[Objective] This research aims to investigate the function of S-adenosylmethionine synthetase (SAMS) gene in the resistant response to Helicoverpa armigera in Gossypium hirsutum. [Method] Real-time quantitative polymerase chain reaction (qRT-PCR) was used to analyze the expression pattern of GhSAMS gene under the H. armigera attack. Virus-induced gene silencing (VIGS) technology was adopted to suppress the expression of GhSAMS gene. The insect-resistant function of GhSAMS gene was preliminally investigated by analyzing the growth and development(changes in body weight and body length) as well as feeding preference of H. armigera, and the damage profile of cotton leaves. [Result] qRT-PCR results showed that the expression level of GhSAMS gene was increased during H. armigera feeding process. Compared with those fed with wild-type (WT) cotton leaves, H. armigera fed with pTRV2::GhSAMS leaves grew and developed faster. And H. armigera exhibited stronger feeding preferences towards pTRV2::GhSAMS leaves. 3,3'-diaminobenzidine (DAB) staining showed that pTRV2::GhSAMS cotton leaves accumulated more H₂O₂ compared with WT cotton. [Conclusion] Inhibiting the expression of GhSAMS gene reduces the resistance of G. hirsutum to H. armigera, and GhSAMS can be used as a candidate gene to improve the cotton resistance to H. armigera.

[Objective] Frego bract can greatly reduce the attachment of bract to boll and help to reduce the percentage of trash of machine-harvested cotton. In this study, we aimed to fine mapping the frego bract fg gene in cotton, so as to provide reference for its cloning and breeding utilization. [Method] Two F₂ segregating populations were constructed by crossing Gossypium hirsutum T582 (as the female parent) with G. hirsutum TM-1 and G. barbadense 3-79, respectively. Population 1 (T582 × TM-1) included 370 individual plants, and population 2(T582 × 3-79) contained 2 667 individual plants. The developed Indel (insertion-deletion) markers based on the reference genomic data of TM-1 and 3-79 were used to fine mapping fg. Functional annotation and expression pattern analysis of genes within the mapped sequence were performed using cotton functional genomics and multi-omics data. [Result] Genetic analysis showed that frego bract is controlled by a single recessive gene. Based on the previous mapping result of fg gene, cotton fg gene was further mapped between molecular markers M3 and M4 on chromosome A03, with an interval size of 188 kb in this study. A total of fourteen annotated functional genes were predicted in the mapping region. Among them, Gh_A03G021700, Gh_A03G021900, Gh_A03G022600 and Gh_A03G022700 were highly expressed in sepal and epicalyx. [Conclusion] Frego bract fg gene was finely mapped on chromosome A03, with an interval size of 188 kb, and 14 candidate genes in the mapping interval were preliminarily analyzed, which lays the foundation for map-based cloning of this gene.

[Objective] This study aims to investigate the effects of different short-season cotton cultivars and sowing dates on the spatial distribution of cotton yield and fiber quality, and to provide a reference for the selection of suitable sowing date and cultivar for the application of mechanized wheat-cotton intercropping system in the Yellow River basin cotton production region. [Method] A two years' field experiment was conducted using split zone design in 2019-2020, two short-season cotton cultivars (JX 707 and LM 2387) were taken as the main plot, and the four sowing dates were set as the sub-plot, including May 10th (SD1), May 20th (SD2), May 30th (SD3), June 10th (SD4). The cotton biomass, plant architecture, lint yield and yield components were investigated, and the main fiber quality index and comprehensive index of fiber quality Q score were measured. [Result] Late sowing date (SD4 treatment) showed prolonged flowering and boll development period of cotton, while leaf area index, number of fruit branches and number of fruit nodes decreased with the delayed sowing date. The sowing dates significantly affected the lint yield and boll distribution. There were no significant differences among lint yield of SD1, SD2, and SD3 in both experimental years. However, when the sowing dates was postponed to June 10th (SD4), the average lint yield of two cultivars in two years was reduced by 38.7%, 37.2%, 32.7% compared with SD1, SD2, and SD3, respectively. In addition, when the sowing dates was delayed, the proportion of bolls from the first to third fruit branches increased significantly and the proportion of bolls formed above the sixth fruit branch decreased significantly. Comparing the comprehensive index of fiber quality, Q score, the quality of the fibers from middle and upper branches of SD1, SD2, and SD3 were better than that of the late sowing treatment (SD4). There were significant differences between two cultivars in terms of yield and fiber quality. Specifically, the cotton lint yield was higher in LM 2387, and the fiber quality was better in JX 707 in both years. [Conclusion] In summary, for both cotton varieties, the sowing date in May (SD1, SD2, and SD3) showed no significant effect on lint yield, and with relatively better fiber quality. In order to avoid a significant reduction in yield, the cotton sowing date of the intercropping system of wheat and short-season cotton in the Yellow River basin cotton production region should not be later than May 30th.

[Objective] Deficit irrigation is an effective irrigation method used in water-saving agriculture. This study aims to quantitatively analyze the influence on cotton yield and irrigation water productivity under deficit irrigation in China, and to provide the reference for further application of deficit irrigation in China. [Method] A meta-analysis was used to quantitatively evaluate the influence of different factors on cotton yield and irrigation water productivity under deficit irrigation in China by integrating 53 literatures published from 2010 to 2022. [Result] The result showed that compared with full irrigation, the average yield of seed cotton under deficit irrigation was decreased by 16.2%, while the irrigation water productivity was increased by 32.2% on average. The subgroup analysis showed that the highest increase of irrigation water productivity was observed in Northwest China under deficit irrigation, particularly in Xinjiang which had the best effect with less yield reduction. Field plantation and areas with relatively low precipitation had increased efficiency of water productivity under irrigation deficit condition. In areas with the annual average temperature ≥ 10 ℃, adopting the planting method of dry sowing and wet emergence, and moderately increasing irrigation frequency can effectively reduce the risk of yield reduction under deficit irrigation condition. Under the condition of soil bulk density <1.5 kg·cm^-3, the risk of seed cotton yield reduction was lower than that of the high soil bulk density under deficit irrigation condition. The application of 80%-100% of full irrigation, and application rate of 200-300 kg·hm^-2 nitrogen, 100-150 kg·hm^-2 potassium and 150-200 kg·hm^-2 phosphorus can effectively promote water utilization rate and reduce the risk of yield reduction under deficit irrigation condition. [Conclusion] It is suggested that the planting method of dry sowing and wet emergence is suitable to conserve water and stabilize yield under mild deficit irrigation condition in the Northwest China arid region with relatively high temperature. And appropriate increase of irrigation frequency and moderate fertilizer application rate can reduce the influence of deficit irrigation on cotton production.

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

[Objective] Polyploidization is an important way for plant evolution and new species formation. Using the gene dosage effect caused by chromosome doubling and polyploid advantage, it aims to cultivate new autotetraploid germplasm of Gossypium herbaceum with multiple excellent characters, so as to broaden the cotton germplasm resources effectively. [Method] The autopolyploid S₁ and progeny S₂ of G. herbaceum were used as materials, and the ploidy was identified by flow cytometry. The morphological, cytological, physiological, and biochemical indexes of autotetraploid were determined. [Result] Ploidy identification showed that there were 1 triploid plant and 4 tetraploid plants in 5 S₁ plants, and 1 aneuploid plant and 6 tetraploid plants in 7 S₂ plants. S₂ plants were more stable than S₁ plants in terms of plant morphology, leaf characters, flower phenotype, and stomata characters. The cytological identification results showed that the proportion of normal tetrads (85.17%) and normal pollen grains (87.33%) in S₂ was higher than that in S₁, which indicated the meiosis in autotetraploid tending to be normal. The activity of superoxide dismutase, peroxidase, and catalase, the content of malondialdehyde, soluble protein, soluble sugar, proline, and chlorophyll in S₂ plants were all higher than those in S₁ plants and their diploid parents. In terms of seed setting rate, seed size, and fiber length, S₂ was better than S₁. [Conclusion] The new autotetraploid germplasm of G. herbaceum is successfully synthesized through chromosome doubling, and the restoration of fertility tends to be stable in S₂ generation with higher polyploid advantage.

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

[Objective] The effects of adjuvants on the physicochemical properties, evaporation resistance, deposition and distribution of droplet, and control effect of nanopesticide against cotton aphid were studied through spray tests carried out by plant protection unmanned aerial vehicle (UAV) in cotton field. [Method] The dynamic light scatterometer, automatic interfacial tensiometer, BP100 tensiometer, contact angle meter and super depth of field photography system were used to evaluate influences of adding adjuvants (0.1% volume fraction of Youruopai, 0.1% volume fraction of Jiexiaofeng, 0.6% volume fraction of Aero-Mate 320) on the physicochemical properties and anti-evaporation of solutions with 20% reduced nanopesticide 8% (mass fraction, the same as below) dinieramine dinotefuran compared to the recommended dosage of 1 200 g·hm^-2, in the laboratory. The effect of droplets with adjuvant on the deposition and distribution in the canopy of cotton and its effect on the cotton aphid were explored. [Result] The physicochemical properties of the solutions were improved by adding Youruopai, Jiexiaofeng and Aero-Mate 320 adjuvants into the nanopesticide solutions with 20% reduced dosage. The static surface tension of solutions decreased from 36.43 mN·m^-1 to 31.82-34.99 mN·m^-1. The contact angles decreased to 12.25°-14.85°, which were decreased by about 22.97%-36.46%. The wetting areas increased by 18.34%-33.57% and the inhibition rates of spray evaporation reached 27.72%-73.40%. The results of field test showed that, the median diameters of the droplets in the upper and lower canopy of cotton were significantly increased from 122.4 μm and 106.7 μm to 154.3 μm and 148.5 μm, respectively. After 7 days of application, the control efficacy of treatment with 20% reduction of nanopesticide against aphids was 47.6%. However, the efficacies increased to 63.2%, 65.0% and 73.3%, respectively, after three adjuvants were added in the above treatments. The efficiencies were comparable to that of conventional dosage sprayed by UAV (71.8%) and traditional pesticide sprayed by artificial knapsack sprayer (74.9%). [Conclusion] The results indicated that adding adjuvant could improve physicochemical properties, enhance wetting area, reduce evaporation and drift of droplets, and increase the efficiency of nanopesticide against A. gossypii.