[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 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.

[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 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 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] 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 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.