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With the increasing demands for crop yield and production mechanization, improvement of plant architecture is getting more imperative in cotton. In the present study, we investigated the plant height (PH) and the node of first fruiting branch (NFFB) of 719 upland cotton accessions in six different environments. We used the 10,511 high‐quality single nucleotide polymorphisms (SNPs) to perform single‐locus and multi‐locus genome‐wide association study (GWAS). As many as 278 associated SNPs were identified, 142 by the mixed linear model (MLM) in the single‐locus model and 192 by six multi‐locus models. A total of 42 SNPs were identified in at least four environment‐traits or methods, of which 28 SNPs were significantly associated with PH, 22 were significantly associated with NFFB, and eight were co‐associated with the two traits. Notably, most of loci were novel besides i33922Gh located in the reported QTL for PH. Furthermore, we identified nine promising candidate genes, among which the three genes Gh_D03G0738, Gh_D10G2028, and Gh_D05G3600 contained non‐synonymous SNP mutation. The accessions with alleles of the mutations resulted in significant phenotypic differences. The expression of these genes showed significant differences between short‐PH and high‐PH varieties. Moreover, overexpression of Gh_D03G0738 led to reduction of PH in Arabidopsis. These results provided insights into genetic basis of plant architecture in cotton. Core Ideas: We identified 278 single nucleotide polymorphisms (SNPs) associated plant height (PH) and node of the first fruiting branch with single‐ and multi‐locus genome‐wide association study by using 719 cotton accessions.A total of 42 SNPs were identified in at least four environment‐traits or methods.Overexpression of Gh_D03G0738 led to reduction of PH in Arabidopsis. [ABSTRACT FROM AUTHOR]

In saline and salinity-affected soils, the global productivity and sustainability of cotton are severely affected by soil salinity. High salt concentrations hinder plant growth and yield formation mainly through the occurrence of osmotic stress, specific ion toxicity, and nutritional imbalance in cotton. A number of agronomic practices have been identified as potential solutions to alleviate the adverse effects induced by salinity. While genetic breeding holds promise in enhancing the salinity tolerance of cotton, agronomic practices that improve the root zone environment, ameliorate soil conditions, and enhance salinity tolerance are currently considered to be more practical. This compressive review highlights the effectiveness of agronomic practices, such as furrow seeding, plastic mulching, their combination, densely planting, and the appropriate application of fertilizer and plant growth regulators, in mitigating the negative impact of salinity on cotton. By implementing these agronomic practices, cotton growers can improve the overall performance and resilience of cotton crops in saline and salinity-affected soils. This review provides valuable insights into practical agronomic measures that can be adopted to counteract the adverse consequences of soil salinity on cotton cultivation. [ABSTRACT FROM AUTHOR]

Weeds seriously affect the yield and quality of crops. Because manual weeding is time-consuming and laborious, the use of herbicides becomes an effective way to solve the harm caused by weeds in fields. Both 5-enolpyruvyl shikimate-3-phosphate synthetase (EPSPS) and acetyltransferase genes (bialaphos resistance, BAR) are widely used to improve crop resistance to herbicides. However, cotton, as the most important natural fiber crop, is not tolerant to herbicides in China, and the EPSPS and BAR family genes have not yet been characterized in cotton. Therefore, we explore the genes of these two families to provide candidate genes for the study of herbicide resistance mechanisms. In this study, 8, 8, 4, and 5 EPSPS genes and 6, 6, 5, and 5 BAR genes were identified in allotetraploid Gossypium hirsutum and Gossypium barbadense, diploid Gossypium arboreum and Gossypium raimondii, respectively. Members of the EPSPS and BAR families were classified into three subgroups based on the distribution of phylogenetic trees, conserved motifs, and gene structures. In addition, the promoter sequences of EPSPS and BAR family members included growth and development, stress, and hormone-related cis-elements. Based on the expression analysis, the family members showed tissue-specific expression and differed significantly in response to abiotic stresses. Finally, qRT-PCR analysis revealed that the expression levels of GhEPSPS3, GhEPSPS4, and GhBAR1 were significantly upregulated after exogenous spraying of herbicides. Overall, we characterized the EPSPS and BAR gene families of cotton at the genome-wide level, which will provide a basis for further studying the functions of EPSPS and BAR genes during growth and development and herbicide stress. [ABSTRACT FROM AUTHOR]

Crops must efficiently allocate their limited energy resources to survival, growth and reproduction, including balancing growth and defense. Thus, investigating the underlying molecular mechanism of crop under stress is crucial for breeding. Chloroplasts immunity is an important facet involving in plant resistance and growth, however, whether and how crop immunity modulated by chloroplast is influenced by epigenetic regulation remains unclear. Here, the cotton lysine 2‐hydroxyisobutyrylation (Khib) and succinylation (Ksuc) modifications are firstly identified and characterized, and discover that the chloroplast proteins are hit most. Both modifications are strongly associated with plant resistance to Verticillium dahliae, reflected by Khib specifically modulating PR and salicylic acid (SA) signal pathway and the identified GhHDA15 and GhSRT1 negatively regulating Verticillium wilt (VW) resistance via removing Khib and Ksuc. Further investigation uncovers that photosystem repair protein GhPSB27 situates in the core hub of both Khib‐ and Ksuc‐modified proteins network. The acylated GhPSB27 regulated by GhHDA15 and GhSRT1 can raise the D1 protein content, further enhancing plant biomass‐ and seed‐yield and disease resistance via increasing photosynthesis and by‐products of chloroplast‐derived reactive oxygen species (cROS). Therefore, this study reveals a mechanism balancing high disease resistance and high yield through epigenetic regulation of chloroplast protein, providing a novel strategy to crop improvements. [ABSTRACT FROM AUTHOR]

Crop rotation and intercropping are important ways to increase agricultural resource utilization efficiency and crop productivity. Alternate intercropping, or transposition intercropping, is a new intercropping pattern in which two crops are intercropped in a wide strip with planting positions switched annually on the same land. Transposition intercropping combines intercropping and rotation and thus performs better than either practice alone. Compared with traditional intercropping or rotation, it can increase yield and net return by 17–21% and 10–23%, respectively, and the land equivalent ratio (LER) by 20% to 30%. In crop growth and development, a balanced root–shoot relation is essential to obtain satisfactory yields and yield quality. Intercropping, rotation, or the combination can alter the original root–shoot relation by changing the ecology and physiology of both root and shoot to achieve a rebalancing of the relation. The crop yield and yield quality are thus regulated by the root–shoot interactions and the resulting rebalancing. The review examines the effects of above- and belowground interactions and rebalancing of root–shoot relations on crop yields under cotton-based intercropping, rotation, and particularly alternate intercropping with the practices combined. The importance of signaling in regulating the rebalancing of root–shoot relations under intercropping, rotation, and the combination was also explored as a possible focus of future research on intercropping and rotation. [ABSTRACT FROM AUTHOR]

Verticillium wilt (VW), a fungal disease caused by Verticillium dahliae, currently devastates cotton fiber yield and quality seriously, yet few resistance germplasm resources have been discovered in Gossypium hirsutum. The cotton variety Nongda601 with suitable VW resistance and high yield was developed in our lab, which supplied elite resources for discovering resistant genes. Early nodulin-like protein (ENODL) is mainly related to nodule formation, and its role in regulating defense response has been seldom studied. Here, 41 conserved ENODLs in G. hirsutum were identified and characterized, which could divide into four subgroups. We found that GhENODL6 was upregulated under V. dahliae stress and hormonal signal and displayed higher transcript levels in resistant cottons than the susceptible. The GhENODL6 was proved to positively regulate VW resistance via overexpression and gene silencing experiments. Overexpression of GhENODL6 significantly enhanced the expressions of salicylic acid (SA) hormone-related transcription factors and pathogenicity-related (PR) protein genes, as well as hydrogen peroxide (H2O2) and SA contents, resulting in improved VW resistance in transgenic Arabidopsis. Correspondingly, in the GhENODL6 silenced cotton, the expression levels of both phenylalanine ammonia lyase (PAL) and 4-coumarate-CoA ligase (4CL) genes significantly decreased, leading to the reduced SA content mediating by the phenylalanine ammonia lyase pathway. Taken together, GhENODL6 played a crucial role in VW resistance by inducing SA signaling pathway and regulating the production of reactive oxygen species (ROS). These findings broaden our understanding of the biological roles of GhENODL and the molecular mechanisms underlying cotton disease resistance. [ABSTRACT FROM AUTHOR]

Lipids are major and essential constituents of plant cells and provide energy for various metabolic processes. However, the function of the lipid signal in defence against Verticillium dahliae, a hemibiotrophic pathogen, remains unknown. Here, we characterized 19 conserved stearoyl‐ACP desaturase family proteins from upland cotton (Gossypium hirsutum). We further confirmed that GhSSI2 isoforms, including GhSSI2‐A, GhSSI2‐B, and GhSSI2‐C located on chromosomes A10, D10, and A12, respectively, played a dominant role to the cotton 18:1 (oleic acid) pool. Suppressing the expression of GhSSI2s reduced the 18:1 level, which autoactivated the hypersensitive response (HR) and enhanced cotton Verticillium wilt and Fusarium wilt resistance. We found that low 18:1 levels induced phenylalanine ammonia‐lyase‐mediated salicylic acid (SA) accumulation and activated a SA‐independent defence response in GhSSI2s‐silenced cotton, whereas suppressing expression of GhSSI2s affected PDF1.2‐dependent jasmonic acid (JA) perception but not the biosynthesis and signalling cascade of JA. Further investigation showed that structurally divergent resistance‐related genes and nitric oxide (NO) signal were activated in GhSSI2s‐silenced cotton. Taken together, these results indicate that SA‐independent defence response, multiple resistance‐related proteins, and elevated NO level play an important role in GhSSI2s‐regulated Verticillium wilt resistance. These findings broaden our knowledge regarding the lipid signal in disease resistance and provide novel insights into the molecular mechanism of cotton fungal disease resistance. [ABSTRACT FROM AUTHOR]

Summary: Cotton (Gossypium hirsutum) is constantly attacked by pathogens and insects. The most efficient control strategy is to develop resistant varieties using broad‐spectrum gene resources. Several resistance loci harboured by superior varieties have been identified through genome‐wide association studies. However, the key genes and/or loci have not been functionally identified. In this study, we identified a locus significantly associated with Verticillium wilt (VW) resistance, and within a 145.5‐kb linkage disequilibrium, two non‐specific lipid transfer protein genes (named GhnsLTPsA10) were highly expressed under Verticillium pathogen stress. The expression of GhnsLTPsA10 significantly increased in roots upon Verticilliumdahliae stress but significantly decreased in leaves under insect attack. Furthermore, GhnsLTPsA10 played antagonistic roles in positively regulating VW and Fusarium wilt resistance and negatively mediating aphid and bollworm resistance in transgenic Arabidopsis and silenced cotton. By combining transcriptomic, histological and physiological analyses, we determined that GhnsLTPsA10‐mediated phenylpropanoid metabolism further affected the balance of the downstream metabolic flux of flavonoid and lignin biosynthesis. The divergent expression of GhnsLTPsA10 in roots and leaves coordinated resistance of cotton against fungal pathogens and insects via the redirection of metabolic flux. In addition, GhnsLTPsA10 contributed to reactive oxygen species accumulation. Therefore, in this study, we elucidated the novel function of GhnsLTP and the molecular association between disease resistance and insect resistance, balanced by GhnsLTPsA10. This broadens our knowledge of the biological function of GhnsLTPsA10 in crops and provides a useful locus for genetic improvement of cotton. Significance Statement: Cotton (Gossypium hirsutum) fibre quality and yield often decline sharply when infected with various diseases and insects. Here, we identified a locus which links two non‐specific lipid transfer proteins in cotton. The divergent tissue expression of the genes in the roots and leaves coordinated resistance of cotton to pathogens and insects via redirection of metabolic flux. [ABSTRACT FROM AUTHOR]

Alpha-linolenic acid (ALA, 18:3Δ9,12,15) and γ-linolenic acid \ (GLA, 18:3Δ6,9,12) are important trienoic fatty acids, which are beneficial for human health in their own right, or as precursors for the biosynthesis of long-chain polyunsaturated fatty acids. ALA and GLA in seed oil are synthesized from linoleic acid (LA, 18:2Δ9,12) by the microsomal ω-3 fatty acid desaturase (FAD3) and Δ6 desaturase (D6D), respectively. Cotton (Gossypium hirsutum L.) seed oil composition was modified by transforming with an FAD3 gene from Brassica napus and a D6D gene from Echium plantagineum , resulting in approximately 30% ALA and 20% GLA, respectively. The total oil content in transgenic seeds remained unaltered relative to parental seeds. Despite the use of a seed-specific promoter for transgene expression, low levels of GLA and increased levels of ALA were found in non-seed cotton tissues. At low temperature, the germinating cottonseeds containing the linolenic acid isomers elongated faster than the untransformed controls. ALA-producing lines also showed higher photosynthetic rates at cooler temperature and better fiber quality compared to both untransformed controls and GLA-producing lines. The oxidative stability of the novel cottonseed oils was assessed, providing guidance for potential food, pharmaceutical and industrial applications of these oils. [ABSTRACT FROM AUTHOR]

Cotton is sensitive to waterlogging stress, which usually results in stunted growth and yield loss. To date, the molecular mechanisms underlying the responses to waterlogging in cotton remain elusive. Cotton was grown in a rain-shelter and subjected to 0 (control)-, 10-, 15- and 20-d waterlogging at flowering stage. The fourth-leaves on the main-stem from the top were sampled and immediately frozen in liquid nitrogen for physiological measurement. Global gene transcription in the leaves of 15-d waterlogged plants was analyzed by RNA-Seq. Seven hundred and ninety four genes were up-regulated and 1018 genes were down-regulated in waterlogged cotton leaves compared with non-waterlogged control. The differentially expressed genes were mainly related to photosynthesis, nitrogen metabolism, starch and sucrose metabolism, glycolysis and plant hormone signal transduction. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis indicated that most genes related to flavonoid biosynthesis, oxidative phosphorylation, amino acid metabolism and biosynthesis as well as circadian rhythm pathways were differently expressed. Waterlogging increased the expression of anaerobic fermentation related genes, such as alcohol dehydrogenase (ADH), but decreased the leaf chlorophyll concentration and photosynthesis by down-regulating the expression of photosynthesis related genes. Many genes related to plant hormones and transcription factors were differently expressed under waterlogging stress. Most of the ethylene related genes and ethylene-responsive factor-type transcription factors were up-regulated under water-logging stress, suggesting that ethylene may play key roles in the survival of cotton under waterlogging stress. [ABSTRACT FROM AUTHOR]

Deficit irrigation is a new strategy to increase water use efficiency of cotton in arid areas, but it is not clear if it interacts with plant density. The objective of this study was to determine the effects of deficit irrigation and plant density as well as their interaction on the growth, yield and fiber quality of irrigated cotton. Two field experiments were conducted at three sites in 2013 and one site from 2014 to 2015 in an arid area of Xinjiang. A randomized complete block design with three replicates was used to determine the effects of 6 irrigation regimes on seedcotton yield in the first experiment, while a split-plot design was used in the second experiment with the main plots assigned to irrigation regime (saturation, regular and deficit) and the subplots to plant density (high, medium and low) to examine cotton yield, fiber quality and water productivity as affected by plant density under deficit irrigation. Averaged across the three sites, drip irrigation ranging from 3650 to 4700 m 3 /ha did not significantly affect cotton yield, but seedcotton yield under 3650 m 3 /ha in S1 was 6.3% lower than that under 4000 m 3 /ha. Thus, it is quite appropriate to regularly drip-irrigate at 4000 m 3 /ha in the experimental area. Deficit irrigation at high plant density also maintained a relatively higher leaf area index (LAI) and net assimilation rate (NAR), particularly at late stages of plant growth and development, than saturation or regular irrigation. Plant density ranging from 18 to 24 plants/m 2 produced more seedcotton than 12 plants/m 2 under regular irrigation. Increasing irrigation to saturation levels had little effects on cotton yield regardless of plant density; saturation irrigation at high plant density even reduced cotton yield compared with regular irrigation at medium plant density. Under deficit irrigation, the high plant density produced 9.1-17% greater yield and 9.3-16.8% higher irrigation water productivity (IWP) than low or medium plant density, and comparable yield to medium or high plant density under regular irrigation. This high yield under deficit irrigation at high plant density was due to increased plant biomass occasioned by high plant population and improved harvest index. Deficit irrigation did not affect fiber quality in 2014, but reduced fiber length and increased fiber micronaire value in 2015. Conclusively, use of high plant density under deficit irrigation can be a promising alternative for water saving without compromising cotton yield under arid conditions. [ABSTRACT FROM AUTHOR]

Fiber quality is a major breeding goal in cotton, but phenotypically direct selection is often hindered. In this study, we identified fiber quality and yield related loci using GWAS based on 2.97 million SNPs obtained from 10.65× resequencing data of 1081 accessions. The results showed that 585 novel fiber loci, including two novel stable SNP peaks associated with fiber length on chromosomes At12 and Dt05 and one novel genome regions linked with fiber strength on chromosome Dt12 were identified. Furthermore, by means of gene expression analysis, GhM_A12G0090 , GhM_D05G1692 , GhM_D12G3135 were identified and GhM_D11G2208 function was identified in Arabidopsis. Additionally, 14 consistent and stable superior haplotypes were identified, and 25 accessions were detected as possessing these 14 superior haplotype in breeding. This study providing fundamental insight relevant to identification of genes associated with fiber quality and yield will enhance future efforts toward improvement of upland cotton. • A total of 909 novel fiber and yield loci were detected via WGRS with 10.65× coverage depth in 1,081 cotton accessions. • Three novel stable SNP peaks associated with FL and FS were found. • GhM_D11G2208 can promote cell elongation based up leaf trichome and dark-grown hypocotyls in Arabidopsis. • 14 consistent and stable superior haplotypes were detected based on 915 SNPs in Dt11 region. [ABSTRACT FROM AUTHOR]

Since the beginning of the 21 st century, the rapid economic development and accelerated urbanization of China have caused major changes to the country's cotton cultivation technology. China has not replicated the completely mechanized approach used in developed countries. Rather, taking into account the underdeveloped economy and family-scale based cotton growing, China has established and implemented a light and simplified system of sustainable cotton production. Light and simplified cultivation (LSC) involves using modern agricultural equipment and technology adapted to the local economic level and mode of management of cotton production instead of manual operations. This method reduces labor intensity, simplifies cultivation management, reduces the frequency of field operations, integrates agricultural machinery and agronomic technology, and uses high-quality seeds and improved techniques to achieve light, simplified, and cost-effective cotton production. Cotton LSC includes the following key technologies: Single-seed precision sowing, simplified plant pruning, light and simplified fertilization, water and fertilization integration technology, and plant population structure control. Single seed precision sowing technology ensures robust seedling growth via differential expression of the key genes controlling hook formation and hypocotyl elongation at seed germination. Cotton planting at a relatively high plant density inhibits the growth of vegetative branches via differential expression of genes for hormone metabolism and compartmentation of hormones within a cotton plant. The high and stable yield of LSC lies in the adaptive coordination between the cotton yield components and between the biomass and the harvest index. According to the appropriate leaf area index and its dynamics, quantitative indicators such as suitable plant height, the ratio of fruiting nodes to branches in number, and the ratio of seed cotton to stalks in weight can produce plant populations with high solar efficiency. The basis of light and simplified fertilization is that the absorption of fertilizer N by cotton is concentrated within 20 days after flowering, and the fertilizer applied at early flowering was mainly distributed to reproductive organs and had higher N use efficiency than that applied at other stages. The water saving mechanism of partial root-zone irrigation is that methyl jasmonate serves as a signal substance to enhance the water absorption from the hydrated root side. Future development of cotton cultivation must include an in-depth investigation of the ecophysiology of LSC to further reform and optimize the planting systems and patterns. Innovation in cultivation technologies, development of new materials and equipment, and integration of agronomic technology and materials may provide solid theoretical and technical support for LSC and promote the sustainable cotton production in China. [ABSTRACT FROM AUTHOR]

Plant density, nitrogen (N) fertilization rate and plant pruning are important measures used globally to cultivate cotton. A typical combination of 52,500 plants ha −1 , intensive pruning and 255 kg N ha −1 has been widely applied in the Yellow River Valley of China. The main objective of this study is to determine whether more beneficial combinations exist than the typical one for profitable cotton production in this region. Using a split–split plot design with four replications, we conducted a three-year field experiment to study the individual and interaction effects of plant density (52,500 and 82,500 plants ha −1 ), plant pruning (intensive and extensive) and N fertilizer rate (195 and 255 kg N ha −1 ) on yield, plant biomass and partitioning, N uptake and use efficiency, as well as input and output values. The results showed that cotton yield was affected by individual and interaction effects of the three agronomic factors. When planted at a moderate density (52,500 plants ha −1 ), the seedcotton yield of intensively pruned cotton under a low N rate (195 kg N ha −1 ) and of extensively pruned cotton under low and high (255 kg N ha −1 ) N rates was reduced by 6.9, 6.7 and 5.4%, respectively, whereas the four combinations with high plant density (82,500 plants ha −1 ) produced a yield value that was comparable to that of the typical combination, indicating a relatively stable yield at high plant density irrespective of pruning mode and N rate. Vegetative branches of the extensively pruned cotton accounted for 18.7–23.6% of the total biomass at moderate plant density compared with only 2.8–2.9% of the total biomass at high plant density. At moderate plant density, intensively pruned cotton exhibited a higher harvest index than the extensively pruned plants. By contrast, the harvest index for the four combinations with high plant density did not differ, suggesting a relatively stable harvest index among these combinations. There was no difference in the N biomass utility index (NBI) among all combinations. The combination of high plant density, extensive pruning and reduced N rate had a 6.7% lower nitrogen yield utility index (NYI) than the typical combination but a 5.4% higher NYI than the combination of high plant density, extensive pruning and high N rate. More importantly, the combination of high plant density, extensive pruning and reduced N rate produced comparable yield with less input, leading to 21.7% more net revenue than the typical combination. Our results support the use of high plant density, reduced N rate and extensive pruning to ensure profitable cotton production in the Yellow River Valley and other cotton-growing areas with similar ecologies. [ABSTRACT FROM AUTHOR]

Basal and topdressing split application of nitrogen (N) fertilizer is widely used in cotton in many cotton-growing countries, including China. Recently, in the Yellow River valley of China, one-off basal application of N fertilizer has been applied to meet the challenge of increasing labor costs. However, how one-off basal application of N fertilizer affects cotton yields and N use efficiency and by what mechanisms are not clear. Therefore, an experiment was conducted using full-season (K836) and short-season (LM532) cotton cultivars in a moderate fertility field in the Yellow River valley in 2019 and 2020. A split-plot design was established for each variety with the main plots assigned to a mulching pattern (with or without plastic film mulching) and the subplots assigned to an N rate (0 or 195 kg N ha−1, abbreviated as N0 and N195). Cotton yield and yield components, biomass accumulation and distribution, and total N and 15N absorption and utilization were determined each year. Compared with N0, one-off basal application of N fertilizer (N195) did not increase boll density, boll weight, lint percentage or seedcotton yield regardless of cultivar or mulching. Biomass and total N uptake of cotton increased significantly in N195 compared with N0, but the increases occurred primarily in vegetative organs, leading to reductions in the harvest index and N yield efficiency index. With one-off basal application of N fertilizer, more than 80 % of the N in cotton plants derived from soil. Approximately 28 % of 15N-labeled urea was absorbed by cotton plants, of which only approximately 35 % was used in forming seedcotton yield. Therefore, cotton plants with one-off basal application of N fertilizer only recovered a small amount of fertilizer N, and even less of the fertilizer N was used in yield formation. As a result, the harvest index of cotton decreased, and thus, one-off basal application of N fertilizer failed to increase seedcotton yield. Cultivar and plastic film mulching did not alter the effects of one-off basal application of N fertilizer. Therefore, although one-off basal application of N fertilizer in cotton is a labor-saving approach, it should not be encouraged in moderate fertility soil in the Yellow River valley or other areas with similar ecology. • One-off basal N application did not increase the seedcotton yield compared with no-N fertilization. • One-off N application led to a low proportion of plant N derived from 15N and even less for yield formation. • Both N uptake and N distribution to vegetative organs was improved by one-off basal N application. • Cultivar and plastic mulching did not alter the effects of one-off basal application of N fertilizer. [ABSTRACT FROM AUTHOR]

Productivity and benefits in intercropping systems are influenced by the overlapping period and competitive dynamics between species, which are contingent upon variety selection and planting schedules. However, there is limited research on improving the productivity of intercropping systems by adjusting sowing dates for combinations with minimal plant height differences. A two-year field experiment utilizing a strip intercropping with four rows of cotton and five rows of soybeans was conducted. Three soybean varieties (Qihuang 34, Jidou 12, and Jidou 17) with varying plant heights and types, along with early and late sowing dates, were examined. Intercropping cotton and soybeans resulted in higher yields than monoculture, with Jidou 12 identified as the most suitable variety for intercropping with cotton. The land equivalent ratio (LER) for the cotton-soybean intercropping system averaged between 1.04 and 1.15 over two years. Notably, intercropping cotton with late-sown Qihuang 34, Jidou 12, and Jidou 17 demonstrated increased LER by 4 %, 5 %, and 3 % respectively, compared to early-sown. This demonstrates that adjusting the soybean sowing date can modulate the competition dynamics between cotton and soybean, mitigating interspecific competition. Furthermore, intercropping cotton with late-sown Jidou 12 exhibited superior performance in terms of dry matter, canopy photosynthesis, photosynthetically active radiation, and root morphology in cotton compared to other treatments. Within the distance of 100–150 mm from the soybean, cottons were more competitive than soybeans, indicating subtle interspecific competition between the two species. By carefully selecting soybean varieties and adjusting sowing dates, temporal complementarity and spatial niche differentiation can be achieved, alleviating interspecific competition and enhancing the productivity of cotton-soybean intercropping systems. • Intense competition between cotton and soybean limits intercropping productivity. • Intercropping cotton with late-sown Jidou 12 mitigates interspecific competition. • It enhances niche differentiation through improved light utilization and root growth. • Niche differentiation increases the productivity in intercropping cotton with late-sown Jidou 12. [ABSTRACT FROM AUTHOR]

Flooding irrigation prior to sowing during the winter or spring seasons has been widely employed to mitigate soil salinity and generate adequate soil moisture for cotton seedling emergence in saline fields. In an effort to conserve water, a technique known as "dry sowing and wet emergence" has been utilized in arid regions of Northern Xinjiang, China, where the soil is not irrigated before sowing, and a single drip irrigation is applied to facilitate cotton emergence immediately after sowing. However, the successful implementation of this technique has not been achieved due to high soil salinity in Southern Xinjiang, China. In light of these challenges, we hypothesize that modifying the traditional "dry sowing and wet emergence" technique from a one-time irrigation to multiple irrigations during the seedling stage could improve the microenvironment of the root-zone soil, thereby mitigating salinity stress and promoting seedling emergence and stand establishment. We conducted a two-year field experiment employing a randomized block experimental design to assess the impacts of various irrigation methods during the seedling stage on soil microenvironment, seedling emergence, stand establishment, plant physiological response to salinity stress, and yield formation of cotton. The experiment encompassed three treatments, including pre-sowing flood irrigation (flood irrigation), the traditional single drip irrigation for dry sowing and wet emergence (single drip irrigation), and the modified dry sowing and wet emergence with three rounds of drip irrigation (multiple drip irrigation). Multiple drip irrigation resulted in consistently higher soil temperatures during the period of 5–30 days after sowing (DAS), lower soil salinity from 15 to 30 DAS, and also maintained relatively higher soil moisture levels than single drip irrigation between 20 and 30 DAS. In contrast to flood irrigation, multiple drip irrigation led to an increase in soil temperature from 5 to 30 DAS and a reduction in soil salinity levels during the period of 15–30 DAS. Conversely, single drip irrigation led to a decrease in soil salinity during 5–10 DAS, but a substantial increase in soil salinity and decrease in soil moisture from 20 to 30 DAS. Multiple drip irrigations used only 40 % of the irrigation amount needed for flood irrigation but achieved comparable seedling emergence and stand establishment rates. Compared to single drip irrigation, multiple drip irrigations decreased Na+ and malondialdehyde (MDA) content in the leaves by 21.7 % and 15.6 %, and increased photosynthetic (Pn) rate and stand establishment rate by 22.0 % and 36.3 %, respectively. Moreover, multiple drip irrigation produced seedcotton yields equal to those of flood irrigation, with an increase of 24.2 % compared to single drip irrigation. The results demonstrate that multiple drip irrigations enhance seedcotton yield through improving stand establishment compared to single drip irrigation. This improvement is attributed to reduced salinity stress, as evidenced by the decreased soil salinity, Na+ content, and MDA content in the leaves when using multiple drip irrigation during seedling emergence. Therefore, multiple drip irrigation is a promising technique for promoting cotton seedling emergence and stand establishment in saline fields of Southern Xinjiang and other cotton-growing areas with similar ecological conditions. • The "Dry sowing and wet emergence" technique with single irrigation is not effective in saline fields. • Including multiple drip irrigations during emergence improves stand establishment and seedcotton yield. • This improvement is due to reduced soil salinity and decreased salinity stress. [ABSTRACT FROM AUTHOR]

Apical hook formation is essential for the emergence and stand establishment of cotton plants. Searching for agronomic measures to regulate apical hook formation and clarifying its mechanism are important for full stand establishment in cotton. In this study, cotton seeds were sown at varying seeding rates or depths in sand to determine if and how apical hook formation was regulated by seeding rates or depths. The results showed that deep seeding or low seeding rates increased mechanical pressure and then increased ethylene content by increasing GhACO1 and GhACS2 expression to improve apical hook formation. Silencing of the GhACO1 and GhACS2 genes or exogenous application of 1-methylcyclopropene (1-MCP) decreased the ethylene content and inhibited apical hook formation in the cotton seedlings. Deep seeding, a low seeding rate, or 1-amino cyclopropane-1-carboxylic acid (ACC) treatment increased the expression of GhHLS1 and GhPIF3 genes, but their expression was decreased in theVIGS- ACO1 and VIGS- ACS2 seedlings. Silencing of the GhHLS1 and GhPIF3 genes inhibited apical hook formation, although the expression of GhACO1 and GhACS2 was unchanged. GhPIF3 may act upstream of GhHLS1, as the expression of GhPIF3 in the VIGS- HLS1 seedlings was unchanged, while the expression of GhHLS1 in the VIGS- PIF3 seedlings decreased. These results suggested that raised mechanical pressure could increase ethylene content by inducing GhACO1 and GhACS2 gene expression, which promoted apical hook formation by increasing the expression of GhHLS1. Therefore, adjusting the mechanical pressure through changing the seeding depth or seeding rate is an important means to regulate apical hook formation and emergence. • Mechanical pressure improves apical hook formation of cotton through ethylene. • Mechanical pressure increases ethylene content by increasing ACO1 and ACS2 expression of cotton. • GhHLS1 plays key role in regulating apical hook formation of cotton. [ABSTRACT FROM AUTHOR]

Mechanical monoseeding has been widely adopted in cotton planting; however, it can result in either double seedlings per hole or a decrease in seedling density due to missed seeding or seedling mortality. The impact of these conditions on cotton yield remains uncertain. In this study, we hypothesized that neither double seedlings per hole nor a reduction in seedling density would negatively affect cotton yield. Furthermore, we propose that yield stability can be achieved by manipulating vegetative branching and photoassimilate partitioning. We conducted two experiments in 2020, 2021 and 2022. The first experiment included a monoseeding treatment, where one seed per hole was sown without seedling thinning after emergence, and a cluster seeding treatment, where ten seeds per hole were sown and one seedling was left after emergence. In the second experiment, a double seedlings per hole (2 S) treatment was set up by sowing ten seeds per hole and leaving two seedlings per hole after thinning, while a one seedling per hole (1 S) treatment with the same plant density served as the control. The growth of vegetative branches (VB), boll-setting on both vegetative and sympodial branches (SB), yield, canopy apparent photosynthesis (CAP), and assimilate partitioning were evaluated. In the first experiment, monoseeding decreased the final plant density by 16.8% compared to cluster seeding, but there was no difference in seedcotton yield between the two treatments. Monoseeding exhibited higher values for VB biomass, number of bolls on VB, and their contribution to yield, indicating improved vegetative branching and VB fruiting, compensating for the yield loss due to plant density reduction. Although monoseeding did not show superiority in terms of leaf area and CAP, it increased photoassimilate partitioning to VB and VB bolls by 1.4 and 2 times compared to cluster seeding, respectively, which played a key role in the improved vegetative branching under monoseeding. In the second experiment, there were no difference in leaf area index, CAP and seedcotton yield between 2 S and 1 S. However, the VB biomass and its percentage to total biomass, the number of bolls on VB an their percentage contribution to yield under 2 S significantly decreased relative to 1 S, indicating inhibited vegetative branching and VB fruiting. Furthermore, the photoassimilate partitioning of 2 S to VB and VB bolls decreased by 32.6% and 29.4% compared with 1 S, but the partitionging to SB and bolls on SB increased by 2.4 and 4.1 times, respectively. Thus, the yield stability was achieved by suppressing vegetative branching while promoting sympodial branching under the 2 S treatment. The expression patterns of phytohormone (IAA, GA and CKs)-related genes and hormone contents in the VB tips were consistent with the observed changes in vegetative branching. This study indicated that the reduced seedling density and double plants per hole caused by monoseeding did not reduce cotton yield, which was achieved through manipulation of photoassimilate partitioning and vegetative branching associated with the expression of phytohormone-related genes and phytohormone levels in VB tips. This study provides a strong evidence in favor of monoseeding, and offers new insights into enhancing yield stability through manipulation of photoassimilate partitioning and branching in cotton. • Monoseeding may lead to double seedlings per hole or reduced seedling density. • Neither double seedlings nor seedling density reduction decreased cotton yield. • Yield stability was due to vegetative branching and photoassimilate partitioning. • The study provides new insights for monoseeding without seedling thinning. [ABSTRACT FROM AUTHOR]

Cotton has a complex branching pattern including sympodial and vegetative branching. Traditionally managed cotton mainly depends on sympodial branching for formation of yield-contributing fruit. Whether seedcotton yield based solely on vegetative branching is comparable with that based solely on sympodial or both types of branching is unclear. The study determined how terminal removal at first square to avoid formation of sympodial branches (SBs) regulated vegetative branching and yield under different plant densities. A two-year split-plot design field experiment had main plots with plant density (4.5 and 9.0 plants m−2) and subplots with plant pruning mode. Pruning modes were terminal removal at first square (TRS) to avoid formation of sympodial branches but retain only vegetative branches (VBs), removal of VBs (RVB) to retain only SBs, and no pruning (CK), with both branch types remaining intact. Canopy photosynthesis, dry matter accumulation and partitioning, and seedcotton yield and yield components were examined. At low plant density (4.5 plants m−2), compared with other pruning modes, TRS increased seedcotton yield and biological yield but did not affect harvest index. At high plant density (9.0 plants m−2), compared with other pruning modes, TRS decreased seedcotton yield and harvest index, although biological yield increased. The yield increase with TRS at low plant density was attributed to the increase in biological yield, which was due to significantly higher canopy photosynthesis with TRS than with other pruning modes. At high plant density, photosynthesis with TRS was higher than that with no pruning at peak boll-setting and boll-opening stages and higher than that with RVB from peak squaring to boll-opening. Compared with other pruning modes, TRS increased dry matter partitioning to vegetative organs but decreased partitioning to reproductive organs. Pearson correlation analysis revealed a significant positive correlation between canopy apparent photosynthesis and biological yield, biomass partitioning, and harvest index, irrespective of plant pruning and plant density. Plant pruning and plant density interacted to affect seedcotton yield. With TRS, cotton yield at low plant density was higher than that with other pruning modes, which was attributed to an increase in biological yield associated with an increase in canopy photosynthesis. At high plant density, the yield decrease with TRS was attributed to low harvest index associated with reduced reproductive partitioning. Cotton cultivation relying solely on vegetative branching can be an alternative to obtain moderate yields and economic benefits under conditions of low plant density. • Plant pruning and density affected cotton branching and yield formation. • Terminal removal at first square led to the highest seed cotton yield at low plant density. • Terminal removal at first square increased yield by promoting canopy photosynthesis. [ABSTRACT FROM AUTHOR]

Alternate intercropping of cotton and peanut is an emerging cropping practice that involves the intercropping of two crops in a wide strip, with annual switching of planting positions. The productivity achieved through alternate intercropping, which combines intercropping and rotation, surpasses that of either mode used alone. However, the underlying mechanisms responsible for the observed increase in crop productivity remain elusive. We put forth the hypothesis that alternate intercropping enhances productivity by promoting canopy photosynthesis and nutrient uptake, facilitated by the influence of rhizosphere bacteria. A two-year field experiment was conducted employing a randomized block design to investigate the effects of monoculture, traditional intercropping, and alternate intercropping on yield, yield components, canopy photosynthesis, 13C photoassimilate partitioning, uptake of major nutrients, and diversity of rhizosphere bacterial communities. Alternate intercropping increased biological by 9.3% and seed cotton yield by 20.0% compared to monocultures without sacrificing peanut yields. In comparison to traditional intercropping, alternate intercropping also increased seed cotton yield by 3.9%, peanut pod yield by 6.7%, and total productivity by 10.6%. The cotton harvest index in alternate intercropping was similar to that in traditional intercropping but 9.9% higher than in monoculture. However, the peanut harvest index did not differ between alternate intercropping, traditional intercropping, and monoculture. Net ecosystem CO 2 exchange (NEE) under alternate intercropping was higher in cotton than that under traditional intercropping and monoculture, and 13C partitioning to reproductive organs in cotton was higher in alternate intercropping than in monoculture, although there was no difference between alternate and traditional intercropping. In peanut, NEE was higher under alternate intercropping than under traditional intercropping at all stages. At peak pod setting, 13C partitioning to reproductive organs was higher under both alternate intercropping and monoculture than under traditional intercropping. Alternate intercropping resulted in a 7.2% increase in cotton nitrogen uptake compared to traditional intercropping, and a 8.8% increase in nitrogen uptake, 10.9% increase in phosphorus uptake, and 8.5% increase in potassium uptake compared to monoculture cotton. Peanut uptake of nitrogen, phosphorus, and potassium was greater in alternate intercropping than in traditional intercropping and was approximately the same as that in monoculture. Alternate intercropping increased the relative abundances of plant growth promoting rhizobacteria (PGPR). Significant correlations were detected between NEE and biological yield, 13C partitioning and harvest index, as well as the relative abundance of PGPR and uptake of major nutrients. The enhanced crop productivity observed in alternate intercropping can be attributed to improved shoot-root coordination, as evidenced by the increased canopy photosynthesis and nutrient uptake associated with altered rhizosphere bacterial communities. • Alternate intercropping was more productive than other cropping modes. • Alternate intercropping increased photosynthesis and assimlate partitioning. • Alternate intercropping improved rhizobacteria communities and nutrient uptake. • Productivity was associated with photosynthesis, nutrient uptake and rhizobacteria. [ABSTRACT FROM AUTHOR]

Relay intercropping of garlic with full-season cotton is currently one of the dominant cropping systems in China, but the net benefit is decreasing because the system is labor-intensive. Direct planting of short-season cotton after garlic harvest may increase net revenue through reducing labor and material input. Three field experiments were consecutively conducted in Jinxiang County of China, to determine the effects of plant density and soil fertility on yield, yield components, boll load and leaf senescence in the 1st and 2nd experiments. In the third experiment, we compared the economic benefits of the two cropping systems. Data from the 1st experiment showed that plant density affected yield and yield components, with the optimum plant density being 3.0 plants m −2 for full-season cotton and 9.0 plants m −2 for short-season cotton. In the 2nd experiment, the seedcotton yield of full-season cotton was 9.1% higher under high than medium soil fertility, but there was no yield difference between the two soil fertility levels for short-season cotton. Full-season cotton exhibited larger boll load, earlier leaf senescence and lower boll weight under medium than high fertility. Results of the third experiment showed that seedcotton yield or output value of short-season cotton was 14.5% lower than that of full-season cotton, but the gross return for short-season cotton was 69.2% higher than that for full-season cotton because the short-season cotton required 27.3% less labor and material inputs. The overall results showed that late planted short-season cotton after garlic harvest can be a promising alternative for enhancing the benefits of garlic-cotton production in China. [ABSTRACT FROM AUTHOR]

Waterlogging stress is an increasing threat to cotton production worldwide. The use of cultivation measures to combat waterlogging stress is a promising approach. As a traditional cultural practice, ridge intertillage is usually conducted before flowering to form a ridge along a row and a furrow between two rows in order to reduce lodging and control weeds in cotton fields. However, it is unclear whether ridge intertillage can alleviate waterlogging stress in field-grown cotton. Flat and ridge intertillage were conducted at 10 days after squaring of cotton to establish flat and ridge–furrow configurations, respectively, with or without 10-d waterlogging. To determine effects of intertillage pattern on mitigating waterlogging stress, changes in rhizosphere bacterial communities and plant physiological parameters were examined in waterlogged cotton. Compared with flat tillage, ridge intertillage significantly decreased hydrogen peroxide production, malonaldehyde content, and alcohol dehydrogenase and pyruvate decarboxylase activities in both roots and leaves of waterlogged cotton but significantly increased nitrogen, phosphorus, and potassium concentrations, leaf area, and plant biomass. Compared with flat intertillage under waterlogging (FIW), ridge intertillage under waterlogging (RIW) changed the abundance and composition of rhizosphere bacterial communities. In addition, several taxa of bacteria with beneficial functions were enriched in the rhizosphere under ridge intertillage. Pearson correlations indicated that changes in rhizosphere bacteria and plant physiological parameters in waterlogged cotton were significantly correlated (P < 0.05), suggesting that adjustments in rhizosphere bacterial communities were involved in the physiological response to waterlogging stress. Moreover, compared with FIW, RIW increased canopy photosynthesis and lint yield of waterlogged cotton by 51.5% and 18.3%, respectively, and decreased lint yield loss by 61.3%. Compared with flat intertillage, ridge intertillage induced adjustments in rhizosphere bacterial communities, reduced oxidative membrane damage, improved nutrient uptake and canopy photosynthesis, and ultimately reduced the stress damage and yield loss of waterlogged cotton. Ridge intertillage before flowering is a promising agronomic measure to combat waterlogging stress in cotton and possibly other major field crops. • Ridge intertillage produced ridge-furrow configuration by piling up the topsoil to cotton plants base before flowering. • Effects of flat and ridge intertillage on waterlogged cotton were compared. • Ridge intertillage adjusted rhizosphere microbe and nutrient uptake of waterlogged cotton. • The adjustments induced a set of physiological changes and reduced the yield loss of waterlogged cotton. [ABSTRACT FROM AUTHOR]

Plastic film mulching has been widely applied to improve crop productivity of full-season cotton (Gossypium hirsutum L.). However, in a previous study, plastic mulching did not increase seed cotton yield of short-season cotton compared with non-mulching. The aim of this study was to determine why plastic mulching fails to increase seed cotton yield of short-season cotton. A short-season cultivar Lumian 532 was planted with or without plastic mulching at an experimental station in Linqing in the Yellow River valley of China in 2020 and 2021. Yield, yield components, leaf senescence, photoassimilate accumulation and partitioning, photohormone contents, expression of senescence-related genes, and root traits were examined each year. Seed cotton yield produced with plastic mulching was not significantly different from that produced with non-mulching in short-season cotton. Although number and size of early- and mid-season bolls were significantly greater with plastic mulching than with non-mulching, plastic mulching decreased number and size of late-season bolls by 34.0% and 8.8%, respectively. At the initial boll opening stage, photosynthetic rate and chlorophyll content in main-stem functional leaves were 36.2% and 24.1% lower, respectively, with plastic mulching than with non-mulching, but malondialdehyde content was 34.2% higher, suggesting that plastic mulching accelerated late-season leaf senescence. Canopy photosynthesis and photoassimilate partitioning to reproductive organs at the initial boll-opening stage were 68.1% and 9.4% lower, respectively, with plastic mulching than with non-mulching. Compared with non-mulching, plastic mulching increased abscisic acid and methyl jasmonate contents but decreased those of cytokinins content because of differential expression of hormone metabolism-related genes in late-season main-stem leaves. Plastic mulching also increased root distribution in the shallow soil layer and lowered root vigor in the late season, compared with non-mulching. Overall, plastic mulching negatively affected root distribution and function and altered expression of senescence-related genes and hormone metabolism-related genes to affect hormone balance, which led to accelerated late-season leaf senescence. Because of late-season leaf senescence, canopy photosynthesis and photoassimilate partitioning to cotton bolls were suppressed with plastic mulching, which led to fewer and smaller late-season bolls than those with non-mulching. Thus, plastic mulching failed to improve the seed cotton yield. This study provides a clear explanation of how plastic mulching causes late-season leaf senescence and further demonstrates that plastic film mulching is not required for planting short-season cotton in the Yellow River valley of China or in other cotton growing areas with similar ecology. • Plastic mulching did not increase yield compared with non-mulching because of fewer and smaller late-season bolls in short-season cotton. • Reduced number and size of late-season cotton bolls was attributed to accelerated late-season leaf senescence in short-season cotton. • Accelerated leaf senescence was due to shallow root distribution and weak root vigor, and differential expression of senescence-related genes. [ABSTRACT FROM AUTHOR]

Cotton ( Gossypium hirsutum L.) yield under extensive field management across a certain range of plant population densities can be stabilized by manipulating the number of bolls and boll weight, but little is known of similar yield stability under intensive management and how the yield stability is achieved by dry matter accumulation and partitioning under various plant densities. A field experiment was conducted to study the effects of plant density (1.5, 3.3, 5.1, 6.9, 8.7 and 10.5 plants m −2 ) on dry matter accumulation and partitioning in relation to cotton yield. The seedcotton and lint yields at 1.5 plants m −2 were significantly lower than those at other plant densities, but there was little difference in either seedcotton or lint yield among plant densities ranging from 3.3 to 10.5 plants m −2 . Plant biomass increased gradually with increasing plant density. The ratio of dry weight of fruiting forms to plant biomass (DWFF/PB) at 135 days after sowing (DAS) at 1.5 plants m −2 exceeded those under 5.1 plants m −2 by 12.3%, 6.9 plants m −2 by 12.7%, 8.7 plants m −2 by 20.5% and 10.5 plants m −2 by 21.8%. Also, the harvest index at 1.5 plants m −2 exceeded those at 5.1, 6.9, 8.7 and 10.5 plants m −2 densities by 16.2, 16.2, 34.3, 38.7%, respectively. Seedcotton yield was positively correlated with total biomass at extremely low plant density (1.5 plants m −2 ), but was better correlated with DWFF/PB at higher densities (5.1–10.5 plants m −2 ). The boll weight of the last harvest was 6.0–6.3% lower than those of the first two harvests at 1.5 plants m −2 . Leaf senescence as indicated by reduced Pn and leaf area index (LAI) in later season occurred earlier at 1.5 plants m −2 than other plant densities. It was concluded that cotton yield is relatively stable across a wide range of plant densities even under intensive field management. The stability was achieved mainly through manipulation of dry matter accumulation and partitioning. The reduced boll weight of the last harvest was mainly due to earlier leaf senescence at 1.5 plants m −2 , which might explain the lower cotton productivity per unit ground area at such a low plant density. [ABSTRACT FROM AUTHOR]

Waterlogging stress hampers cotton growth and development, ultimately causing yield loss. Nitric oxide (NO) was previously found to alleviate waterlogging damage to cotton plants, but it is unclear whether NO can enhance compensatory growth after waterlogging relief. Herein, field-grown cotton (Gossypium hirsutum L.) plants at peak flowering were subjected to a 10-day waterlogging stress treatment, and the effects of foliar spraying of sodium nitroprusside (SNP)—a NO donor—during waterlogging were evaluated. The NO concentrations in the plant tissues, plant biomass, and related physiological events at 10 d post-waterlogging relief, as well as the seedcotton yield and yield components at harvest, were measured over two consecutive years. Non-waterlogged and waterlogged cotton exhibited 38.5% and 48.3% increased plant biomass at 10 d post-waterlogging relief, respectively, compared with that on the day of stress relief, indicating that significant compensatory growth occurred following stress relief. Foliar spraying cotton with SNP during waterlogging not only increased the NO concentration (40–183%) before stress relief, but also increased the NO concentration (30–75%) after stress relief compared with no SNP application. As the NO concentration increased, plant biomass at 10 d post-waterlogging, as well as biological yield, boll density, and seedcotton yield of waterlogged cotton at harvest, were increased by 54.4%, 8.0%, 7.5%, and 7.6% under foliar SNP spraying compared to no SNP spraying, indicating that NO promoted compensatory growth and reduced the yield loss of waterlogged cotton. Correlation analysis showed that yield loss reduction was positively correlated with compensatory growth (R2 = 0.83**). Foliar spraying of SNP decreased the malondialdehyde content and the activities of alcohol dehydrogenase and pyruvate decarboxylase in waterlogged cotton at 10-d post stress relief by 15.2%, 42.4%, and 38.2%, but increased the contents of auxin (IAA), gibberellic acid (GA), and chlorophyll and the photosynthetic rate by 28.6%, 59.6%, 12.1%, and 6.4%, respectively, and decreased the abscisic acid (ABA) and ethylene contents by 12.5% and 8.5%, respectively, compared to no SNP spraying. In conclusion, foliar spraying of SNP increased the content of NO in waterlogged cotton plants even at 10-d post stress. Hormonal rebalance was realized through increased IAA and GA and reduced ABA and ethylene due to the elevated NO content, which promoted photosynthetic recovery and compensatory growth after stress relief, ultimately reducing yield loss. The overall results indicated that enhancing the compensatory growth of cotton after waterlogging is an important mechanism by which NO mitigates waterlogging stress. • Nitric oxide enhanced the compensatory growth of waterlogged cotton and reduced the yield loss. • Enhanced compensatory growth by nitric oxide was achieved through physiological adjustments after waterlogging relief. • The reduction of yield loss was correlated with the compensatory growth of waterlogged cotton. • Enhanced compensatory growth by NO is an important attribute to the yield loss reduction under waterlogging. [ABSTRACT FROM AUTHOR]

Manual removal of the main-stem growth tip is traditionally used to break the apical dominance of cotton (Gossypium hirsutum L.). Chemical topping with plant growth regulators also effectively inhibits apical dominance. However, the effect of chemical topping on yield increases and whether plant density or ecological conditions affect its efficacy are unclear. Therefore, a three-year field experiment with a split-plot design was conducted to determine the effects of plant topping, plant density, and their interactions on cotton yield and related physiological and agronomical parameters at three sites with different ecological conditions in China. In each site, the main plots were assigned low, moderate, or high plant density and the subplots were assigned no topping, manual topping, or chemical topping. Growth, yield, yield components, earliness, and late-season leaf photosynthesis as well as labor and material inputs were examined each year. Compared with no topping, both chemical and manual topping greatly reduced plant height at all sites. Manual topping increased seed cotton yield and earliness in all tested plant densities and sites. However, plant density but not ecological condition greatly mediated the effect of chemical topping on yield. At low plant density, the yields with chemical topping were 4–6% lower than those with no topping and 5.5–10.8% lower than those with manual topping at the three sites. Although yields with chemical topping were comparable with those of manual topping at moderate and high plant densities, they were 8.6–12.8% higher at moderate density and 13.8–16.4% higher at high plant density than those with no topping across years and sites. Averaged across the sites, chemical topping reduced biological yield by 12.7% at low plant density. Although biological yield decreased slightly, chemical and manual topping increased the harvest index by 12.4% and 13.3% at moderate density and by 15.6% and 17.4% at high density, respectively. In comparison with no topping, the reduction in seed cotton yield with chemical topping at low plant density was attributed to insufficient biological yield, whereas the increase in yield at moderate and high plant densities was mainly due to greater partitioning of assimilates to reproductive tissues. Compared with manual topping, chemical topping produced 23.2% lower net returns as a result of lower seed cotton yield at low plant density but produced 8.1% and 20.9% higher net returns at moderate and high plant densities, respectively, because of savings in labor inputs and comparable seed cotton yields. In addition, chemical topping increased the earliness percentage compared with that of no topping. Overall, this study demonstrates that chemical topping is a promising alternative to traditional manual topping under moderate or high cotton plant density. • Manual topping increased cotton yield regardless of plant densities and ecological conditions relative to non-topping. • Chemical topping decreased yield at low plant density relative to non-topping because of greater biomass reduction. • Chemical topping increased cotton yield at moderate and high plant densities via greater assimilates partitioning to fruits. • Chemical topping could replace manual topping at moderate and high plant densities without ecological dependence. [ABSTRACT FROM AUTHOR]

• Cotton yield did not differ between vegetative branch retention and removal. • Chemical topping increased cotton yield mainly by increasing canopy photosynthesis. • Manual topping increased yield also by increasing reproductive partitioning. • The mechanism of yield formation differed between chemical and manual topping. Fine pruning, or the artificial removal of vegetative branches (VB) and main stem tips (plant topping), is a traditional cotton (Gossypium hirsutum L.) cultivation practice. Pruning can be simplified without reducing yield by retaining the vegetative branches and adopting chemical topping; however, cotton yield formation under different plant pruning modes remains unclear. We aimed to determine if and how simplified pruning results in comparable yields to fine pruning in terms of canopy photosynthesis and photoassimilate partitioning. A two-year field experiment was thus conducted to determine the effects and interactions of vegetative branch management (retaining and removing of vegetative branches) and plant topping pattern (non-topping, manual topping, and chemical topping) on yield, canopy photosynthesis, and photoassimilate partitioning. Seed cotton yield, canopy photosynthesis, and photoassimilate partitioning were significantly affected by VB removal or retention and plant topping modes, but not by their interaction. Boll weight and harvest index under VB retention were reduced compared to VB removal, while boll density and biological yield increased. Compared with non-topping, the biological and seed cotton yield increased and the harvest index decreased under chemical topping, whereas these all increased under manual topping. Seed cotton yield was comparable between chemical and manual topping. The leaf area index (LAI) under VB retention was higher than under VB removal at peak squaring, peak flowering, and peak boll-setting, and comparable at boll-opening. The carbon assimilation rate (CAR) under VB retention increased compared with that under VB removal at peak flowering, peak boll-setting, and boll-opening. Meanwhile, VB retention partitioned more photoassimilates to the vegetative organs, and less to the reproductive organs, than VB removal at peak flowering and peak boll-setting. Compared with no topping, LAI and CAR under chemical and manual topping increased at peak-boll setting and boll-opening. Furthermore, the partitioning of photoassimilates to the reproductive organs under chemical topping was similar to that of non-topping at the peak boll-setting and boll opening stages, whereas this increased under manual topping. Cotton yield did not vary between VB managements due to the coordination between canopy carbon assimilation and assimilate partitioning. Manual topping improved both CAR and photoassimilate partitioning to the bolls, and thus increased the seed cotton yield compared with non-topping. By contrast, chemical topping reduced the photoassimilate partitioning to the reproductive organs, and the increased yield was attributed to the improved carbon assimilation rate. In summary, chemical topping achieved the same yield as manual topping, but the mechanism of yield increase differed from the perspective of photosynthetic production and assimilate partitioning. [ABSTRACT FROM AUTHOR]

• Non-mulched short-season cotton produced less fiber but greater returns than mulched full-season cotton as it consumed less inputs. • Non-mulched short-season cotton delayed leaf senescence due to reduced boll load and produced comparable cotton yields to the mulched. • Non-mulched short-season cotton reduced the residual film pollution, thus offering an alternative to mulched full-season cotton. The early planting of full-season cotton (Gossypium hirsutum L.) at a moderate plant density under plastic mulching is a traditional means of growing cotton in the Yellow River valley of China. However, it is labor intensive, consumes a large amount of materials, and also results in residual plastic pollution in the soil. While our previous studies indicated that late planted short-season cotton under plastic mulching greatly reduces labor and material inputs and increases net revenue, the residual plastic pollution remains an issue. It is unclear if short-season cotton can be managed without yield loss in the absence of plastic mulching. A field experiment was therefore conducted using a random complete block design with four treatments, including the early planting of full-season cotton with (FCM) and without plastic mulching (FC), and the late planting of short-season cotton with (SCM) and without plastic mulching (SC), in the Yellow River valley from 2017 to 2019. The yield, yield components, input and output values, earliness, dynamics of flowering and boll setting, and late-season leaf senescence in cotton were examined. The results showed that early planted full-season cotton under mulching (FCM) produced a 21.1 and 20.4 % higher seedcotton yield and boll density, respectively, and improved earliness over the non-mulched treatment, while the boll weight did not differ significantly. Short-season cotton without plastic mulching produced comparable seedcotton yields to that with mulching (SCM), and there was no significant difference in average boll weight, boll density, or earliness between the mulching and non-mulching treatments. However, SC had a 7.0 and 12.1 % smaller boll density and boll weight, respectively, than FCM and thus produced a 17.9 % lower seedcotton yield. Therefore, SC produced 14.9 and 14.4 % greater net returns than SCM and FCM, respectively, because it consumed less labor and material inputs. Short-season cotton without plastic mulching delayed leaf senescence due to reduced boll load and thus increased boll weight in the late season compared with SCM. In addition, SC exhibited improved earliness as a result of a higher flowering rate, faster fruiting, and more concentrated boll opening than FCM. Short-season cotton without plastic mulching also avoided the residual film pollution in the soil. The overall results demonstrated that the late planting of short-season cotton without mulching is a promising alternative for sustainable cotton production in the Yellow River valley region of China as well as other cotton growing areas with similar ecology. [ABSTRACT FROM AUTHOR]

• Foliar spray of exogenous nitric oxide increased its concentration in waterlogged cotton. • Increased nitric oxide concentration triggered a series of physiological and molecular events. • Foliar spray of nitric oxide ultimately reduced yield loss under waterlogging. Waterlogging is a major abiotic stress that reduces crop growth and productivity. Nitric oxide (NO) is an essential signaling molecule involved in abiotic stress responses in many plant species. However, it is unclear if and how NO mitigates waterlogging stress in field-grown cotton. In this study, the NO donor sodium nitroprusside (SNP) or its scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl -imidazoline-1-1-oxyl-3-oxide (cPTIO) was foliar-applied to waterlogged and non-waterlogged cotton plants. The NO concentrations in different plant parts, plant growth, yield and yield components, as well as related physiological and molecular events, were examined over three consecutive years under field conditions. Foliar application of SNP increased NO concentration in leaves by 83.6 and roots by 80.2 % under waterlogging, while cPTIO decreased the NO concentration by 18.9 and 5.3 %, respectively. Biomass and lint yield were reduced by 17.2 and 36.0 % under waterlogging without the application of SNP or cPTIO, but the reductions were 8.8 and 28.4 % following SNP application and 29.5 and 43.4 % respectively, following cPTIO application. Foliar applied SNP increased biomass by 10.2 % and lint yield by 12.0 % under waterlogging, whereas cPTIO caused 5.0 and 11.5 % reductions in biomass and lint yield. Quantitative real-time PCR analysis showed that the SNP up-regulated the NO synthesis gene (Gh NIR), but down-regulated the genes involved in glycolysis and fermentation (Gh ADH 2 and Gh PDC), ethylene production (Gh ACO and Gh ACS 8), and abscisic acid (ABA) synthesis (Gh NCED 2). It also reduced hydrogen peroxide (H 2 O 2) production and malonaldehyde (MDA) content in the leaves, but increased the leaf chlorophyll content and photosynthetic rate. The levels of auxin (IAA) and gibberellic acid (GA) were increased by SNP but those of ABA and ethylene contents as well as the activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) in leaves were decreased. The cPTIO showed an opposite effect to SNP in almost all physiological and molecular responses to waterlogging. The overall results indicated that increasing the concentrations of NO in plant tissues via the foliar application of SNP mitigates waterlogging stress through a series of physiological and molecular events, ultimately reducing biological and lint yield loss under waterlogging. Therefore, increasing the concentration of NO in plant tissues by genetic breeding or agronomic measures might be a potential strategy for improving waterlogging tolerance and reducing yield loss in cotton. [ABSTRACT FROM AUTHOR]