[Objective] The purpose of this study was to explore the function of GhWRN in the growth and development of cotton. [Methods] GhWRN was analyzed in aspects of gene structure, evolutionary relationship, and gene promoter features through bioinformatic methods. Its expression patterns among different cultivars, tissues, and hormone conditions were gained via quantitative real-time polymerase chain reaction (qRT-PCR). The phenotype of Arabidopsis thaliana with overexpressed GhWRN was observed. The expression pattern of marker genes involved in A. thaliana flowering signal pathway was detected by qRT-PCR. [Results] The GhWRN gene was successfully cloned according to the reference genome of upland cotton. Bioinformatic analysis showed this gene contained a conserved WRN-exo domain, without intron or transmembrane structure, and was not a secretory protein. qRT-PCR showed GhWRN was up-regulated at the second leaf stage in early-maturing cotton cultivars and was expressed in all tissues, especially in stamens and bracts. It was significantly up-regulated at 0.5 h after treatment with exogenous ABA and IAA. The transgenic A. thaliana lines showed early flowering time and decreasing rosettes number compared with the wild-type. The qRT-PCR analysis in A. thaliana indicated that GhWRN could up-regulate the expression of key genes related to flower development, i.e., AtSOC1, AtFT, and AtFUL. [Conclusion] GhWRN could promote plant flowering, which sheds light on further exploration of flowering mechanism in cotton.
[Objective] The aim of the present study is to investigate the harvest aids efficiency applied by plant protection unmanned aerial vehicles (UAVs), and to provide a basis for the construction of harvest aids application technology system by UAVs in Xinjiang area. [Method] Field experiments were carried out to evaluate the harvest-aid performance applied by different UAVs and ground-based machine. [Result] The defoliation rate and boll opening rate were 82.2%-92.1% and 85.8%-100% at 22 days after spraying twice by UAVs, respectively. The defoliation rate is significantly higher than that of spraying once with a ground-based machine. But the difference of boll opening rate is not obvious. In addition, the defoliation rate differs in UAVs types and spraying areas. Among the eight working areas of UAVs, only one can achieve the defoliation and boll opening rate required for mechanical harvesting of cotton. Using UVAs to spray harvest aids, improper selection of working parameters, irregular operations and poor performance of UAVs will cause uneven or missed spraying. [Conclusion] The technology of applying cotton harvest aids with UAVs needs to be further optimized.
[Objective] Excessive application of nitrogen fertilizer is a common phenomenon in cotton production. The effects of nitrogen reduction combined with biostimulants on cotton growth and nitrogen utilization were studied to provide theoretical basis for optimal nitrogen management, reducing nitrogen use and improving nitrogen efficiency. [Methods] In this study, field experiments were carried out in two seasons, with a series of nitrogen levels combined with various biostimuli applied in the experimental field. Nitrogen application setup includes the standard quantity of nitrogen fertilizer (360 kg·hm-2, N1), the reduction of 20% (288 kg·hm-2, N0.8) and the reduction of 40% (216 kg·hm-2, N0.6). The biostimulant application setup includes no stimulant (0 g·kg-1, S0), fulvic acid (0.12 g·kg-1, F), chitosan (0.1 g·kg-1, C), alginic acid (0.24 g·kg-1, A). Cotton dry matter accumulation, chlorophyll content, soluble protein content, root morphology, cotton yield, total nitrogen uptake and utilization efficiency in plants among the above-mentioned conditions were analyzed. [Results] Appropriate amount of nitrogen reduction combined with chitosan, fulvic acid and alginic acid promotes the growth of cotton, increases the yield and the use efficiency of nitrogen fertilizer. Cotton plant height, dry weight, chlorophyll content, soluble protein content, yield, and total nitrogen uptake reached the maximum in the 40% nitrogen reduction plus chitosan treatment. During the initial flowering stage to peak boll-setting stage, the soluble protein content in bolls from 40% nitrogen reduction plus chitosan treatment was 41.41% higher than the control, and the number of cotton buds and bolls, the single boll weight and the yield of seed cotton was 7.85, 6.79 and 46.47 g, which were significantly increased by 19.69%, 23.39%, and 37.92% compared with the control. The 40% reduction in nitrogen combined with chitosan had the largest total nitrogen uptake during the cotton harvest period, which was 11.06 g per plant, 142.37% higher than the control. The partial factor productivity of nitrogen fertilizer, the agronomic efficiency of nitrogen, and the recovery efficiency of applied nitrogen were increased by 37.93%, 247.87%, 77.53% compared with the control. Nitrogen reduction by 20% combined with fulvic acid treatment had the greatest improvement in root morphology. The root surface area, root length, root volume, average diameter, root tip number, and branch number increased by 63.56%, 28.96%, 305.74%, 103.22%, 100.16%, 105.69% than the control, respectively. The combined application of 20% nitrogen reduction plus alginic acid significantly increased cotton boll weight and boll number, and improved seed cotton yield and nitrogen use efficiency compared with N0.8S0 fertilizer application. [Conclusions] Appropriate nitrogen reduction combined with chitosan, fulvic acid and alginic acid can promote cotton plant height and chlorophyll content, optimize the accumulation of dry matter in different organs and maximize the transportation of soluble protein from vegetative organs to buds and bolls, promote nitrogen fertilizer accumulation at maturation stage, and increase boll weight and the number of bolls, and eventually increase yield and nitrogen fertilizer use efficiency.
[Objective] Above-ground biomass is an important parameter of plant life activity. Exploring different spectral pretreatment methods and modeling methods to achieve rapid, nondestructive and accurate estimation of cotton above-ground biomass is of great significance for cotton growth monitoring and field precision management. [Method] Xinluzao 53 and Xinluzao 45 were selected as the research objects, and different nitrogen application treatments were set up to obtain cotton above-ground biomass and UAV hyperspectral data at different stages after emergence. The successive projections algorithm (SPA) was used to select the characteristic wavelengths after different pretreatments [first derivative, second derivative, Savitzky-Golay (SG smoothing), multiple scatter correction]. Based on the selected wavelengths, partial least squares regression (PLSR) and random forest regression (RFR) were used to construct cotton above-ground biomass (dry matter) estimation models, respectively, and the optimal estimation model was determined by comparison of the model estimation accuracy. [Result] (1) The SPA algorithm can effectively remove the redundant bands from the spectra, and the number of above-ground biomass-sensitive characteristic wavelengths after different pretreatments ranges from 9 to 26, which could be used to reduce the dimension of spectral information. (2) Based on SG smoothing-SPA processing, the model established by PLSR is the best, with a coefficient of determination (R2) of 0.63, root mean square error (RMSE) of 0.42, and validation set R2, RMSE of 0.67, 0.44. (3) After the first derivative-SPA processing, the model constructed by RFR is the best, with R2 of 0.87, RMSE of 0.45, validation set R2 and RMSE of 0.81 and 0.37. [Conclusion] Using the first derivative pretreatment combined with SPA to select biomass-sensitive wavelengths, the RFR model has the best results and validation performance, which can be used for quantitative estimation of cotton above-ground biomass.
[Objective] A cotton stem rot disease has been observed in Xinjiang Uygur Autonomous Region of China since 2016. In wet conditions, part of the diseased stem can produce rot symptoms such as longitudinal cracks and collapse of epidermal tissue; in dry conditions, the expansion of the diseased spots is significantly slower, or even no longer expands, showing symptoms of necrotic spots. In severe cases, the stems will die. Hence, it is vital to understand the species and biological characteristics of pathogens for disease control. [Method] A total of 18 stems of cotton with symptoms rot were collected from 11 cotton planting locations in the north and south of Xinjiang Uygur Autonomous Region. The pathogens were isolated and purified by conventional dilution separation and 20 representative strains were obtained by single spore purification. The pathogens were identified by morphology, molecular biology, and pathogenicity. To understand the suitable conditions for the growth and sporulation of the pathogens, the biological characteristics of the pathogens such as different temperatures, light, pH values, media and lethal temperatures were tested. [Result]The pathogens of cotton stem rot in Xinjiang were Fusarium incarnatum and F. proliferatum, among which F. incarnatum was the dominant species. The suitable temperature for the growth and sporulation of the two pathogens are 25 ℃. Light is beneficial to the growth of F. incarnatum, and dark culture is beneficial to the sporulation of two pathogens. The optimal pH for the growth of these two pathogens is 8, and the optimal pH for sporulation is 7. These two kinds of pathogens grow and produce spores better on potato sucrose agar and potato dextrose agar. The lethal temperatures of F. incarnatum and F. proliferatum spores were 48 ℃ and 60 ℃, respectively, and the lethal temperatures of hyphae were 50 ℃ and 61 ℃, respectively. [Conclusion] The pathogens of cotton stem rot in Xinjiang were F. incarnatum and F. proliferatum. F. incarnatum was identified as the dominant species. It is beneficial to the growth of the two species of Fusarium under the conditions of 20-30 ℃, pH 7-8 and full light; and the spore will be more productive under dark. Both potato sucrose agar and potato dextrose agar medium are beneficial to the growth and sporulation of the two pathogens.
[Objective] The effect of soil physical and chemical properties on the quantity and activity of cotton Verticillium wilt antagonist bacteria were analyzed under laboratory conditions, to reveal the adaptability of antagonistic bacteria under different physical and chemical conditions of soil. [Method] Four cotton Verticillium wilt antagonist bacteria isolated in the laboratory were raised to estimate their quantity under different soil physical and chemical factors (moisture, temperature, salinity, fertility, salinity, soil type) in petri dishes by coating. Through the pot experiment under the most suitable soil physical and chemical environments, the quantity of these biocontrol bacteria in the rhizosphere of cotton plants was evaluated and the incidence of cotton plants was counted. [Result] Both SHZ-24 and BHZ-29 strains have relatively high relative numbers of viable bacteria in the soil. SHZ-24 reaches 27.74% in soil with 15% water content, and BHZ-29 strain reaches 24.81% and 15.24% in medium fertilizer and gray desert soil, respectively. Under the conditions of high fertility and soil moisture content of less than 20%, four antagonistic bacteria have the best control effect on cotton Verticillium wilt. Among them, the control effect of BHZ-29 reached the maximum of 87.12%, and the control effect of SMT-24 had the minimum of 35.04%. [Conclusion] The four strains of antagonistic bacteria have good adaptability in suitable water and fertilized soil, the quantity and activity of antagonistic bacteria could be maintained well.
[Objective] This research aims to characterize the phenotype, phytotoxin types and pathogenicity among a new genotype strain H70, race 7 and Australian genotype strain ATCC96291 of Fusarium oxysporum f. sp. vasinfectum (FOV). [Method] The phytotoxins were extracted from FOV strains with ethyl acetate and analyzed by high performance liquid chromatography (HPLC), as well as mass spectrometry. The toxicity of toxin was evaluated on detached cotton leaves, and the pathogenicity was compared among three different types of soil (light load collected from Dingxing county in Baoding city, cinnamon soil collected from Cheng'an county in Handan city and saline-alkali soil collected from Huanghua county in Cangzhou city). [Result] New genotype strain H70 could produce abundant aerial mycelia and mononuclear conidium but failed to produce pigment with light brown. The fusaric acid was the main phytotoxin produced either by H70, race 7 and ATCC96291. Fusaric acid had the highest yield from race 7 and the lowest yield from the strain H70. Toxin extracted from race 7 caused the largest necrosis and the toxin of strain H70 caused the smallest necrosis. Compared with race 7, strain H70 showed weaker pathogenicity in the three different types of soil. [Conclusion] The fusaric acid was the main phytotoxin produced by H70, race 7, ATCC96291, and the pathogenicity were positively correlated with the concentration of fusaric acid.
[Objective] The study aims to establish the relationship between flower bud length and anther development in sea-island cotton. [Method] Anther development with different lengths of flower buds in Gossypium barbadense L. Xinhai 35 were observed by semi-thin section and toluidine blue staining. [Results] The color, shape, and size of sepals, petals, anthers, the lengths of filaments and stigmas changed with the development of flower buds in sea-island cotton. From flower buds development to anther dehiscence, the process have 14 stages including flower primordia formation, anther primordia occurrence, microspore mother cells formation, tetrad stage, tapetum degradation, meiosis, and anther dehiscence. At the pollen mother cell formation stage, tetrad stage, the stage of microspore release, and tapetum degradation, the bud length are 5-6 mm, 7-8 mm, 8-9 mm and 11-14 mm of Gossypium barbadense L. Xinhai 35, respectively. They are four key stages in the process of flowering. The whole process of fertilization including pollen germination, pollen tube elongation, fertilization and endosperm development were observed and clarified. [Conclusion] The morphology of flower bud at different stages in sea-island cotton are different from upland cotton. The size of flower bud and the color changed with the development of anther cells. At the same time, metabolic process happened and some substances were transported in normal cell development. According to the morphology of flower bud, sea-island cotton developing periods can be determined. After pollen maturation, pollen germination, pollen tube elongation, double fertilization and endosperm development occurred at 0.5-1 h, 8 h, 24 h and 50 h after pollination, respectively.
[Objective] The expansins (EXPs) are a kind of cell wall proteins, which can loosen the cell wall and promote cell elongation. The purpose of this study is to explore the specific expansin genes in cotton fiber development. [Methods] The expression pattern of four GhEXPs was analyzed in different tissues using the RNA-seq and qRT-PCR (Quantitative real-time polymerase chain reaction) technology, respectively. The phylogenetic tree, three-dimensional structure prediction of GhEXPs, and locations of key amino acid were analyzed by bioinformatics. [Results] The four GhEXPs, GhEXPA1d, GhEXPA4b, GhEXPA23b, and GhEXPB3a, were cloned from the upland cotton cDNA (complementary DNA), the intact ORF (Open read frame) of them are 768 bp, 795 bp, 798 bp and 804 bp, respectively. The evolutionary analysis showed that GhEXPA1d, GhEXPA4b and GhEXPA23b belonged to the EXPA (α-expansin) subfamily, and GhEXPB3a belongs to EXPB (β-expansin) subfamily. Tissue-specific expression analysis indicated that the four genes were specific-expressed genes in fiber development, and predominantly expressed in the early stage of fiber development, and the reliability of the results was verified by qRT-PCR. According to sequence alignment and three-dimensional structure prediction, we have predicted the key amino acid residues of four GhEXPs, including the phenylalanine, tryptophan and tyrosine. The results showed that they were all aromatic amino acids and located the same surface. [Conclusion] The four GhEXPs specifically expressed at the initiation and elongation stages of cotton fiber development which provided a reference for further elucidating the molecular mechanism of GhEXPs during cotton fiber development.
In the process of crop production, pests and diseases pose a great threat to crop production, which can directly or indirectly lead to yield reduction or even crop failure. Rapid and efficient grasping of the dynamics of occurrence of pests and diseases and timely prevention and control are important for crop yield and income. Unmanned aerial vehicle (UAV) remote sensing is an important technology for monitoring crop pests and diseases at this stage. It has the advantages of real-time, fast, efficient, objective, large-area, non-destructive monitoring, which will promote the development of agricultural production in the direction of high quality, high efficiency, safety, informatization and wisdom. We summarize the situation, data source types, data acquisition methods, data processing procedure and methods of UAV remote sensing monitoring of crop diseases and insect pests, etc.; also point out the main problems of pest and disease feature selection, pest and disease classification identification, sensor optimization and data processing in UAV remote sensing monitoring of crop pests and diseases. In view of the existing problems, this paper puts forward an algorithm to deepen the selection of pest and disease characteristics, establishes an exclusive pest and disease spectrum database, develops a dedicated pest and disease monitoring sensor, and develops a platform for processing pest, in order to provide a reference for the research related to UAV remote sensing monitoring of crop pests and diseases.
