Cotton is an important economic crop in the world, occupying a significant position in the national economy. Cottonseed, as the main product of cotton production, is rich in high-quality protein and oil. Against the backdrop of the current shortage of protein and oil resources, fully exploring and utilizing the protein and oil resources in cottonseed can ensure the safety of edible oil supply and alleviate food security issues. With the increasing attention paid to the comprehensive utilization of cottonseed, the research on the genetic improvement of cottonseed nutritional quality is gradually increasing. This review provides an overview of the common methods for determining cottonseed protein and oil content, and summarizes the genetic characteristics and influencing factors of these traits. The relationships among cottonseed protein and oil content and fiber yield as well as the fiber quality traits were analyzed. A total of 335 quantitative trait locus (QTL) for oil content and 196 QTL for protein content were collected to construct a consistent physical map. In addition, the research progress of cottonseed protein and oil related synthetic pathways and regulatory genes were introduced, and the future research directions of biological breeding for cottonseed nutritional quality was prospected, which can provide a reference for the genetic improvement of nutritional quality in cottonseed.

Cotton straw is a by-product of cotton production and an important renewable biomass resource, and the study on its comprehensive utilization is of great significance to optimize energy structure and achieve 'dual carbon' goals. Due to the structural differences, the successful application methods of corn, wheat, and rice straw cannot be directly applied to cotton straw. Traditional treatment and application of cotton straw cause resource waste and environmental pollution. Therefore, it is essential to enhance the comprehensive utilization of cotton straw to improve agricultural waste utilization efficiency, optimize energy structure, and reduce environmental pollution. From the perspective of enhancing the comprehensive utilization efficiency of cotton straw, this article summarizes various utilization modes, including straw returning to the field, using them as feed, energy substrate, and raw material, and prospects the future multiuse of cotton straw which will provide methodological reference and research ideas for the diversified utilization of cotton straw.

[Objective] This research aims to study the effects of delayed sowing on cotton root growth and development characteristics and yield, so as to provide a basis for the timely sowing of cotton in the cotton planting area of the Yellow River Basin. [Methods] A field experiment was carried out at Weixian Experimental Station of Hebei Agricultural University from 2022 to 2023. Two treatments were set as conventional sowing date (15 April) and delayed sowing date (1 May). And the effects of delayed sowing on the root distribution, root growth rate, root-shoot ratio, dry matter accumulation, and yield of a cotton variety Jinongda 23 were analyzed. [Results] Compared with the conventional sowing date, under the delayed sowing condition, the maximum growth rate of cotton root length and root biomass increased by 2.92-5.35 cm·d^-1 and 0.40-0.76 mg·d^-1, respectively. The proportion of cotton roots in deep soil increased, with root length and biomass in the 30-60 cm soil layer increased by 2.99-3.55 percentage points and 3.94-4.42 percentage points, respectively. There was no obvious difference in aboveground biomass and root-shoot ratio in the late growth stage of cotton. The boll capacity of root system significantly decreased by 6.43%-17.69%. There was no significant difference in seed cotton yield in 2022. In 2023, the number of bolls per unit area and seed cotton yield increased significantly by 9.72% and 7.66%, respectively. Correlation analysis showed that root length density in 0-60 cm soil layer, root biomass density in 0-60 cm soil layer, maximum growth rate of root length, and the proportion of root length in 30-60 cm soil layer are extremely significantly correlated with seed cotton yield. [Conclusion] Delaying the sowing date (1 May) in cotton planting area of the Yellow River Basin can enhance the absorption function of cotton roots by increasing the growth rate of roots, the proportion of root length and biomass in deep soil layers, so as to ensure the accumulation of aboveground dry matter and promote the high yield of cotton.

[Objective] Heat damage is the most important meteorological disaster during the flowering and boll setting stage of cotton, which severely limits the safe production of cotton in Xinjiang. The evolution characteristics of heat damage in this area are clarified, which provides a reference for the scientific formulation of disaster prevention and mitigation measures. [Methods] This research used the daily maximum air temperature of 55 national basic meteorological stations in Xinjiang cotton planting areas from 1961 to 2022, and the observation data during the flowering stage and boll opening stage of 24 cotton meteorological observation stations from 1991 to 2022. Combined with the monitoring indices of high temperature and heat damage during flowering and boll setting stage of cotton, this research revealed the temporal and spatial variation of high temperature and heat damage with different grades during cotton flowering and boll setting stage by climate tendency rate and Mann-Kendall mutation test. [Results] The results showed that the maximum air temperature, extreme high temperature（daily maximum temperature ≥38.0 ℃） and cumulative days of the extreme high temperature during the flowering and boll setting stage of cotton in Xinjiang showed a significant upward trend from 1961 to 2022, with trend rates of 0.16 ℃·(10 a)^-1, 0.07 ℃·(10 a)^-1 and 0.45 d·(10 a)^-1, respectively. The frequency and intensity of high temperature and heat damage during the flowering and boll setting stage of cotton in Xinjiang have increased. From 1961 to 2022, the years of high temperature and heat damage during flowering and boll setting stage with different intensities in the cotton planting area of eastern Xinjiang subregion accounted for more than 96.0%, and the mild and moderate heat damage in the cotton planting area of southern Xinjiang subregion accounted for 88.7% and 51.6%, respectively. And the frequency of mild heat damage during the flowering and boll setting stage of cotton in the northern Xinjiang subregion was 64.5%. [Conclusion] The frequency and intensity of heat damage during flowering and boll setting stage in Xinjiang cotton planting area showed the regional characteristics of "strong in the east and weak in the west, more in the south and less in the north". Therefore, more attention should be paid in Xinjiang cotton planting areas to the breeding and application of high temperature resistant varieties, rationally adjustment of the cotton planting layout, strengthening the monitoring and early warning of meteorological disasters, and ensuring the safe and stable development of cotton production.

[Objective] This study aims to provide a theoretical basis for molecular breeding of disease-resistant cotton by cloning Gh_D11G050000 gene, and to analyze its function and mechanisms in cotton resistance to Verticillium wilt. [Methods] Bioinformatic method was utilized to analyze the sequence characteristics and phylogenetic relationship of Gh_D11G050000. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to investigate the expression pattern of this gene, and it's expression level changes after infected by Verticillium dahliae. The function of this gene was validated using virus-induced gene silencing (VIGS) technique. Transcriptome sequencing analysis and the detection of relative expression levels of related genes were conducted to explore the mechanisms of disease resistance. [Results] Gh_D11G050000 exhibited close relationship with Gh_A11G049600 and Gr_11G034620 protein. qRT-PCR analysis revealed that Gh_D11G050000 was highly expressed in cotton roots, and the expression level of Gh_D11G05000 was significantly increased after V. dahliae infection. Gh_D11G050000 silenced cotton plants showed reduced resistance against V. dahliae, characterized by aggravated browning of stem vascular bundles, increased the number of stem segments with bacterial propagation, as well as significantly increased the rate of diseased plants and disease index. Transcriptome analysis combined with qRT-PCR demonstrated that Gh_D11G050000 silenced cotton plants showed decreased transcription levels for several genes in jasmonic acid (JA) signaling pathway, ethylene (ET) signaling pathway, and lignin synthesis pathway. [Conclusion] Gh_D11G050000 positively regulates cotton resistance to Verticillium wilt by influencing the expression of several genes involved in lignin synthesis, JA, and ET signaling pathways.

Cotton is the most important natural fiber crop in the world, as well as also an important cash crop and raw material for textile industry in China. The change of fruit branch angle directly or indirectly affects the canopy structure, light energy distribution, boll formation structure and mechanical characteristics. In order to provide reference for the improvement of cotton plant architecture breeding and further promote cotton breeding, this paper reviews the current research status of cotton fruit branch angle from the perspective of cultivation and molecular, summarizes the previous research results and probes into the research trend of cotton fruit branch angle.

[Objective] This research aims to investigate the impact of different nitrogen (N) fertilizer rates on cotton under the machine picked with(66 + 10) cm row spacing, so as to provide scientific basis for improving the high-yield cultivation technology of cotton. [Methods] N top-dressing experiments was carried out in Korla of Xinjiang during 2021 and 2022. A field experiment was conducted using Ba 43541 as the test material, and four pure N application levels were set: 0, 112.5, 225.0, and 337.5 kg·hm^-2. Canopy structure characteristics, yield traits, and N use efficiency of cotton in middle position of the wide line (MW), middle position of the narrow line (MN), adjacent to plant (AP) and intermediate position of the adjacent two membranes (MC) were compared under different treatments. [Results] Under different treatments, with the advancement of growth process, leaf area index (LAI) of cotton at the four test sites increased first and then decreased, while photosynthetically active radiation (PAR) decreased first and then increased, but mean leaf angle (MLA) and gap fraction transmission coefficient (GFTC) showed different change trends. During the full budding stage, the LAI was lower, while MLA, PAR, and GFTC were higher in MC. The differences of LAI, PAR, and GFTC among the four test sites gradually decreased from the flowering and boll setting stage to the boll opening stage. During the full boll setting stage and boll opening stage, MLA were higher in MN and AP. Applying N 112.5 kg·hm^-2(N1) obtained appropriate LAI, MLA, PAR, and GFTC during the full boll setting stage, the boll number of per unit area increased. In 2021 and 2022, compared with the other three treatments, seed cotton yield of N1 increased by 1.38%-16.50% and 1.66%-11.57%, and lint yield increased by 1.57%-16.37% and 0.59%-12.40%, respectively; partial productivity and agronomic utilization of N were also increased. In terms of cotton LAI and PAR, there were extremely significant positive correlation among the four test sites. Overall, the best positive correlation of cotton canopy structure index was found among AP and MW, AP and MN. [Conclusion] Under the same N application rate, the change trends of LAI and PAR at four test sites were consistent, while the change trends of MLA and GFTC were inconsistent. The application of 112.5 kg·hm^-2 N could promote the high yield of Ba 43541, and improve the N use efficiency of cotton.

[Objective] This research aims to investigate the effects of planting density and varieties on the morphological structure of vegetative organs and yield of machine-picked cotton in northern Xinjiang. [Methods] Field trials were conducted in 2022 and 2023 at Wulanwusu Agricultural and Meteorological Experiment Station and Manas Agricultural Experiment Station, respectively. Two varieties, CCRI 127 (V1) and Xinshi 518 (V2), were selected, and three planting densities were designed as 11 plants·m^-2 (D1), 22 plants·m^-2 (D2), and 28 plants·m^-2 (D3), respectively. The effects of different treatments on leaf length, petiole length, petiole diameter, internode length, and internode diameter of cotton main stems and fruiting branches as well as yield traits were compared. [Results] In 2022 and 2023, V1 showed the smallest leaf length, petiole length, and internode length of main stems and fruiting branches under D1 and D2 treatments, respectively. In 2022, V2 showed the smallest leaf length, petiole length, petiole diameter, and internode length of main stems and fruiting branches under D3 treatment. In 2023, V2 showed the smallest petiole length and internode diameter of main stems and fruiting branches under D3 treatment. Leaf length and internode length of main stems and fruiting branches showed V1 ≥ V2 under the same density in 2022. Leaf length, internode length, and internode diameter of main stems and fruiting branches of V1 and V2 were not significantly different under the same density in 2023. The lint percentage of V2 was significantly higher than that of V1 under the same density both in 2022 and 2023. Seed cotton yield and lint yield of V1 and V2 in 2022 as well as that of V2 in 2023 increased with the increase of planting densities. Seed cotton yield of V1D3 treatment was highest in 2022, and relatively higher in 2023. V2D3 treatment had the highest lint yield in 2022 and 2023. [Conclusion] The preferred planting density under the conditions of this experiment was 28 plants·m^-2, and the lint yield of Xinshi 518 was higher. The results of this study can provide a support for the improvement of the CottonXL model, and provide a reference for the selection of appropriate varieties and planting densities of machine-picked cotton in the northern Xinjiang.

[Objective] Assessing cotton growth status through chlorophyll content offers a swift, accurate, and extensive monitoring of cotton development, which aids in precision farming. [Methods] To enhance the accuracy of chlorophyll content evaluation in cotton, fractional-order differentiation ranging from 0 to 2(with a step size of 0.2) and wavelet transform within scales from 1 to 10 to process the hyperspectral reflectance data collected from both upland cotton and sea island cotton fields were employed. By analyzing the correlation between different spectral processing techniques and chlorophyll content, sensitive spectral bands were identified. Subsequently, support vector machine regression(SVR) and random forest regression (RFR) models were employed to construct hyperspectral estimation models for cotton chlorophyll content. [Results] (1) In the wavelength range from 325 to 1 075 nm, the spectral reflectance curves of the two cotton species show similar overall trends, with reflectance increasing with the increase in chlorophyll content.(2) Following continuous wavelet transform and fractional-order differentiation, the correlationship between hyperspectral data and chlorophyll content improved for both cotton species. Inversion models revealed that using RFR and wavelet energy coefficient 7 had the best results for upland cotton chlorophyll content estimation, with a coefficient of determination (R²) of 0.931, root mean square error (RMSE) of 0.782, and residual prediction deviation (RPD) of 2.162. Similarly, for sea island cotton, employing RFR and wavelet energy coefficient 6 resulted in the most effective chlorophyll content estimation, with the R² of 0.932, RMSE of 1.198, and RPD of 2.687. [Conclusion] This study provides technical insights for remotely estimating chlorophyll content in cotton plants.

[Objective] This study aims to understand the changes in the agglomeration level of cotton production in China and its influencing factors. These findings hold practical significance for optimizing the layout of the cotton industry, promoting high-quality development of the cotton industry, and enhancing regional economic development. [Methods] Using the location quotient index to measure the agglomeration level of cotton production in China from 2001 to 2022, comparing the agglomeration growth and competitive status changes of cotton production in major producing provinces using the competitive state model, and finally empirically analyzing the factors affecting agglomeration changes. [Results] From 2001 to 2022, the cotton production aggregation level in inland regions of Northwest China has been consistently higher than that in the Yangtze River basin and the Yellow River basin, and has continued to rise. The production aggregation level and competitiveness of cotton in Xinjiang have been continuously strengthened. However, the production aggregation level and comprehensive competitiveness of cotton in other major cotton-producing provinces have notably declined. Factors affecting the changes in cotton production aggregation in China include conflicts between grain and cotton for land, water resources, the quantity of agricultural labor, agricultural technology levels, transportation costs, the synthetic fiber industry, and cotton target price policy. [Conclusion] For the sustainable development of the cotton industry, it is recommended to scientifically promote the allocation of resources for cotton production, implement the cotton industrial policies in accordance with local conditions, improve the technical level of cotton production, improve the cotton production infrastructure, promote the development of related industries and improve target price subsidy policies.

[Objective] To improve the yield of summer direct seeding cotton in the Yangtze River basin, this study focuses on the effects of nitrogen (N) and potassium (K) application frequency on cotton. [Methods] Field experiment was conducted in 2021 and 2022 under a randomized complete block design in a split-plot arrangement, where K fertilizer (210 kg·hm^-2) application frequency K1 [pre-plant fertilizer (PP) 100%] and K2 [PP 50% + first flowering fertilizer (FF) 0 d 50%] were kept in the main plot, and the sub-plots were allocated with N fertilizer (210 kg·hm^-2) application frequency: N2 [PP 20% + FF 0 d 80%], N3 [PP 20% + FF 0 d 60% + FF 21 d 20%], and N4[PP 10% + FF 0 d 50% + FF 7 d 30% + FF 21 d 10%]. The effects of different treatments on cotton dry matter accumulation and allocation, N and K accumulation and allocation, yield and yield components, and nutrient utilization efficiency were studied. [Results] The dry matter mass and the accumulation of N and K at plant removal stage, and the duration and average accumulation rate of the rapid accumulation period of dry matter in cotton plant, source, flow, and sink organs under K2N3 treatment were lower than those of K2N4 treatment, but the distribution ratio of dry matter, N, and K in the sink organs were higher than those of K2N4 treatment. K2N3 resulted in higher seed cotton yield and lint cotton yield, which were 31.4% and 31.9% significantly higher than the lowest yield treatment K1N2, respectively. However, further increase of N application times (K2N4 treatment) did not result in significantly higher cotton yield. There is no significant difference in the partial productivity of N and K between K2N3 and K2N4 treatments, but both are significantly higher than the other treatments. Principal component analysis showed that the main difference in cotton yield comes from the number of bolls, and promoting the allocation of biomass, N and K nutrients to sink organs is beneficial for improving yield. [Conclusion] For the direct seeding cotton after wheat in the Yangtze River basin, two times of K application combined with three times of N application can increase the absorption of N and K, promote dry matter as well as N and P distribution to sink organs, thus increase the number of bolls, and improve cotton yield.

[Objective] Cotton is a relatively tolerant crop to cadmium (Cd) stress. It is of great significance to breeding and extending the Cd tolerant cotton cultivars for remediation of Cd contaminated soil. This study aims to analysis the inheritance of cotton tolerance to Cd stress and to map the quantitative trait locus (QTL) related to Cd stress. [Methods] In this study, 188 recombinant inbred lines (RIL) called HM188 derived from an intraspecific hybrid between HS46 and MARCABUCAG8US-1-88 were used to study the phenotypic data of germination rate, germination potential, chlorophyll content, plant height, dry and fresh weight at seedling stage under Cd stress, and the Cd stress coefficient of each material was calculated as well. QTL mapping was conducted for each trait and Cd stress coefficient of HM188 population by using complete interval mapping method. [Results] According to the performance and Cd stress coefficient of each trait under Cd stress, MARCABUCAG8US-1-88 was the Cd tolerant parent, while HS46 was a sensitive one. The Cd tolerance of 188 RIL was basically normal distribution, including 23 strong Cd tolerant lines, 49 Cd tolerant line, 67 medium tolerant lines, and 49 sensitive lines. A total of 28 QTL for Cd stress coefficient was identified, which were distributed on 14 chromosomes with explaining of variation of 1.58%~8.41%. Among them, qRFW-13-1 related to root fresh weight was detected in both environments, which explained variation of 7.66% and 7.71%, respectively. [Conclusion] Cd tolerance in upland cotton is a quantitative trait controlled by multiple genes, which was greatly affected by the environment. However, qRFW-13-1 for Cd tolerance may be a stable QTL, which has some application values in molecular breeding for Cd tolerant cotton.

[Objective] This research aims to analysis the function of GhWRKY44 gene under drought stress, and to provide candidate gene resources for drought-resistant breeding in cotton. [Methods] The coding sequence of GhWRKY44 gene was obtained by polymerase chain reaction (PCR) from the cDNA of CQJ-5 (Gossypium hirsutum) leaves. And bioinformatics analysis was performed. The expression pattern of GhWRKY44 gene under the treatment of abscisic acid (ABA) and polyethylene glycol (PEG) 6000 were analyzed by quantitative real-time PCR (qRT-PCR). The function of GhWRKY44 genes under drought stress was investigated by using the virus-induced gene silencing (VIGS) technology. [Results] The protein encoded by GhWRKY44 is a member of class Ⅰa WRKY, and is closely related to GbWRKY44. The expression of GhWRKY44 was induced by PEG 6000 and ABA. Compared with the control cotton plants, GhWRKY44 silenced cotton plants showed more severe leaf wilting, and plant survival rate and leaf chlorophyll content (soil and plant analyzer development, SPAD value) were significantly reduced under drought stress. With 6 h and 7 h of dehydration treatment, the leaf water loss rate of GhWRKY44 silenced cotton plants was significantly higher than that of control plants. [Conclusion] Silencing of GhWRKY44 gene reduced drought tolerance of cotton, and GhWRKY44 is a positive regulator of drought tolerance in cotton.

[Objective] This study aims to explore the response of Gossypium hirsutum under artificial seawater and NaCl stresses, and to assess the feasibility of using artificial seawater to simulate salt stress for evaluating salt tolerance of cotton germplasms. [Methods] Utilizing 135 distinct G. hirsutum germplasms as the experimental materials, this study investigated the impact of artificial seawater and NaCl stresses on cotton seed germination and seedling growth. Through the integration of principal component analysis, membership function analysis, and cluster analysis methodologies, the comprehensive evaluation of cotton salt tolerance was conducted. The results of two identification methods were verified by field experiments under natural salt stress. [Results] The consistency of the identification results under the two salt stresses were only 52.38%, and there were great differences in the results. The identification results under artificial seawater stress were significantly and positively correlated with the results of field experiments, with a correlation coefficient of 0.720; while that under NaCl stress were not significantly correlated with the field identification results. Under artificial seawater and NaCl stress treatments, 21.90% and 33.33% of the 105 glandless cotton germplasms were resistant or tolerant to salt stress, respectively. Among them, Lu 17 and Handifen 29 showed strong salt tolerance under the two salt treatments. [Conclusion] Using artificial seawater that simulates the composition of coastal soil can identify the salt tolerance of cotton germplasms more accurately. Glandless cotton generally exhibits poorer salt tolerance, but there are still some germplasms with strong salt tolerance that can be used to breed new salt tolerant glandless cotton cultivars.

[Objective] This study aims to reveal the effects of different irrigation treatments at the flowering and boll setting stage on the photosynthetic characteristics and yield of cotton, and to provide a reference for the optimization of irrigation system in cotton planting areas of northern Xinjiang. [Methods] A field experiment was conducted in Changji, Xinjiang in 2023, with CCRI 125 as the test variety. Three lower limits of irrigation were set at the flowering and boll setting stage, which were 55% field capacity (T1), 60% field capacity (T2), and 70% field capacity (T3), respectively. The local conventional drip irrigation mode was used as the control (CK). The effects of different treatments on the soil moisture content, photosynthetic characteristics, and yield traits of cotton during the flowering and boll setting stage were analyzed. And the correlation and regression relationships between the photosynthetic index, foliar temperature, and the meteorological factors were also explored. [Results] The soil moisture content of 0-60 cm soil layer of T3 treatment was maintained in a relatively high and stable range (18.5%-21.6%) during the flowering and boll setting period. During the early flowering and boll setting period (11 July), the daily average of net photosynthesis rate of T3 treatment was the highest, showing a daily trend of increasing-decreasing-ascending-decreasing. Correlation analyses showed that net photosynthetic rate and transpiration rate were positively correlated with 0-60 cm soil moisture content, foliar temperature, solar radiation intensity, and ambient temperature. Seed cotton yield and irrigation water use efficiency were the highest under T3 treatment, which were significantly increased by 26.46% and 71.43%, respectively, compared with that of CK. The multi-objective evaluation based on the rank-sum ratio method showed that T3 treatment had the best overall effect. [Conclusion] In the northern Xinjiang where water resources are scarce, the lower and upper limits of irrigation at the flowering and boll setting stage setting at 70% and 90% field capacity, respectively, is a reasonable water-saving and high-yield irrigation mode for cotton fields under the drip irrigation with plastic-film mulching.

[Objective] GbTMEM214 transgenic Gossypium hirsutum line, obtained using Agrobacterium-mediated method, was used to clarify the sequence characteristics and detection methods of the T-DNA insertion site, and further promote its biosafety evaluation. [Methods] Based on the genome resequencing technology, the sequencing data was compared with the G. hirsutum standard line TM-1 genome sequence by BLASTn, and specific primers were designed to verify the insertion site by polymerase chain reaction (PCR). [Results] The T-DNA carrying the target gene GbTMEM214 was integrated into the position of 57 019 068-57 019 106 bp on chromosome D13 of G. hirsutum genome, resulting in 37 bp deletion of cotton genome. Combined with the flanking sequence of T-DNA insertion site obtained by PCR amplification, the specific detection method for GbTMEM214 transgenic cotton was established. [Conclusion] The T-DNA insertion site and flanking sequence of GbTMEM214 transgenic cotton was obtained based on genome resequencing technology, which can provide technical reference for biosafety evaluation of the transgenic cotton.

[Objective] This study aims to perform genome-wide asscciation study of cotton yield traits, such as lint percentage (LP) and boll weight(BW), and to mine the candidate genes, and may be helpful for improving cotton yield through molecular marker-assisted selection and molecular design breeding. [Methods] Genome-wide association study was performed using 300 upland cotton germplasms resequencing (10×) data and 3 055 642 high-quality single nucleotide polymorphism (SNP) for LP and BW in five environments and best linear unbiased predictive value (BLUP) for two years to detect significant association loci and candidate genes. [Results] The cotton LP and BW showed wide variations in different environments, with an average coefficient of variation of 9.40% and heritability of 92.81% for LP, and an average coefficient of variation of 11.96% and heritability of 86.67% for BW. BW is significantly positively correlated in different environments. It’s the same with LP. Population structure analysis, principal component analysis, and phylogenetic analysis classified the 300 upland cotton lines into six subgroups. Genome-wide association study detected a total of 223 quantitative trait locus (QTL) associated with LP and 89 QTL associated with BW. The three stable QTL qLP_Gh5.18, qLP_Gh12.43, and qLP_Gh17.2 screened in LP were further analyzed, and 17 related candidate genes were found. Two stable QTL qBW_Gh7.5 and qBW_Gh19.5 related to BW were further analyzed, and 8 related candidate genes were identified. [Conclusion] Five stable QTL were identified in 300 up land cotton lines associated with cotton LP and BW, and a total of 25 candidate genes related to LP and BW were mined.

[Objective] This research aims to explore the effects of adjuvants during pesticide spraying by plant protection unmanned aerial vehicle (UAV) on droplet deposition characteristics and control efficiency on Aphis gossypii. [Methods] Dajiang T30 UAV was selected to conduct a field spray experiment during the cotton budding stage. The effects of 6 adjuvants (Yaketou, Beidatong, Zhiwusancan, Nongjianfei, Qigong, and Beibeijia) in 39% spirotetramat buprofezin on the size, density, coverage, and deposition amount of droplets and control efficiency on A. gossypii were compared. [Results] Compared with the control without adjuvant, treatments with the adjuvants increased the droplet density, coverage, and deposition amount on the upper, middle, and lower leaves of cotton plant. The droplet size, density, coverage, and deposition amount treated with Beibeijia and Beidatong were all higher; of which the density, coverage, and deposition amount on the upper, middle, and lower leaves of cotton plants were significantly higher than those of the control treatment. The control efficiency on A. gossypii of treatments with adjuvants in the upper, middle, and lower parts of cotton plant was higher than that of the control treatment at 1 d, 3 d, 7 d, and 14 d after application. The control efficiency of the treatment with Beibeijia was the best, followed by the treatment with Beidatong. [Conclusion] The addition of Beibeijia and Beidatong can improve the deposition characteristics of droplets and has a good control effect on A. gossypii. It also has a good synergism on the control of A. gossypii with 39% spirotetramat buprofezin suspension.

[Objective] This paper aims to solve the problem of accurate recognition and localization of cotton with different postures and grades by cotton picker under the requirement of high-quality cotton picking. A cotton detection method YOLOX-Cotton based on the improved YOLOX is proposed. [Methods] YOLOX-Cotton uses YOLOX as the main framework, including a recognition module and a localization module, and incorporates coordinate attention (CA) module and SIoU loss function, and takes various posture and grade cotton pictures as data sets to train and test. [Results] The detection module of YOLOX-Cotton was capable of detecting cotton with different postures and grades, and the model precision, recall and average precision reached 92.9%, 86.8% and 92.4%, which were improved by 5.2, 5.5 and 6.1 percentage points, compared with the original YOLOX, respectively. The localization module of this model was capable of accurately obtaining the location of the cotton, the measurements were kept within the threshold range of the validated results of the field trial, and the standard deviation of all samples was less than 0.01. [Conclusion] The experiment proves that the YOLOX-Cotton can effectively solve the problem of cotton detection and localization by cotton picker under the requirement of high-quality cotton picking, and provides strong technical support for the realization of high-quality cotton picking.

[Objective] This study aims to investigate the regulatory effect of exogenous melatonin (MT) on cotton growth and development under salt stress. [Methods] Guoxinmian 9 was used as the material, and the indoor pot method was adopted with the soil salt content of 0.3%, and after screening out the appropriate MT concentration, four treatments were set: irrigate water + spray water (CK), irrigate salt water + spray water (S), irrigate water + spray MT (MT), and irrigate salt water + spray MT (MS). The plant height, stem diameter, leaf area, relative chlorophyll content (soil and plant analyzer development, SPAD value), biomass per plant, root-shoot ratio, antioxidant enzyme activity, reactive oxygen species content, and osmotic adjustment substance content of cotton under different treatments were studied. And correlation analysis of the above indexes was carried out. [Results] Compared with CK treatment, S treatment significantly reduced plant height, stem diameter, leaf area, SPAD value, aboveground fresh matter mass, underground fresh matter mass, aboveground dry matter mass, and underground dry matter mass, and significantly increased root-shoot ratio of cotton. In the later stage of salt stress treatment, S treatment significantly reduced the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in cotton leaf; significantly increased the contents of hydrogen peroxide, superoxide anion, and malondialdehyde; and significantly decreased the contents of soluble sugar, soluble protein, and proline. Compared with S treatment, foliar spraying 200 μmol·L^-1 MT under salt stress (MS treatment) significantly increased plant height, stem diameter, leaf area, SPAD value, aboveground and underground fresh matter mass, and aboveground dry matter mass per plant; significantly reduced root-shoot ratio; significantly increased SOD, POD, and CAT activities; significantly reduced the contents of hydrogen peroxide, superoxide anion, and malondialdehyde; and significantly increased the contents of soluble sugar, soluble protein, and proline. Aboveground dry matter mass was significantly and positively correlated with plant height, stem diameter, leaf area, SPAD value, aboveground fresh matter mass, underground fresh and dry matter mass, SOD activity, POD activity, CAT activity, soluble sugar content, soluble protein content, and proline content; while was significantly and negatively correlated with superoxide anion content and malondialdehyde content. [Conclusion] Foliar spray 200 μmol·L^-1 MT can effectively alleviate the oxidative stress and osmotic stress of cotton under high salt environment (soil salt content of 0.3%), promote cotton growth, and improve salt tolerance of cotton.