigera, seedling disease, and Fusarium wilt showed a decreasing trend, and the occurrence area ratio of T. cinnabarinus and O. furnacalis showed no obvious change. The actual losses of H. armigera, A. gossypii, and boll disease accounted for a large proportion. [Conclusion] The main pests and diseases in the cotton planting area of the Yellow River Basin were identified, which provided theoretical support for the prediction and prevention of cotton diseases and pests in production.

[Objective] Transposable elements are a major driver of genome evolution, yet the functions of the gag gene family in upland cotton remain unclear. This study aimed to identify members of the gag gene family in upland cotton and analyze their structural characteristics, evolutionary relationships, and expression patterns to explore their potential roles in cotton growth, development, and stress responses. [Methods] Based on the TM-1 reference genome of upland cotton, gag gene family members were identified using HMMER software, NCBI-CDD database and the Pfam database. Bioinformatics tools were employed to analyze their physicochemical properties, subcellular localization, and chromosomal distribution. Phylogenetic trees were constructed using ClustalX and MEGA X. Cis-acting elements in promoter regions were predicted using PlantCARE website, and LTR transposon distribution was analyzed with RepeatMasker and LTR_retriever. Transcriptome data and quantiative real-time polymerase chain reaction were performed to analysis the expression patterns and functions of gag genes. [Results] A total of 166 gag genes was identified in upland cotton with significantly more genes in the A sub-genome than in the D sub-genome. Phylogenetic analysis divided the family into two major subfamilies (nine subgroups) with diverse gene structures, most of which are located in LTR transposons. Promoter analysis revealed abundant cis-acting elements related to cotton growth, development, hormone responses, and stress adaptation. Expression profiling showed that certain genes, such as Ghir_A09G013490 and Ghir_D04G004460, were highly expressed in specific tissues(e.g., ovules, fibers) or under stress conditions(e.g., high temperature, salt stress). [Condusion] The gag gene family exhibits significant diversity in upland cotton, with its evolution closely linked to LTR transposon activity. Some members may play roles in abiotic stress responses and seed development, offering potential targets for cotton genetic improvement.

[Objective] This study aims to investigate the suitable planting density of different cotton varieties in southern Xinjiang and to provide a theoretical basis for the construction of high-yield cultivation model. [Methods] The experiment was conducted in Yuli County from 2023 to 2024, with five planting density levels: 9.0 plants·m^-2 (D1), 13.5 plants·m^-2 (D2), 18.0 plants·m^-2 (D3), 22.5 plants·m^-2 (D4), 27.0 plants·m^-2 (D5), and three cotton varieties: Xinluzhong 79 (C1), Xinluzao 73 (C2), and Xinshi 518 (C3). The optimal planting density was determined by measuring the cotton reproductive period, dry matter accumulation and distribution, and seed cotton yield. [Results] The growth period of cotton was prolonged as the density increased. With the increase of planting density, the maximum dry matter accumulation and maximum growth rate of vegetative organs, reproductive organs, and aboveground parts of C1 and C2 showed trends of increasing and then decreasing, peaking at D3. The average highest seed cotton yields were 6 458.66 kg·hm^-2 at D3 for C1, and 6 083.64 kg·hm^-2 at D3 for C2, respectively. For C3, the maximum dry matter accumulation and maximum growth rate of vegetative organs, reproductive organs, and aboveground parts continued to rise with the increase in planting density, and the highest seed cotton yield of 5 875.30 kg·hm^-2 was reached at D5. The planting density does not show a clear pattern in its effect on the time at which different organs reach their maximum dry matter accumulation and the time at which they achieve their maximum growth rate. [Condusion] For Xinluzhong 79 and Xinluzao 73 varieties, a planting density of 18 plants·m^-2 is suitable, while for Xinshi 518 variety, a high-density cultivation pattern of 27 plants·m^-2 is recommended.

[Objective] This study aims to clarify the flight capacity of adults of Sylepta derogata. [Methods] Using an insect flying mill system, the flight capacity for 24 h of male and female adults of S. derogata at 1 day old, and flight parameters for 12 h of adults in different genders and ages of S. derogata were measured; the flight distance, flight time, and flight speed of S. derogata under different mating states, ambient temperatures, and complementary nutrition conditions were also measured in the laboratory. [Results] The adults of S. derogata can be divided into three types: short flying type, intermediate flying type, and long flying type. The dividing points of 24 h cumulative flight time of short and intermediate flying type, intermediate and long flying type were 0.90 h and 2.02 h, respectively. The 1- or 2-day-old adults of S. derogata had relatively weak flight capacity, while the 5-day-old adults had the strongest flight capacity. And there is no significant difference in flight parameters between female and male adults of S. derogata at the same ages. Compared with unmated adults, the flight distance, flight time, and flight speed of 5-day-old mated female adults of S. derogata decreased by 49.85%, 35.63%, and 31.97%, respectively; as for 5-day-old mated male adults, the flight distance, flight time, and flight speed significantly decreased by 82.28%, 66.58%, and 53.65%, respectively. The 5-day-old adults of S. derogata were able to fly normally under the temperature of 22-28 ℃. Under different ambient temperatures, the average flight distance and speed of male and female adults were 26 ℃ > 28 ℃ > 22 ℃. The flight time is the longest under 26 ℃. In addition, after feeding on 8% honey water, the flight capacity of 5-day-old unmated male and female adults of S. derogata was significantly better than that of those fed on water or sugar-vinegar solution. [Conclusion] The adults of S. derogata had a certain level of flight capacity, and the ages, mating status, ambient temperature, and complementary nutrition have important effects on its flight capacity.

[Objective] This study aimed to explore the impact of drought stress, lower canopy shading, and their interaction on the light energy utilization capacity of cotton leaves. [Methods] The photosynthetic physiological indexes, such as plant height, leaf area, leaf thickness, chlorophyll content, and chlorophyll fluorescence parameters, were measured in an artificial climate chamber under drought stress and lower canopy shading conditions using the cotton variety Xinluzao 80 as the material. [Results] Under moderate and severe drought stress, the shading treatment of the lower canopy in cotton significantly increased the plant height and leaf area of lower leaves, significantly decreased the leaf area of upper leaves and leaf thickness of lower leaves, and simultaneously increased the chlorophyll content of upper and lower leaves, which were conducive to the enhancement of the light energy capture capacity, compared with those under the non-shading treatment. Under moderate and severe drought stresses, the actual quantum efficiency of photosystem Ⅱ (Φ_PSⅡ), electron transport rate (ETR), photochemical quenching coefficient (q_P), and non-photochemical quenching (NPQ) of the lower leaves under the shading treatment were reduced compared with those under the non-shading treatment. Φ_PSⅡ of upper leaves under the shading treatment was increased by 19.4% and 31.4%, respectively; ETR was increased by 19.5% and 31.4%, respectively; and q_P was increased by 26.2% and 34.7%, respectively. When shading treatment was applied to the lower leaves, the photochemical reaction in the upper leaves was enhanced under both moderate and severe drought stress. Meanwhile, the heat dissipation capacity of the upper leaves decreased under moderate drought stress but increased under severe drought stress. [Conclusion] The effects of shading treatment on the photosynthetic apparatus of upper leaves were different under different drought stress conditions. Under moderate drought stress, systemic regulation helped to improve the light energy utilization capacity of upper leaves in cotton.

[Objective] This research aimed to investigate the function of the ghr-miR394-GhFBX6 module in cotton resistance to Verticillium wilt and to provide candidate genes for cotton disease-resistant breeding. [Methods] The expression patterns of ghr-miR394a and GhFBX6 were analyzed using quantitative real-time polymerase chain reaction (qRT-PCR). Virus-induced gene silencing (VIGS) was employed to transiently silence ghr-miR394a and GhFBX6 individually, and in combination with the transient overexpression of ghr-miR394a in cotton, to investigate their roles in resistance to Verticillium wilt. The regulatory effect of ghr-miR394a on GhFBX6 was analyzed using the 5'-RNA ligase-mediated rapid amplification of cDNA ends (5' RLM-RACE) technique combined with a luciferase (LUC) reporter system. [Results] qRT-PCR analysis revealed that ghr-miR394a was highly expressed in cotton leaves, followed by stems and roots. Compared with the water treatment, inoculation with Verticillium dahliae significantly downregulated the expression level of ghr-miR394a in roots, while significantly upregulated the expression level of GhFBX6. Compared with control plants, transient silencing of ghr-miR394a in cotton resulted in a significantly reduced disease index and rate of diseased plants, and less fungal biomass accumulation in stem segments during recovery culture, indicating enhanced resistance to Verticillium wilt. In contrast, transient overexpression of ghr-miR394a or silencing of GhFBX6 led to decreased resistance to V. dahliae, as evidenced by a significantly higher disease index and rate of diseased plants, increased fungal biomass accumulation in stem segments of ghr-miR394a-overexpressing plants, and more severe browning of vascular bundles in GhFBX6-silenced plants. The results from 5' RLM-RACE and the LUC reporter system demonstrated that ghr-miR394a inhibits the expression of GhFBX6 at the post-transcriptional level. [Conclusion] ghr-miR394a targets and inhibits the expression of GhFBX6. ghr-miR394a and GhFBX6 play negative and positive regulatory roles, respectively, in the cotton response to Verticillium wilt.

[Objective] This research aimed to investigate the effects of different planting densities on the plant architecture and yield of cotton in southern Xinjiang, then to provide a theoretical basis for optimizing cultivation techniques. [Methods] From 2023 to 2024, field experiments were carried out in Yuli County, Xinjiang, with five kinds of cotton planting densities designed: 280 000 plants·hm^-2 (D1), 220 000 plants·hm^-2 (D2), 180 000 plants·hm^-2 (D3), 130 000 plants·hm^-2 (D4), and 90 000 plants·hm^-2 (D5). The cylinder-type variety, Xinluzhong 79 (T1), and the tower-type variety, Xinshi 518 (T2) were taken as research objects. The effects of different planting densities on plant height, internode length of fruiting branches, insertion angle and azimuth angle of fruiting branches and leaves, leaf area index (LAI), and yield traits of cotton were analyzed. [Results] The plant height of the T1 variety was the highest under D3 or D4 treatment, and the plant height of the T2 variety was the highest under D4 treatment. With the decrease of cotton planting density, the average internode length of fruiting branches of the T1 and T2 varieties gradually increased, and the insertion angle of fruiting branches in the lower, middle, and upper parts increased as a whole. Under D4 or D5 treatment, the leaf insertion angle in the lower, middle, and upper parts of the two varieties was the largest. Under different cotton planting densities, there were no significant differences in the leaf insertion angle in the lower, middle, and upper parts of the T1 variety; there were no significant differences in the fruiting branch azimuth angle in the lower part and leaf azimuth angle in the middle and upper parts of the T1 and T2 varieties. The LAI of the T1 and T2 varieties was the largest under D4 and D3 treatments, respectively. With the increase of cotton planting density, the number of bolls per plant decreased. T1 and T2 varieties showed the highest seed cotton yields under D3 and D1 treatments, respectively. [Condusion] Different planting densities affect the plant architecture and yield of cylinder- and tower-type cotton varieties. The suitable planting densities for Xinluzhong 79 and Xinshi 518 in southern Xinjiang are 180 000 plants·hm^-2 and 280 000 plants·hm^-2, respectively.

[Objective] This study aimed to explore the biological functions of one of the aluminum-activated malate transporter (ALMT) family genes, GhALMT10, in the drought resistance of cotton, thereby establishing a foundation for a deeper understanding of the mechanisms of drought resistance in cotton. [Methods] The coding sequence of GhALMT10 gene was amplified from Gossypium hirsutum TM-1 by polymerase chain reaction (PCR), followed by bioinformatics analysis. The expression patterns of this gene in various cotton tissues, as well as under drought stress, were assessed using quantitative real-time PCR (qRT-PCR). Additionally, the biological function of this gene in cotton's response to drought stress was preliminarily verified using virus-induced gene silencing (VIGS) technology. [Results] The coding region of GhALMT10 spans 1 401 bp, encoding a protein composed of 466 amino acid residues, which is predicted to be stable and hydrophobic. Phylogenetic analysis indicated that GhALMT10 is closely related to GrALMT10, GaALMT10-like, HsALMT10, and TcALMT10. Results by qRT-PCR indicated that GhALMT10 is expressed in cotton roots, stems, and leaves, with the highest expression level observed in the roots. Compared with the control treatment with clear water, the expression level of GhALMT10 was low at 3 h of drought sress, and then significantly increased at 6 h and 9 h of drought stress treatment, while it significantly decreased at 24 h. Furthermore, the survival rate of GhALMT10-silenced cotton plants was significantly higher under drought stress compared with the negative control plants. The water loss rate of detached leaves was significantly reduced, the chlorophyll content in leaves after drought treatment was significantly increased, and the malondialdehyde content was significantly decreased in GhALMT10-silenced cotton plants. [Condusion] The drought tolerance of GhALMT10-silenced plants was significantly enhanced, indicating that GhALMT10 gene negatively regulates drought resistance in cotton.

This study mainly based on the Xinjiang Statistical Yearbook, the annual global supply and demand information of extra-fine cotton published by the International Cotton Advisory Committee (ICAC), combined with the data provided by agricultural departments of Xinjiang prefectures (autonomous prefectures), Development and Reform Commission of Xinjiang Uygur Autonomous Region, and other relevant institutions. The development status and its influencing factors of sea island cotton production in Xinjiang from 1955 to 2024 were analysed, and relevant recommendations were offered, to provide references for the sustainable development of sea island cotton production in Xinjiang. From 1955 to 2024, the planting area, yield per unit area, and total production of Xinjiang sea island cotton showed inter-annual fluctuations. From 1955 to 1990, the fluctuating growth trend was obvious, while in the 21st century, the planting area and total production fluctuated obviously. Sea island cotton varieties in Xinjiang have fully achieved independent breeding, with 88 excellent varieties developed, of which 20 varieties have been widely promoted and planted, supported by the planting technology of "short, dense, early, film, drip irrigation". It was analysed that the key factors influencing the production of sea island cotton include varieties, technology, economic returns, trade wars, and natural disasters. Sea island cotton production currently faces a historical low point in the 21st century in Xinjiang. To overcome these challenges, both technological support and policy guidance are needed.

[Objective] In order to provide technical guidance and a theoretical basis for the safe application of insect-resistant cotton in production, the effect of exogenous growth regulator on insecticidal protein content of Bt cotton and its underlying physiological mechanism under high temperature and drought stress were studied. [Methods] The transgenic insect-resistant cotton cultivar Sikang 1 (SK-1) and hybrid cultivar Sikang 3 (SK-3) were used as experimental materials, the daily temperature of 32 ℃ and 75% field capacity were used as control, and the artificial climate chamber was subjected to different high temperature levels (34 ℃ and 38 ℃) and drought stress (50% and 60% field capacity) during the peak flowering period in 2021-2022. After 7 days of stress, cotton plants were sprayed with water (W), 200 mg·L^-1 salicylic acid (SA), and 20 mg·L^-1 mepiquat chloride (DPC), respectively. Three days later, the boll shells were sampled to determine the activities of glutamic oxaloacetate transaminase (GOT), glutamate pyruvate aminotransferase (GPT), glutamine synthetase (GS), glutamate synthase (GOGAT), nitrate reductase (NR), protease and other key enzymes of nitrogen metabolism, as well as soluble protein and free amino acid content. [Results] High temperature and drought stress inhibit the content of Bt protein in the boll shells of two tested varieties, while treatments with SA and DPC can alleviate this inhibitory effect. The Bt protein content under SA or DPC treatments is significantly higher than that of W treatment under various stress conditions, with the increase in SA treatment being more pronounced. The Bt protein content remains lower than that under the non-stressed control. In 2021, the Bt protein content in SK-1 treated with SA and DPC after heat and drought stresses increased by 51.3%-104.0% and 22.0%-85.4%, respectively, compared with the W treatment. In 2022, the increase was 14.7%-91.1% and 4.5%-67.8%. In SK-3, the Bt protein content in 2021 increased by 46.4%-98.3% and 22.9%-60.4% under SA and DPC treatments after heat and drought stresses, respectively, compared with the W treatment. In 2022, the increase was 18.8%-77.4% and 14.6%-57.6%, respectively. Among the varieties, SK-1 showed a more significant response to SA and DPC, with a higher increase in Bt protein content than that of SK-3. Physiological mechanism studies showed that SA and DPC treatments after heat and drought stresses significantly increased the activities of GPT, GOT, GOGAT, and NR, as well as the soluble protein content in SK-1 and SK-3. They also significantly reduced the free amino acid content, peptidase, and protease activities. Compared with the W treatment in 2021, SA and DPC treatments increased GOT activity in SK-1 by 70.3%-104.2% and 36.7%-61.9%, GPT activity by 58.2%-231.2% and 27.7%-88.9%, GS activity by 167.9%-197.3% and 79.7%-139.4%, NR activity by 22.4%-53.6% and 7.6%-42.8%, soluble protein content by 11.3%-40.6% and 7.5%-20.3%, while free amino acid content decreased by 15.6%-23.2% and 6.3%-14.1%, and protease activity decreased by 5.5%-13.5% and 2.7%-10.5%, respectively. The trend of changes in the indicators of SK-1 in 2022 was consistent with that in 2021. In the two-year experiment, SK-3 showed similar performance to SK-1. Overall, the effects of SA on the above indicators were superior to those of DPC. Stepwise regression analysis further indicated that NR activity, free amino acid content and GS activity was a key index to reflect the content of insecticidal protein in Bt cotton boll shell after growth regulator treatment under high temperature and drought stress. [Condusion] Spraying SA and DPC can enhance the activity of enzymes related to protein synthesis, reduce the activity of proteases and peptidases, and decrease the content of free amino acids. The primary mechanism is to enhance the capacity of protein synthesis, thereby increasing the Bt protein content in the boll shell of Bt cotton after high temperature and drought stress. Additionally, the effect of SA was better than DPC. This provides theoretical and practical guidance for the safe application of insect-resistant cotton.

[Objective] This research aimed to investigate the optimal row spacing and planting density of mechanically harvested cotton in the Yangtze River Basin. [Methods] Field trials were conducted in Changsha, Yueyang, and Hengyang Cities in Hunan Province in 2024, using the JX0010 cotton variety as the experimental material. The main plot included three row spacing treatments: 90 cm (L1), 83 cm (L2), and 76 cm (L3), while the subplot had three planting density treatments: 60 000 plants·hm^-2 (D1), 75 000 plants·hm^-2 (D2), and 90 000 plants·hm^-2 (D3). The plant architecture, aboveground dry matter mass, net photosynthetic rate (P_n), chlorophyll content (soil and plant analyzer development, SPAD value), leaf area index (LAI), and yield traits were compared under different treatments. [Results] At the same row spacing, as planting density increased, plant height tended to increase, while the number of fruiting branches, stem diameter, and length of the fourth fruiting branch tended to decrease. The height of the first fruiting branch was higher under L1D3 treatment. At the full squaring stage, the aboveground dry matter mass per plant tended to increase with the increasing of planting density at the same row spacing. The dry matter mass of stems, leaves, reproductive organs, and whole plant were higher under L1D3 treatment at the full squaring stage, full flowering stage, full boll-setting stage, and boll opening stage. At the full flowering stage and full boll-setting stage, P_n was higher under the D2 treatment at the same row spacing; at the boll opening stage, P_n tended to increase with the increasing of planting density, and P_n was higher under L1D3 treatment. At the same row spacing, SPAD value and LAI (except for the L1 treatment in Changsha at the full squaring stage) increased with the increasing of planting density from the full squaring stage to boll opening stage. The L1D3 treatment had the highest number of bolls per plant. Under the same row spacing, seed cotton yield and lint yield increased with the increasing of planting density, with L1D3 treatment showing the highest seed cotton yield and lint yield, which were significantly higher than the other seven treatments(expcept L2D3 treatment) at both Yueyang and Hengyang test sites. [Condusion] Under the conditions of this experiment, the optimal row spacing for JX0010 cotton is 90 cm, and the optimal planting density is 90 000 plants·hm^-2.

[Objective] This study aims to evaluate the effects of different arbuscular mycorrhizal fungi (AMF) on cotton growth under salt stress, and screen for AMF strains that promote cotton growth more efficiently under salt stress. [Methods] Using the main varieties of Zhongmian 113 and Tahe 2 in Xinjiang as materials, the effects of inoculation with different AMF on cotton seedling growth, dry matter accumulation, gas-exchange parameters, nitrogen, phosphorus, potassium accumulation, and K/Na ratio were studied. The optimal strain was determined through a comprehensive evaluation method based on entropy weight. [Results] The results showed that AMF inoculation significantly promoted the growth of cotton seedlings under salt stress. Compared with cotton plant without AMF inoculation, the plant height of Zhongmian 113 inoculated with different AMF strain significantly increased by 62.13%-89.55%, the dry matter mass per plant significantly increased by 122.58%-141.94%, the root-shoot ratio decreased by 20.38%-49.34%, the aboveground water content increased by 8.40%-12.65%, and the root water content increased by 9.78%-15.61%; Compared with cotton plant without AMF inoculation, the plant height of Tahe 2 inoculated with different AMF straub was significantly increased by 70.23%-103.88%, the dry matter mass per plant was significantly increased by 80.95%-188.10%, the root shoot ratio was reduced by 42.40%-59.28%, the aboveground water content was increased by 5.88%-11.11%, and the root water content was increased by 12.05%-18.51%. Inoculation of AMF enhanced the absorption of nitrogen, phosphorus and potassium by cotton. Compared with no inoculation, the K/Na ratio in shoots of Zhongmian 113 and Tahe 2 increased by 53.81%-102.96% and 40.54%-122.10%, respectively. The effects of inoculating different AMF showed significant difference. The comprehensive score results showed that the optimal strain of Zhongmian 113 was XJ04B, and the optimal strain of Tahe 2 was XJ02. [Condusion] Inoculation with different AMF can significantly improve the growth of cotton seedlings under salt stress, and different strains have different performances in promoting cotton growth under salt stress. This experiment provides a reference for screening effective AMF strains in cotton under salt stress environment.

Transgenic crops, including insect-resistant cotton, have been widely cultivated globally, yielding significant economic and social benefits. Cotton is the foremost natural fiber source and one of the most important cash crops worldwide. The genetic transformation technology mediated by Agrobacterium tumefaciens, based on somatic embryogenesis or organogenesis, has become the primary method for obtaining transgenic plants. Particularly for cotton, a crop that typically regenerates through somatic embryogenesis, this process is not only crucial for the application of modern biotechnology in cotton, but also plays a vital role in genetic improvement and variety innovation in cotton. However, cotton somatic embryogenesis is a complex process; although its regulatory mechanisms have been extensively studied, genotype-dependence and low regeneration efficiency remain significant challenges in cotton genetic transformation. This article provides an overview of the research progress in cotton somatic embryogenesis, summarizing the status of the cotton somatic embryogenesis system, including key influencing factors and molecular mechanisms, and offers perspectives on future research in this area.

[Objective] The study aimed to examine the effects of nitrogen, phosphorus, and potassium fertilizers on soil nutrient contents, cotton growth, and yield-related traits in the arid and nutrient-deficient Heilonggang region. [Methods] The experiment was conducted from 2022 to 2024 at the Weixian Experimental Station of the Cotton Research Institute, Hebei Academy of Agriculture and Forestry Sciences. A randomized block design was adopted with five treatments: no fertilizer, conventional fertilization, nitrogen deficiency, phosphorus deficiency, and potassium deficiency. Soil total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium contents were measured after cotton harvest. At the square stage, early flowering stage, peak boll stage, and boll opening stage, dry matter accumulation of aboveground parts and plant nutrient contents were determined, and fertilizer utilization efficiency was calculated. Boll number per plant were counted on July 15, August 15, and September 10. The boll weight and lint percentage were measured after harvest, and the seed cotton yield and lint yield were calculated. [Results] The effects of nitrogen deficiency on soil total nitrogen and alkali-hydrolyzable nitrogen content were not significant. In the three-year experiment, the phosphorus deficiency treatment significantly reduced soil available phosphorus content by 8.5%, 14.6%, and 19.9%, compared with conventional fertilization, while potassium deficiency treatment significantly reduced available potassium content by 10.3%, 18.9%, and 24.6%, respectively. Compared with conventional fertilization, nitrogen uptake of aboveground parts of cotton in the nitrogen deficiency treatment significantly decreased by 35.7%, 35.4%, and 47.1%, while phosphorus uptake of aboveground parts of cotton in the phosphorus deficiency treatment showed no significant difference, and potassium uptake of aboveground parts of cotton in the potassium deficiency treatment significantly decreased by 15.3%, 13.0%, and 21.1% in 2022, 2023, and 2024, respectively. For agronomic efficiency, fertilizer contribution rate, and apparent utilization rate, nitrogen was the most efficient, followed by potassium, with phosphorus showing near-zero efficiency. Seed cotton yield in the nitrogen deficiency treatment significantly decreased by 5.5%, 13.1%, and 25.7%, while phosphorus deficiency had no significant effect on yield, and potassium deficiency led to a reduction of 3.1% over three years. [Conclusion] In the arid and nutrient-deficient Heilonggang region, fertilizer strategy should follow the principle of "applying efficient nitrogen, moderating potassium use, and reducing phosphorus".

[Objective] This study aimed to comprehensively evaluate the drought resistance of major cotton cultivars in southern Xinjiang, screen drought resistance indicators, and identify superior drought-resistant cultivars (lines). [Methods] A sand culture experiment was conducted using 15% PEG6000 to simulate drought stress on 15 cotton cultivars from southern Xinjiang. Phenotypic and physiological traits were investigated, and drought resistance coefficients were calculated. Comprehensive evaluation of drought resistance was performed through correlation analysis, principal component analysis (PCA), entropy-weighted TOPSIS method, and cluster analysis. A multiple stepwise regression model was established to optimize the evaluation system for drought resistance. [Results] Compared with the control, drought stress reduced the germination energy (GE), germination index (GI), root number (RN), main root length (MRL), hypocotyl length (HL), fresh weight (FW), and dry weight (DW) by over 30%, with HL showing the most significant decline (50.55%) and hypocotyl diameter (HD) the least (24.66%). Conversely, superoxide dismutase (SOD) and peroxidase (POD) activities, along with malondialdehyde (MDA) content, increased by over 20%. PCA condensed the original 12 indicators into two independent comprehensive factors, explaining 82.80% of variance, and identified five key drought resistance indicators during germination: MDA, SOD, DW, HD, and GR. Using entropy-weighted TOPSIS, a comprehensive drought resistance index was determined, and cluster analysis classified the 15 cultivars into four drought resistance types, including three high drought-resistant cultivars (Tahe 2, Zhongmian 113, and Xinluzhong 40), four moderate drought-resistant cultivars (Zhongmian 88, CCRI 979, Xinluzhong 61, and Jiumian 20), four drought-tolerant resistant cultivars (Xinluzhong 88, Zhongmian 619, Zhongmian 96A, and Zhongshengmian 17), and four drought-susceptible cultivars (Xinluzao 50, Xinluzhong 67, JBK16, and Xinluzhong 37). A reliable regression model for drought resistance evaluation was established: I=0.74-0.51C_MDA+0.15C_SOD+0.20C_DW+0.24C_HD+0.45C_GE, with a coefficient of determination of 0.99. [Conclusion] High drought-resistant cultivars exhibited significantly lower stress impacts and higher antioxidant capacity compared to sensitive ones. The entropy-weighted TOPSIS method identified Tahe 2 as the most drought-resistant cultivar. This study established a precise and efficient drought resistance evaluation system, providing a theoretical and technical support for cotton breeding and cultivation under drought conditions.

[Objective] This study aimed to investigate the effects of different defoliants on the seed vigor and storage substance content of machine-harvested cotton seeds with different maturities, providing references for the rational selection of defoliants in cotton production. [Methods] Field experiments were conducted in Shihezi City, Xinjiang, from 2020 to 2021. The main plot involved the application of two different defoliants: Ruituolong and Yeluokong. The subplots included two cotton materials: an early-maturing variety, Shidamian 268 (S268), and a late-maturing line, Shidamian 451 (S451). On September 27, cotton bolls that had developed for 30 d, 35 d, 40 d, 45 d, and 50 d on August 31 (the first application of defoliant) were harvested. Naturally-opened cotton bolls before defoliant application served as the control (CK). Seed coat color was observed, and seed index, seed specific weight, oil content, and protein content were measured. Seed germination percentage, germination potential, germination index, and vigor index were determined at 18 ℃ and 28 ℃. [Results] Compared with CK, the white seed rate (the proportion of immature seeds) of 30-day bolls and 35-day bolls of S268 significantly increased under Ruituolong and Yeluokong treatments; while the black-brown seed rate (the proportion of mature seeds), seed index, seed specific weight, protein content, oil content, germination percentage, germination index, and vigor index of cotton seeds all significantly decreased in 2020 and 2021. For S451, the white seed rate of bolls at 30 d, 35 d, and 40 d significantly increased; while the black-brown seed rate, seed index, seed specific weight, protein content, oil content, germination percentage (except for the 40-day bolls), germination potential (except for the 40-day bolls at 28 ℃), germination index, and vigor index of seeds all significantly decreased. After spraying Ruituolong and Yeluokong, there were no significant differences in the black-brown seed rate, germination percentage, and germination potential for 45-day and 50-day cotton bolls of S268 and S451 compared with CK; as well as the seed oil content and protein content of 50-day cotton bolls compared with CK. For S268 and S451, compared with Ruituolong, the black-brown seed rate of 30-day bolls, seed index of 50-day bolls, protein content of 35-day bolls, seed germination index of 35-day bolls at 28 ℃, and vigor index of 40-day bolls at 18 ℃ all significantly decreased. [Conclusion] Under the conditions of this experiment, the superior defoliant was Ruituolong. Spraying Ruituolong had a relatively minor impact on seed vigor and the content of storage substances of 45-50 days cotton bolls.