[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] 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] Gibberellin 20 oxidase gene GhGA20ox6 was cloned and the preliminary functional analysis was performed for plant height. [Method] The GhGA20ox6 gene was successfully cloned from the stem of upland cotton standard line TM-1. The evolutionary relationships of GhGA20ox6 and its homologous genes in Arabidopsis thaliana and rice were confirmed by phylogenetic analysis and multiple alignment of amino acid sequences. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyse the expression pattern of GhGA20ox6 in multiple tissues of TM-1. In addition, subcellular localization was used to analyze its specific subcellular localization. And its function in Arabidopsis was analysed. [Result] The open reading frame of GhGA20ox6 is 1 155 bp and encodes 384 amino acids. The molecular mass of GhGA20ox6 is 43.32 ku and the predicted isoelectric point is 6.37. Phylogenetic analysis showed that GhGA20ox6 was highly similar to the green revolution gene sd1(OsGA20ox2) in rice. The qRT-PCR results showed that GhGA20ox6 was higher expressed in the stem than in other tissues of TM-1. Furthermore, according to the results of subcellular localization analysis in tobacco epidermd cells, GhGA20ox6 was localized in the cell membrane. Overexpression of GhGA20ox6 in Arabidopsis significantly increased the expression of a downstream gene GID1 (gibberellin insensitive dwarf1), resulting in the increase of plant height and earlier bolting. [Conclusion] Based on the cloning and functional analysis of GhGA20ox6, it is speculated that the gene may be related to gibberellin synthesis in cotton, and may affect the plant height of cotton. These results lay a foundation for further molecular verification of the biological function of GhGA20ox6 in cotton growth and development.

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

[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.

本刊2022年34卷第2期张素君等《陆地棉主要育种性状SSR关联位点的验证及优异材料鉴定》的基金项目中河北省农林科学院创新工程（2021-3-7-1、2021-3-7-4）更改为河北省农林科学院科技创新专项（2022KJCXZX-MHS-1），特此声明。

[Objective] Adenosine diphosphate-glucose pyrophosphorylase(AGPase) is the rate limiting enzyme in the starch biosynthesis pathway, which plays an important role in starch synthesis and accumulation of plant "source" and "sink" organs. However, the systematic study of AGPase gene family has not been carried out in cotton. [Method] In this study, the whole genome identification of AGPase gene family was carried out by bioinformatics based on the published genomic data of Gossypium hirsutum standard line TM-1. The physical and chemical properties, evolutionary relationship, gene structure, cis-acting elements in the promoter region were systematically analyzed. Transcriptomic data and real-time quantitative polymerase chain reaction (qRT-PCR) were used to analyze the expression patterns of AGPase family genes in different tissues and under various abiotic stresses. [Result] A total of 20 AGPase genes (GhAGP) were identified in G. hirsutum, and they were unevenly distributed on 16 chromosomes. There were 12 AGPase gene encoding AGPase large subunit and 8 AGPase gene encoding AGPase small subunit, and had similar conserved motifs and exon-intron structure in different groups. The promoter region of GhAGP had multiple cis-acting elements related to plant hormones and abiotic stress response. Expression analysis showed that GhAGP had different tissue expression patterns. The expression level analysis under abiotic stress showed that most GhAGP were induced by low temperature, high temperature, salt and drought stress, in which GhAGPL1 and GhAGPL7 were involved in the response to a variety of stresses in cotton. [Conclusion] The distribution, structural and phylogenetic characteristics of AGPase genes were clarified in G. hirsutum, and the function of AGPase gene family in response to external environmental stress was preliminarily revealed, which provide important candidate gene resources for genetic improvement of starch traits and stress resistance breeding in cotton.

[Objective] This study aims to build a cotton yield prediction model at seedling stage for cotton field management. [Method] This study was conducted based on UAV (unmanned aerial vehicle) high-resolution image data. Firstly, the cotton seeding at 3-4 leaf stage were identified and extracted on the UAV images using green leaf index (GLI). Then, cotton seedlings were graded according to the diameters of cotton in the trial area by the natural breakpoint method, and the number of cotton bolls per plant and the boll weight were evaluated at harvest time. Finally, the cotton yield estimation model NDCS (number and diameter of cotton seedlings) based on the growth state at the seedling stage was constructed to predict the cotton yield by combining the grade of cotton seedlings in the trial area and the number of cotton bolls per plant and the boll weight. [Results] Among the 34 vegetation indices, GLI showed the best image segmentation effect. The average rate of precision extraction of cotton seedlings on multiple repeated trial at different scales was 96.2%. A total of 380 715 cotton plants were extracted from the trial area, including 2 657 seedlings of A grade, 103 753 seedlings of B grade, 214 691 seedlings of C grade and 59 614 seedlings of D grade. The NDCS model showed relative high accuracy on yield prediction, with the coefficient of determination of 0.919 2. The root mean squared error(RMSE) of the yield estimation model was 0.168 7. The estimated accuracy of the yield prediction model was 94.7% when compared with the actual yields. [Conclusion] This study used the high resolution UAV image of cotton seedling combined with the performance of yield-related traits to achieve cotton yield prediction, which provided a new route and method for cotton yield estimation.

[Objective] At the seedling stage, plant growth regulators and their appropriate concentrations were screened to improve the high temperature tolerance of cotton, and the alleviating effects were determined at the flowering and boll setting stage. [Method] In this study, the cotton cultivar Zhongmian 425 was selected as the test material. Two kinds of temperature treatments were set: normal temperature (average temperature was 28 ℃, and maximum/minimum temperature were 24 ℃/32 ℃) and high temperature (average temperature was 38 ℃, and maximum/minimum temperature were 42 ℃/34 ℃). Water, 200, 400, 600 μmol·L^-1 1-methylcyclopropene (1-MCP), 0.01, 0.02, 0.05 μmol·L^-1 coronidine (COR) and 0.5, 1.0, 2.0 μmol·L^-1 2, 4-epibrassinolide (EBR) spraying treatments were set at the seedling stage. Water and 400 μmol·L^-1 1-MCP spraying treatment were set at the flowering and boll setting stage. The effects of different plant growth regulators on the dry mass, leaf photosynthetic characteristics, chlorophyll content, antioxidant enzyme activity, yield and fiber quality of cotton under the normal temperature and high temperature conditions were explored. [Result] The results showed that the suitable concentrations of three plant growth regulators could improve the high temperature tolerance of cotton. Under high temperature stress at the seedling stage, compared with water treatment, spraying 400 μmol·L^-1 1-MCP could significantly increase the dry mass of aboveground and underground parts of cotton, and increase the net photosynthetic rate, the contents of chlorophyll a and chlorophyll b, and the activities of antioxidant enzymes (superoxide dismutase, peroxidase, glutathione peroxidase and ascorbate peroxidase), and decrease malondialdehyde content in newly expanded cotton leaves. Principal component analysis proved that 400 μmol·L^-1 1-MCP could effectively improve the high temperature tolerance of cotton. Meanwhile, under high temperature stress at the flowering and boll setting stage, spraying 400 μmol·L^-1 1-MCP could significantly improve the net photosynthetic rate, stomatal conductance and transpiration rate of subtending leaves to cotton bolls, the number of bolls per plant, boll weight, seed cotton yield per plant and fiber quality compared with spraying water. [Conclusion] 400 μmol·L^-1 1-MCP can increase the chlorophyll content, photosynthetic capacity and antioxidant enzyme activity, and reduce the accumulation of malondialdehyde and other harmful substances in cotton leaves, thus enhancing the high temperature tolerance of cotton, and finally improve the cotton yield and fiber quality to a certain extent.

[Objective] Leaf area index (LAI) is one of the important indexes for crop growth diagnosis, biomass estimation and yield prediction in agriculture. Rapid inversion of LAI using unmanned aerial vehicle (UAV) multispectral remote sensing is important for cotton growth monitoring and field management. [Methods] Cotton at flowering and boll-setting stage in Aral reclamation area in Xinjiang was taken as the research object. The ground measured cotton LAI data and UAV multispectral images were used as data sources. After the image stitching was completed, spatial resampling was performed to obtain six different resolutions of multispectral images, vegetation index and texture features were extracted, and the texture index was constructed with texture features. Using the vegetation index, texture index and the combination of the two indices as input quantities, the cotton LAI prediction model based on the partial least squares regression (PLSR), support vector machine (SVM) and random forest algorithm (RF) were constructed and the prediction performance of the three input features and the models were compared under different resolutions, respectively. [Results] (1) The correlation between the two indices and LAI tended to increase and then decrease when the resolution of the multispectral image decreased, and the correlation between the two indices and LAI reached maximum when the image resolution was under the 1.0 m. The estimation performance of the three models were first increased and then decreased with the reduction of image resolution, and the estimation performance was the best under the 1.0 m resolution. (2) When the multispectral image was under the 1.0 m resolution, the RF algorithm model has the best estimation results, followed by the SVM algorithm model, and the PLSR algorithm model has the worst results. (3) The order of the accuracy of three input feature quantities were the follow: vegetation index and texture index, vegetation index, and texture index. [Conclusion] The RF algorithm model constructed by vegetation index and texture index extracted from UAV remote sensing image with 1.0 m spatial resolution had the highest accuracy in estimating cotton LAI at flowering and boll-setting stage.

[Objective] This research aims to investigate the effects of male sterile cytoplasm of Gossypium harknessii (CMS-D2) and Gossypium trilobum (CMS-D8) on ATP and H₂O₂ contents. [Method] The contents of ATP and H₂O₂ in leaves and flower buds of CMS-D2 and CMS-D8 "three lines" (sterile line, maintainer line, and restorer line) at different developmental stages were determined, and combined with the subject of existing research, ATP and H₂O₂ contents in Arabidopsis plants overexpressing the sterile candidate gene orf610a were determined. The expression levels of ATP synthesis-related genes in the flower buds of sterile lines, maintainer lines and transgenic Arabidopsis were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). [Result] During the development of cotton, compared with its maintainer line and restorer line, the leaves of CMS-D2 sterile line showed an extremely significant decrease in ATP content and an extremely significant increase in H₂O₂ content at both the bud stage and boll stage; the leaves of CMS-D8 sterile line showed an extremely significant decrease in ATP content and an extremely significant increase in H₂O₂ content at the bud stage, and an extremely significant increase in ATP content at the boll stage. The ATP content in 3 mm and 4 mm flower buds of CMS-D2 sterile line was extremely significantly decreased, and the H₂O₂ content in 4 mm flower buds was extremely significantly increased; the ATP contents in 5 mm and 6 mm flower buds of CMS-D8 sterile line were extremely significantly decreased. Compared with the maintainer lines, the expression levels of several ATP synthesis-related genes in the flower buds of the CMS-D2 and CMS-D8 sterile lines were extremely significantly reduced. Compared with wild-type Arabidopsis, the H₂O₂ contents in siliques and flower buds of orf610a-overexpressed Arabidopsis were significantly increased, and the ATP content were extremely significantly decreased, and most ATP synthesis-related genes were extremely significantly down-regulated. [Conclusion] The male sterile cytoplasm have certain effects on the contents of ATP and H₂O₂ in leaves and flower buds at different developmental stages of cotton, and the disruption of the dynamic balance may affect the development of pollen.

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

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

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

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

[Objective] The aim of this study is to explore the elite gene/quantitative trait loci (QTL) resources of yield and fiber quality, and to provide useful information for developing cotton varieties with high yield and excellent fiber quality. [Methods] A superior chromosome segment substitution line MBI9626, and a high-yield and wide-adaptability upland cotton CCRI 36 were selected to construct a secondary segregation population BC₆F₂ which contained 152 individuals. And 109 selected simple sequence repeat(SSR) markers were used to genotyping parents and the population, and QTL mapping for yield and fiber quality traits was conducted based on genotype data and phenotype data. [Results] Genotyping resutts showed MBI9626 recovered to 94.8% of the genetic background of CCRI 36. A total of 28 QTLs related to yield and fiber quality traits were detected in BC₆F₂, BC₆F_2:3, and BC₆F_2:4 populations, which were distributed on 6 chromosomes. Among them, there are 16 QTLs related to yield, accounting for 2.25%-6.14% of the phenotypic variation, including 6 stable QTLs; 12 QTLs related to quality traits, accounting for 2.49%-12.30% of the phenotypic variation, including 2 stable QTLs. There were 19 newly discovered QTLs, including 5 stable QTLs. And 233 genes were identified in a QTL cluster with 6 QTLs on D3 chromosome. Based on gene ontology (GO) cluster and Kyoto encyclopedia of genes and genomes (KEGG) analysis and TM-1 transcriptome data, 6 candidate genes were screened to be involved in fiber development, namely GH_D03G1428、GH_D03G1466, GH_D03G1518, GH_D03G1570, GH_D03G1586, and GH_D03G1640. [Conclusion] Twenty-eight stable QTLs related to cotton yield and fiber quality were identified and would lay a solid foundation for fine mapping and cloning of candidates genes and marker assisted selection.

[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 investigate the effect of irrigation frequency and irrigation quota on the characteristics of temporal and spatial distribution of reproductive organs and yield of filmless cotton, so as to provide references for the irrigation system to the cultivation of filmless cotton in Southern Xinjiang. [Method] From 2020 to 2021, using Zhongmian 619 as the test variety, the single-factor random block design was adopted. In the field trial of the first year, treatments of 3 irrigation frequencies were set, including 4 times (W4), 6 times (W6), and 8 times (W8) irrigation during the flowering and boll-setting period. The corresponding irrigation interval of each treatment was 12 d，8 d and 6 d, respectively. In the second year, treatments of 4 irrigation frequencies were set, and the W7 treatment of 7 times irrigation with 7 days irrigations interval was included during the flowering and boll-setting period on the basis of the first year's experimental setup. The irrigation quota of all treatments of filmless cotton in two years were 69 mm per time, besides the last round of irrigation in W8 treatment which used 52.2 mm water. The cotton with mulching film was set as control (CK) with irrigation frequency of 8 times and irrigation quota of 45 mm per time during the flowering and boll-setting stage in both years. The plant architecture map of each cotton developmental stage was collected, and the actual yield and corresponding traits were evaluated. [Result] The statistical analysis of the boll formation rate at each fruit node was conducted on the horizontal and vertical directions during the boll-opening stage. The results showed that the number of bolls and the boll-formation rate of the upper fruit branches and peripheral bolls of W4 were lower than those of other treatments. And the boll number and boll-formation rate are similar in W6 and W8. In 2021, the number of bolls and the rate of boll formation in W7 were higher than those in W4, W6, and W8. The result of the shedding rate of bolls in the boll-opening period showed that the shedding rate of the peripheral bolls and the upper fruit branches were higher in two years, but the specific site of the shedding bolls and the shedding rate varies among treatments. The analysis of yield components showed that W7 had significantly higher number of bolls per unit area, higher boll weight, and higher seed cotton yield than W4, but were not significantly different from CK. And the water use efficiency of W7 was higher than that of W6 and W8. [Conclusion] Application of extreme high or low irrigation frequency and irrigation quota during the flowering and boll-setting period affect the number of bolls, spatio-temporal distribution of cotton bolls, shedding rate as well as boll weight of filmless cotton, which in turn affects yield. In this study, the W7 treatment can provide a reference for the designing of the irrigation system for filmless cotton production in Southern Xinjiang. In detail, the recommended irrigation frequency is 2 times in the squaring period with the irrigation interval of 10 days, 7 times irrigation in the flowering and boll-setting period with the irrigation interval of 7 days, and the irrigation quota in total is 573 mm.

[Objective] The purpose of this study was to screen and identify a strain of highly efficient biocontrol bacteria against cotton Verticillium wilt, and to clarify its control mechanism, so as to provide technical support for the disease control. [Method] An endophytic bacterial strain EBV02 against Verticillium dahliae was screened in our laboratory, the species were identified by morphological, physiological, and biochemical characteristics and molecular biological analysis, and its control effect on cotton Verticillium wilt was determined by the indoor bacteriostatic test, greenhouse test, field test, and induced resistance test. The control mechanism of EBV02 was analyzed by measuring the burst of reactive oxygen species, accumulation of callose, and expression of defense-related genes in cotton leaves. [Result] EBV02 was identified as the Bacillus velezensis through morphological observation and molecular biological analysis. The results of confrontation culture and plate-to-plate culture showed that the inhibition rates of EBV02 on mycelium growth of V. dahliae Vd080 were 63.27% and 59.83%, respectively. The inhibition rates of EBV02 on Vd080 sporulation and microsclerotia germination were 31.90% and 45.95%, respectively. In the greenhouse experiment, the highest control effect of EBV02 on cotton Verticillium wilt was 68.33%, and could significantly promote the growth of cotton seedlings. In the field experiment, the control effect of EBV02 fermentation broth spraying on cotton Verticillium wilt was 37.25%. In addition, seed cotton yield and lint yield with EBV02 treatment by seed soaking, root irrigation and spraying of fermentation broth were significantly increased by 8.34% and 8.26%, 3.38% and 5.60%, 7.04% and 7.06%, respectively. In the induced resistance test, EBV02 induced the burst of reactive oxygen species and the accumulation of callose in cotton leaves. The results of gene expression showed that EBV02 induced upregulation of defense-related genes such as POD, PPO, PAL, PR10, and JAR1 in cotton leaves, which enhanced the resistance of cotton to V. dahliae. [Conclusion] EBV02 has a good biocontrol potential of inhibiting the growth of V. dahliae, activating the systemic disease resistance, enhancing the cotton resistance to Verticillium wilt, and increasing the yield in cotton.