Since its commercial release in China in 1997, transgenic Bacillus thuringiensis (Bt) cotton has fundamentally improved the control of cotton bollworm, markedly reduced chemical insecticide use, and profoundly reshaped cotton production practices in the country. However, during the initial phase of adoption, premature senescence, characterized by mid- to late-season leaf yellowing, reddening, scorching, abscission, and root functional decline, emerged as a conspicuous problem in some Bt cultivars and was initially misattributed to a direct negative effect of Bt gene insertion or constitutive Bt protein expression. More than two decades of research and field practice have made it clear that premature senescence in Bt cotton is neither a direct consequence of Bt gene insertion or Bt protein expression itself nor an inherent attribute of Bt cotton. Rather, it is a maturity imbalance driven by source-sink imbalance, root-shoot uncoupling, insufficient nutrient supply, environmental adversity, and disease pressure under specific genetic backgrounds and heavy boll load. Its physiological basis includes the photosynthetic function decline, chlorophyll degradation, reactive oxygen species accumulation, membrane lipid peroxidation, imbalanced mineral nutrient uptake and remobilization, reduced root activity, decreased cytokinin level, and enhanced abscisic acid, jasmonic acid, and ethylene signaling. At the molecular level, premature senescence involves changes in sugar transport and metabolism, hormonal signaling, reactive oxygen species-associated oxidative regulation, and the structural and functional deterioration of chloroplasts, along with senescence-related transcription factors and genes networks that coordinate chlorophyll degradation and nutrient remobilization. Systematic studies by several research groups in China have contributed to an integrated management framework involving maturity-stable cultivars, rational plant density, optimized sowing date, coordinated nitrogen and potassium supply, precise late-season nitrogen management, chemical regulation, root promotion and leaf protection, moderate sink reduction, disease resistance/tolerance, and harvest-aid coordination. This review summarizes the research trajectory of premature senescence in Bt cotton from initial controversy and conceptual correction to mechanistic integration and technical control, with emphasis on the evolution of understanding, key evidence chain, representative research progress, molecular regulatory network, integrated management strategies, and unresolved issues.

[Objective] Over the past four decades, the area of cotton planting in Shandong Province has fluctuated sharply, and significant changes have occurred in the planting regions and the structure of pests and diseases. It is necessary to clarify the characteristics of their changes and evolution in order to provide a basis for the scientific prevention and control of pests and diseases. [Methods] Based on the relevant data of National Bureau of Statistics and National Plant Protection Statistics released by National Agro-Tech Extension and Service Center, the changing trends of cotton planting area, occurrence and control of diseases and pests, and yield loss in the cotton planting region of Shandong Province were analyzed. [Results] From 1985 to 2024, the cotton planting area in Shandong Province followed a declining trajectory with pronounced fluctuations, with a trend of "rise-fall-rise-sustained-decline". And the cotton-growing areas was concentrated in the saline-alkali and infertile lands and areas lacking fresh water resources in western and northern Shandong. The total pest-disease control was larger than the occurrence area, and the control area, occurrence area, the losses averted, and the actual losses caused by pests were all higher than diseases. Ranked by the annual average occurrence area, the main pests and diseases were: Helicoverpa armigera, Aphis gossypii, seedling disease, cotton spider mites, Bemisia tabaci, cotton mirid bugs, boll disease, cotton thrips, and Fusarium wilt. The proportion of the occurrence area of cotton mirid bugs, cotton thrips, Bemisia tabaci, cotton spider mites, and boll disease showed an increasing trend, while those of A. gossypii, H. armigera, seedling disease, and Fusarium wilt decreased. The actual cotton yield loss caused by cotton mirid bugs, B. tabaci, cotton thrips, and cotton spider mites were increasing. [Conclusion] It has been clarified that the main cotton planting areas in Shandong are migrating to the saline-alkali and infertile regions in the west and north of the province. H. armigera, A. gossypii, and cotton seedling diseases were the main pests and diseases threatening cotton production. The above results provide basic data support for the prediction, early-warning and scientific prevention and control of cotton pests and diseases in this region.

[Objective] This study aims to systematically identify and characterize the composition of the adenosine diphosphate-ribosylation factor (ARF) gene family in upland cotton (Gossypium hirsutum) and to explore its potential roles in growth, development, and abiotic stress responses, thereby providing a theoretical basis for subsequent functional studies. [Methods] Based on the upland cotton reference genome, a genome-wide identification of the ARF gene family was performed, followed by analyses of phylogenetic relationships, gene structures, conserved motifs, chromosomal localization, colinearity, and cis-acting elements. Public databases and quantitative real-time polymerase chain reaction were further employed to systematically analyze the expression patterns of 42 ARF genes in different tissues, at different ovule and fiber developmental stages, and under low-temperature, high-temperature, drought, and salt stress conditions, with a comparative analysis of expression differences of Group Ⅳ members among different cultivars. [Results] A total of 42 ARF genes were identified in upland cotton and classified into four groups, with members within each group showing highly conserved gene structures and motif compositions. The ARF genes were relatively evenly distributed between the A and D subgenomes. Overall expression levels of ARF genes were obviously higher in reproductive organs than those in vegetative tissues, and most genes exhibited stage-specific high level expression during 0-5 d of ovule development and fiber development. The Group Ⅳ ARF genes showed significant expression differences among cultivars and displayed differential induction or suppression under low-temperature, salt, and drought stresses. [Conclusion] The ARF gene family in upland cotton is evolutionarily highly conserved with evidence of functional diversification. ARF genes exhibit pronounced stage-specific and functional differentiation during fiber development and abiotic stress responses, and Group Ⅳ members, together with their unique conserved motif (Motif 9), may play important regulatory roles in stress responses.

[Objective] This study aims to elucidate the potential correlation between body color polymorphism and associated bacterial community structure in Aphis gossypii. [Methods] Full-length 16S rRNA gene sequencing of bacteria from green and yellow morphs of A. gossypii was performed using the PacBio sequencing platform. Operational taxonomic unit (OTU) clustering was conducted at 97% similarity level, followed by taxonomic annotation based on the Silva database (v138.2) using Blast and Bayesian algorithms. [Results] A total of 117 bacterial OTUs were identified in both green morph and yellow morph, belonging to 9 phyla, 13 classes, 35 orders, 57 families, 89 genera, and 114 species, with notable differences in bacterial composition between the two types. The green individuals harbored a greater diversity of bacteria (9 phyla, 13 classes, 34 orders, 54 families, 80 genera, and 100 species) compared to the yellow ones (6 phyla, 9 classes, 30 orders, 47 families, 75 genera, and 97 species). The classes of Acidobacteriia, Kapabacteria, Cyanophyceae, and Desulfuromonadia were unique to the green morph, encompassing 14 exclusive genera such as Verrucomicrobiaceae and Comamonas. No unique bacterial groups at the class level were identified in the yellow morph. Significant differences in bacterial relative abundance were observed between the two morphs. For instance, the relative abundance of Enterobacter was significantly higher in the yellow morph (2.39%) than that in the green morph (1.08%). Conversely, Pantoea was significantly more abundant in the green morph (1.45%) than that in the yellow morph (0.93%). Among the unique genera of the green morph, Comamonas had the highest relative abundance (1.02%), whereas Arsenophonus was the most abundant unique genus in the yellow morph (3.43%). [Conclusion] There are significant differences in the bacterial community composition between green and yellow morphs of A. gossypii. Analyses of key characteristics, including genus-level diversity, relative abundance, and the distribution of unique genera, indicate a certain correlation between color polymorphism and bacterial community composition in the cotton aphid. This study lays a solid foundation for further investigation into the mechanisms of microbial-mediated regulation of color differentiation in A. gossypii.

[Objective] This study aims to investigate the molecular mechanism underlying the resistance of Zhongzhimian 2 to Verticillium wilt. [Methods] Roots and leaves of Zhongzhimian 2 (disease-resistant variety) and Jimian 11 (disease-susceptible variety) were collected at 48 h after inoculation with Verticillium dahliae strain Vd991, followed by freeze-drying. Non-targeted metabolomics technology was employed to analyze the differential metabolites in the roots and leaves of Zhongzhimian 2 and Jimian 11, and the differential metabolic pathways were further analyzed. [Results] Compared with Jimian 11, the abundance of tryptophan and chorismate in the roots of Zhongzhimian 2 decreased, while the abundance of 13 metabolites including salicylic acid, anthranilate, and indole increased. The abundance of 13 metabolites, including tryptophan, chorismate, and anthranilate, was upregulated in the leaves of Zhongzhimian 2, while the abundance of 10 metabolites, including salicylic acid and indole, was downregulated. These differential metabolites were primarily enriched in the biosynthesis of unsaturated fatty acids, tryptophan metabolism, the biosynthesis of phenylalanine, tyrosine, and tryptophan, and linoleic acid metabolism. Comprehensive analysis revealed that the tryptophan metabolism showed the most significant differences. Zhongzhimian 2 inhibited tryptophan synthesis by downregulating the expression levels of the tryptophan synthase genes GhTSA1 and GhTSB1, leading to the accumulation of indole and subsequently promoting salicylic acid synthesis in the roots, thereby activating root immune responses to pathogen infection and conferring resistance to Verticillium wilt. [Conclusion] This study analyzed and compared the differences in secondary metabolites between the roots and leaves of Zhongzhimian 2 and Jimian 11, elucidated the mechanism by which Zhongzhimian 2 exerts its resistance to Verticillium wilt by regulating tryptophan metabolism and provided a theoretical basis for disease-resistant breeding.

[Objective] This study aims to characterize the fiber quality traits of Gossypium hirsutum germplasm resources and to determine their genetic diversity and potential for improvement. [Methods] A panel of 180 G. hirsutum germplasm resources was planted across two experimental locations (Manas and Yuepuhu) for two consecutive cotton growing seasons. Five fiber quality-related traits were measured, and multiple statistical approaches, including genetic diversity analysis, variance analysis, correlation analysis, cluster analysis, and principal component analysis, were adopted to conduct a comprehensive evaluation of the tested germplasms. [Results] The genetic diversity index of the test materials ranged from 0.68 to 1.37. The coefficient of variation for breaking elongation was highest (15.81%) at the Yuepuhu trial site in 2025, and lowest (0.98%) at the Manas trial site in 2024. Highly significant differences (P < 0.01) in fiber quality traits were observed among both genotypes and environments for the cotton germplasm accessions tested. Introduced varieties from other breeders showed higher variation in fiber length, uniformity index, and breaking tenacity, whereas self-bred varieties by our team possessed greater variation in micronaire and breaking elongation. All fiber quality traits were significantly correlated with each other. The tested germplasms were classified into five clusters based on cluster analysis. Two principal components were extracted, with a cumulative contribution rate of 73.56%. Ultimately, ten elite accessions with superior comprehensive performance were screened according to the comprehensive D value: Jinfeng T299, Shouxin H-157, ZJL1224, Jinfeng T390, Shouxin HS-173, AW1448, ZJL1348, Zhongshengmian 21, AW1031, 1059G. [Conclusion] The tested G. hirsutum population exhibits abundant genetic diversity, and distinct phenotypic differences are observed among germplasms from different sources. The screened elite accessions can serve as outstanding parental materials, providing valuable insights for the directional improvement of fiber quality and the optimization of breeding efficiency in upland cotton.

[Objective] This study aimed to achieve rapid, large-area monitoring of cotton leaf SPAD values using remote sensing technology and to provide technical support for evaluating cotton growth conditions in the Aral reclamation area. [Methods] A total of 22 vegetation indices and color indices were extracted using the Google Earth Engine platform. The mutual information method, recursive feature elimination, and extreme gradient boosting (XGBoost) were separately applied to select spectral features at the seedling, squaring, and flowering and boll-setting stages. The feature-selection performance of the three methods was compared to construct an optimal feature subset for each growth stage and reduce feature redundancy. The tree-structured Parzen estimator (TPE) was used to determine the hyperparameters of K nearest neighbors (KNN), random forest (RF), and categorical boosting (CatBoost). An optimized stacking algorithm (OSA) model was subsequently constructed using the TPE-optimized KNN, RF, and CatBoost models as base learners to improve the accuracy and stability of SPAD value estimation at different cotton growth stages. [Results] When vegetation indices and color indices were jointly used as input variables, the feature combinations selected by XGBoost showed better overall performance. Using the feature subsets selected by XGBoost, the OSA models constructed with TPE-optimized base learners achieved the validation-set coefficients of determination (R²) of 0.805, 0.850, and 0.881 at the seedling, squaring, and flowering and boll-setting stages, respectively. And the corresponding mean absolute percentage error (MAPE) values were 0.026, 0.022, and 0.019, respectively. The model performed best at the flowering and boll-setting stage, with training-set R² and MAPE values of 0.917 and 0.008, respectively. [Conclusion] For estimating cotton SPAD values in the Aral Reclamation Area, GRNDVI, GLI, RESAVI, NDVI, EXR, and TVI are recommended as input features at the seedling stage; GNDVI, VARI, GRNDVI, EXR, NDVI, and SI1 at the squaring stage; and OSAVI, LCI, NDI, GBNDVI, NDVI, and SAVI at the flowering and boll-setting stage. At all three growth stages, the OSA model constructed using TPE-optimized KNN, RF, and CatBoost models as base learners is recommended for SPAD value estimation.