[Objective] The aim of this study is to breed new photosensitive male sterile lines in cotton, and to obtain excellent sterile parents to speed up premium cotton breeding process. [Methode] In this paper, the psm4 photosensitive male sterile line was crossed to W10 firstly, and then the hybrid F₁ was self-pollinated by 3 generations to produce the psm5, which had the same photosensitive male sterile trait as psm4. [Result] The anther of psm5 could not crack and its pollen could not be released normally when the illumination time was more than 12.5 h, but the anther could crack and the pollen could be released normally when the illumination time was less than 11.5 h. [Conclusion] This paper introduces the breeding process and photosensitive characteristics of psm5, which provides a reliable theoretical basis for the application of psm5 in crossbreeding. The fertility transition period of psm4 and psm5 is in 12~15 days before flowering, and both psm4 and psm5 are typical sporophyte photosensitive male sterile lines. psm5, a recessive photosensitive male sterile line, has a wide range of restorer lines, which is easy to make superior hybrid combinations and has a good application prospect in cotton crossbreeding.

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

[Objective] Uridine diphosphate glucose pyrophosphorylase (UGPase) is an important rate-limiting enzyme involved in glucose anabolism, which plays an important role in the development of plant fiber cells. However, there is little research in cotton UGPase genes. This study aimed to identify and analyze the characteristics of members of UGPase gene family in cotton. [Methode] Gossypium hirsutum, G. barbadense, G. arboreum, and G. raimondii were selected as the main research objects. The phylogenetic and expression characteristics of UGPase genes in G. hirsutum were analyzed by combining UGPase genes from 19 kinds of plants, including algae, rice, grape, cocao, durian, and so on. [Result] Phylogenetic analysis showed that UGPase genes were divided into two groups, UGPase-A and UGPase-B. Conserved motif and adaptive evolution analysis showed that UGPase-B type genes were very conservative in evolution, while UGPase-A type genes had great differences with UGPase-B in evolution. Homology analysis of UGPase genes in cotton, grape, cocao and durian showed that most of cotton UGPase genes originated from duplication events before the formation of allotetraploid cotton. The expression levels of UGPase-A type genes were higher at the initiation and elongation stage of cotton fiber development, and the expression levels of UGPase-B type genes were higher in vegetative organs. [Conclusion] The structure, function and evolution of cotton UGPase genes were analyzed, which laid the foundation for further study.

[Objective] Defoliation rate is an important basis for evaluating defoliation and ripening effect of machine-picked cotton. In this study, 14 kinds of color vegetation index were extracted from RGB images to establish a fast and accurate estimation model for cotton defoliation rate, which provides a theoretical and technical basis for timely harvesting of machine-picked cotton. [Methode] Different cotton varieties were set up. The data of cotton defoliation rates of different defoliant concentrations and spraying times were collected, and the canopy RGB images were collected by unmanned arerial vehicle(UAV). The correlation between color vegetation index and cotton defoliation rate was analyzed. Then, the estimation model of cotton defoliation rates was constructed by using the methods of simple linear regression (SLR), multivariate linear regression (MLR) and partial least square regression (PLSR). Meanwhile, the model was evaluated. [Result] The results showed different cotton defoliation rates after different treatments. There was a remarkable correlation between the defoliation rate and the visible light vegetation index; especially, the correlation coefficient between the triangular greenness index (TGI) and cotton defoliation rate is up to 0.81. The results showed that the model based on TGI index was the best in the linear regression model, coefficient of determination (R²) = 0.66, root mean squared error (RMSE) = 10.44%, relative RMSE (rRMSE) = 12.87%; the model based on excess blue index (ExB), green leaf index (GLI), TGI and excess green index (ExG) was outstanding in the multiple linear regression models (R² = 0.70, RMSE = 10.26%, rRMSE = 12.65%). In the PLSR models, the one with ExB, GLI, TGI, ExG, Comprehensive 2 and Comprehensive 1, had higher accuracy, R²= 0.70, RMSE = 10.02%, rRMSE = 12.22%. The external verification showed that there was a good fitting relationship between the measured values and the predicted values of each model. [Conclusion] The model established by MLR and PLSR has high accuracy and great fitting degree. Therefore, considering of the weight computation and complexity, the cotton defoliation rate estimation model established with ExB, GLI, TGI and ExG has excellent performance.

[Objective] The Propylea japonica is an important predator in farmland. It is very important to reveal the growth and development, the regularity of the development of oogenesis and follicular epithelial cell in P. japonica for solving the problem of artificial propagation of ladybirds. [Methode] The parameters related to the development and reproduction of P. japonica were measured. The morphology of ovarioles and follicular epithelial cells of P. japonica were systematically observed by staining of nucleus and cytoskeleton. [Result] (1) The results showed that the average duration of the 1^st, 2^nd, 3^rd and 4^th instar larvae, and pupa, female adults, and male adults of P. japonica were 1.13 d±0.09 d, 1.48 d±0.11 d, 1.34 d±0.08 d, 2.34 d±0.06 d, 2.81 d±0.08 d, 51.08 d±1.13 d and 48.36 d±1.29 d, respectively. The body length increased rapidly from the 2^nd to the 3^rd instars larvae. The larva reached the longest body length of 9.32 mm±0.27 mm at the 4^th instar, and the body width reached the widest of 3.70 mm±0.05 mm in adult. (2) The highest daily average oviposition of a female was 14.42±2.36. The average number of eggs laid by a single female was 414±41.27, and the maximum number was 654. (3) The dynamic changes of follicles and oocytes were defined, and the formation of space (patency) between the follicular epithelial cells during yolk deposition phase was observed, which was mainly used for the uptake of vitellogenin by the oocytes. [Conclusion] In this study, we confirmed the regularity of body length, body width, oogenesis, and follicular epithelial cell development of P. japonica. This study provides a theoretical basis for us to further explore the molecular mechanism of reproductive regulation and to solve the problem of artificial propagation.

[Objective] The aim of this study is to evaluate the genetic effect of FBP7::iaaM gene on fiber yield, quality and seed vigor in different upland cotton varieties. [Methode] In this study, IF1-1 was used as a male parent to produce hybrids with 27 cotton varieties of different genetic backgrounds, which are CCRI 12 and Ekangmian No. 9 and their originated parent lines. The lint percentage, seed index, fiber quality traits, germination potential and seed germination rate of F₁ were detected to evaluate the breeding value of FBP7::iaaM gene in IF1-1. [Result] The lint percentage of F₁ hybrids with FBP7::iaaM gene increased by an average of 6.60 percentage points, and seed index decreased with an average of 1.8 g, and the FBP7::iaaM gene had no negative effect on seed germination potential and germination rate. Most F₁ hybrids showed better fiber quality, such as fiber micronaire, fiber length, breaking tenacity, and breaking elongation. [Conclusion] In one word, IF1-1 germplasm line with FBP7::iaaM gene showed important potential in genetic improvement in upland cotton.

[Objective] This study aims to analyze the composition and difference of flavonoid metabolites in yellow, milky white and white petals of cotton, which provides theoretical basis for the further research and utility of pigmentation in cotton flower. [Method] In this study, firstly, the Ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) detection platform and Analyst 1.6.3 were employed to analyze the flavonoids in three types of cotton petals from Hai 7124(yellow flower), TM-1 (milk white flower), and Shixiya 1 (white flower). Then the multivariate statistical analysis was used to analyze different metabolites. Finally, KEGG and K-means was used to investigate the synthetic pathways of different metabolites. [Result] A total of 184 types of flavonoid metabolites were detected in petals of three colors, among which 76 were flavonol (accounting for 41.30%) and 51 were flavone (accounting for 27.72%). And 171 different metabolites were obtained, which were significantly enriched in the biosynthetic pathway of flavone and flavonols and the biosynthetic pathway of flavonoids. By analyzing the relative content of flavonoids metabolites in yellow, milky white and white petals, 15 different metabolites were found to show an increasing trend and 15 metabolites content were decreasing. Among them, 5 metabolites were annotated in the known KEGG pathway, and the content of chrysoeriol, astragalin and rutin were all increased in the biosynthesis pathway of flavone and flavonoid. In addition, in flavonoid biosynthesis pathway, the content of aromadendrin and epicatechin increased, and the content of isosalipurposide were decreased. [Conclusion] Different flavonoid metabolites in the three cotton materials were found to be mainly involved in the biosynthesis pathway of flavone and flavonol as well as the biosynthesis pathway of flavonoids. As the content of isoaridin was decreased gradually in yellow, milky white and white petals, we speculate that this substance was related to the formation of yellow cotton petals.

[Objective] The aim of this article is to study the function of GhRH39, a DEAD-box RNA helicase gene, in leaf development of upland cotton. [Methode] The gene structure and evolutionary relationships of GhRH39 were analyzed using bioinformatic approaches. The expression patterns of GhRH39 in different tissues and different leaf development stages were analyzed by quantitative real-time polymerase chain reaction. The virus-induced gene silencing (VIGS) was applied to silence the gene. The phenotypes of GhRH39-silenced plants were observead and pigment contents were detected. The expression levels of those genes related to chloroplast development and photosynthetic pigments synthesis in the GhRH39-silenced plants were detected. [Results] Bioinformatic analysis showed that GhRH39 encoding 620 amino acids had conservative sequence. The expressions of GhRH39 were detected in root, stem, leaf, apical bud, petal and fiber. Its expression level is higher in leaf, and changed with the development process of leaf. The expression of GhRH39 was successfully suppressed by VIGS. The virescent leaves were appeared in GhRH39-silenced cotton plants, in which the contents of chlorophyll a, chlorophyll b, and carotenoid all decreased. To some extent, the expressions of those genes related to development of chloroplast and photosynthetic pigments synthesis decreased in the GhRH39-silenced plants. [Conclusion] GhRH39 gene may affect the synthesis of chlorophyll a and b, and carotenoid, and affect the development of chloroplast in cotton.

[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.

Cotton fiber is not only the most important raw material for textile industry, but also an ideal model for studying plant cell differentiation, elongation, and cell wall synthesis. The differentiation and development of cotton fiber is regulated by a complex and interrelated regulatory network. Transcription factors, functional genes, plant hormones, non-coding RNAs, and epigenetic modifications all play important regulatory roles during cotton fiber development. With the assembly, resequencing, and association analysis of different cotton genomes, more and more key factors regulating cotton fiber development have been uncovered, which is of great significance for further elucidating the molecular regulation mechanism of cotton fiber development and helping cotton biological breeding.

[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] A cotton stem rot disease has been observed in Xinjiang Uygur Autonomous Region of China since 2016. In wet conditions, part of the diseased stem can produce rot symptoms such as longitudinal cracks and collapse of epidermal tissue; in dry conditions, the expansion of the diseased spots is significantly slower, or even no longer expands, showing symptoms of necrotic spots. In severe cases, the stems will die. Hence, it is vital to understand the species and biological characteristics of pathogens for disease control. [Method] A total of 18 stems of cotton with symptoms rot were collected from 11 cotton planting locations in the north and south of Xinjiang Uygur Autonomous Region. The pathogens were isolated and purified by conventional dilution separation and 20 representative strains were obtained by single spore purification. The pathogens were identified by morphology, molecular biology, and pathogenicity. To understand the suitable conditions for the growth and sporulation of the pathogens, the biological characteristics of the pathogens such as different temperatures, light, pH values, media and lethal temperatures were tested. [Result]The pathogens of cotton stem rot in Xinjiang were Fusarium incarnatum and F. proliferatum, among which F. incarnatum was the dominant species. The suitable temperature for the growth and sporulation of the two pathogens are 25 ℃. Light is beneficial to the growth of F. incarnatum, and dark culture is beneficial to the sporulation of two pathogens. The optimal pH for the growth of these two pathogens is 8, and the optimal pH for sporulation is 7. These two kinds of pathogens grow and produce spores better on potato sucrose agar and potato dextrose agar. The lethal temperatures of F. incarnatum and F. proliferatum spores were 48 ℃ and 60 ℃, respectively, and the lethal temperatures of hyphae were 50 ℃ and 61 ℃, respectively. [Conclusion] The pathogens of cotton stem rot in Xinjiang were F. incarnatum and F. proliferatum. F. incarnatum was identified as the dominant species. It is beneficial to the growth of the two species of Fusarium under the conditions of 20-30 ℃, pH 7-8 and full light; and the spore will be more productive under dark. Both potato sucrose agar and potato dextrose agar medium are beneficial to the growth and sporulation of the two pathogens.

[Objective] SHI-related sequence (SRS) family is a group of plant-specific transcription factors that play important roles in regulating plant development and response to adversity stress. However, the function of SRS gene family in cotton has not been well characterized. [Method] Based on the published genomic data of Gossypium hirsutum, G. barbadense and Arabidopsis thaliana, the genome-wide identification and phylogenetic analysis of SRS genes in cotton were conducted. And the expression pattern of SRS genes in ovule and fiber at different developmental stages, in different organs and under different abiotic stress conditions were analyzed. [Result] In total, 27 and 26 SRS genes were identified in G. hirsutum and G. barbadense, respectively. According to the phylogenetic analysis, SRS genes in cotton could be divided into three groups, and different groups had similar conserved motifs. There were multiple pairs of homologous genes in each subgroup. Some SRS genes were highly expressed in ovules at different developmental stages, and were also responsive to various abiotic stresses. [Conclusion]The evolution and potential functions of SRS gene family were analyzed and predicted, which provided a theoretical basis for the functional analysis of SRS genes in cotton.

[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] The aim of this study is to clone and analyze the epidermis-specific secreted glycoprotein EP1-like gene GhA01EP1 in cotton, which provided a basis for further understanding of the regulatory mechanism of extracellular protein in the resistance to environmental stress. [Method] The sequence of GhA01EP1 from Ji 2658 was obtained by homologous cloning strategy, the expression level of GhA01EP1 was analyzed by quantitative real-time polymerase chain reaction. The physical and chemical properties, structure and subcellular localization of GhA01EP1 protein were analyzed by bioinformatics method. Subcellular localization of protein was carried out by transient expression of tobacco transformation mediated by Agrobacterium. The drought resistance of transgenic Arabidopsis thaliana obtained by Agrobacterium-mediated transformation method was analyzed. [Result] We designated the epidermis-specific secreted glycoprotein EP1-like gene as GhA01EP1, without intron, which has an 1 317 bp open reading frame and encodes 456 amino acids. GhA01EP1 is located on chromosome A01 and contains two domains: B-lectin and Plant PAN/APPLE-like. GhA01EP1 is expressed in root, stem and leaf, and with highest expression level in root. KEGG pathway analysis showed that GhA01EP1 is most likely involved in glycine, serine and threonine metabolism and phenylalanine metabolism. Subcellular localization analysis showed that the GhA01EP1 is a secretory protein. The result of drought resistance analysis showed that transgenic Arabidopsis grew better under drought stress than wild type, with longer root and stronger recovery ability after rehydration. [Conclusion] The GhA01EP1 plays a positive role in drought resistance of cotton and Arabidopsis.

[Objective] This study aims to explore the effect of embedded depth of drip irrigation belt on cotton yield in the field without plastic mulching in Northern Xinjiang, and to provide scientific theory for green and efficient cotton cultivation techniques in Xinjiang. [Method] Using Xinluzao 74 as the material, three embedded depths of drip irrigation belt (D₁: 10 cm, D₂: 15 cm, D₃: 20 cm) were set to study the effects on the developmental course, dry matter accumulation, yield and quality of cotton. [Result] Compared with D₁ treatment, the seedling stage was prolonged by 4 d in D₃ treatment. After full-blooming stage, the dry matter accumulation of reproductive organs and vegetative organs of cotton increased along with the increase of the depth of embedded drip irrigation belt. The dry matter accumulation in reproductive organs of D₃ treatment was 25.5% and 54.3% higher than that of D₂ and D₁ treatment at boll-opening stage, respectively. The total boll number, boll weight and seed cotton yield were the lowest in D₁ treatment, and no significant differences were found between D₂ and D₃ treatment. There were no significant differences in cotton fiber length, fiber elongation and breaking tenacity between D₂ and D₃, but significantly increased by 5.9%, 0.29 percentage point and 10.2% in D₃ treatment compared with D₁ treatment, respectively. [Conclusion] Without plastic film mulching, the increased embedded depth of drip irrigation belt lead to increased accumulation of dry matter in reproductive organs and higher yield and improved fiber quality of cotton. Considering the stability of yield, 15 cm is the most suitable embedded depth of the drip irrigation belt for cotton plantation without plastic mulching.

[Objective] The aim of this research is to study the regulation mechanism of plant growth regulator mepiquat chloride (MC/DPC) in improving the drought tolerance of cotton seedlings. [Method] In this study, CCRI 41(Gossypium hirsutum L.) was used as the test material, and four treatments including CK-Ctrl (sufficient water supply + spraying water), CK-DPC (sufficient water supply + spraying 30 mg·L^-1 DPC), DS-Ctrl (drought stress + spraying water), and DS-DPC (drought stress + spraying 30 mg·L^-1 DPC) were performed. At the two-leaf stage, DPC or water was sprayed on leaves, and then irrigation was stopped at five days as drought treatment, and using sufficient water supply as the control. [Result] The experimental results showed that under sufficient water conditions, DPC has no significant effect on the relative water content, total chlorophyll content, net photosynthetic rate, and water use efficiency of leaves. Under drought stress, DPC can significantly increase the accumulation of proline and relative water content. Meanwhile, DPC can slightly enhance the stomatal conductance and transpiration rate of leaves, and significantly increase the net photosynthetic rate, to improve the water use efficiency finally. In addition, DPC can also promote the accumulation of soluble protein of leaves in response to drought stress. [Conclusion] Spraying DPC can significantly increase the relative water content, net photosynthetic rate and water use efficiency of cotton seedlings, and can enhance the ability of cotton to resist drought stress by adjusting water balance and photosynthetic performance.

[Objective] The purpose of this study was to investigate the effects of different forms of boron on the absorption and utilization of boron and other minerals. [Methods] Using the potted soil culture method, CCRI 83 as the experimental material three treatments were set up: control (CK), inorganic boric acid (B), organic boron (OB), and the boron application amount was 1 mg·kg^-1. Cotton was sampled at 65 days after growth and related indicators were determined. [Results] The application of B and OB promoted the development of cotton cell wall and chloroplast, increased the boron contents in the leaves, stems, roots, and cell wall, and promoted the absorption of phosphorus and magnesium, but reduced the absorption of calcium by cotton, and increased the biomass per plant by 15.09% and 22.49%, in comparison with CK, respectively. Compared with B treatment, OB treatment has a more significant effect on increasing boron content (mainly free or protoplasmic boron with high mobility) in cotton leaves and stems, increasing by 16.88% and 10.72%, respectively. [Conclusion] Organic boron was more conducive to the absorption and utilization of boron by plants than inorganic boric acid.

[Objective] L-D₁ regulates leaf shape in upland cotton. This study develops specific molecular markers for L-D₁ alleles and provides a basis for the application of L-D₁ alleles in improving canopy structure. [Method] Morphological traits were investigated to analyze the effect of different combinations of L-D₁ alleles with the genetic background of Lumianyan 28 (LMY28) on leaf shape. Specific molecular markers based on polymorphism of alleles' promoters and CDS (Coding sequence) were used to check the combinations of L-D₁ alleles in different materials. [Result] L-D₁ alleles regulated the formation of leaf lobes from the 3-leaf stage. The lobes deepened from the 4-leaf stage to 8-leaf stage and stabilized from the 9-leaf stage. It was difficult to distinguish the combination of L-D₁ alleles from similar leaf shapes. A total of 24 SNPs (Single nucleotide polymorphism) and a 14 bp and a 133 bp insertion-deletion(InDel) were identified in the promoter of 4 alleles. Based on the SNPs and InDels in the promoter and coding sequences, three specific molecular markers, InDel_8, dCAPS_192, and dCAPS_519, were developed for l₂, L₂^o, and L₂^s, respectively. [Conclusion] Specific molecular markers were developed and could be used to identify L-D₁ alleles, which controlled leaf shape of cotton.