[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 study aims to investigate the effect of proper postponement of soybean sowing on the productivity of cotton-soybean intercropping system. [Methods] Field experiments were conducted in Linqing City, Shandong Province in 2022 and 2023, and five treatments were set up: cotton monoculture (CM), early-sown soybean monoculture (ESM), late-sown soybean monoculture (LSM), cotton intercropped with early-sown soybean (C||ES), and cotton intercropped with late-sown soybean (C||LS). Various agronomic traits, leaf area index (LAI), canopy photosynthetic rate (CAP), crop yield, harvest index, and land equivalent ratio (LER) were compared among the treatments. [Results] Intercropping is beneficial to reduce the number of rotten bolls per cotton plant at the boll-opening stage. Compared with CM and C||ES treatments, cotton LAI of C||LS at the peak boll-setting stage and boll-opening stage were significantly increased, and the average CAP of cotton under C||LS treatment at the peak squaring stage, peak flowering stage, and peak boll-setting stage were significantly increased. Compared with CM, seed cotton yield of C||LS treatment significantly increased by 11.8%-13.5%, and significantly increased by 21.4%-23.5% in the border row. Compared with C||ES treatment, seed cotton yield of C||LS treatment showed a significant increase of 6.4%-9.4%, with a significant increase of 12.9%-14.8% in the border row. Compared with CM and C||ES treatments, the biological yield of C||LS treatment was increased by 14.6%-18.1% and 8.1%-8.6%, respectively; with an increase of 22.9%-31.3% and 11.9%-21.2% in the border row, respectively. There was no significant difference in harvest index among different treatments. Soybean yield under different treatments was as follows: C||ES > C||LS > ESM > LSM. The biological yield of early sowing soybean was higher than that of late sowing soybean. The soybean harvest index of C||LS treatment was the highest. The LER of C||LS treatment was significantly increased by 4.8% compared with that of C||ES treatment. [Conclusion] Properly delaying the sowing date of soybean can alleviate soybean' competition with cotton in the intercropping system, thereby enhancing the overall productivity of the cotton-soybean intercropping system.
[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.
[Objective] The objective of this study is to study the effects of exogenous application of proline on carbon source utilization by soil microorganisms in the cotton rhizosphere and soil enzyme activities, and deeply understand the ecological mechanism of proline in disease prevention and cotton growth promotion. [Methods] In this study, the application of different proline concentrations (0, 50, 100, 200 and 400 mmol·L-1) were set, with a cotton Verticillium wilt-susceptible variety Ejing 1 as the experimental material, and the Biolog-ECO plate method was used to evaluate the functional diversity and carbon source utilization of rhizosphere soil microbial communities under different treatments. Principal component analysis was used to compare the carbon source utilization characteristics of rhizosphere soil microorganisms under different treatments. The activities of neutral phosphatase (NP), arylsulfatase (ASF), urease (UE), and β-glucosidase (β-GC) in cotton rhizosphere soil of different treatments were determined, respectively. Redundancy analysis was used to analyze the correlation between soil enzyme activities and the utilization ability of soil microorganisms for different types of carbon sources. [Results] The McIntosh index of soil microorganisms treated with 400 mmol·L-1 proline increased significantly, while there were no significant differences in the Simpson index, Shannon-Wiener index, Richness index, and Pielou index of soil microorganisms treated with proline compared with control. The soil microbial metabolic activities treated with 50-200 mmol·L-1 proline were all lower than that of the blank control after incubating for 6 to 20 days, while the soil microbial metabolic activity treated with 400 mmol·L-1 proline was significantly higher than that of the blank control. Soil microorganisms treated with proline have higher utilization ability for amino acids, carboxylic acids, and carbohydrates. The utilization ability of soil microorganisms treated with 50-400 mmol·L-1 proline was significantly enhanced for L-phenylalanine, D-galactonolactone, β-methyl-D-glucoside, and glycogen; while the utilization ability for L-arginine, D-galacturonic acid, D-xylose, and i-erythritol was significantly reduced. Compared with the blank control, proline treatments significantly reduced the activities of soil β-GC and UE, and had no significant effect on the activity of NP. The activity of ASF showed a trend of first decreasing and then increasing with the increase of proline concentration. Redundancy analysis shows that UE activity was positively correlated with the utilization ability of soil microorganisms for L-arginine, D-galacturonic acid, γ-hydroxybutyric acid, D-xylose, and i-erythritol; β-GC activity was positively correlated with the utilization ability of soil microorganisms for L-arginine, pyruvic acid methyl ester, D-xylose, and i-erythritol; NP activity was positively correlated with the utilization ability of soil microorganisms for L-asparagine, D-galacturonic acid, γ-hydroxybutyric acid, glycogen, and β-methyl-D-glucoside; ASF activity was positively correlated with the utilization ability of soil microorganisms for L-phenylalanine, L-serine, L-threonine, glycyl-L-glutamic acid, D-glucosaminic acid, D-galactonolactone, itaconic acid, and D-mannitol, respectively. With carbohydrates as carbon source, the activities of β-GC and UE are negatively correlated with the utilization ability of soil microorganisms for glycogen. [Conclusion] The proline treatments can change the soil microbial metabolic activities, leading to a significant decrease in the activities of soil β-GC and UE. With carbohydrates as carbon source, the activities of β-GC and UE are positively correlated with the utilization ability of soil microorganisms for D-xylose and i-erythritol, but negatively correlated with the utilization ability of soil microorganisms for glycogen.
[Objective] This research aims to explore the impact of planting pattern and irrigation quota on the growth, yield, and fiber quality of cotton in southern Xinjiang. [Methods] Using Xinluzhong 67 as the experimental material, field trial was conducted in Tumxuk City, Xinjiang in 2023. Two planting patterns were set: (66 cm + 10 cm) wide and narrow row configuration (M1), and 76 cm equal row spacing configuration (M2). Three irrigation quotas were set: 3 600 m3·hm-2 (W1), 4 500 m3·hm-2 (W2), and 5 400 m3·hm-2 (W3). The differences in soil moisture content, cotton plant height, stem diameter, leaf area index, photosynthetic performance, yield, irrigation water use efficiency, and fiber quality under different treatments were compared. Additionally, the entropy weight technique for order preference by similarity to ideal solution (TOPSIS) was applied for a comprehensive evaluation to identify the optimal treatment. [Results] All treatments showed the largest increase in average soil moisture content in 0-30 cm soil layer after irrigation during the flowering and boll-setting stage (12.18-15.13 percentage point), followed by 30-60 cm soil layer. Under the same irrigation quota, the average soil moisture content in 0-30 cm soil layer after irrigation of M2 treatment was higher than that of M1 treatment. Under the same irrigation quota, plant height, stem diameter, and leaf area index under M2 treatment were higher than those under M1 treatment. Under the same planting pattern, plant height, stem diameter, and leaf area index of cotton all increased with the increasing of irrigation quota. During the flowering and boll-setting stage, the net photosynthetic rate and water use efficiency of leaf under M2W2 treatment were significantly higher than other treatments. The seed cotton yield of M2W2 treatment was the highest, which was significantly increased by 3.26%-17.70% compared with other treatments, and its irrigation water use efficiency was significantly higher than that of M1W2, M1W3, and M2W3 treatments. M2W1 treatment had the highest irrigation water use efficiency. The cotton fiber of M2W2 treatment showed the largest uniformity index, the upper half mean length and breaking elongation were also higher. The evaluation results of entropy weight TOPSIS method indicated that M2W2 treatment had the optimal overall performance. [Conclusion] Adopting the planting pattern of 76 cm equal row spacing with an irrigation quota of 4 500 m3·hm-2 can effectively promote the growth and development of cotton, and improve the seed cotton yield and fiber quality in southern Xinjiang.
[Objective] The aim of this study is to analyze the structural and molecular characteristics of Propylea japonica tyrosine decarboxylase (TDC) genes, and their expression pattern and to explore their regulatory role as a key octopamine synthetase gene in the reproductive development of ladybird beetle. [Methods] Four PjTDC genes and their basic structural characteristics were identified by bioinformatics software. PjTDC1 gene was cloned by polymerase chain reaction. The expression pattern of PjTDC1 gene in different tissues and at different developmental stages were investigated by quantitative real-time polymerase chain reaction. And the function of PjTDC1 gene in P. japonica were studied by RNA interference techniques. [Results] There were four TDC genes in the P. japonica, which were named PjTDC1-4. All the TDC proteins of P. japonica have PLN02880 domain, and PjTDC1 gene has an open reading frame of 1 728 bp, encoding 575 amino acid residues. PjTDC1 protein has the highest homology with the TDC protein of Cylas formicarius. PjTDC1 gene was expressed in P. japonica at different developmental stages, with the highest expression level in the 1st instar larvae but lower expression level in the egg stage larvae, the 4th instar larvae, and 7-day-old female adults. Generally speaking, the expression level of PjTDC1 decreased gradually at larval stages and in the adults after eclosion for 1 to 7 days. PjTDC1 gene is also expressed in different tissues, but it is mainly expressed in the ovaries, dorsal cuticula and head of the 5-day-old female adults. The results of RNA interference experiment showed that silencing of PjTDC1 gene inhibited the deposition of vitellogenin in the oocytes of P. japonica. In addition, on the 1st and 3rd day after injection of double strand RNA, the width of primary oocytes in the treatment group was significantly 10.03% and 18.60% lower than that in the control group. These results suggest that PjTDC1, as a key gene for octopamine synthesis, also plays an important regulatory role in the reproductive development of P. japonica. [Conclusion] In this study, the basic structural features of PjTDC genes and the spatial and temporal expression pattern of PjTDC1 at different developmental stages and in different tissues of P. japonica were studied, and its positive regulatory role in the process of vitellogenin deposits in the oocytes of P. japonica were clarified, which will provide theoretical basis for further solving the problem of large-scale artificial propagation of P. japonica.
