[Objective] In order to improve the efficiency of variety selection and reduce the cost of experiment, it was necessary to select the multi-objective characters comprehensively and make clear the effect of each objective character on the yield of seed cotton. [Method] Through the statistical analysis of 8 years, 607 breeding materials (339 conventional varieties and 268 hybrids) of Guoxin Rural Technical Service Association in Hejian City, Hebei Province, the effects of plant type, yield, maturity and fiber quality on the yield of seed cotton were comprehensively evaluated. [Result] Correlation analysis, regression analysis and general analysis showed that boll weight, lint percentage, first fruiting branches node, percentage of seed-cotton before frost and growth period had significant effects on seed cotton yield in the Heilonggang Cotton Region of the Yellow River Basin. The correlation coefficient between percentage of seed-cotton before frost and seed cotton yield were the highest (r=0.320 97), and the boll weight decision coefficient was the largest (R2=0.30), which were the main traits affecting the seed cotton yield. Plant height had the largest direct effect on seed cotton yield, but the total effect was the smallest after indirect effects of other variables (r2y=-0.04). Both regression and general analysis showed that neither fiber length (upper half mean length) nor micronaire had significant effects on seed cotton yield. [Conclusion] During the breeding of new cotton lines in the Heilonggang Cotton Region of the Yellow River Basin, boll weight and lint percentage can be used as important agronomic characters for breeders to improve. Shortening the growth period and increasing the percentage of seed-cotton before frost can increase yield. Plant height and first fruiting branches node affect seed cotton yield through interaction with other traits. Neither the fiber length nor the micronaire value have a significant effect on the seed cotton yield, which can be increased simultaneously with the yield during the breeding process.
[Objective] Chemical defoliation is a necessary technical measure for machine-harvested cotton, and the effect of chemical defoliation directly affects the efficiency of mechanical-picking and fiber quality. Study on the molecular mechanism of defoliant in regulating defoliation could effectively guide the screening and improvement of defoliant-sensitive cotton germplasms. [Method] In this study, 200 cotton accessions were collected and planted in greenhouse, and treated with defoliant at the early flowering stage. Different varieties with high or low sensitivity to defoliant were selected according to the defoliation rate on the 4th day after treatment. The selected cotton varieties were also treated with defoliant at the boll opening stage in the field, and the defoliation rate on the 7th day after treatment was calculated. Meanwhile, samples from the abscission zone of the selected varieties were collected on the first and third day after treatment. And the expression of ethylene-, cytokinin- and hydrolase- related genes were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). [Result] Six defoliant sensitive and 6 insensitive varieties were selected from greenhouse and field tests. According to the qRT-PCR results, cytokinin-related genes, ethylene-related genes and hydrolase-related genes showed different expression patterns following defoliant treatment in different varieties, and most of these genes showed significant different expression in the defoliant sensitive and insensitive varieties. [Conclusion] This study indicates that different cotton germplasms respond to differently to defoliant, which might be the result of differential expression of cytokinin- and ethylene-related genes.
[Objective] The aim of this study is to investigate the cotton differential metabolites in the interaction between Verticillium dahliae and cotton plant, and to explore new clues for the further study on the defense mechanism of cotton against V. dahliae. [Method] To obtain the cotton root, stem and leaf samples of the pathogen treated and healthy controls, the upland cotton cultivar CCRI 24 was selected as tested cotton material in this paper, and inoculated with V. dahliae conidia or sterile water by injuring root at the 2-true-leaf stage. The 70% (volume fraction) methanol extracts of these samples were separated and detected by ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS), and the metabolite data were obtained by the online XCMS software. Through multivariate statistics and student's t-test, the differential metabolites were investigated. The types of metabolites were putatively identified based on the comparison of the experimental molecular mass and the monoisotopic accurate molecular mass of cotton metabolites. [Result] The efficiency of negative ion mode was higher than that of positive ion detection mode in the cotton metabolites in UPLC-ESI-MS analysis. 576 ions mainly distributed in cotton root were found in the cotton seedling tissues including root, stem and leaf, which were the distinguished differential metabolites between V. dahliae treatment and healthy control. Among them, 77 ions were identified as sesquiterpenoids, diterpenoids, flavonoids, carbohydrates, aliphatics and phenols. In addition to sesquiterpenes, 17 compounds, including caffeic acid, astragalin, isoastragalin, dillenetin, ent-catechin, gossypetin 8-rhamnoside, gossypicyanin, herbacetin 7-glucoside, leucocyanidin, quercetin 3'-glucoside, quercetin 3-glucoside, quercetin 7-glycosides, α,2',3,3',4,4',6-heptahydroxychalcone 2'-glucoside, melibiose, sucrose, sucrose 6-phosphate and 1-tetratriacontanol, had not been reported in the literatures on the interaction between V. dahliae and cotton, which may be the novel pathogenesis-related metabolites on cotton Verticillium wilt. [Conclusion] The putative pathogenesis-related metabolites of cotton Verticillium wilt may play an important role in the interaction of cotton defense against V. dahliae, which provides an important clue for exploring the new resistant mechanism of cotton to Verticillium wilt.
[Objective] Verticillium wilt is a vascular fungal disease spread by soil, which causes serious loss of cotton yield and reduction in quality every year. This study provides a theoretical basis for the innovation of cotton multi-resistant germplasms by identifying disease resistance genes and studying disease resistance mechanisms. [Method] Yeast one hybrid was performed to screen the upstream regulatory factors of GhLac1, and the construction of phylogenetic trees, multiple alignment of amino acid sequences, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), transient tobacco transformation, dual luciferase assay system, virus-induced gene silencing and cotton genetic transformation technology were performed to verify the function of this transcription factor. [Result] Gh_D12G0544 is the most homologous to AtMYB43 in Arabidopsis thaliana, so its encoding gene was named GhMYB43. GhMYB43 is located on chromosome 12 of the Dt subgroup of upland cotton and encodes a protein containing 376 amino acids that contains two MYB domains. RT-qPCR analysis showed that GhMYB43 was predominantly transcribed in the stem and was up-regulated by salicylic acid (SA) and H2O2, but down-regulated by methyl jasmonate (Me-JA); at the same time, the transcription level was induced by Verticillium dahliae. Subcellular localization results showed that GhMYB43 protein is localized in the nucleus. The dual luciferase assay system verified that the gene has transcriptional activation activity. Disease resistance identification found that the inhibition GhMYB43 transcription level enhanced the resistance of cotton to V. dahliae, and overexpression of GhMYB43 increased the susceptibility of plants to this pathogen. Histochemical staining and content determination of lignin showed that the lignin content of GhMYB43 overexpressing transgenic lines was significantly lower than that of control materials. RT-qPCR analysis showed that GhMYB43 negatively regulates the transcription level of enzyme genes involved in the lignin synthesis and JA signaling pathway. [Conclusion] GhMYB43 negatively regulates lignin synthesis and JA signal.
[Objective] The aim of this study is to evaluate nitrogen efficient cotton germplasms and improve nitrogen use efficiency. [Method] Eighty cotton germplasms were selected and evaluated in the hydroponic experiment under low (0.25 mmol·L-1) and high (5 mmol·L-1) nitrogen concentration. Different traits for screening were identified and nitrogen use efficiency types were classified. Field experiments were also performed for comparison and confirmation of the identified germplasms. [Result] The results showed that there were significant differences in the total plant dry matter, shoot nitrogen accumulation and nitrogen absorption efficiency in cotton germplasms at the two nitrogen levels. Based on coefficient of variation, principal component analysis and correlation, six traits including total plant dry matter, shoot dry matter, root dry matter, total nitrogen accumulation, shoot nitrogen accumulation and nitrogen absorption efficiency were used as screening indicators. According to the Heatmap clustering analysis and the nitrogen efficiency comprehensive index, two germplasms (Lu05R59 and CCRI 69) were identified as low nitrogen tolerant and nitrogen efficient, and two germplasms (Coker 201 and Xinluzhong 30) as low nitrogen sensitive and nitrogen inefficient. The results of field experiment were consistent with the results of the hydroponic culture at the seedling stage. [Conclusion] It was finally determined that Lu05R59 and CCRI 69 were the low nitrogen tolerant and nitrogen efficient germplasms, and Coker 201 and Xinluzhong 30 were low nitrogen sensitive and nitrogen inefficient germplasms. The results of these studies provide the possibility for screening and rapid identification of nitrogen use efficiency in cotton at the seedling stage, and provide the ideal materials and theoretical basis for further study of cotton nitrogen efficient.
[Objective] The aim of this research is to study the effects of planting density and Miantaijin(diethyl aminoethyl hexanoate·mepiquat chloride of mass fraction 27.5%) chemical control on physiological leaf characteristics and boll setting characteristics of direct-seeded cotton after wheat harvest. [Method] In 2011-2012, the early-maturing variety Guoxinzao 11-1 was used as the experimental material. The study was conducted in Yangzhou University in 2011-2012 under the direct-seeded after wheat harvest cropping system, and the randomized complete block design was arranged with planting densities and Miantaijin rates. [Result] Under the density 105 000 plant·hm-2 combined with 1 170 mL·hm-2 Miantaijin, the boll setting was mainly concentrated before August 31. The SPAD value, soluble sugar content, soluble protein content, free amino acid content on July 15, July 30, August 15 of direct-seeded cotton after wheat harvest showed significant or extremely significant open-down parabola relationship with the number of bolls before August 31. It indicates that keeping the appropriate level of carbon and nitrogen physiological activity in cotton leaves is beneficial to high-quality bolls. [Conclusion] High density (105 000 plant·hm-2) combined with proper Miantaijin control (1 170 mL·hm-2) would contribute to forming quality bolls of direct-seeded cotton after wheat harvest, and the physiological activities of leaf carbon and nitrogen are suitable.
[Objective] Early initiation and early maturity are the foundation of high yield and good quality of cotton. The purpose of this study is to determine the effects of plant growth regulators applied at the seedling and squaring stage on the early initiation of flower bud and the rate of the opened cotton boll (ROCB) during later development period, and to provide practical measures for hastening the maturity of cotton. [Method] Several plant growth regulators were applied from cotyledonary to squaring stage under greenhouse and field conditions, water was used as the control. The first fruiting branch node (indicating the initiation of flower bud), the number of bud prior to blooming and the ROCB at mid-term of boll maturation period (23 September, 2017) were compared among treatments. [Result] Under greenhouse conditions, gibberellic acid (GA3) applied at the cotyledonary stage with 140 μmol·L-1 as well as the three consecutive applications of sodium nitrophenolate (CSN, 2.23 μmol·L-1) at the cotyledonary, two-leaf and four-leaf stage made the first fruiting branch node move down by about 0.9 nodes. In field experiments, the application of gibberellin4+7(GA4+7, 288 and 576 μmol·L-1) at the cotyledonary stage significantly decreased the first fruiting branch node by about 0.4 nodes. Also, the application of 6-benzylaminopurine (6-BA, 44.4 μmol·L-1) at the three-leaf stage significantly decreased the first fruiting branch node by 0.2 nodes. However, there was no significant correlation between the first fruiting branch node and the ROCB in late September. Moreover, the application of Brassinolide (BR, 0.10 μmol·L-1) at the bud stage increased the ROCB in late September, which was mainly associated with the increased boll set in the lower and middle fruiting branches. [Conclusion] The reasonable distribution of bolls (concentrated in the lower and middle fruiting branches as well as inner fruiting sites) is more important for the earliness of cotton than lowering the first fruiting branch node.
[Objective] The leaf temperature is an effective parameter reflecting crop physiological process and energy exchange. This study aimed to put forward a method to quantify the temperature distribution within cotton leaves. [Method] The infrared images of cotton leaves of potassium deficiency and normal cotton plants cultivated in nutrient solution were taken and studied. The irrelevant background in the infrared images was removed by using software of Stata and Surfer. The geostatistical spatial grid method was used to quantify the temperature distribution within cotton leaves. Finally, the temperature scales of different images were unified for better and faster comparison of leaf temperature differences among images. [Result] The processed image clearly reflected the differences among different treatments in leaf temperature. The mean leaf temperature, leaf vein temperature and leaf temperature outside leaf vein of potassium-deficient cotton were 0.52 ℃, 0.59 ℃ and 0.47 ℃higher than those of normal leaf, respectively. In addition, the temperature variation amplitude (0.76 ℃) and coefficient of variation (0.38%) of potassium deficient leaf were higher than those of normal leaf (0.54 ℃, 0.27%), and the temperature of the leaf vein increased the most (0.53 ℃). The analysis of the frequency distribution of temperature within the cotton leaf showed that the quartile deviation of temperature distribution of potassium-deficient leaf was 0.07 ℃ higher than that of normal leaf, indicating that the temperature distribution of normal leaf was relatively concentrated. [Conclusion] The proposed method is helpful for further monitoring of cotton growth and may guide cotton precise management.
