[Objective] Gibberellin 20 oxidase gene GhGA20ox6 was cloned and the preliminary functional analysis was performed for plant height. [Method] The GhGA20ox6 gene was successfully cloned from the stem of upland cotton standard line TM-1. The evolutionary relationships of GhGA20ox6 and its homologous genes in Arabidopsis thaliana and rice were confirmed by phylogenetic analysis and multiple alignment of amino acid sequences. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyse the expression pattern of GhGA20ox6 in multiple tissues of TM-1. In addition, subcellular localization was used to analyze its specific subcellular localization. And its function in Arabidopsis was analysed. [Result] The open reading frame of GhGA20ox6 is 1 155 bp and encodes 384 amino acids. The molecular mass of GhGA20ox6 is 43.32 ku and the predicted isoelectric point is 6.37. Phylogenetic analysis showed that GhGA20ox6 was highly similar to the green revolution gene sd1(OsGA20ox2) in rice. The qRT-PCR results showed that GhGA20ox6 was higher expressed in the stem than in other tissues of TM-1. Furthermore, according to the results of subcellular localization analysis in tobacco epidermd cells, GhGA20ox6 was localized in the cell membrane. Overexpression of GhGA20ox6 in Arabidopsis significantly increased the expression of a downstream gene GID1 (gibberellin insensitive dwarf1), resulting in the increase of plant height and earlier bolting. [Conclusion] Based on the cloning and functional analysis of GhGA20ox6, it is speculated that the gene may be related to gibberellin synthesis in cotton, and may affect the plant height of cotton. These results lay a foundation for further molecular verification of the biological function of GhGA20ox6 in cotton growth and development.
[Objective] This study aims to build a cotton yield prediction model at seedling stage for cotton field management. [Method] This study was conducted based on UAV (unmanned aerial vehicle) high-resolution image data. Firstly, the cotton seeding at 3-4 leaf stage were identified and extracted on the UAV images using green leaf index (GLI). Then, cotton seedlings were graded according to the diameters of cotton in the trial area by the natural breakpoint method, and the number of cotton bolls per plant and the boll weight were evaluated at harvest time. Finally, the cotton yield estimation model NDCS (number and diameter of cotton seedlings) based on the growth state at the seedling stage was constructed to predict the cotton yield by combining the grade of cotton seedlings in the trial area and the number of cotton bolls per plant and the boll weight. [Results] Among the 34 vegetation indices, GLI showed the best image segmentation effect. The average rate of precision extraction of cotton seedlings on multiple repeated trial at different scales was 96.2%. A total of 380 715 cotton plants were extracted from the trial area, including 2 657 seedlings of A grade, 103 753 seedlings of B grade, 214 691 seedlings of C grade and 59 614 seedlings of D grade. The NDCS model showed relative high accuracy on yield prediction, with the coefficient of determination of 0.919 2. The root mean squared error(RMSE) of the yield estimation model was 0.168 7. The estimated accuracy of the yield prediction model was 94.7% when compared with the actual yields. [Conclusion] This study used the high resolution UAV image of cotton seedling combined with the performance of yield-related traits to achieve cotton yield prediction, which provided a new route and method for cotton yield estimation.
[Objective] Adenosine diphosphate-glucose pyrophosphorylase(AGPase) is the rate limiting enzyme in the starch biosynthesis pathway, which plays an important role in starch synthesis and accumulation of plant "source" and "sink" organs. However, the systematic study of AGPase gene family has not been carried out in cotton. [Method] In this study, the whole genome identification of AGPase gene family was carried out by bioinformatics based on the published genomic data of Gossypium hirsutum standard line TM-1. The physical and chemical properties, evolutionary relationship, gene structure, cis-acting elements in the promoter region were systematically analyzed. Transcriptomic data and real-time quantitative polymerase chain reaction (qRT-PCR) were used to analyze the expression patterns of AGPase family genes in different tissues and under various abiotic stresses. [Result] A total of 20 AGPase genes (GhAGP) were identified in G. hirsutum, and they were unevenly distributed on 16 chromosomes. There were 12 AGPase gene encoding AGPase large subunit and 8 AGPase gene encoding AGPase small subunit, and had similar conserved motifs and exon-intron structure in different groups. The promoter region of GhAGP had multiple cis-acting elements related to plant hormones and abiotic stress response. Expression analysis showed that GhAGP had different tissue expression patterns. The expression level analysis under abiotic stress showed that most GhAGP were induced by low temperature, high temperature, salt and drought stress, in which GhAGPL1 and GhAGPL7 were involved in the response to a variety of stresses in cotton. [Conclusion] The distribution, structural and phylogenetic characteristics of AGPase genes were clarified in G. hirsutum, and the function of AGPase gene family in response to external environmental stress was preliminarily revealed, which provide important candidate gene resources for genetic improvement of starch traits and stress resistance breeding in cotton.
[Objective] The aim of this study is to determine the control effect and mechanism of a cotton endophytic fungus Penicillium simplicissimum CEF-818 on cotton Verticillium wilt. [Method] The inhibition rate of CEF-818 against a virulent strain Vd080 of Verticillium dahliae was assessed using the confront culture method, plate-to-plate culture method, and exudate filtering culture method, and the control effect on cotton Verticillium wilt was tested by root irrigation and substrate inoculation methods in greenhouse and by fertilizer broadcast and seed soaking inoculation methods in field. The activity of reactive oxygen species(ROS), and callose accumulation in cotton leaves were measured, and the expression level of defense genes in cotton leaves were detected by real-time fluorescence quantitative polymerase chain reaction. The induced disease resistance by CEF-818 in cotton were evaluated. [Result] The volatile and non-volatile metabolites of CEF-818 significantly inhibited the growth of Vd080, and the control effects on cotton Verticillium wilt in greenhouse and field were 69.77%(substrate inoculation method) and 63.73%(fertilizer broadcast method), respectively. CEF-818 can induce oxidative burst and callose accumulation in cotton leaves, cause up-regulation of some defense genes, such as peroxidase gene POD, phenylalanine ammonia-lyase gene PAL and pathogenesis-related protein gene PR10, and suppress the infection of cotton by V. dahliae. [Conclusion] Strain CEF-818 effectively inhibits cotton Verticillium wilt by directly inhibiting the growth of V. dahliae and inducing host resistance, which has good prospects for biological control applications.
Based on the dataset of planting area of individual cotton varieties released by National Extension and Service Center of Agricultural Technology in the past 40 years, the varieties with planting area ranking the first in the main cotton producing regions in one year, or with more than 0.33 million hm2 planting area and ranking the top three in one or more years were defined as mega varieties. The cumulative planting area, the maximum annual area, the number of years with area ranking in top three, and the planting area percentage of the mega varieties were analyzed. Around forty-four cotton mega varieties were selected in the main cotton production regions (i.e. the Yellow River basin, the Yangtze River basin and the Northwest inland cotton production region) in the past 40 years, among of which the cultivar Lumianyan 15 was found to be a mega cultivar both in the Yellow River basin and the Yangtze River basin cotton production regions. The total number of cotton varieties applied in production every year was generally on the rise during 1981-2020. The increase step of variety number was slow during 1981-2000, but speeded up during 2001-2020. Meanwhile, the proportion of mega varieties planting area to the total area of main cotton producing regions in each year showed significant historical characteristics. The proportion was relatively stable during 1981-1995, with a proportion of around 61%, 36%, and 83% in the Yellow River basin, the Yangtze River basin and the Northwest inland cotton production regions respectively. After then, the area proportion of mega varieties suffered a sharp decline to about 20% on average during 1996-2006, and followed by a slow drop period to around 15% on average till 2020. Cotton mega varieties contributed greatly indeed to the stability and development of cotton production in the history. However, the cotton breeding target at current and also in the future will be more functional and regional oriented to meet the versatile needs of seed industry and market development.
[Objective] Leaf area index (LAI) is one of the important indexes for crop growth diagnosis, biomass estimation and yield prediction in agriculture. Rapid inversion of LAI using unmanned aerial vehicle (UAV) multispectral remote sensing is important for cotton growth monitoring and field management. [Methods] Cotton at flowering and boll-setting stage in Aral reclamation area in Xinjiang was taken as the research object. The ground measured cotton LAI data and UAV multispectral images were used as data sources. After the image stitching was completed, spatial resampling was performed to obtain six different resolutions of multispectral images, vegetation index and texture features were extracted, and the texture index was constructed with texture features. Using the vegetation index, texture index and the combination of the two indices as input quantities, the cotton LAI prediction model based on the partial least squares regression (PLSR), support vector machine (SVM) and random forest algorithm (RF) were constructed and the prediction performance of the three input features and the models were compared under different resolutions, respectively. [Results] (1) The correlation between the two indices and LAI tended to increase and then decrease when the resolution of the multispectral image decreased, and the correlation between the two indices and LAI reached maximum when the image resolution was under the 1.0 m. The estimation performance of the three models were first increased and then decreased with the reduction of image resolution, and the estimation performance was the best under the 1.0 m resolution. (2) When the multispectral image was under the 1.0 m resolution, the RF algorithm model has the best estimation results, followed by the SVM algorithm model, and the PLSR algorithm model has the worst results. (3) The order of the accuracy of three input feature quantities were the follow: vegetation index and texture index, vegetation index, and texture index. [Conclusion] The RF algorithm model constructed by vegetation index and texture index extracted from UAV remote sensing image with 1.0 m spatial resolution had the highest accuracy in estimating cotton LAI at flowering and boll-setting stage.
[Objective] This research aims to investigate the effects of male sterile cytoplasm of Gossypium harknessii (CMS-D2) and Gossypium trilobum (CMS-D8) on ATP and H2O2 contents. [Method] The contents of ATP and H2O2 in leaves and flower buds of CMS-D2 and CMS-D8 "three lines" (sterile line, maintainer line, and restorer line) at different developmental stages were determined, and combined with the subject of existing research, ATP and H2O2 contents in Arabidopsis plants overexpressing the sterile candidate gene orf610a were determined. The expression levels of ATP synthesis-related genes in the flower buds of sterile lines, maintainer lines and transgenic Arabidopsis were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). [Result] During the development of cotton, compared with its maintainer line and restorer line, the leaves of CMS-D2 sterile line showed an extremely significant decrease in ATP content and an extremely significant increase in H2O2 content at both the bud stage and boll stage; the leaves of CMS-D8 sterile line showed an extremely significant decrease in ATP content and an extremely significant increase in H2O2 content at the bud stage, and an extremely significant increase in ATP content at the boll stage. The ATP content in 3 mm and 4 mm flower buds of CMS-D2 sterile line was extremely significantly decreased, and the H2O2 content in 4 mm flower buds was extremely significantly increased; the ATP contents in 5 mm and 6 mm flower buds of CMS-D8 sterile line were extremely significantly decreased. Compared with the maintainer lines, the expression levels of several ATP synthesis-related genes in the flower buds of the CMS-D2 and CMS-D8 sterile lines were extremely significantly reduced. Compared with wild-type Arabidopsis, the H2O2 contents in siliques and flower buds of orf610a-overexpressed Arabidopsis were significantly increased, and the ATP content were extremely significantly decreased, and most ATP synthesis-related genes were extremely significantly down-regulated. [Conclusion] The male sterile cytoplasm have certain effects on the contents of ATP and H2O2 in leaves and flower buds at different developmental stages of cotton, and the disruption of the dynamic balance may affect the development of pollen.
