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    The GhMAX2 gene regulates plant growth and fiber development in cotton
    HE Peng, ZHANG Hui-zhi, ZHANG Li, JIANG Bin, XIAO Guang-hui, YU Jia-ning
    2022, 21 (6): 1563-1575.   DOI: 10.1016/S2095-3119(21)63603-1
    Abstract231)      PDF in ScienceDirect      
    Strigolactones (SLs) are a new type of plant endogenous hormones that have been found to regulate plant growth and architecture.  At present, some genes related to the biosynthesis and signaling pathway of SLs have been isolated in plants such as Arabidopsis thaliana, Pisum sativum and Oryza sativa.  However, the signaling pathway and specific mechanism of SLs in cotton remain unclear.  In this study, we identified the SLs signaling gene GhMAX2 and demonstrated its function in plant growth and architecture in Gossypium hirsutum.  Bioinformatics analysis showed that GhMAX2 mainly consists of an α-helix and a random coil and includes a large number of leucine-rich repeats.  GhMAX2 was highly expressed in root, stem, flower, and fibers at 20 days post-anthesis (DPA).  GhMAX2 promoter-driven β-glucuronidase expression was present exclusively in the root, main inflorescence, flower, and silique.  Subcellular localization showed that GhMAX2 is targeted to the nucleus.  Heterologously expressed GhMAX2 can rescue the phenotype of Arabidopsis max2-1 mutant, indicating that the function of MAX2 is highly conserved between G. hirsutum and A. thaliana species.  In addition, the knockdown expression of GhMAX2 in cotton resulted in significantly reduced plant height, slow growth, short internodes, and reduced fiber length.  These findings indicate that GhMAX2 probably contributes to plant growth, architecture and fiber elongation in cotton. The study reveals insights into the roles of GhMAX2-mediated SL/KAR signaling in cotton and provides a valuable foundation for the cultivation of cotton plants in the future.
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    Cotton maturity and responses to harvest aids following chemical topping with mepiquat chloride during bloom period
    QI Hai-kun, DU Ming-wei, MENG Lu, XIE Liu-wei, A. Egrinya ENEJI, XU Dong-yong, TIAN Xiao-li, LI Zhao-hu
    2022, 21 (9): 2577-2587.   DOI: 10.1016/j.jia.2022.07.008
    Abstract193)      PDF in ScienceDirect      

    Early maturity, complete defoliation and boll opening are essential for the efficient machine harvesting of cotton.  Chemical topping, involving one extra application of mepiquat chloride (MC) in addition to its traditional multiple-application strategy, may be able to replace manual topping.  However, it is not known whether this chemical topping technique will influence maturity or cotton responses to harvest aids.  In this 2-yr field study, we determined the effects of the timing of chemical topping using various rates of MC on boll opening percentage (BOP) before application of harvest aids (50% thidiazuron·ethephon suspension concentrate, referred to as TE), and the defoliation percentage (DP) and BOP 14 days after TE application.  The results indicated that late chemical topping (near the physiological cutout, when the nodes above white flower is equal to 5.0) significantly decreased BOP before TE by 5.9–11.2% compared with early (at peak bloom) or middle (seven days after peak bloom) treatments in 2019, which was a relatively normal year based on crop condition.  Also, a high MC rate (270 g ha–1) showed a significantly lower (22.0%) BOP before TE than low (90 g ha–1) or medium (180 g ha–1) rates.  In 2020, which was characterized by stronger vegetative growth in the late season, the late chemical topping reduced the number of leaves before TE application relative to early or middle treatments, but had lower DP (23.2–27.2%) 14 days after TE application.  The high MC rate showed a leaf count before TE application that was similar to the low and medium rates, but it showed the most leaves after TE and much lower (15.0–21.7%) DP in 2020.  These results suggest that late timing of chemical topping and a high MC rate decreased the sensitivity of leaves to harvest aids.  Further analysis indicated that the late chemical topping mainly affected the leaf drop from the mainstem and fruiting branches where the late regrowth occurred, and the high MC rate reduced leaf shedding from these parts and also from the vegetative branches.  In conclusion, chemical topping with MC during the bloom period affected cotton maturity and responses to harvest aids in different ways according to the crop condition.  To avoid the risks of delayed maturity and poor defoliation after the application of harvest aids, chemical topping should not be performed too late (i.e., near the physiological cutout) by using MC at more than 180 g ha–1.  The optimum timing of chemical topping probably varies from peak bloom to around seven days later, and the safest MC rates for chemical topping should be less than 180 g ha–1.

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    Effects of chemical topping on cotton development, yield and quality in the Yellow River Valley of China
    ZHU Ling-xiao, LIU Lian-tao, SUN Hong-chun, ZHANG Yong-jiang, ZHANG Ke, BAI Zhi-ying, LI An-chang, DONG He-zhong, LI Cun-dong
    2022, 21 (1): 78-90.   DOI: 10.1016/S2095-3119(20)63559-6
    Abstract298)      PDF in ScienceDirect      
    Topping is a cultivation method that is widely practiced due to the indeterminate growth character of cotton (Gossypium hirsutum L.).  Among the different methods of accomplishing topping, manual topping is common in the Yellow River Valley of China, although it is time- and labor-intensive.  The objective of this study was to characterize the responses of cotton to different topping treatments with respect to development, yield and quality.  This study included field experiments from 2015 to 2016 with three different topping methods: manual topping (MT), chemical topping (CT) using mepiquat chloride, and a non-decapitation treatment (NT).  We found that the plant height, the number of fruiting branches and the length of upper fruiting branches of cotton treated with CT were significantly lower than NT.  The chlorophyll content of cotton treated with CT was not significantly different from NT, but was higher than that of MT in the later season.  CT enhanced plant development with reduced endogenous gibberellic acid and abscisic acid contents, and the apical development of the main stem was inhibited.  Compared with MT, CT significantly increased the biomass of the vegetative parts.  Most importantly, there were no significant differences in the yield or fiber quality between MT and CT.  These findings suggested that CT, a simplified and effective topping method, could be utilized as an alternative in the Yellow River Valley of China.
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    Systematical regulation involved in heterogeneous photosynthetic characteristics of individual leaf in pima cotton
    ZHANG Yu-jie, HAN Ji-mei, LEI Zhang-ying, MENG Hao-feng, ZHANG Wang-feng, ZHANG Ya-li
    2022, 21 (4): 995-1003.   DOI: 10.1016/S2095-3119(20)63565-1
    Abstract118)      PDF in ScienceDirect      
    Light heterogeneity leads to anatomically and physiologically heterogeneous features in leaves.  However, little attention has been paid to the effects of nonuniform illumination on the anatomical and photosynthetic performance on both sides along the leaf main vein.  This study explored such effects by combining in situ determination in the field with shading simulation in the phytotron, on pima cotton that has cupping leaves.  Photosynthetic characteristics and morphological structures were measured in the field on both sides along the main vein of eastward, westward, southward, and northward leaves.  The results showed that the difference in photosynthetic capacity between the two sides along the main vein in different directions was closely related to the daily photo irridiance (DPI).  This result indicates that the photosynthetic heterogeneity between the two sides is related to their intercepted light energy.  The conclusion was further verified by the shading simulation experiments.  Photosynthetic capacity and leaf thickness of the unshaded sides of leaves in the half-shaded treatment decreased, compared to those in the unshaded treatment.  Therefore, it is conjectured that the development of  photosynthetic characteristics on one side is systematically regulated by that on the other side.  The study provides theoretical guidance on accessing the feasibility of sampling and directional planting.   

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    Predictive models of drought tolerance indices based on physiological, morphological and biochemical markers for the selection of cotton (Gossypium hirsutum L.) varieties
    Yeison M QUEVEDO, Liz P MORENO, Eduardo BARRAGÁN
    2022, 21 (5): 1310-1320.   DOI: 10.1016/S2095-3119(20)63596-1
    Abstract102)      PDF in ScienceDirect      
    The use of tolerant crop varieties is a strategy that mitigates the water deficit effect in a sustainable way.  The generation of these varieties is more efficient when variables associated with this tolerance have been identified, since they can facilitate the breeding processes.  This study aimed to establish the relationships between water deficit tolerance of four cotton varieties (Nevada-123, Oasis-129, Guatapuri, and Festivalle) and morphological variables (monopodial branches, boll weight, root/shoot ratio, and leaf and root dry matter), physiological variables (relative water content, net photosynthesis, stomatal conductance, electron transport rate, photochemical quenching, photochemical efficiency of PSII, chlorophyll a/b ratio (Chl a/b), C12/C13 isotope ratio, and electrolyte leakage), and biochemical variables (contents of sugars, proline, carotenoids, and malondialdehyde).  Furthermore, calibrated predictive models of the drought tolerance indices were developed based on the key variables identified.  For this purpose, a pot experiment was established where plants were subjected to a moderate or severe water deficit during the blooming stage for 12 days.  The stress tolerance index (STI) and mean productivity (MP) were calculated.  For the evaluated variables, the differences between well-watered and water deficit plants (Δ) were calculated and ANOVA, partial least squares, Pearson’s correlation, and multiple linear regression analyzes were performed.  A model was generated that explained 95% of the STI and was composed of Δmalondialdehyde, Δproline, and Δboll weight.  For MP, the model was comprised of Δstomatal conductance, Δroot/shoot ratio, and ΔChl a/b, and explained 89% of the MP.  The analysis of the assessed variables allowed the identification of key variables and the development of calibrated predictive models that can be used in screening to obtain cotton varieties with different levels of water deficit tolerance.
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    Growth and yield responses to simulated hail damage in drip-irrigated cotton
    WANG Le, LIU Yang, WEN Ming, LI Ming-hua, DONG Zhi-qiang, CUI Jing, MA Fu-yu
    2022, 21 (8): 2241-2252.   DOI: 10.1016/S2095-3119(21)63672-9
    Abstract174)      PDF in ScienceDirect      
    The frequent occurrence of hailstorm in Xinjiang affects cotton (Gossypium hirsutum L.) production and causes enormous economic loss.  The indeterminate growth habit of cotton allows for varying degrees of recovery and yield when different hail damage levels occur at different stages, which brings inconvenience to agricultural insurance claims and post-damage management.  Therefore, this study aimed to elucidate cotton recovery and yield responses to different levels of simulated hail damage at different growth stages.  Four levels of hail damage (0, 30, 60, and 90%) were simulated every 15 d from the five-leaf stage to the boll opening stage in 2018 and 2019, for a total of six times (I, II, III, IV, V, and VI).  The results showed that seed cotton yield decreased as the damage level increased and yield reduction increased when the damage was applied to older plants (for 30, 60 and 90% damage levels, yield reduction was 9–17%, 22–37% and 48–71%, respectively).  One possible reason was that the leaf area index and leaf area duration of plant canopy decreased after hail damage, resulting in a reduction in the accumulation of above-ground biomass.  However, when hail damage occurred before bloom, due to the indeterminate growth habit of cotton, the vegetative organs produced a strong compensation ability that promoted the bud development.  The compensation ability of vegetative organs decreased when hail damage occurred after bloom and the recovery time was too short to promote new boll maturity.  As the first study to understand the recovery of cotton after hail damage, it analyzed the leaf area index, leaf area duration, above-ground biomass accumulation and yield, rather than the yield alone.  The findings are of great importance for cotton production as they inform decisions about post-damage management practices, yield forecasts and insurance compensation.
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    Screening of drought resistance indices and evaluation of drought resistance in cotton (Gossypium hirsutum L.)
    ZOU Jie, HU Wei, LI Yu-xia, HE Jia-qi, ZHU Hong-hai, ZHOU Zhi-guo
    2020, 19 (2): 495-508.   DOI: 10.1016/S2095-3119(19)62696-1
    Abstract138)      PDF in ScienceDirect      
    Sixteen cotton cultivars widely planted in China were sowed under five different drought concentrations (0, 2.5, 5, 7.5, and 10%) using PEG6000 to screen the indices of drought resistance identification and explore the drought resistance of different cotton cultivars.  Eighteen physiological indices including root, stem, and leaf water contents (RWC, SWC, and LWC), net photosynthetic rate (Pn), the maximum photochemical quantum yield (Fv/Fm), the actual photochemical quantum yield (ΦPSII), non-photochemical quenching coefficient (NPQ), leaf water potential (LWP), osmotic potential (Ψs), leaf relative conductivity (REC), leaf proline content (Pro), leaf and root soluble protein contents (LSPC and RSPC), leaf and root malondialdehyde (MDA) contents (LMDA and RMDA), root superoxide dismutase, peroxidase, and catalase activities (RSOD, RPOD, and RCAT) were measured.  Results indicated the 18 physiological indices can be converted into five or six independent comprehensive indices by principal component analysis, and nine typical indices (Fv/Fm, SWC, LWP, Pro, LMDA, RSPC, RMDA, RSOD, and RCAT) screened out by a stepwise regression method could be utilized to evaluate the drought resistance.  Moreover, the 16 cotton cultivars were divided into four types: drought sensitive, drought weak sensitive, moderate drought resistant, and drought resistant types.  The resistance ability of two selected cotton cultivars (drought resistant cultivar, Dexiamian 1; drought sensitive cultivar, Yuzaomian 9110) with contrasting drought sensitivities were further verified by pot experiment.  Results showed that the responses of final cotton biomass, yield, and yield composition to drought were significantly different between the two cultivars.  In conclusion, drought resistant cultivar Dexiamian 1 and drought sensitive cultivar Yuzaomian 9110 were screened through hydroponics experiment, which can be used as ideal experimental materials to study the mechanism of different cotton cultivars with contrasting drought sensitivities in response to drought stress.
     
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    One-time fertilization at first flowering improves lint yield and dry matter partitioning in late planted short-season cotton
    LUO Hong-hai, WANG Qiang, ZHANG Jie-kun, WANG Lei-shan, LI Ya-bing, YANG Guo-zheng
    2020, 19 (2): 509-517.   DOI: 10.1016/S2095-3119(19)62623-7
    Abstract101)      PDF in ScienceDirect      
    Cotton producers have substantially reduced their inputs (labor, nutrients, and management) mainly by adopting a short-season cropping management that is characterized by late sowing, high density, and reduced fertilization with one-time application at the first bloom stage without lint yield reduction.  However, it has been hypothesized that one-time fertilization at an earlier growth stage could be a more effective and economic management practice.  A two-year field experiment was conducted by applying five fertilizer one-time fertilization at 0 (FT1), 5 (FT2), 10 (FT3), 15 (FT4), and 20 (FT5) days after the first flower appeared in the field and one three-split fertilizer application taken as the conventional control (FT6), making six treatments altogether.  Cotton growth period, biomass accumulation, yield, and its formation were quantified.  The results showed that the one-time fertilization did not affect the cotton growth progress as compared to FT6, however, the total crop cycles for FT3–FT5 were 3 days shorter.  FT1 produced the highest cotton lint yield (1 396 kg ha–1), which was similar to the FT6 but higher than the other treatments, and could be attributed to more bolls per unit area and higher lint percentage. Cotton yield was positively correlated with cotton plant biomass accumulated.  FT1 had both the highest average (VT) (193.7 kg ha–1 d–1) and the highest maximum (VM) (220.9 kg ha–1 d–1) rates during the fast biomass accumulation period.  These results suggest that one-time fertilizer application at the first flower stage might be an adjustment that is more effective than at first bloom, and allowed for easier decision making for application date due to non counting of plants with flowers is needed.
     
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    Architecture of stem and branch affects yield formation in short season cotton
    ZHANG Xiang, RUI Qiu-zhi, LI Yuan, CHEN Yuan, CHEN Yuan, ZHANG Xi-ling, CHEN De-hua, SONG Mei-zhen
    2020, 19 (3): 680-689.   DOI: 10.1016/S2095-3119(19)62626-2
    Abstract89)      PDF in ScienceDirect      
    The cotton direct seeding after wheat (rape) harvested is under trial and would be the future direction at the Yangtze River Valley region of China.  The objective of this study was to quantify the effects of branch and stem architecture on cotton yield and identify the optimal cotton architecture to compensate the yield loss due to the reduction of individual production capacity under high planting density in the direst seeding after wheat harvested cropping system.  The characteristics of the stem and branch architecture and the relationships between architecture of the stem and branch with yield formation were studied on eight short season cotton cultivars during 2015 and 2016 cotton growth seasons.  Based on the two years results, three cultivars with different architectures of stem and branch were selected to investigate the effect of mepiquat chloride (MC) application on the architecture of the stem and branch, boll retention, and the yield in 2017.  Significant differences were observed on plant height, all fruiting nodes to branches ratio (NBR) in the cotton plant, and the curvature of the fruiting branch (CFB) among the studied cultivars.  There were three types of stem and fruiting branch structures: Zhong425 with stable and suitable plant height and NBR (about 90 cm and 2.5, respectively), high CFB (more than 10.0), and high boll retention speed and seed cotton yield; Siyang 822 with excessive plant height and NBR, low CFB, and low boll retention speed and seed cotton yield; and other studied cultivars with unstable structure of stem and branch, boll retention speed, and seed cotton yield across years.  And MC application could promote the appropriate plant height and NBR and high CFB and thus resulted in high boll retention speed and the yield.  The results suggested that the suitable plant height and NBR (about 90 cm and 2.5 respectively), and high CFB (more than 10.0), which was related to both genotype and cultural practice, could promote the higher boll retention speed and seed cotton yield.
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    Flumetralin and dimethyl piperidinium chloride alter light distribution in cotton canopies by optimizing the spatial configuration of leaves and bolls
    LIANG Fu-bin, YANG Cheng-xun, SUI Long-long, XU Shou-zhen, YAO He-sheng, ZHANG Wang-feng
    2020, 19 (7): 1777-1788.   DOI: 10.1016/S2095-3119(19)62792-9
    Abstract117)      PDF in ScienceDirect      
    Plant growth regulators (PGRs) are frequently used to adjust cotton growth and development.  The objectives of this study were to determine how PGRs affect plant morphology, light distribution and the spatial distribution of leaves and bolls within the cotton canopy.  The field experiments were carried out at Shihezi (Xinjiang Uyghur Autonomous Region, China) in 2014 and 2015.  The experiment included two PGR treatments: (i) flumetralin (active ingredient (a.i.), N-N-ethyl-2,6-dinitro-4-aniline) and (ii) mepiquat chloride (a.i., 1-dimethyl-piperidiniuchloride) plus flumetralin.  No PGR (manual topping) was applied in the control treatment.  The chemically-topped plants were taller and had more main stem internodes than the manually-topped plants.  Furthermore, the PGRs significantly reduced the length of fruiting branches in the upper canopy, resulting in a more compact canopy.  The maximum leaf area index was significantly greater in the chemically-topped treatments than that in the control.  In particular, the PGRs increased leaf area index by 25% in the upper canopy.  The leaf area duration was also longer in the chemically-topped treatments than in the control.  Compared with the control, the chemically-topped treatments increased canopy diffuse non-interceptance by 35.75% in the upper canopy layer, while reducing the fraction of intercepted photosynthetically active radiation by 14.45% in the upper canopy layer.  Light transmittance in the upper and middle canopy layers was greater in the chemically-topped treatments than in the control, which increased boll numbers in both the upper canopy and the middle canopy.  However, the chemically-topped treatments resulted in less light-leakage through the lower canopy layer during the late growth stages, which had a tendency to increase boll numbers in the whole canopy.  In summary, the PGRs optimized canopy shape, light distribution and the spatial distribution of bolls and leaves.
     
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    Reduced square Bacillus thuringiensis insecticidal protein content of transgenic cotton under N deficit
    CHEN Yuan, LIU Zhen-yu, Leila I. M. TAMBEL, ZHANG Xiang, CHEN Yuan, CHEN De-hua
    2021, 20 (1): 100-108.   DOI: 10.1016/S2095-3119(20)63190-2
    Abstract100)      PDF in ScienceDirect      
    To clarify the effect of the N deficit on the amount of square Bt insecticidal protein, different N application rates (0, 75, 150, 225, and 300 kg ha–1) were imposed on the conventional cultivar Sikang 1 (SK-1) and hybrid cultivar Sikang 3 (SK-3) during 2015–2016 cotton growth seasons.  Under different N application rates, the square number per plant, square volume and square dry weight reduced when the N rates decreased from conventional rate (300 kg ha–1) to 0 kg ha–1.  And the square Bt protein content decreased accordingly.  The analysis of N metabolism showed that soluble protein content, GPT and GOT activities decreased, free amino acid, peptidase and protease activities increased under N deficit.  Correlation analysis indicated that the reduced Bt protein content under N deficit was related to altered N metabolism.  In conclusion, square development and the amount of square Bt toxin both decreased under N deficit, indicating that promoting the square development under appropriate N application rate would also promote the insect resistance during squaring stage.
     
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    Nitrogen spraying affects seed Bt toxin concentration and yield in Bt cotton
    ZHANG Xiang, ZHOU Ming-yuan, LI Ya-bing, LIU Zhen-yu, CHEN Yuan, CHEN De-hua
    2021, 20 (5): 1229-1238.   DOI: 10.1016/S2095-3119(20)63243-9
    Abstract101)      PDF in ScienceDirect      
    Cotton bolls exhibit the lowest insecticidal efficacy among all organs of Bt cotton, which would ultimately affect the yield formation.  The objective of this study was to investigate the effects of different urea concentrations on the seed Bt protein contents, seed cotton yield and the corresponding protein metabolism mechanism.  The experiments were conducted during 2017–2018 cotton growing seasons.  Two cultivars, Sikang 3 (hybrid, SK3) and Sikang 1 (conventional, SK1), were treated with six urea concentrations and their seed Bt protein contents were compared during boll formation period.  The urea spray concentration had a significant effect on the seed Bt toxin content and seed cotton yield.  Spraying of either 5 or 6% urea led to higher insecticidal protein contents and higher seed cotton yield for both cultivars.  Moreover, the highest amino acid and soluble protein contents, as well as GPT and GOT activities, and lower protease and peptidase activities were observed at the 5 to 6% urea levels.  Significant positive correlations between the seed Bt toxin and amino acid contents, and between the seed Bt toxin content and GPT activities were detected.  The lower boll worm number and hazard boll rate were also observed with the 5 to 6% urea treatments, which may be the reason why nitrogen spraying increased the seed cotton yield.  Therefore, our results suggested that the seed Bt toxin content and insect resistance were impacted markedly by external nitrogen application, and 5 to 6% urea had the greatest effect on insect resistance.
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    High plant density increases seed Bt endotoxin content in Bt transgenic cotton
    CHEN Yuan, LIU Zhen-yu, HENG Li, Leila I. M. TAMBEL, CHEN De-hua
    2021, 20 (7): 1796-1806.   DOI: 10.1016/S2095-3119(20)63232-4
    Abstract107)      PDF in ScienceDirect      
    Plant density is the cultivation practice usually employed to manipulate boll distribution, boll setting and yield in cotton production.  In order to determine the effect of plant density on the insecticidal protein content of Bacillus thuringiensis (Bt) cotton plants, a study was conducted in Yangzhou University of China in 2015 and 2016.  Five plant densities (PD1–PD5, representing 15 000, 30 000, 45 000, 60 000, and 75 000 plants ha–1) were imposed on two Bt cotton cultivars, Sikang 1 (the conventional cultivar, SK-1) and Sikang 3 (the hybrid cultivar, SK-3).  The boll number per plant, boll weight and boll volume all decreased as plant density increased.  As plant density increased from 15 000 to 75 000 plants ha–1, seed Bt protein content increased, with increases of 66.5% in SK-1 and 53.4% in SK-3 at 40 days after flowering (DAF) in 2015, and 36.8% in SK-1 and 38.6% in SK-3 in 2016.  Nitrogen (N) metabolism was investigated to uncover the potential mechanism.  The analysis of N metabolism showed enhanced soluble protein content, glutamic-pyruvic transaminase (GPT) and glutamate oxaloacetate transaminase (GOT) activities, but reduced free amino acid content, and protease and peptidase activities with increasing plant density.  At 20 DAF, the seed Bt toxin amount was positively correlated with soluble protein level, with correlation coefficients of 0.825** in SK-1 and 0.926** in SK-3 in 2015, and 0.955** in SK-1 and 0.965** in SK-3 in 2016.  In contrast, the seed Bt protein level was negatively correlated with free amino acid content, with correlation coefficients of –0.983** in SK-1 and –0.974** in SK-3 in 2015, and –0.996** in SK-1 and –0.986** in SK-3 in 2016.  To further confirm the relationship of Bt protein content and N metabolism, the Bt protein content was found to be positively correlated with the activities of GPT and GOT, but negatively correlated with the activities of protease and peptidase.  In conclusion, our present study indicated that high plant density elevated the amount of seed Bt protein, and this increase was associated with decreased boll number per plant, boll weight and boll volume.  In addition, altered N metabolism also contributed to the increased Bt protein content under high plant density.
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    Effects of plant density and nitrogen rate on cotton yield and nitrogen use in cotton stubble retaining fields
    WANG Shi-hong, MAO Li-li, SHI Jia-liang, NIE Jun-jun, SONG Xian-liang, SUN Xue-zhen
    2021, 20 (8): 2090-2099.   DOI: 10.1016/S2095-3119(20)63323-8
    Abstract126)      PDF in ScienceDirect      
    Increasing nitrogen (N) rate could accelerate the decomposition of crop residues, and then improve crop yield by increasing N availability of soil and N uptake of crops.  However, it is not clear whether N rate and plant density should be modified after a long period of cotton stubble return with high N rate.  This study seeks to assess the effects of N rate and plant density on cotton yield, N use efficiency, leaf senescence, soil inorganic N, and apparent N balance in cotton stubble return fields in Liaocheng, China, in 2016 and 2017.  Three plant densities 5.25 (D5.25), 6.75 (D6.75) and 8.25 (D8.25) plants m–2 and five N rates 0 (N0), 105 (N105), 210 (N210), 315 (N315), and 420 (N420) kg ha–1  were investigated.  Compared to the combination used by local farmers (D5.25N315), a 33.3% N reduction and a 28.6% increase in plant density (D6.75N210) can maintain high cotton yield, while a 66.7% N reduction at 6.75 plants m–2 (D6.75N105) can only achieve high yield in the first year.  Biological yield increased with the increase of N rate and plant density, and the highest yield was obtained under 420 kg N ha–1 at 8.25 plants m–2 (D8.25N420) across the two years under investigation.  Compared to D5.25N315, N agronomic efficiency (NAE) and N recovery efficiency (NRE) in D6.75N210 increased by 30.2 and 54.1%, respectively, and NAE and NRE in D6.75N210 increased by 104.8 and 88.1%, respectively.  Soil inorganic N decreased sharply under 105 kg N ha–1, but no change was found under 210 kg N ha–1 at 6.75 plants m–2.  N deficit occurred under 105 kg N ha–1, but it did not occurr under 210 kg N ha–1 at 6.75 plants m–2.  Net photosynthetic rate and N concentration of leaves under N rate ranging from 210 to 420 kg ha–1 were higher than those under N rate of 0 or 105 kg N ha–1 at all three densities.  The findings suggest that D6.75N210 is a superior combination in cotton stubble retaining fields in the Yellow River Valley and other areas with similar ecologies.
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    Effects of plant density and mepiquat chloride application on cotton boll setting in wheat–cotton double cropping system
    CHEN Yuan, LIU Zhen-yu, HENG Li, Leila I. M. TAMBEL, ZHANG Xiang, CHEN Yuan, CHEN De-hua
    2021, 20 (9): 2372-2381.   DOI: 10.1016/S2095-3119(20)63286-5
    Abstract93)      PDF in ScienceDirect      
    Sowing cotton directly after harvesting wheat in the Yangtze River Valley of China requires early mature of cotton without yield reduction.  Boll-setting period synchronisation and more yield bolls distributed at the upper and middle canopy layers are also required for harvesting.  The objective of this study is to quantify the individual and interaction effects of plant density and plant growth regulator mepiquat chloride (MC) on temporal and spatial distributions of yield bolls, as well as yield and yield components.  During the 2013–2016 cotton growing seasons, the experiments were conducted on a short-season cotton cultivar CRRI50 at Yangzhou University, China.  Various combinations of plant density (12.0, 13.5 and 15.0 plants m–2) and MC dose (180, 270 and 360 g ha–1) were applied on cotton plants.  The combination of 13.5 plants m–2 and 270 g ha–1 MC resulted in the greatest boll number per unit area, the highest daily boll setting number and more than 90% of bolls positioned within 45–80 cm above the ground.  In conclusion, appropriate MC dose in combination of high plant density could synchronize boll-setting period and retain more bolls at the upper and middle canopy layers without yield reduction in the system of direct-seeded cotton after wheat harvest, and thus overcome the labor-intensive problem in current transplanting cropping system. 
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    Control of cotton pests and diseases by intercropping: A review
    CHI Bao-jie, ZHANG Dong-mei, DONG He-zhong
    2021, 20 (12): 3089-3100.   DOI: 10.1016/S2095-3119(20)63318-4
    Abstract281)      PDF in ScienceDirect      
    Cotton (Gossypium hirsutum L.) is a globally important crop that is often damaged by pests and diseases.  Current cotton pests and diseases management is dependent on chemical pesticides.  Although chemical pesticides are usually effective, long-term application of these pesticides often leads to increased insecticide resistance in the pests, fewer natural enemies, reduced natural control, and a degraded environment.  Because of increased environmental awareness and the need for sustainable cotton production, the control of cotton pests and diseases using biological means like intercropping is increasingly receiving attention.  Intercropping of cotton with other crops can often boost the total yield and output of the intercropping system and provide significant economic benefits without sacrificing cotton quality.  Intercropping also increases the number of natural enemies, and reduces the occurrence of cotton pests and diseases by altering the ecological structure and environmental conditions in the fields.  Cotton-based intercropping is an effective strategy to reduce the competition between cotton and grain or other economic crops for arable land.  It is also an important way to increase the populations of natural enemies in cotton fields for the management of pests and diseases.  However, inappropriate intercropping can also increase labor requirements and even result in inadequate control of pests and diseases.  This review focuses on the performance and the mechanisms of intercropping for reducing cotton pests and disease as well as on the effective management of intercropping systems.  The risks and limitations, as well as the study approaches needed and the prospects of intercropping for the control of cotton pests and diseases, are also discussed.  This information is intended to aid researchers and growers in designing economically viable and ecologically friendly pest and disease management strategies that will reduce the use of chemicals and the cost of cotton production.
     
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