[Objective] This study aims to investigate the dynamic changes of flavonoids in cotton leaves at different growth and development periods. [Methods] Cotton leaves of sGK156 at seedling stage, flourishing flowering stage, and boll opening stage were used as study materials, and the differential metabolites were analysed and flavonoids abundance was detected by ultra-high-performance liquid chromatography-tandem mass spectrometry. [Results] Differential compounds of cotton leaves at three different periods were mainly enriched in the biosynthesis of flavone and flavonol, and the biosynthesis of flavonoids. Compared with those at the flourishing flowering stage and boll opening stage, kaempferol-3-O-arabinopyranoside and naringenin in cotton leaves were significantly higher at the seedling stage, and the contents of 16 flavonoids such as astragalin, tiliroside, and quercetin in cotton leaves at flourishing flowering stage were significantly higher than those at seedling stage and boll opening stage, and the contents of 5 compounds of epicatechin, kaempferol-3-O-rutinoside, kaempferol-3-O-vicianoside, procyanidin B2, and fraxin were significantly higher at the boll opening stage compared with seedling stage and flourishing flowering stage. [Conclusion] This study further analyses the dynamic changes of flavonoid secondary metabolites in cotton leaves during different growth periods, and discover the dominantly expressed flavonoid metabolites in cotton leaves during different growth periods. It provides a theoretical basis for the further study and utilization of flavonoid metabolites in cotton leaves and the selection and breeding of excellent cotton varieties.

[Objective] This study aimed to clarify the effect of N-life Ⅱ (the main active ingredient is nitrapyrin) on soil nutrient contents and soil nitrogen (N) cycle-related enzyme activities under different application levels of N, so as to provide a basis for the application of N-life Ⅱ in cotton production. [Methods] Field experiments were carried out at Sanya, Hainan province in 2021 and 2022 with Zheda 12 as the experimental material. The field experiment was designed with two factors split-pot. The main plot was N-life Ⅱ application level: 22.5 kg and 0 kg (control) per hectare, respectively; the secondary plot was pure N application level: 285.0 kg (conventional level), 256.5 kg (10% N reduction), 228.0 kg (20% N reduction), and 199.5 kg (30% N reduction, 2022 only) per hectare, respectively. N, phosphorus and potassium contents as well as urease, ammonia monooxygenase (AMO), hydroxylamine oxidoreductase (HAO), nitrite oxidoreductase (NXR), nitrate reductase (NR), and nitrite reductase (NiR) activities in soil were analyzed at the seedling stage, flowering and boll setting stage, and boll opening stage of cotton under different treatments. [Results] Compared with the respective control treatments at the same N application level, soil ammoniacal N content increased at the flowering and boll setting stage and boll opening stage under the N-life Ⅱ treatment; soil nitrate N content decreased at the seedling stage and flowering and boll setting stage, and increased at the boll opening stage; and there were no significant differences in the contents of soil total N, P₂O₅ and K₂O at the seedling stage, flowering and boll setting stage, and boll opening stage. Compared with the mean values of all control treatments, the average soil total N content under N-life Ⅱ treatments was significantly increased by 6.10% to 6.63% at the boll opening stage; the average soil P₂O₅ and K₂O contents under N-life Ⅱ treatments were significantly reduced during the flowering and boll setting stage and boll opening stage. Application of N-life Ⅱ reduced the activities of soil urease, AMO, NR, and NiR at the seedling stage and flowering and boll setting stage; reduced soil NXR activity at the seedling stage; enhanced soil urease activity at the boll opening stage; and enhanced soil NiR activity at the boll opening stage under the normal N application level; while had no significant effect on soil HAO activity at different growth stages. [Conclusion] Under different application levels of N, N-life Ⅱ reduced soil nitrate N content at the seedling stage and flowering and boll setting stage, and increased soil ammoniacal N content at the flowering and boll setting stage and boll opening stage by inhibiting the activities of urease, AMO, NXR, NR, and NiR in soil.

[Objective] This study aims to investigate the effects of nitrogen (N) fertilizer top dressing frequency under drip irrigation on soil N content and cotton yield in southern Xinjiang, and to provide references for the rational N application. [Methods] Field experiments were conducted in Xayar County, Aksu Prefecture, Xinjiang, from 2021 to 2022. With the same total amount of pure N applied (300 kg·hm^-2, 20% basal application, and 80% top dressing with water), four treatments of N fertilizer top dressing frequency were set up (4, 6, 8, and 10; recorded as N4, N6, N8, and N10, respectively). The effects of different treatments on soil total N content and alkali-hydrolyzable N content in the cotton field, cotton dry matter mass and N content, cotton yield, and N partial productivity were analyzed. [Results] The effects of different treatments on soil N content in cotton field changed with cotton growth process. The soil total N and alkali-hydrolyzable N supply under N10 were relatively sufficient at the seedling stage, peak boll-setting stage, and boll opening stage, but was unfavorable to N supply at the squaring stage and peak flowering stage. Whereas soil total N and alkali-hydrolyzable N content were maintained at a higher level during the whole growth stage of cotton under N8. Also under N8, the maximum accumulation rate of dry matter and nitrogen in cotton plants, vegetative organs, and reproductive organs were the highest in 2022; the maximum accumulation rate of N in reproductive organs was the highest in 2021; the dry matter mass and N content of cotton plants, vegetative organs, and reproductive organs were relatively higher in 2021 and 2022. With the increase of N fertilizer top dressing frequency, seed cotton yield and N partial productivity increased firstly and then decreased, and all the highest ones were under N8. Compared with other treatments, seed cotton yield under N8 increased by 3.3%-39.2% and 13.3%-72.8% in 2021 and 2022, respectively; N partial productivity showed the same change range. [Conclusion] Under the water and fertilizer integration mode in the cotton field in southern Xinjiang, top dressing N fertilizer applied with irrigation for 8 times is beneficial to ensure the N supply of the cotton field, and to promote the accumulation of the dry matter and nitrogen in cotton, thus improving cotton yield and N partial productivity.

[Objective] This study aims to clarify the sequence structure of cytochrome P450 (CYP450) gene and glutathione S-transferase (GST) gene of Thrips tabaci, and the expression of these genes at the different growth and development stages of T. tabaci and emamectin benzoate stress. [Methods] Based on the transcriptome data of different growth and development stages of T. tabaci, CYP450 genes and GST genes were mined, specific primers were designed, and polymerase chain reaction (PCR) was used to amplify the cDNA of these genes. Bioinformatics software was used to predict the structural characteristics of CYP450 and GST proteins. The indoor toxicity of emamectin benzoate to adult T. tabaci was determined by leaf dipping method. Quantitative real time PCR (qRT-PCR) was used to analyze the expression patterns of CYP450 and GST genes at the different development stages of T. tabaci and under the stress of emamectin benzoate. [Results] Three CYP450 genes (CYP4C101, CYP4C102, CYP6K1) and two GST genes (GST1, GSTX1) were cloned. The results of physicochemical analysis showed that CYP4C101, CYP4C102, CYP6K1, GST1, and GSTX1 were composed of 507, 528, 513, 215 and 207 amino acid residues, respectively, all of which were hydrophilic proteins. Phylogenetic analysis showed that CYP4C101 had the highest homology with CYP4C1 of Frankliniella fusca. CYP4C102, CYP6K1 and GST1 of T. tabaci had the highest relationships with the homologous proteins from F. occidentalis and F. fusca. GSTX1 had the highest homology with F. occidentalis. Domain prediction showed that CYP4C101, CYP4C102 and CYP6K1 had conserved domains of CYP450, and GST1 and GSTX1 had conserved domains of GST. The results of indoor toxicity test showed that the LC₂₀ value of emamectin benzoate was 4.01 mg·L^-1 at 48 h. The results of qRT-PCR showed that CYP4C101, CYP4C102, CYP6K1, GST1, and GSTX1 genes were expressed at all development stages, and the expression levels were the highest on the 9^th day of adult emergence. The expression levels of the above-mentioned genes were significantly up-regulated under the stress of emamectin benzoate LC₂₀ for 24 h. Among them, CYP4C101, CYP4C102, and CYP6K1 were significantly up-regulated to 4.43, 22.91 and 8.48 times, respectively, and GST1 and GSTX1 were significantly up-regulated to 9.06 and 5.26 times, respectively. At 48 h after emamectin benzoate LC₂₀ treatment, the expression levels of CYP4C102 and CYP6K1 were significantly up-regulated by 3.84 and 1.43 times, respectively. The expression levels of CYP4C101, GSTX1, and GST1 were up-regulated but did not reach a significant difference level. [Conclusion] Three CYP450 genes and two GST genes of T. tabaci were cloned, and the expression levels of the five genes were the highest on the 9th day of adult emergence. Under the stress of emamectin benzoate LC₂₀, although these five detoxification genes were induced to express at different times, they may be involved in the response of T. tabaci to emamectin benzoate, providing clues for subsequent functional studies of CYP450 and GST genes.

[Objective] The purpose of this study was to trace the breeding process of Hai 7124, and clarify the characteristics of strains thorough analyzing the evolution of several traits, so as to provide reference for further exploring the value of Hai 7124 in cotton genetic breeding and resource utilization. [Methods] By consulting the historical research archives preserved by Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, the growth period, boll setting capacity, yield, fiber quality, disease resistance, plant architecture and other informations of the original materials and the selected breeding materials involved in the selection process of Hai 7124 were analyzed. [Results] The breeding of Hai 7124 began in 1959 with the introduction of the original material named Menoufi from Egypt, and went through ten generations of systematic selection. The key individual plant 65-3049-6 was obtained in 1965, and the selected line numbered 7124 with excellent characteristics was obtained in 1974, which named Hai 7124. Systematic selection not only promoted the early maturity of Hai 7124, but also preserved the excellent characteristics of the original material Menoufi and the related breeding materials, including good fiber quality, high yield, and strong resistance to Verticillium wilt. Additionally, it contributed to the formation of compact plant architecture. [Conclusion] Hai 7124 was derived from the original material Menoufi. The systematic selection promoted early maturity, and retained excellent traits, such as good fiber quality, high yield, and resistance to Verticillium wilt.

[Objective] The occurrence of Amrasca biguttula in the cotton field of Hunan Province is increasingly growing. The purpose of this study was to analyze the genetic diversity and genetic differentiation of A. biguttula in Hunan Province. [Methods] In 2023, 14 geographical population samples of A. biguttula were collected in Hunan Province. Based on the mitochondrial DNA (mtDNA) cytochrome c oxidase subunit Ⅰ (COⅠ) gene sequences obtained by polymerase chain reaction (PCR), the genetic diversity, genetic differentiation, population dynamics, and systematic evolution of the 14 geographical populations of A. biguttula in Hunan Province were analyzed using MEGA 7.0, DnaSP 6.1, Arlequin 3.5, Network 10.2, and other softwares. [Results] The mtDNA COⅠ sequences of 568 bp were obtained from 140 individuals by PCR. A total of 14 haplotypes (Hap1-Hap14) were detected, among which Hap1 was shared by all populations. Hapl had a frequency of 87.86%, and was the original haplotype. The haplotype diversity index of the whole A. biguttula community was 0.226 95, the nucleotide diversity was 0.000 52, and the average number of nucleotide difference was 0.296 25. The genetic distance between haplotypes ranged 0.001 76 to 0.007 09. The whole A. biguttula community had a low degree of genetic differentiation (the genetic differentiation coefficient is 0.016 84), and active gene exchange (the gene flow is 29.19). Molecular variance analysis (AMOVA) results indicated that genetic variation mainly originated within the population. The Tajima's D, Fu and Li's D, and Fu and Li's F neutral tests for the whole A. biguttula community were significantly negative, suggesting that the A. biguttula population in Hunan Province is undergoing expansion. [Conclusion] The geographical population of A. biguttula in Hunan Province showed low genetic diversity, active gene exchange, and low genetic differentiation; and the total population is experiencing obvious expansion. Active monitoring and control measures should be taken to ensure the healthy development of cotton industry in Hunan Province.