[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.

[Objective] The acyl-coenzyme A oxidase (ACX) gene family was identified in Gossypium hirsutum and their expression patterns were analyzed, which would lay the foundation for further studies of the function of ACX genes. [Method] The members of ACX gene family in G. hirsutum genome were identified by bioinformatics method, and their physical and chemical properties, gene structure, evolutionary relationships, gene replication, cis-acting elements in promoter region and expression patterns were analyzed systematically, and the virus-induced gene silencing (VIGS) technique was used to preliminary explore the function of GhACX16 gene. [Results] A total of 20 ACX genes were identified in G. hirsutum genome and distributed on 13 chromosomes, which were divided into 4 subfamilies by cluster analysis. The results of non-synonymous mutation rate/synonymous mutation rate (K_a/K_s) analysis showed that the ACX genes in G. hirsutum had undergone strong purifying selection. The promoter region of ACX genes contain cis-acting elements related to heat stress, drought, plant hormone responses, etc. The expression patterns under abiotic stresses showed that the ACX genes responded obviously to high-temperature, low-temperature, salt, and simulated drought stress. The expression patterns of ACX genes in the anthers at different developmental stages of high temperature-tolerant/sensitive cotton lines under high temperature conditions were analyzed, and it was found that the expression levels of GhACX5 and GhACX16 changed obviously. Compared with the negative control, the GhACX16 silenced cotton seedlings showed obvious characteristics of high temperature tolerance, and the proline content, chlorophyll content, and catalase activity were significantly higher, while the malondialdehyde content was significantly lower in the leaves. [Conclusion] The identification and expression patterns of ACX genes in G. hirsutum showed that ACX genes were widely involved in abiotic stresses response, and GhACX16 gene was preliminary speculated to play an important role in high temperature stress response according to the VIGS verification and physiological and biochemical analysis.

[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 effect of arbuscular mycorrhizal fungi (AMF) inoculation on photosynthetic characteristics and mesophyll cell ultrastructure in cotton under arsenic stress were studied. [Method] Cotton germplasm Dalingmian 69 were used as the test material in the pot experiment. Two species of AMF including Rhizophagus intraradices and Funneliformis mosseae were inoculated into the cotton roots respectively in order to investigate the effects of AMF on stomatal morphological characteristics, gas exchange parameters, chlorophyll fluorescence parameters and mesophyll cell ultrastructure under different arsenic concentrations (0, 100, 200 mg·kg^-1) in soil. [Result] (1) Arsenic stress significantly reduced stomatal length, width, density, conductance, transpiration rate, intercellular CO₂ concentration and net photosynthetic rate, and significantly affected chlorophyll fluorescence parameters of cotton leaves. However, compared with the control treatment, inoculation of AMF increased the length, width, aperture, density, and conductance of cotton stomata, and significantly increased the net photosynthetic rate, transpiration rate, intercellular CO₂ concentration, actual photosynthetic efficiency, the maximum photochemical quantum yield and photochemical quenching coefficient, and reduced the non-photochemical quenching coefficient under different concentrations of arsenic. Under 100 and 200 mg·kg^-1 arsenic concentration, the net photosynthetic rate and actual photosynthetic efficiency of F. mosseae treatment were significantly higher than those of R. intraradices treatment. (2) Arsenic stress led to the gradual swelling of chloroplast, the overall structure was destroyed, the disordered and uneven arrangement of grana thylakoids, the loose and deformed arrangement of cristae in mitochondria, the appearance of voids in some mitochondrial structures, and the fuzzy double-layer membrane structure. However, under arsenic stress, the lamellae of chloroplast grana in the mesophyll cells of cotton inoculated with AMF were clearly visible, and the cristae in mitochondria were closely arranged, and the degree of arsenic damage was significantly reduced. The palliative effect of F. mosseae was even stronger. [Conclusion] Under arsenic stress, inoculation of F. mosseae and R. intraradices significantly increased the net photosynthetic rate and light energy utilization efficiency, and improved the photosynthetic capacity of cotton, and reduced the damage of arsenic to the ultrastructure of mesophyll cells. And the inoculation effect of F. mosseae was better.

[Objective] Na₂SO₄ stress is a major type of salt stress in Xinjiang and has seriously restricted the cotton production in Xinjiang. This study aims to explore the effect of Na₂SO₄ stress on cotton metabolism and to investigate the key metabolites and metabolic pathways in the stress response of cotton. [Method] The metabolic analysis was applied in cotton roots and leaves under two treatment settings, including control (CK) and sulfate stress (Na₂SO₄, SS), to explore the changes of metabolite content and metabolic pathways in cotton under Na₂SO₄ stress. [Result] Sulfate stress significantly inhibited the growth of cotton. Compared with CK, the dry mass of leaves, stems, and roots, and total mass of plant under SS treatment decreased by 46.9%, 50.9%, 43.0% and 47.9%, respectively. Under sulfate stress, there were 42 up-regulated and 10 down-regulated organic acids, 32 up-regulated and 16 down-regulated amino acids and amino acid derivatives, 23 up-regulated and 1 down-regulated carbohydrate in root. There were 37 up-regulated organic acids and 7 down-regulated organic acids, 16 up-regulated and 17 down-regulated amino acids and amino acids derivatives, 16 up-regulated and 4 down-regulated carbohydrate in leaves. A total of 30 differential metabolic pathways were selected in roots, including 9 pathways related to amino acid metabolism, 7 pathways related to organic acid metabolism, and 7 pathways related to carbohydrate metabolism. A total of 17 differential metabolic pathways were selected in leaves, including 7 pathways related to amino acid metabolism, 4 pathways related to organic acid metabolism, and 3 pathways related to carbohydrate metabolism. [Conclusion] Cotton responded to sulfate stress by accumulating organic acids, carbohydrate and alcohols in roots and leaves. The up-regulation of citric acid, succinic acid, pyruvic acid and linoleic acid in leaves suggested the enhanced tricarboxylic acid (TCA) cycle and β-enhanced oxidation. And up-regulation of citric acid, succinic acid and pyruvic acid in roots indicated the enhanced TCA cycle. This study explored the mechanism of Na₂SO₄ stress response in cotton and provided a theoretical basis for cotton cultivation in Xinjiang.

[Objective] Screening and study of cotton disease resistance genes will provide theoretical basis and genetic resources for cotton disease resistance breeding. [Method] The senescence associated gene 101 (GhSAG101) was cloned from Gossypium hirsutum L. TM-1. The expression levels of GhSAG101 in different organs of cotton seedlings, as well as in cotton roots under Verticillium dahliae inoculation were analyzed by real time quantitative polymerase chain reaction (qRT-PCR). The conserved domains and active sites of GhSAG101 were predicted through protein sequence analysis. Knockdown lines of GbSAG101 generated through virus induced gene silencing (VIGS) system were employed for the examination of Verticillium dahliae resistance by inoculation of the whole plant and detached leaves, and the empty vector transferred plants were used as the negative control. [Result] The coding region of GhSAG101 gene is 1 764 bp in length, encodes a protein with 587 amino acid residues that includes a nucleophilic elbow and the conserved domains belonging to the abhydrolase superfamily and enhanced disease susceptibility 1 (EDS1) family. The highest expression level of GhSAG101 was found in roots, followed by stems, and the lowest expression level was found in leaves. GhSAG101 expression was induced by V. dahliae infection in roots at the middle and late infection stage. Suppression of GhSAG101 expression in cotton reduced the spread of V. dahliae and retarded the disease process. [Conclusion] GhSAG101 negatively regulates cotton resistance to V. dahliae and can be used as a candidate gene in the breeding of cotton with improved disease resistance.

[Objective] This study aims to set up a near infrared spectrum(NIR) calibration model for the protein content and oil content in fuzz cottonseed. [Method] In this study, the SPXY (sample set partitioning based on joint X-Y distance sampling) method was used to divide the 426 samples into 320 as calibration set and 106 as prediction set according to the ratio of 3∶1, and the model was optimized by combining spectral pretreatment methods such as multiplicative scatter correction and first derivative. Three methods, linear partial least square method (PLS), support vector machine (SVM), and random forest (RF) were used to build the NIR rapid determination models of cotton seeds protein content and oil content. The coefficient of determination (R²), root mean square error (RMSE), and residual prediction deviation (RPD) were used as the evaluation indexes of the models. [Result] The results showed that the SVM model and PLS model performed better in the calibration set with R² more than 0.8, but with R² less than 0.8 in the prediction set, indicating that the models were overfitting. While the RF model was very well trained on both the calibration set and prediction sets with R² more than 0.9. The R², predicted RMSE, and RPD of RF model were 0.945 9, 0.935 2, and 4.539 1 for protein content, and 0.909 7, 0.770 4, and 3.489 1 for oil content, respectively. [Conclusion] The prediction model based on RF method can be well applied to the NIR spectroscopy determination of protein content and oil content of fuzz cottonseed, which could replace the chemical method. The results of the study not only lay a foundation for the rapid and nondestructive evaluation of the nutritional quality of cotton seed for seed quality breeding, processing production and marketing, but also provide technical references for the nondestructive analysis of seeds of other crops.

[Objective] Ethylene (ET) insensitivity protein 3 (EIN3)/EIN3-like (EIL) family genes are key genes in ethylene pathway, which are involved in the biological stress response of plants. Its function was studied to provide a basis for analyzing the response mechanism of upland cotton to Fusarium wilt. [Method] GhEIN3 of EIN3/EIL gene family were selected from TM-1 genome database based on the data of gene expression profile from root infected with cotton Fusarium wilt in our laboratory. The gene coding protein and related sequence information were analyzed by bioinformatics methods, and the expression pattern of GhEIN3 in Fusarium wilt and different hormone treatments were analyzed by real-time fluorescent quantitative polymerase chain reaction (qRT-PCR). The role of GhEIN3 in disease resistance was preliminarily analyzed by virus induced gene silencing (VIGS) technique. [Result] A new gene GhEIN3 was isolated from upland cotton (Genbank accession: KY744279), which was from EIN3/EIL family. Bioinformatic analysis showed that the open reading frame of this gene was 1 842 base pairs. The encoded amino acids sequence contains a typical EIN3 domain. After Fusarium oxysporum f. sp. vasinfectum (FOV) and different exogenous hormones ET, salicylic acid (SA) and jasmonic acid (JA) treatment, the expression of GhEIN3 was up-regulated by FOV and ET induction, but down-regulated by SA and JA induction. The VIGS results showed that the GhEIN3 gene silenced plants were more susceptible to FOV than the control. The results of gene expression analysis showed that compared with the control, the expression levels of pathogenesis-related genes PR1, PR2, and PR4, ethylene response factor gene ERF1 and 1-aminocyclopropane-1-carboxylate oxidase gene ACO were decreased, while the expression level of PR5 gene was increased after GhEIN3 gene silencing. [Conclusion] A EIN3/EIL family gene GhEIN3 identified from G. hirsutum responds to Fusarium wilt and hormones ET, SA and JA induction. Combined the GhEIN3 gene expression analysis of the cotton plants under ET, SA, JA and FOV treatments with VIGS results, this study showed that the GhEIN3 gene plays a positive role in the process of cotton to resist Fusarium wilt.

[Objective] The aim of this study is to determine the control effect and mechanism of a cotton endophytic fungus Penicillium simplicissimum CEF-818 on cotton Verticillium wilt. [Method] The inhibition rate of CEF-818 against a virulent strain Vd080 of Verticillium dahliae was assessed using the confront culture method, plate-to-plate culture method, and exudate filtering culture method, and the control effect on cotton Verticillium wilt was tested by root irrigation and substrate inoculation methods in greenhouse and by fertilizer broadcast and seed soaking inoculation methods in field. The activity of reactive oxygen species(ROS), and callose accumulation in cotton leaves were measured, and the expression level of defense genes in cotton leaves were detected by real-time fluorescence quantitative polymerase chain reaction. The induced disease resistance by CEF-818 in cotton were evaluated. [Result] The volatile and non-volatile metabolites of CEF-818 significantly inhibited the growth of Vd080, and the control effects on cotton Verticillium wilt in greenhouse and field were 69.77%(substrate inoculation method) and 63.73%(fertilizer broadcast method), respectively. CEF-818 can induce oxidative burst and callose accumulation in cotton leaves, cause up-regulation of some defense genes, such as peroxidase gene POD, phenylalanine ammonia-lyase gene PAL and pathogenesis-related protein gene PR10, and suppress the infection of cotton by V. dahliae. [Conclusion] Strain CEF-818 effectively inhibits cotton Verticillium wilt by directly inhibiting the growth of V. dahliae and inducing host resistance, which has good prospects for biological control applications.

[Objective] This study explored the spatial variation of soil salinity of the cotton field during different cotton growth stages in Shihutan irrigation area, Manas river region, Xinjiang, and provided the theoretical basis for the improvement and sustainable utilization of saline soil in this area. [Method] The spatial variation of groundwater depth and soil salinity during the cotton growth period was explored by combining field measurement, geostatistics, and GIS (geography information system) technology. [Results] The groundwater depth in the irrigation area varied in the range of 3.5-9.0 m. Compared with the period of before sowing, the groundwater depth in the north of Shihutan at the squaring stage and flowering stage were increased, and the groundwater depth in the south of Shihutan at the seedling stage and flowering stage were decreased. In general, the total salt content of farmland soil in the Shihutan irrigation area belonged to the moderate salinization soil category. The salt content in the 20-40 cm soil layer showed strong variation, and the salt content in other soil layers showed moderate variation. Before sowing, the 20-40 cm soil layer had obvious salt accumulation in the northwest of Shihutan. Soil salinity gradually increased in the middle and southeast of Shihutan at the seedling stage and squaring stage, and the overall soil salinity decreased to the lowest level at the flowering stage. In the 20-100 cm soil layer, the proportion of moderately and severely salinized soil area increased along with the increased soil depth, and the deep soil layer were facing a potential risk of salt accumulation. [Conclusion] The total soil content of the 20-40 cm soil layer in the study area had the strongest variability during the overall growth period, and there was a potential risk of salt accumulation at the 40-100 cm soil layer. These results provided a scientific basis for formulating and implementing the restoration measurement of saline soil in Shihutan area.

[Objective] This study aims to detect the metabolites and candidate genes which affect the polymorphsim of cotton flower color. [Method] Before and after petal color was changed, the flower buds of yellow flower cotton variety CCRI 24 and pink flower cotton line Zhongyihong were extracted to perform anthocyanin content detection and RNA-seq analysis. [Result] Before flowering, the color of CCRI 24 buds and Zhongyihong buds was different, and the difference was gradually increased with the development of buds. Among them, pelargonidin-3-O-glucoside, cyanidin-3-O-galactoside, cyanidin-3-O-glucoside (Kuromanin) and cyanidin-3-O-(6''-O-malonyl)-glucoside were specifically accumulated in Zhongyihong buds. A total of 8 790 up-regulated and 8 521 down-regulated genes were obtained by differentially expressed gene (DEG) analysis between CCRI 24 and Zhongyihong, which were enriched in pathways such as proton-transporting V-type ATPase complex and flavonoid biosynthesis. Further analysis showed that there was no significant difference in the expression of genes related to anthocyanin synthesis between the two materials, while Gh_A07G083500, bHLH gene Gh_D11G130400, GST gene Gh_A07G079800， and V-type ATPase genes Gh_A09G123000, Gh_A08G012100, and Gh_D09G115200 involved in regulating anthocyanin synthesis, transporting and vacuolar acid-base balance were highly expressed in CCRI 24. [Conclusion] This study demonstrated the gene expression pathway of pink flower formation, and identified several candidate genes related to the flower color of cotton, which provide genetic resources for cotton breeding.

[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.

[Objective] The effects of nitrogen application depth and amount on cotton dry matter and nitrogen accumulation, distribution and yield in rape-cotton rotation cropping system around Dongting Lake cotton planting region were studied, so as to provide a scientific basis for reducing the application and increasing the efficiency of chemical fertilizer of direct seeding cotton after harvesting rape. [Method] The nitrogen application experiment was carried out at Changde, Hunan Province in 2018 and 2019. A field experiment was conducted using Xiang FZ001 with the treatments of two nitrogen application depths (15 cm and 5 cm, marked by H₁₅ and H₅), and five nitrogen rates (0, 90, 180, 270 and 360 kg·hm^-2, marked by N₀, N₉₀, N₁₈₀, N₂₇₀, N₃₆₀, respectively). [Result] The trends of cotton nitrogen and dry matter accumulation were consistent, and the accumulation dynamics were in line with the logistic model. Deep application of nitrogen fertilizer increased the accumulation of nitrogen and dry matter in cotton plants and their distribution proportion in reproductive organs. With the increase of nitrogen application rate, the accumulation of nitrogen and dry matter and their distribution proportion in reproductive organs all showed a trend of increase at first and decrease afterward. Under the interaction of nitrogen application depth and amount, the accumulation of nitrogen was maximum under H₁₅N₂₇₀; the proportion of nitrogen distribution in reproductive organs, dry matter accumulation and its distribution proportion in reproductive organs were maximum under H₁₅N₁₈₀. From the characteristic values of nitrogen and dry matter accumulation, it could be seen that the accumulation and distribution of nitrogen and dry matter in cotton was basically sychronized, with the average rapid accumulation of nitrogen starting slightly earlier than that of dry matter accumulation, indicating that cotton nitrogen absorption was likely the basis and premise of dry matter accumulation. Compared with H₅, H₁₅ improved the utilization efficiency of nitrogen fertilizer, and the apparent utilization rate, agronomic utilization rate and biased productivity of nitrogen fertilizer decreased with the increase of nitrogen application rate. With the interaction of nitrogen application depth and amount, the H₁₅N₁₈₀ treatment could obtain desirable apparent utilization rate, agronomic utilization rate, biased productivity and production efficiency and highest seed cotton yield. [Conclusion] This study indicated that applying suitable nitrogen application rate and increasing fertilization depth could promote high yield. And it was recommended that the depth of nitrogen application should be increased from 5 cm to 15 cm,and the quantity should be reduced from 270-300 kg·hm^-2 to 180 kg·hm^-2 for the tested region.

[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.

[Objective] In order to establish a theoretical basis for sustainable development of dry-sowing and wet-emergence, and determine the critical content of salinity in soil for cotton seedling development under this planting mode, this study analyzed the effects of dry-sowing and wet-emergence technique on emergence rates and the development of cotton seedling under different levels of salt stress. [Method] The pot experiment was conducted to study the agronomic traits, dry weight and K⁺/Na⁺ ratio of cotton with dry-sowing and wet-emergence technique under salt stress. A control treatment (CK, soil salt content: 0.30 g·kg^-1) and ten treatments with different soil salt content (T1: 1.13 g·kg^-1, T2: 2.47 g·kg^-1, T3: 4.03 g·kg^-1, T4: 5.43 g·kg^-1, T5: 6.75 g·kg^-1, T6: 7.96 g·kg^-1, T7: 9.31 g·kg^-1, T8: 10.66 g·kg^-1, T9: 12.10 g·kg^-1, T10: 13.48 g·kg^-1) were applied. Additionally, the experiment of sowing under suitable moisture was applied to compare the effect of dry-sowing and wet-emergence mode on the seedling emergence rates. [Result] Soil salinity significantly inhibited the germination and emergence of cotton seeds. By using the dry-sowing and wet-emergence technique, the germination rate of cotton significantly improved under salt stress. Compared with sowing under suitable moisture, treatments of T4-T10 using dry-sowing and wet-emergence technique resulted in an increase in the emergence rate to 69.1%-93.3%. Salt stress had significant effects on agronomic traits and dry matter accumulation in cotton by dry-sowing and wet-emergence technique. Plant height, stem diameter, leaf number, square number, and dry matter accumulation of cotton were significantly decreased with the increase of soil salt content. And above-mentioned indexes of CK, T1, and T2 are significantly higher than that of T4-T10. The K⁺/Na⁺ value of cotton plant was also decreased significantly with the increase of soil salt content, in which treatments of T4-T10 were significantly lower than CK, T1, and T2. The result of the principal component analysis based on cotton growth indexes indicated that soil salt stress had a more significant effect on cotton growth and development in T4-T10 compared with CK, T1-T3. [Conclusion] The findings showed that when the soil salt content surpassed that of the T3 treatment (4.03 g·kg^-1), the salt stress significantly inhibited the seedling growth and dry matter accumulation of cotton, while the K⁺/Na⁺ value in cotton plant were significantly decreased. Despite the dry-sowing and wet-emergence technique significantly increased the emergence rate, it mitigated the negative impact of salt stress on the growth and development of cotton. Based on the result of this study, the critical value of soil salt content for the development of cotton seedling under dry-sowing and wet-emergence mode was 4.03 g·kg^-1.

[Objective] This study aims to explore factors affecting the fertility of cotton transgenic regenerated plants produced by Agrobacterium-mediated transformation system via somatic cell embryogenesis. [Method] In this study, several factors, including vector size, transgene insertion size, and different duration of culturing period were analyzed for evaluating their effects on the fertility of regenerated transgenic plants (T₀ generation). [Result] There were significant differences in sterility rate among transgenic plants of 6 different transgene and expression vector size. But there was no obvious correlation between sterility rate and vector/insertion size. Further analysis showed that the sterility of regenerated transgenic cotton plant had significantly positive correlation with the duration of embryogenic callus differentiation to plantlet regeneration. The sterility rate of regenerated plants from the duration of embryogenic callus differentiation to plantlet regeneration of <110 d, 110-130 d, 130-150 d, 150-170 d, and >170 d were 19.6%, 45.5%, 63.8%, 72.3%, and 94.5%, respectively. However, transgenic cotton plant sterility was not correlated with the duration of callus induction to callus embryogenesis. [Conclusion] Through Agrobacterium-mediated cotton genetic transformation, the sterility of cotton regenerated plants was mainly affected by the duration of embryogenic callus differentiation to plantlet regeneration, and accelerating the procedure of embryogenic callus differentiation could increase the fertility of regenerated transgenic plants.

[Objective] This study aimed to analyze the mechanism of GhCDPK28-A10 in Verticillium wilt response in cotton, and to provide genetic resources for disease resistance breeding in cotton. [Methods] The homologous sequence of the GhCDPK28-A10 gene was obtained from the cotton genome database and bioinformatic analysis was performed. Real-time quantitative polymerase chain reaction(qRT-PCR) was used to detect the effect of GhCDPK28-A10 gene on the resistance to Verticillium dahliae, methyl jasminate (MeJA), salicylic acid(SA), or H₂O₂-treated cotton plants. The role of GhCDPK28-A10 in cotton resistance to Verticillium wilt was verified by virus-induced gene silencing (VIGS) technique. [Results] Phylogenetic tree and gene structure analysis showed that the six GhCDPK28-A10 homologs in upland cotton shared similar number of motifs and contained the typical serine/threonine protein kinase structural domain of the CDPK family. Analysis of the promoter sequence revealed that GhCDPK28-A10 contains a cis-acting element in response to jasmonic acid (JA). Tissue-specific expression analysis showed that GhCDPK28-A10 was expressed in root, stem and true leaves. And the highest expression level was found in true leaves. The expression of GhCDPK28-A10 was significantly increased under stress induction by V. dahliae, MeJA, and H₂O₂. The expression of disease resistance-related genes PR1, NPR1, and PR4 was enhanced and the negative regulator of JA synthesis gene JAZ1 was decreased in GhCDPK28-A10 silenced cotton plants. This indicated that the JAZ1 regulated JA synthesis was inhibited and reactive oxygen species was enriched when the CDPK28-A10 expression level was decreased, which in turn enhanced the resistance to Verticillium wilt of cotton plants. [Conclusion] GhCDPK28-A10 negatively regulates the resistance response of cotton to Verticillium wilt by regulating the expression of defense-related genes, and is a candidate gene for improving the resistance of cotton to Verticillium wilt.

[Objective] This study aimed to explore the effects of water and nitrogen management on cotton growth and development, water and nitrogen use efficiency, and soil greenhouse gas emissions under non-film drip irrigation cotton fields in Xinjiang. [Method] Two irrigation quotas (W1: 450 m³·hm^-2, W2: 540 m³·hm^-2) and three nitrogen application rates (150 kg·hm^-2, 225 kg·hm^-2, 300 kg·hm^-2 nitrogen) were set. The differences of total nitrogen content of soil and plant, cotton plant height, cotton stem diameter, seed cotton yield, water and nitrogen use efficiency and soil greenhouse gas emissions were analyzed under different water and nitrogen treatments. [Result] At 225 kg·hm^-2 and 300 kg·hm^-2 nitrogen application rates, the average total nitrogen content in the 0-80 cm soil layer of W1 was higher than that in the W2 treatment at different growth stages. At the same nitrogen application level, the cumulative emissions of soil CO₂, CH₄, N₂O, global warming potential (GWP), greenhouse gas emission intensity (GHGI) and water use efficiency under W1 treatment were all increased compared with W2. Under W1 treatment, the average total nitrogen content of 0-80 cm soil layer at seedling and squaring periods, cotton plant height and stem diameter at different growth stages, seed cotton yield and water use efficiency all increased with the increase of nitrogen application rate. The cumulative emissions of soil CO₂ and CH₄, GWP, GHGI and partial productivity of nitrogen fertilizer decreased with the increase of nitrogen application rate, while the total nitrogen content of plant increased first and then decreased with the increase of nitrogen application rate. Under W2 breatment, total nitrogen content of cotton plant, seed cotton yield and water use efficiency all increased first and then decreased with the increase of nitrogen application rate. The cumulative emissions of soil CO₂ and CH₄, GWP and partial productivity of nitrogen fertilizer all decreased with the increase of nitrogen application rate, while cotton plant height and stem diameter increased with the increase of nitrogen application rate. Through fitting analysis, it was found that the fitting curves of seed cotton yield under W1 treatment and that under W2 treatment intersected when the nitrogen application rate was 278.07 kg·hm^-2. [Conclusion] For the Southern Xinjiang region with water shortage, 450 m³·hm^-2 irrigation quota and 300 kg·hm^-2 nitrogen application rate are efficient water and nitrogen application modes for increasing water use efficiency and cotton yield and reducing emission of soil greenhouse gas under non-film drip irrigation condition.

[Objective] Leaf blade is a plant organ that is sensitive to environmental changes. Leaf temperature is an important physiological index of plants. This study aims to explore the day-night variation characteristics of leaf temperature and to clarify the influence of meteorological factors on leaf temperature. [Method] In this study, the temperature of cotton leaves was automatically monitored in real-time based on infrared temperature sensors, and then the characteristics of day-night variation of cotton leaves temperature in different growth periods and under different weather conditions were explored, and the relationship of meteorological factors with leaf temperature and leaf-air temperature difference were explored by correlation analysis, stepwise regression analysis and path statistical analysis. [Result] The day-night variation of leaf temperature was different in various weather conditions and growth stages, and the variation range of leaf temperature was less than that of air temperature. Environmental factors were significantly correlated with cotton leaf temperature (except precipitation) and leaf-air temperature difference (except water vapor pressure) (P<0.05). The correlation between air temperature and leaf temperature was the highest (r = 0.890). The correlation between air relative humidity and leaf-air temperature difference was the highest (r = 0.825). The results of path analysis showed that the order of factors’ effect on leaf temperature according to decision coefficient was air temperature > photosynthetic active radiation > water vapor pressure. Photosynthetic active radiation and water vapor pressure mainly indirectly affected the change of leaf temperature through air temperature. The order of the effects of analyzed environmental factors on the leaf-air temperature difference according to the decision coefficient is air relative humidity > sunshine time > water vapor pressure. Sunshine time and water vapor pressure indirectly affect the change of leaf-air temperature difference through air relative humidity. [Conclusion] This study explored the day-night dynamic changes of cotton leaf temperature, and preliminarily explored the comprehensive effects of environmental factors on leaf temperature and leaf-air temperature difference. The results provide reference for cotton production and intelligent management.

[Objective] The experiment was conducted to study the effect of irrigation frequency on root distribution of cotton plant in Southern Xinjiang under fixed irrigation quota (3 900 m³·hm^-2). [Methods] CCRI 96A was planted as the test material, with 76 cm row spacing. Four irrigation frequency treatments were set up as follows: 6 irrigation times (T6, 650.0 m³·hm^-2 per time), 8 irrigation times (T8, 487.5 m³·hm^-2 per time), 10 irrigation times (T10, 390.0 m³·hm^-2 per time), and 12 irrigation times (T12, 325.0 m³·hm^-2 per time). The roots in the 0-60 cm soil layer of cotton in the middle row was collected and stratified by the soil root excavation method and scanned by root scanner. Then the root surface area, volume and other indexes were statistically analyzed. [Results] The roots with a diameter of less than 1 mm made up 94.5% of the total root length and 71.9% of the total root surface area. The total root volume was closely related to larger roots. With the increase of diameter, root length, root surface area, and root volume of each treatment decreased first and then increased. In the 0-60 cm soil layer, the root length density (11 662.71 m·m^-3), root surface area density (15.61 m²·m^-3) and dry matter mass (21.55 g) of T6 treatment were the largest, but the root volume density of T12 treatment (2.2×10^-3 m³·m^-3) was the largest. Under plough layer (30-60 cm soil layer), the root length density and the dry matter mass of T10 treatment were the largest, at 1 090.46 m·m^-3 and 1.09 g, and the root surface area density and the volume density of T8 treatment were the largest, at 2.52 m²·m^-3 and 2.68×10^-4 m³·m^-3, respectively. [Conclusion] Under the same irrigation quota of 3 900 m²·hm^-2, rational allocation of irrigation frequency can optimize the morphology and distribution of cotton roots in the soil. It could promote root surface area by increasing the irrigation amount per time to extend the irrigation interval. In this study, T6 treatment was beneficial to the elongation and distribution of cotton roots in the 0-60 cm soil layer, and T12 treatment is beneficial to cotton root thickening.