To identify seedling traits closely associated with drought resistance and to screen for drought-tolerant germplasm, 202 cotton varieties (lines) were evaluated under controlled indoor conditions using a nutrient soil cultivation method. Seedling-stage traits measured included plant height, cotyledon node diameter, true leaf number, chlorophyll content, and fresh and dry biomass of both shoots and roots. Drought resistance was assessed using drought resistance coefficients for each trait, followed by descriptive statistics, principal component analysis (PCA), partial correlation analysis, and comprehensive evaluation via the entropy weight method. PCA and partial correlation analysis revealed that plant height, cotyledon node diameter, aboveground fresh weight, and underground fresh weight were strongly associated with drought resistance at the seedling stage. The comprehensive drought resistance index (D-value) classified the 202 cotton lines into four categories: highly drought-resistant, moderately drought-resistant, drought-sensitive, and highly drought-sensitive. Physiological assays indicated that malondialdehyde (MDA) content in drought-resistant lines first increased and then declined with prolonged drought stress, while it continued to increase in sensitive lines. In contrast, proline (Pro) content and superoxide dismutase (SOD) activity increased steadily in drought-resistant lines but showed negligible changes in sensitive lines. These four morphological traits and three physiological indicators represent reliable criteria for evaluating drought resistance in cotton seedlings. Four highly drought-resistant and thirteen moderately drought-resistant lines were identified, providing valuable germplasm for genetic improvement of drought tolerance in cotton.

Objective: Yield traits are crucial for cotton breeding. Analyzing the yield traits of terrestrial cotton and exploring their genetic mechanisms through a primary gene + multigene hybrid genetic model provide a theoretical basis for selecting high-quality cotton varieties and identifying associated molecular markers. Methods: Completing the construction of the six populations (P1, P2, F1, F2, B1, B2) using Xinluzhong 37 as the female parent and Xinluzhong 51 as the male parent. Six yield traits were assessed: single boll weight, boll number per plant, lint yield per plant, seed cotton per plant, lint percentage, and seed index. Data were tested for normal distribution, and the inheritance patterns of yield traits were analyzed through combined primary gene + polygenic analysis. Results: The coefficients of variation for the six yield traits ranged from 37.368% to 53.905%, 33.335% to 58.524%, 34.132% to 57.686%, 8.721% to 12.808%, 1.842% to 6.283%, and 8.783% to 12.580%, respectively. These traits displayed either normal or skewed normal distributions. The optimal genetic model for single boll weight and seed index was PG-ADI, while MX2-ADI-AD best fit the traits of boll number per plant and lint percentage. For lint yield per plant and seed cotton per plant, the 2MG-ADI model was optimal. The polygenic heritability for single boll weight was 29.58%; for boll number per plant, main gene heritability was 25.19%, with 0% heritability for polygenes; for lint yield per plant, the heritability of the main gene was 23.47%. For seed cotton per plant, the heritability of main genes was 15.38%, with lint percentage showing 63.25% heritability for main genes and 0.08% for polygenes, and seed index with 45.93% heritability due to polygenes. Overall, single boll weight and seed index were predominantly polygenic, while boll number per plant and lint percentage were largely controlled by main gene inheritance. The inheritance of lint yield per plant and seed cotton per plant was also primarily governed by main genes.

The ADM developmental genetic model containing environmental interaction was used to study the relationship of single boll weight at different developmental stages and developmental characteristics with yield and quality for island cotton parents and F₁ generations in three years. Selecting single boll weight at different developmental stages had a better effect on the selection of final single boll weight and fiber quality traits in island cotton. When the single boll weed heavy, the number of invalid bolls were reduced and lint in the early stage (10, 20 d), while increased in the later stage (60, 70 d). In the medium term (30, 40, 50 d), the boll weight had a certain selection effect on the final yield per plant. At cotton boll volume expansion period (0–10 d, 10–20 d), the net increment was larger, single boll weight increased, other yield traits decreased, and quality traits such as fiber length, reflectivity and yellowness were improved. At cotton boll filling period (30–40, 40–50, 60–70 d), the boll dry weight increased, main fiber quality traits became worse. The yield per plant was increased by selecting materials with boll weight fast increasing in the growth period later. In the process of boll formation, assimilates entered cotton boll earlier and boll volume increased slowly, so that the fiber matured gradually, forming good quality. The fiber development was obviously affected by maternal effect; therefore, it is important to select suitable maternal parents for improving fiber quality traits.

Background: The regulation of oil and protein contents in cottonseed is governed by a complex genetic network. Gaining insight into the mechanisms controlling these traits is necessary for dissecting the formation patterns of cottonseed quality. Method: In this study, Xinluzhong 37 (P₁) and Xinluzhong 51 (P₂) were selected as parental lines for two reciprocal crosses: P₁ × P₂ (F₁) and its reciprocal P₂ × P₁ (F₁′). Each F1 was selfed and backcrossed to both parents to generate the F₂ (F₂′), B₁ (B₁′), and B₂ (B₂′) generations. To assess nutritional traits in hairy (non-delinted) and lint-free (delinted) seeds, two indicators, oil content and protein content, were measured in both seed types. Joint segregation analysis was employed to analyze the inheritance of these traits, based on a major gene plus polygene model. Results: In the orthogonal crosses, the CVs for the four nutritional traits ranged at 2.710–7.879%, 4.086–11.070%, 2.724–6.727%, and 3.717–9.602%. In the reciprocal crosses, CVs ranged at 2.710–8.053%, 4.086–9.572%, 2.724–6.376%, and 3.717–8.845%. All traits exhibited normal or skewed-normal distributions. For oil content in undelinted/delinted seeds, polygenic heritabilities in the orthogonal cross were 0.64/0.52, and 0.40/0.36 in the reciprocal cross. For protein content, major-gene heritabilities in the orthogonal cross were 0.79 (undelinted) and 0.78 (delinted), while those in the reciprocal cross were both 0.62. Conclusions: Oil and protein contents in cottonseeds are quantitative traits. In both orthogonal and reciprocal crosses, oil content is controlled by multiple genes and is shaped by additive, dominance, and epistatic effects. Protein content, in contrast, is largely controlled by two major genes along with minor genes. In the P₁ × P₂ combination, major genes act through additive, dominance, and epistatic effects, while in the P₂ × P₁ combination, their effects are additive only. In both combinations, minor genes contribute through additive and dominance effects. In summary, the oil content in cottonseed is mainly regulated by polygenes, whereas the protein content is primarily determined by major genes. These genetic features in both linted, and lint-free seeds may offer a theoretical foundation for molecular breeding aimed at improving cottonseed oil and protein quality.

Chrysopa pallens Stephens (Neuroptera: Chrysopidae) is a key predatory species in cotton agroecosystems. This study investigated the prey-mediated sublethal effects of imidacloprid and nitenpyram at low concentrations (LC₂₀), on C. pallens when exposed via consumption of contaminated prey, assessing impacts on its development and predatory function. C. pallens is a key predatory species in cotton agroecosystems. This study investigated the prey-mediated sublethal effects of imidacloprid and nitenpyram (LC₂₀) on the developmental performance and predatory capacity of C. pallens. Leaf-dipping bioassays were used to assess the toxicity of imidacloprid and nitenpyram to Aphis gossypii Glover (Hemiptera: Aphididae). Age-stage, two-sex life table analysis was conducted to evaluate their subsequent effects on the life history traits and predation performance of C. pallens. Imidacloprid was more toxic to A. gossypii than nitenpyram. Sublethal exposure marginally prolonged larval development, but the effect was not statistically significant. Both insecticides significantly extended the pupal stage, with nitenpyram inducing a greater delay. Imidacloprid markedly increased adult longevity, and both compounds significantly reduced female fecundity. Imidacloprid also suppress predatory behavior more potently, decreasing daily adult consumption and reducing first-instar attack rates by approximately 30%. Although all treatments followed a Holling type II functional response, both insecticides increased handling time and reduced searching efficiency. Overall, imidacloprid primarily inhibited predatory performance, whereas nitenpyram more strongly prolonged development and reduced critical population growth parameters. These findings provide essential evidence for ecological risk assessment and for refining the incorporation of natural enemies into cotton integrated pest management (IPM) strategies.

Hippodamia variegata is a key natural enemy of various aphid pests in agricultural ecosystems, and its foraging and oviposition behaviors are strongly dependent on chemical signals from prey aphids and host plants. In this study, we functionally characterized the chemosensory protein HvarCSP8 to elucidate its potential role in mediating olfactory responses to aphid-induced plant volatiles. The expression profiles of HvarCSP8 were examined by quantitative real-time PCR (qRT-PCR) across developmental stages and sexes; the recombinant HvarCSP8 was purified; the potential ligands specificity and affinity were studied using fluorescence-based competitive binding assays; and structural characteristics were obtained via homology modeling and molecular docking simulations. The results demonstrated that HvarCSP8 exhibits pronounced sex- and tissue-specific expression, with significant upregulation in adult antennae, particularly in females. The purified protein exhibited selective binding affinity to multiple aphid-induced plant volatiles, such as α-Farnesene, α-Terpinene, and 2-Ethyl-1-hexanol. Molecular docking revealed that HvarCSP8 interacts with these ligands through multiple amino acid binding sites, among which hydrophobic residues such as VAL29, LEU61, ILE64, and LEU65 frequently occur in binding sites for multiple ligands, suggesting that these residues play important roles in binding. These findings indicate that HvarCSP8 may be involved in the olfactory detection of aphid-induced plant volatiles in H. variegata, providing a candidate target for the development of behavior-based biological control strategies against aphid pests.