Cotton whole genome SNP (Single nucleotide polymorphism) markers were evaluated and screened across representative cotton materials, with the aim of obtaining an appropriate set of core SNP markers suitable for high-throughput identification of cotton hybrid purity based on KASP (Kompetitive allele specific PCR) technology. 5474 and 1850 single-copy SNP markers were screened out of a 63K SNP array with reference to two TM-1 genome versions (Institute of Cotton Research of the Chinese Academy of Agricultural Sciences version; Nanjing Agriculture University version), respectively. A set of 26 pairs of core SNP markers (one marker per chromosome) was achieved in view of polymorphism, genotyping quality, and homozygous and heterozygosis rates. The set of core SNP loci were then converted to KASP markers using Kraken^TM software. Genotyping assays of the KASP markers set were then performed on the SNPline platform. High-throughput genotyping assays of large numbers of samples were achieved, especially for the rapid purity tests.

Twenty-three Xincaimian cotton cultivars as authorized until 2012 were used as materials in the construction of DNA fingerprinting and analysis of genetic diversity with simple sequence repeat(SSR) markers. Fifty-two primer pairs with high polymorphism, good repeatability, and even distribution on the 26 chromosomes were screened out from 5000 pairs of SSR primers to genotype the 23 cultivars. A total of 47 SSR primer pairs were polymorphic and generated 162 polymorphic loci among the 23 cultivars; each marker detected 2-7 polymorphic loci with an average of 3.45; the polymorphism information content ranged from 0.4537 to 0.8686, with an average of 0.7096. The results showed that there 14 cultivars could be differentiated by specific or characteristic primer, the rest 9 cultivars could be identified by primer combinations. In the end, 18 specific or characteristic and primer combinations could completely differentiate the 23 Xincaimian cotton cultivars from each other. DNA fingerprinting of Xincaimian 1 to Xincaimian 23 were constructed with 18 pairs of SSR markers. NTSYSpc v2.10 software was used to analyze genetic diversity of the 23 cultivars; the results indicated that genetic similarity coefficient of the 23 cultivars ranged from 0.3781 to 0.9298 with an average of 0.5511, which showed that there was abundant genetic diversity in Xincaimian cotton varieties.

[Objective] The purpose of this study was to evaluate the selection and pyramiding effects of quantitative trait loci (QTL) related to fiber length and fiber strength through molecular marker-assisted selections using populations of chromosome segment substitution lines (CSSLs) from Gossypium hirsutum × G. barbadense. [Method] In this study, CSSL MBI7561 with excellent fiber quality selected from BC₄F_3:5 of CCRI 45 (G. hirsutum) × Hai 1 (G. barbadense) was used to construct the secondary segregating populations of two generations BC₅F₂ and BC₅F_2:3. Then two populations (BC₆F₂ and BC₆F_2:3) were obtained through backcrossing with the recurrent parents and selfing. Four simple sequence repeat markers, CGR6894a, PGML02608, NAU5408 and NAU3594, linked to three major QTL for fiber length (qFL-16-1, qFL-16-4, qFL-16-5) and three major QTL for fiber strength (qFS-16-1, qFS-16-4 and qFS-16-5) on chromosome 16, were used to screen individuals of BC₆F₂ and BC₆F_2:3. [Result] Four markers related to qFL-16-1, qFL-16-4, qFL-16-5, qFS-16-1, qFS-16-4 and qFS-16-5 indicated obvious and significant single marker selection effect and pairwise marker pyramiding effect for fiber length and fiber strength in the two populations of BC₆F₂ and BC₆F_2:3. Furthermore, the excellent individual which contain more than two QTL was screened. [Conclusion] The analyzed QTL related to fiber length and fiber strength on chromosome 16 had significant genetic effects in different generations of the CSSLs, and the fiber length and fiber strength of individuals were significantly increased by pyramiding two QTL. This study laid an important foundation for molecular marker to assist the pyramiding selection of fiber length and strength.

[Objective] The glycosylphosphatidylinositol-anchored lipid transfer protein (LTPG) genes were identified from the whole genome of Gossypium hirsutum to provide support for subsequent research. [Method] Bioinformatics methods were used to screen and identify the LTPG gene family from the TM-1 genome, and the physicochemical properties of proteins, phylogenetic relationship, gene duplication, gene structure, and cis-acting elements in the promoter region were predicted and analyzed. Transcriptome data and real-time quantitative polymerase chain reaction (qRT-PCR) were used to analyze their expression pattern in different tissues and organs and under different abiotic stresses. The subcellular localization of the target proteins was identified by transient transformation in tobacco leaves. [Result] Ninety-five GhLTPG genes were identified in the G. hirsutum genome, which were clustered into 5 categories by phylogenetic tree analysis. Segment duplication is the main reason for the expansion of the GhLTPG gene family. K_a/K_s analysis indicated that GhLTPG underwent strong purification selection. Transcriptome data analysis showed that some GhLTPG responded to low temperature, high temperature, salt, or drought stress. The results of qRT-PCR analysis showed that GhLTPG11/14/52/62 responded to low temperature, high temperature, salt and drought stress, and GhLTPG24/56 responded to low temperature, salt, or drought stress. Subcellular localization experiments showed that both GhLTPG24 and GhLTPG62 were localized in the cell membrane. [Conclusion] Ninety-five GhLTPG genes were identified in the whole genome of G. hirsutum. Some GhLTPG genes responded to abiotic stresses such as low temperature, high temperature, salt and drought, which laid a foundation for in-depth analysis of the function of specific GhLTPG gene.

The Zinc finger-homeodomain (ZF-HD) protein family of homeobox genes plays a vital role during the development processes of plants and animals. The number, subcellular localization, chromosome distribution, motif, evolutionary relationships and tissue-expression patterns of the ZF-HD protein family were studied in the genome of Gossypium hirsutum L. acc. 'TM-1' using bioinformatics methods. In total, 35 GhZHD genes were identified in the 'TM-1' genome, and a majority of the members are located in nucleus. The family members were distributed on 20 chromosomes and two scaffolds, and 11 pairs were orthologous genes. The family could be divided into six groups based on the phylogenetic analysis, and there were similar motif types and arrangements in each group. Most GhZHD genes were expressed in ovules and fibers, some were expressed in roots, stems, buds and flowers, and a fraction were expressed in leaves and calli.

With the development of cotton genomics and transcriptomics, cotton genetics and breeding would be enhanced by the identification of differentially expressed genes and the development of molecular makers based on candidate genes. The salt-tolerant cotton variety Miscott 7913-83 and salt-sensitive variety Su 12 were used as experimental materials in this study. RNA samples prepared from the roots and leaves of the two cultivars were pooled for transcriptome sequencing. Variations in gene expression were then examined after exposing the plants to 200 mmol·L^－1 NaCl for 12 and 72 h. A total of 3232 differentially expressed genes were then examined between Miscott 7913-83 and Su 12, and functional molecular markers such as EST-SSR and EST-InDel were designed by informatics tools according to differentially expressed gene sequences. Some SSR and InDel primers were randomly selected and further confirmed the accuracy. This research provides efficient methods for the rapid development of polymorphic markers in cotton. By focusing on functional molecular markers associated with salt tolerance, this should aid the improvement of salt tolerance by marker-assisted selection in upland cotton.

[Objective] The purpose of this study is to study the influence of cotton-wheat cropping modes on yield and cotton maturity in the Yellow River Basin, to provide technical support for the whole-process mechanization management under the machine-harvested cotton mode. [Method] The experiments were carried out in Anyang, Henan in 2017/2018 and 2018/2019 seasons including 6 treatments with 2 cotton varieties (ZM50, ZM79) and 3 cropping modes, W6C2 (6 rows wheat and 2 rows cotton), W3C1 (3 rows wheat and 1 row cotton) and W2C1 (2 rows wheat and 1 row cotton) under the machine-harvested cotton row space (76 cm) cultivation. Some key indexes such as the wheat yield and side effects, and cotton biomass accumulation, the time distribution of cotton bolls, percentage of seed-cotton yield before frost, and fiber quality were compared and analyzed. [Result] The wheat yield was significantly higher in the mode W3C1 than the mode W2C1 and W6C2 by 16.2%-43.3% and 28.4%-52.3% respectively; the number of effective panicles significantly increased by 29.2%-47.5% and 34.9%-53.6%, respectively; however, the indexes such as wheat yield(2019) and effective panicles per hectare(2018) of W3C1 were significantly lower than W6C2. No significant differences in fiber length, breaking tenacity, and micronaire were found among different cropping modes. There was no significant difference in the seed cotton yield and harvest index(HI) of ZM50 under different modes，while the seed cotton yield and HI of ZM79 in the mode W3C1 in 2018 was lower than that in W6C2 and W2C1. Under W3C1 mode, short season cotton ZM50, compared with ZM79, showed an earlier maturity performance, such as a lower node/branch ratio, and faster reproductive growth, higher ratio of the middle season bolls between July 16 and August 15, lower cotton boll shell ratio, and higher percentage of seed-cotton yield before frost by 38.7%-54.2%; moreover, land equivalent ratio (LER) of this mode is over 1.689-1.697, significantly higher than other modes. [Conclusion] It is suggested that under the machine-harvested cotton row space in the Yellow River Basin, adopting the short-season cotton ZM50 and mode W3C1 can obtain a higher LER and percentage of seed-cotton yield before frost, and is conducive to increasing crop uniformity and yield of wheat. So, taking this configuration for wheat-cotton cropping in the Yellow River Basin is helpful to improve the mechanized management level of the crops and the planting benefit.

Crop maturity is the comprehensive performance reflection of crop growth, development and maturation. It is usually expressed by the growth period or life cycle from seedling emergence to harvest. It is also a critical indicator of crop ecological adaptability. The selection of cotton varieties with appropriate maturity is an important prerequisite to ensure normal maturity, high yield, superior fiber quality, and timely harvest. Accurate evaluation of cotton crop maturity is an important basis for cotton cultivation management and genetic improvement. Due to the indeterminate growth characteristic of cotton, the evaluation of cotton crop maturity is complicated, and there are still controversies so far. This manuscript clarifies the concept of cotton crop maturity, and discusses its main influencing factors (genetic factors, environmental factors, and cultivation measures), and reviews predictors and methods used for cotton crop maturity evaluation based on growth characteristics (the first fruit branch node, fruit branch occurrence speed and flowering time interval, pre-frost seed cotton rate, etc.), growth process (growth period, physiological termination period, the number of fruit branches above cracked boll, early maturity index, etc.) and the comprehensive index. In the end, the following suggestions have been given: enhancing the innovation of evaluation predictors for cotton crop maturity, establishment of the evaluation system for cotton crop maturity, and creation of an innovative information collection system, which will provide theoretical and technical support for cotton simplified and mechanized production.

The expression changes of transcriptome of tender leaves of Z12/Z12YW were analyzed by RNA-Seq to reveal the molecular mechanism of gland formation. Z12/Z12YW are cotton near-isogenic lines with a common genetic background but contrasting a gland phenotype. A total of 306 differentially expressed genes were uncovered, of which 282 were down-regulated and 24 were up-regulated in the glandless material Z12YW. Gene Ontology functional annotation showed that the cell part, the extracellular matrix part and the cell killing played important roles in the process of gland development. Clustering of Orthologous groups and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that the upstream key genes of the mevalonate pathway had a great influence on the biosynthesis of gossypol and other terpene compounds. In addition, we screened 13 transcription factors with different expression levels, which might display key function in gland formation and gossypol biosynthesis.

[Objective] This study aimed to map the fuzzless mutant (i.e., naked seed) gene n₂ in XZ142w cotton plants. [Method] An F₂ population of upland cotton (Gossypium hirsutum L.) was generated from a cross between XZ142 and the lintless-fuzzless mutant XZ142w. First, 108 simple sequence repeat (SSR) markers were used for mapping. High resolution melting (HRM) technology was then applied to screen 50 single nucleotide polymorphism (SNP) primer pairs designed based on a comparative transcriptomic analysis of the two parents. The SNP markers were used for genotyping. [Results] The n₂ gene was first mapped to a 20.2-cM region on chromosome 26 based on 108 SSR markers. Nine pairs of SNP markers from the HRM screening were used to genotype the F₂ progeny. Using the linkage map based on SSR markers, the genetic interval of n₂ was finally narrowed to a 19.5-cM region. At a genetic distance of 5.5 cM, the closest marker was Cricaas20158 (an SNP marker). The linkage map was mostly consistent with an in silico physical map based on a sequenced upland cotton genome. [Conclusion] The application of HRM technology is useful for detecting cotton SNPs and mapping the n₂ gene.

【Objective] In this study, we examined the effect of row spacing and planting density on canopy structure and yield. [Method] Hybrid cotton Lumianyan 24 and conventional cotton Xinluzao 60 were used as materials for field experiments. Our experimental design consisted of three arrangements: a film of three lines with equal row spacing (76 cm+76 cm+76 cm) under low planting density, a film of six lines with wide-narrow row spacing (66 cm +10 cm) under high density, and a film of three lines with equal row spacing (76 cm+76 cm+76 cm) under high density. [Result] Cotton growth in a film of three lines with equal row spacing under low planting density was vigorous, with LAI and R_LI increasing rapidly and peaking at the early growth stage. Under this arrangement, the decrease intensity of LAI and R_LI were 10.4%-13.6% and 3.7%-4.2% lower than the other two treatments, respectively; this arrangement of hybrid cotton also exhibited the highest dry matter accumulation at the late growth stage and gave the highest yield at harvest. [Conclusion] Compared with the other two arrangements, hybrid cotton planted in equally spaced rows under low planting density conditions had the greatest dry matter accumulation in the late growth stage and gave the highest yields because LAI, R_LI and dry matter accumulation increased rapidly in the early growth stage, with photosynthetic efficiency accordingly increased by high LAI and R_LI.

[Objective] Screening the drought- or salt-resistant lines and measurement of key physiological and biochemical indexes for a set of monosomic alien addition lines (MAALs) derived from Gossypium anomalum in G. hirsutum background would provide the theory and material basis for drought and salt resistance breeding in cotton. [Method] The genotypes of all the MAALs were confirmed by chromosome-specific simple sequence repeat (SSR) markers of G. anomalum. The MAALs with drought or salt resistance potential was screened based on the phenotypic observation and related indexes measurement, and physiological and biochemical indexes were determined, including the content of hydrogen peroxide(H₂O₂), malondialdehyde (MDA), proline(PRO) and chlorophyll(SPAD value) and the activity of peroxidase(POD), catalase(CAT) and superoxide dismutase(SOD). [Result] The transmission rate of MAALs ranged from 34.66% to 51.50%. MAAL_1B, MAAL_5B, MAAL_7B, MAAL_8B, MAAL_11B, and MAAL_12B had drought resistance potential, while MAAL_4B, MAAL_6B, MAAL_8B, MAAL_9B, and MAAL_10B showed salt resistance potential. Under drought or salt stress, the content of MDA, H₂O₂ and PRO of all the tested plants increased compared with the control conditions, and the content of MDA and H₂O₂ of the recurrent parent G. hirsutum Su8289 was higher than that of MAALs with drought or salt resistance potential. The CAT and SOD activity in MAAL_1B, the CAT, SOD activity and PRO content in MAAL_5B, the SOD activity in MAAL_7B, the POD, CAT, SOD activity and SPAD value in MAAL_8B, the POD and CAT activity in MAAL_11B, and the CAT activity and SPAD value in MAAL_12B were significantly or extremely significantly higher than that in Su8289 at 10 days after drought treatment. Three days after 350 mmol·L^-1 NaCl treatment, the POD, SOD activity and SPAD value in MAAL_6B, the CAT activity in MAAL_8B, the POD and SOD activity in MAAL_9B, and the SOD activity and SPAD value in MAAL_10B were significantly or extremely significantly higher than that in Su8289. [Conclusion] Some MAALs had drought or salt resistance potential, and may respond to drought or salt stress through different physiological and biochemical process.

In this study, F₂ populations from two chromosome segment substitution lines MBI7455 and MBI7358, were quantified using SSR to evaluate the parents' genotype and detect QTL related to fiber quality plus yield traits of cotton. Results show that the recurrent parent (CCRI45) hosted 96.70% and 95.60% of chromosome segment substitution in MBI7455 with 12 chromosome segments and in MBI7358 with 16 chromosome substitution segments of Gossypium barbadense, respectively. In the F₂ population, the average rate of chromosome substitution of the recurrent parent (CCRI45) was 96.44%, and the average segments of chromosome substitution of Gossypium barbadense was 13.42, with an average segments of homozygous donor chromosome value of 3.90. Analysis showed 19 fiber quality-related QTL with a phenotypic variance of between 2.52%-13.11% and seven yield traits-related QTL with a range of 2.93%-11.40% phenotypic variance, resulting in a total of 26 QTL. The CSSLs could be used to detect QTL for fiber yield and quality traits, which offer an important foundation for the cotton molecular-assisted breeding.

[Objective] This study aims to characterize the GhROP6 and study its roles of resistance to Verticillium wiltin upland cotton (Gossypium hirsutum L.). [Method] The bioinformatics analysis was used to identify Rho-related guanosine triphosphatase from plants (ROP) genes in upland cotton. The chromosome distributions, expression pattern analysis of GhROP genes were investigated. The function of GhROP6 gene was studied by quantitative real-time polymerase chain reaction (qRT-PCR), virus-induced gene silencing (VIGS), plant genetic transformation and metabolism analysis. [Result] Totally, 28 ROP genes were identified in upland cotton. And the corresponding amino acid sequence contained the ROP protein specific structures, including four GTP/GDP binding domains, effector domain binding to downstream target proteins and variable C-terminal regions. Chromosomal mapping analysis showed that 24 ROP genes were symmetrically distributed in subgenome A and subgenome D, and 3 genes specifically distributed in subgenome D. qRT-PCR analysis showed that the transcript levels of GhROP6 varied in different organs, and showed higher expression level in petals, stigma, fiber of 10 days post anthesis. Meanwhile, the transcript level of GhROP6 was upregulated in cotton by methyl jasmonate (MeJA). Knock-down of GhROP6 through VIGS weakened the cotton resistance to Verticillium wilt, and reduced the expression of GhLOX1, GhOPR3-1, GhOPR3-3, GhAOC1, GhAOS involved in jasmonic acid (JA) synthesis, and the expression of GhMYC2 involved in JA signaling pathway, and the expression of GhCCR-1, GhF5H-1, GhCCoAOMT-2, and GhCCoAOMT-3 genes involved in lignin synthesis. However, constitutively activated GhROP6 in Arabidopsis enhanced the plants resistantce to V. dahliae. Further analysis showed that the contents of JA-isoleucine and lignin in transgenic Arabidopsis were higher than those of wild type. [Conclusion] GhROP6 may involve in the resistance of cotton to Verticillium wilt through JA synthesis and signaling pathway and lignin synthesis.

Cotton has obvious heterosis, which is manifested in traits including yield, fiber quality, and resistance to diseases and insects. Hybrid seed production is a very important step in the utilization of cotton heterosis. Recently, as the cost of manual pollination in seed production increases year by year, the simplified, efficient, and low-cost seed production techniques have become an inevitable trend for future hybrid cotton development. The field practice shows that the use of cytoplasmic male sterile lines not only simplify the procedure of seed production but also save labor costs, so it has become a research hotspot in the utilization of crop heterosis. However, the sterile cytoplasm does have certain impacts on cotton morphogenesis, anther development, yield formation, fiber development, and have negative effects on cotton growth and development, thereby limiting the further promotion and utilization of “three-line (male sterile line, maintainer line, and restoring line)” hybrid cotton. In this paper, the effects of male sterile cytoplasm on the main traits of cotton and the molecular basis for its negative effects were systematically reviewed. And the potential ways to overcome the negative effects of male sterile cytoplasm in cotton were preliminarily discussed, which would provide new ideas for breeding and improvement of cotton cytoplasmic male sterile restorer lines and excellent “three-line” hybrids in the future.

Transcription factors play important regulatory roles in various stages of cotton fiber development, beginning with initiation and continuing through secondary cell wall synthesis and maturity. In recent years, many transcription factors related to cotton fiber development have been reported, including MYB, HD-ZIP, MADS, and TCP families. Among them, MYB transcription factors have been identified as essential proteins involved in this process. Arabidopsis trichome development, which has been well characterized at the molecular level, is regulated by a MYB-bHLH-WD40 protein complex. As several studies using cotton fiber-related genes have demonstrated a close relationship between cotton seed fibers and Arabidopsis leaf trichomes, cotton fiber development and Arabidopsis leaf trichome differentiation likely share similar regulatory mechanisms. MIXTA-like MYB genes such as GhMYB25 and GhMYB25-like also have significant regulatory roles in cotton fiber development. GL1-like MYB genes and MIXTA-like MYB genes most likely control cotton fiber development through different regulatory networks. Extensive research on transcription factors related to cotton fiber cells has provided insights into the molecular mechanisms of fiber cell differentiation and development. This paper discusses some achievements in this field.

[Objective] The study aims to examine the rhizosphere soil enzyme activity and bacterial community response to foliar application of 1,1-dimethyl-piperidinium chloride (DPC) and sodium nitroprusside (SNP) at the cotton seedling stage, and to screen rhizoshpere events potentially involved in cotton seedling growth. [Method] An upland cotton line A201 was grown in nursery trays under a controlled environment. The treatment with DPC of 50 mg·L^-1 and SNP of 500 μmol·L^-1, respectively, was foliar-applied at the one-leaf-one-heart stage, and the treatment with deionized water application was selected as the control. The rhizosphere soil was sampled to quantify the activities of sucrase, urease, catalase, and alkaline phosphate at the three-leaf-one-heart stage. The rhizosphere bacteria composition examined by 16S rRNA sequence analysis. [Result] The root growth, stem diameter, and dry mass of whole cotton plant were significantly increased by the DPC and SNP treatments. The activities of urease and sucrase were significantly improved by the DPC treatment. SNP application significantly enhanced sucrase activity but significantly decreased urease activity, while DPC treatment and SNP treatment had no significant effect on the activities of catalase and alkaline phosphatase. DPC application increased the relative abundance of Patescibacteria and Simpson's diversity index of soil bacterial community, but reduced the relative abundances of Chloroflexi and Acidobacteriota and Shannon Wiener’s diversity index of soil bacterial community. The results of redundancy analysis on family and genus level showed that the abundances of Saccharimonadaceae and TM7a were higher in the DPC treatment; the abundance of Cellvibrionaceae was greater in the SNP treatment; the abundance of Rhizobiaceae was greater in the DPC and SNP treatments. The control exhibited greater Nitrospiraceae and Nitrospira abundances compared with the DPC and SNP treatments. Urease activity was positively correlated with Saccharimonadaceae and TM7a relative abundances. [Conclusion] DPC and SNP could promote the growth of cotton roots and aerial parts, and influence the soil enzyme activity and bacterial community composition in the rhizosphere.

[Objective] This study aims to investigate the regulatory effect of "fertigation adjusted water management" on the physiology and the growth of drip-irrigated cotton in alleviating drought stress, and to enhance cotton yield under limited water resource. [Methods] Using Zhongmian 619 as the test material, two types of irrigation quotas for deficient irrigation (W1: 45 mm) and full irrigation (W2: 54 mm) in combination of three nitrogen input doses, including low nitrogen (F1: 150 kg·hm^-2), medium nitrogen (F2: 225 kg·hm^-2), and high nitrogen (F3: 300 kg·hm^-2) were set. The effects of different irrigation quotas and nitrogen doses on cotton physiological growth indicators and seed cotton yield were analyzed. [Results] The results indicated that increased irrigation quotas promoted cotton growth, enhanced two-year average leaf area index (LAI), relative chlorophyll content (soil and plant analyzer development, SPAD value), and net photosynthetic rate (P_n), while redued the activities of cotton superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and malondialdehyde (MDA) content. With the increase of nitrogen application, LAI, SPAD, P_n, and antioxidant enzyme activity were increased, MDA content was decreased on average, and the influence of water deficiency on cotton development was alleviated. Under W1 treatment, increased nitrogen application improved cotton yield, while under W2 treatment, cotton yield showed the trend of increasing first and then decreasing with the increase of nitrogen application. Under water-nitrogen interaction, the highest two-year average seed cotton yield (6 821.86 kg·hm^-2) was recorded under W2F2 treatment followed by W1F3 treatment (6 717.72 kg·hm^-2). In the technique for order preference by similarity to ideal solution(TOPSIS) analysis, the comprehensive scores of W1F3 and W2F2 were 0.57 and 0.56, respectively, and the differences between the two-year yield of W1F3 and W2F2 treatments were not significant. [Conclusion] Increased nitrogen application under deficit irrigation effectively alleviates the adverse effects of drought on the physiological characteristics and yield in cotton. It is recommended to use 45 mm irrigation quota combined with 300 kg·hm^-2 nitrogen application as the fertigation strategy for the filmless drip-irrigated cotton in southern Xinjiang, to effectively ensure cotton yield under limited water resource.

[Objective] Field experiment was carried out to study the effect of different planting systems on lint yield, economic benefit, and nitrogen efficiency of cotton (Gossypium hirsutum L.) in the Yangtze River valley and to provide theoretical support for high yield and efficiency production of cotton. [Method] A split-plot experiment was conducted to explore the biomass accumulation and allocation characteristics, lint yield, economic benefit and nitrogen efficiency of cotton in response to different planting patterns (transplanting and field-seeded), varieties (early-maturing and medium-maturing) and nitrogen applications(no nitrogen and optimum nitrogen). [Result] The growing process fasted especially for the seedling stage under field-seeded pattern compared with that under transplanting pattern. The biomass and nitrogen accumulation at the medium-late stage of cotton under field-seeded pattern were higher than those under transplanting pattern, and the economic coefficients of early-maturing variety were higher than those of medium-maturing variety. The lint yield of the early-maturing variety under field-seeded pattern and the medium-maturity variety under transplanting pattern were higher under nitrogen application, and the difference between them was not significant. Under nitrogen application, the output value of seed cotton under transplanting pattern was 1.0-1.2 times of that under field-seeded pattern, but the cost of the former was 1.8-2.0 times of that of the latter, and the benefit of the former was only 23.0%-43.1% of the latter. The effects of planting pattern on the nitrogen agronomic efficiency (NAE) and nitrogen apparent recovery efficiency (NARE) were greater than those of variety and nitrogen application, and the NAE and NARE under field-seeded pattern were 40.0% and 76.4% (2017) higher than those under transplanting pattern. The effects of variety on nitrogen production efficiency (NPE) were greater than those of planting pattern and nitrogen application, and the NPE of early-maturing variety was 45.3% higher than medium-maturing variety in 2017. [Conclusion] The early-maturing variety with optimum nitrogen application under field-seeded pattern was conducive to higher yield, lower cost and higher benefit, and has higher NAE, NARE and NPE, which is the high yield and efficiency planting system for cotton after wheat in the Yangtze River valley.

[Objective] This study aims to establish a rapid and non-destructive near-infrared spectroscopy (NIRS) detection method for measuring the cottonseed oil content, then to facilitate the genetic improvement of high-oil cotton varieties and the utilization of cottonseed. [Method] The Soxhlet extraction method was used to determine the cottonseed oil content of kernel, delinted seed, and linted seed samples. And the spectral information of 3 morphological types of cottonseed were collected separately. By preprocessing the original spectral data with different mathematical parameters and scattering processing methods, we established the calibration model by modified partial least squares (MPLS) method and used verification sample for model validation. [Result] The best calibration model of NIRS for oil content in kernel, delinted seed, and linted seed were established. The validation of 3 NIRS models had the coefficient of determination of 0.95, 0.94, 0.93, and the residual prediction deviation (RPD) were 4.09, 3.47, 3.15. These results indicated that the 3 NIRS models for cottonseed oil content detection had excellent accuracy and stability. [Conclusion] In this study, 3 NIRS rapid non-destructive detection models for cottonseed oil content in kernel, delinted seed, and linted seed were constructed. The 3 models meet the need of cottonseed detection of different morphological types, and can replace traditional detection methods to avoid the complicated operation procedure and the problem of damaging seeds during the detection of cottonseed oil content. This study provides technical support for improving the comprehensive utilization value of cotton and the genetic improvement of cottonseed oil content.

[Objective] Cadmium (Cd) is one of the serious environmental pollutants, and Cd stress affects seed germination. Melatonin (MT), as an antioxidant, and can promotes seed germination. In this study, the effects of MT on cotton seed germination, antioxidant activity, and osmotic adjustment content under Cd stress were analyzed to clarify the regulatory effect of MT on cotton seed germination under Cd stress. [Method] Seeds of the transgenic insect-resistant cotton variety Nongdamian 601 were used as material, Cd concentration and MT concentration were screened. And four treatments, CK (control, water), MT (melatonin treatment, 50 μmol·L^-1), Cd (cadmium stress 100 μmol·L^-1 treatment), CM (cadmium + melatonin treatment) were set. The germination potential, germination rate, seedling biomass, antioxidant enzyme activity, and osmotic adjustment content of cotton seed under different treatments were studied. [Result] Cd stress of 100 μmol·L^-1 significantly decreased the germination potential, the germination rate, the length of radicle and plumule, the fresh and dry mass of radicle, but had no significant effect on the fresh or dry mass of plumule. Under the stress of Cd, the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and soluble protein content of cotton seed were decreased. The content of proline, soluble sugar and malondialdehyde (MDA) were increased. Application of MT (50 μmol·L^-1) increased the germination potential and germination rate of cotton seed under Cd stress, the activity of SOD, POD and CAT, the content of soluble protein, soluble sugar and proline, while decreased the content of MDA, significantly increased the length of radicle and plumule, and significantly increased radicle biomass. [Conclusion] Exogenous MT (50 μmol·L^-1) could effectively alleviate the inhibitory effeet of Cd stress (100 μmol·L^-1) on cotton seed germination.

[Objective] This study aims to screen the suitable nitrogen (N) concentration and investigate its effects on the growth, macronutrients uptake and N use efficiency of cotton at seedling stage. [Methods] HM3097 was used and cultured with nutrient solution for 21 d of six N concentrations with 0, 0.04, 0.4, 1, 4, 8 mmol·L^-1 Ca(NO₃)₂, named N0, N0.04, N0.4, N1, N4, N8, respectively. The root and shoot morphology, biomass, absorption and distribution of macronutrients, photosynthetic capacity, N uptake efficiency (NUpE) and N utilization efficiency (NUtE) of cotton seedlings were determined. [Results] With the increase of N concentration, the growth (include root and shoot), biomass, macronutrients accumulation and photosynthetic capacity of cotton seedlings increased first and then decreased, and 4 mmol·L^-1 Ca(NO₃)₂ was the most appropriate N concentration for cotton at seedling stage, at which the cotton growth was the most vigorous. The maximum accumulations of N, P, K, and Ca of cotton seedlings were 34.4 mg, 6.3 mg, 41.6 mg, and 16.5 mg per plant, respectively, with the ratio of 1∶0.2∶1.2∶0.5. NUpE and NUtE were positively correlated with root-shoot ratio, and the change trend were also consistent with the root biomass distribution proportion, root average diameter, and the root macronutrients distribution proportion, which decreased with the increase of N concentration. In the range of 0-4 mmol·L^-1 Ca(NO₃)₂, the contents of N, K, and Ca, leaf biomass and the shoot macronutrients distribution proportion all increased with the increase of N concentration. [Conclusion] 4 mmol·L^-1 Ca(NO₃)₂ was the most appropriate N concentration for cotton at seedling stage, which could significantly promote the absorption of N, P, K, and Ca of cotton seedlings. 1 mmol·L^-1 Ca(NO₃)₂ could increase the root macronutrients distribution proportion, promote root elongation and proliferation, and improve NUpE and NUtE.

Cotton Verticillium wilt caused by Verticillium dahliae Kleb. has become one of the main impediments to cotton sustainable production in China in recent years．This disease is a soil-borne and seed-borne vascular disease and difficult to control. The host range of V. dahliae is unusually wide as a plant pathogen．This paper summarized the latest research progresses of the pathogenicity differentiation, genome sequence, pathogenesis mechanism, microsclerotial development and germination mechanism of V. dahliae, molecular mechanism of disease resistance in cotton as well as the control methods of cotton Verticillium wilt．

[Objective] This research aimed to clarify the effect of farmland landscape patterns on the population dynamics of Lygus pratensis in cotton field, so as to provide a theoretical basis for the ecological control of L. pratensis. [Method] A total of 20 cotton fields in Aral Reclamation Area of Xinjiang were selected as experimental sites from 2019 to 2021. The methods of net trapping and sex attracter combined with yellow plate trapping were used to investigate the population dynamics of L. pratensis adults, and the land use status around the cotton field within a radius of 2 000 m was also investigated. A linear mixed model was fitted to the landscape parameters of farmland landscape patterns at 500 m, 1 000 m, 1 500 m and 2 000 m scales and the population number of the L. pratensis adults of the second- and third-generation. [Result] L. pratensis had 4 generations in Aral Reclamation Area every year, and the second and third generations were the main populations in cotton fields. At the four scales, host crop habitat (Host) accounted for the highest area (64.14%-69.85%), followed by single crop (Cotton) habitat (51.21%-55.26%), while the area ratio of forest belt and desolate sands habitat (FBDS), shrub habitat (Shrub), building land habitat (Building), other crop habitat (Other crops) and water habitat (Water) were relatively low. The results of model fitting showed that the control effect of landscape variables on the population number of the second-generation adults in the cotton field gradually weakened with the increase of the scale. There were extremely significant or significant positive correlation between the population number of the second-generation adults and the area ratio of Building (500 m scale) and FBDS (1 500 m scale), and a strong and extremely significant negative correlation between the population number of the second-generation adults and the area ratio of Host (1 000 m scale). There was a strong and extremely significant positive correlation between the population number of the third-generation adults of L. pratensis and the area ratio of Building (500 m scale). The population number of the third-generation adults was negatively correlated with the area ratio of Host (1 000 m), Other crops (1 000 m, P < 0.01) and Water (1 000 km, P < 0.05), and positively correlated with the perimeter area ratio (1 500 m, P < 0.05; 2 000 m, P < 0.01). [Conclusion] The farmland landscape pattern had an obvious regulatory effect on the population number of L. pratensis adults in cotton field. The increase of the area ratio of Host, Other crops and Water in farmland landscape had a certain control effect on the population number of L. pratensis in cotton field. The increase of the area ratio of FBDS and Building promoted the occurrence of L. pratensis in cotton fields.

Based on the dataset of planting area of individual cotton varieties released by National Extension and Service Center of Agricultural Technology in the past 40 years, the varieties with planting area ranking the first in the main cotton producing regions in one year, or with more than 0.33 million hm² planting area and ranking the top three in one or more years were defined as mega varieties. The cumulative planting area, the maximum annual area, the number of years with area ranking in top three, and the planting area percentage of the mega varieties were analyzed. Around forty-four cotton mega varieties were selected in the main cotton production regions (i.e. the Yellow River basin, the Yangtze River basin and the Northwest inland cotton production region) in the past 40 years, among of which the cultivar Lumianyan 15 was found to be a mega cultivar both in the Yellow River basin and the Yangtze River basin cotton production regions. The total number of cotton varieties applied in production every year was generally on the rise during 1981-2020. The increase step of variety number was slow during 1981-2000, but speeded up during 2001-2020. Meanwhile, the proportion of mega varieties planting area to the total area of main cotton producing regions in each year showed significant historical characteristics. The proportion was relatively stable during 1981-1995, with a proportion of around 61%, 36%, and 83% in the Yellow River basin, the Yangtze River basin and the Northwest inland cotton production regions respectively. After then, the area proportion of mega varieties suffered a sharp decline to about 20% on average during 1996-2006, and followed by a slow drop period to around 15% on average till 2020. Cotton mega varieties contributed greatly indeed to the stability and development of cotton production in the history. However, the cotton breeding target at current and also in the future will be more functional and regional oriented to meet the versatile needs of seed industry and market development.

[Objective] This study aims to explore the effects of exogenous methyl jasmonate (MeJA) on cotton tolerance to the heat stress. [Method] The self-bred line ZS08 was used as the test material. Distilled water (CK) and MeJA with different concentrations (200 μmol·L^-1, 400 μmol·L^-1 and 600 μmol·L^-1) were used on plants at the flowering and boll-setting stage. And after the artificial heat stress of 38.0 ℃/30.0 ℃ (day/night) for three days or under natural heat stress of 35.2-37.5 ℃/26.4-27.2 ℃ (day/night) for ten days, the pollen viability, photosynthetic characteristics, antioxidant enzyme activity, malondialdehyde (MDA) content, yield and fiber quality of each treatment were measured. [Result] The pollen viability was reduced under the artificial heat stress. The MeJA treatment of three concentrations all had alleviated the inhibition of heat stress on pollen viability compared with the water control. The net photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s) of the fourth leaf from top of the main stem in the 400 μmol·L^-1 and 600 μmol·L^-1 MeJA treated plants were increased in various degree than those of the control under 2-3 days heat stress by 1.6%-3.7%, 7.2%-15.7%, and 44.4%-53.4%, respectively. The activity of superoxide dismutase (SOD) and peroxidase (POD) of the second leaf from top on the main stem in 400 μmol·L^-1 and 600 μmol·L^-1 MeJA treatment were increased by 3.1%-7.2% and 5.7%-20.0% than those of the control under 2-3 days heat stress. While the content of MDA was reduced by 10.9%-17.9%. Under the natural heat stress, plants which were treated by different concentrations of MeJA had improved boll-setting rate and boll weight in varying degree, and had significantly improved lint yield by 9.0%-18.3% compared with the control. [Conclusion] When encountering heat stress during the flowering and boll-setting stage, the application of MeJA can increase P_n and the activities of SOD and POD, reduce the degree of leaf damage, and improve pollen viability, thereby enhance the heat tolerance of cotton, and reduce the impact of heat stress on boll-setting rate, boll weight, and yield loss.

[Objective] The unmanned aerial vehicle (UAV) multi-spectral remote sensing technology was used to monitor the severity of cotton Verticillium wilt, which will provide theoretical guidance for the precise prevention and control of cotton Verticillium wilt. [Method] By analyzing the spectral characteristics of canopy in cotton field affected by Verticillium wilt, the best vegetation index, the best wavelength combination and the best time phase for multi-spectral identification of Verticillium wilt by UAV were selected. The images of cotton fields differing in the severity of Verticillium wilt were established based on the optimal time phase. Parallelepiped method, maximum likelihood method and support vector machine radial basis function classification method were used to classify and evaluate the accuracy of the images. [Result] The results showed that the canopy spectral reflectance of cotton plants differing with occurrence of Verticillium wilt increased obviously with the increase of wavelength at 710-760 nm, the spectral reflectance of cotton canopy decreased obviously with the aggravation of Verticillium wilt at the wavelength of 760-950 nm. With the aggravation of Verticillium wilt, the chlorophyll content of leaves, fresh mass of aerial tissue per plant, dry mass of aerial tissue per plant, plant water content and leaf area index of cotton plants were all decreased. The best vegetation index and best band combination for UAV multi-spectral remote sensing to identify cotton Verticillium wilt were difference vegetation index (DVI) and B_3-5-8 (the corresponding wavelengths are 550 nm, 656 nm and 800 nm). Mid to late August was the best time to identify the occurrence degree of cotton Verticillium wilt by UAV multi-spectral remote sensing. Support vector machine radial basis function classification method, best band combination B_3-5-8 and DVI integrated image had the highest classification accuracy for Verticillium wilt in cotton field (classification accuracy was 96.64%, and Kappa coefficient was 95.61%). The classification results of Verticillium wilt severity in cotton fields corresponded to the changes in canopy spectral reflectance and agronomic parameters of cotton plants, and were consistent with the field investigation results. [Conclusion] It is feasible to classify the severity of Verticillium wilt in cotton field by using support vector machine radial basis function classification method, optimal band combination B_3-5-8 and DVI integrated images. The results can provide theoretical ground for monitoring similar crop pests and diseases by remote sensing technology.

 A laboratory experiment was carried out to study the root morphology and leaf photosynthetic characteristics of three colored cottons (CCRI 51, light brown cotton; CCRI 81, dark brown cotton; and CCRI 82, dark green cotton) and one white cotton under different levels of phosphorus. The results showed that lower level phosphorus treatments significantly increased root length and surface area, while no-phosphorus treatments seriously inhibited root growth. As the duration of the treatment increased, we found that the cotton root had carried out self-regulation and reduced the impact of phosphorus deficiency. Under treatments of lower levels of phosphorus the increased ratio of root length, root surface area, root volume and root/shoot ratio of GX 3 were the highest 10 days after treatment. In CCRI 51, levels were the highest 20 days after treatment. Under no-phosphorus treatments, the inhibition rates of GX 3 and CCRI 81 root morphology 20 days after treatment were higher than 10 days after treatment. Levels in the other varieties improved as the period of stress continued. The ranking of the different varieties with respect to light saturation point, maximum photosynthetic rate and light compensation point of leaves was CCRI 51＞GX 3＞ CCRI 81＞CCRI 82. As the supply of phosphorus decreased,  light saturation point and the maximum photosynthetic rate of GX 3 were gradually reduced, but light saturation point of CCRI 51 and CCRI 81 were shown as lower phosphorus＞no phosphorus ＞suitable phosphorus. Under these experimental conditions, we found that white cotton had a short-term ability to compensate for phosphorus stress; light-brown cotton and dark-green cotton had a long-term ability to compensate for phosphorus stress; and dark-brown cotton was less sensitive to phosphorus phosphate stress.

[Objective] The experiment was conducted to study the effect of irrigation frequency on root distribution of cotton plant in Southern Xinjiang under fixed irrigation quota (3 900 m³·hm^-2). [Methods] CCRI 96A was planted as the test material, with 76 cm row spacing. Four irrigation frequency treatments were set up as follows: 6 irrigation times (T6, 650.0 m³·hm^-2 per time), 8 irrigation times (T8, 487.5 m³·hm^-2 per time), 10 irrigation times (T10, 390.0 m³·hm^-2 per time), and 12 irrigation times (T12, 325.0 m³·hm^-2 per time). The roots in the 0-60 cm soil layer of cotton in the middle row was collected and stratified by the soil root excavation method and scanned by root scanner. Then the root surface area, volume and other indexes were statistically analyzed. [Results] The roots with a diameter of less than 1 mm made up 94.5% of the total root length and 71.9% of the total root surface area. The total root volume was closely related to larger roots. With the increase of diameter, root length, root surface area, and root volume of each treatment decreased first and then increased. In the 0-60 cm soil layer, the root length density (11 662.71 m·m^-3), root surface area density (15.61 m²·m^-3) and dry matter mass (21.55 g) of T6 treatment were the largest, but the root volume density of T12 treatment (2.2×10^-3 m³·m^-3) was the largest. Under plough layer (30-60 cm soil layer), the root length density and the dry matter mass of T10 treatment were the largest, at 1 090.46 m·m^-3 and 1.09 g, and the root surface area density and the volume density of T8 treatment were the largest, at 2.52 m²·m^-3 and 2.68×10^-4 m³·m^-3, respectively. [Conclusion] Under the same irrigation quota of 3 900 m²·hm^-2, rational allocation of irrigation frequency can optimize the morphology and distribution of cotton roots in the soil. It could promote root surface area by increasing the irrigation amount per time to extend the irrigation interval. In this study, T6 treatment was beneficial to the elongation and distribution of cotton roots in the 0-60 cm soil layer, and T12 treatment is beneficial to cotton root thickening.

[Objective] This study aimed to explore the effects of water and nitrogen management on cotton growth and development, water and nitrogen use efficiency, and soil greenhouse gas emissions under non-film drip irrigation cotton fields in Xinjiang. [Method] Two irrigation quotas (W1: 450 m³·hm^-2, W2: 540 m³·hm^-2) and three nitrogen application rates (150 kg·hm^-2, 225 kg·hm^-2, 300 kg·hm^-2 nitrogen) were set. The differences of total nitrogen content of soil and plant, cotton plant height, cotton stem diameter, seed cotton yield, water and nitrogen use efficiency and soil greenhouse gas emissions were analyzed under different water and nitrogen treatments. [Result] At 225 kg·hm^-2 and 300 kg·hm^-2 nitrogen application rates, the average total nitrogen content in the 0-80 cm soil layer of W1 was higher than that in the W2 treatment at different growth stages. At the same nitrogen application level, the cumulative emissions of soil CO₂, CH₄, N₂O, global warming potential (GWP), greenhouse gas emission intensity (GHGI) and water use efficiency under W1 treatment were all increased compared with W2. Under W1 treatment, the average total nitrogen content of 0-80 cm soil layer at seedling and squaring periods, cotton plant height and stem diameter at different growth stages, seed cotton yield and water use efficiency all increased with the increase of nitrogen application rate. The cumulative emissions of soil CO₂ and CH₄, GWP, GHGI and partial productivity of nitrogen fertilizer decreased with the increase of nitrogen application rate, while the total nitrogen content of plant increased first and then decreased with the increase of nitrogen application rate. Under W2 breatment, total nitrogen content of cotton plant, seed cotton yield and water use efficiency all increased first and then decreased with the increase of nitrogen application rate. The cumulative emissions of soil CO₂ and CH₄, GWP and partial productivity of nitrogen fertilizer all decreased with the increase of nitrogen application rate, while cotton plant height and stem diameter increased with the increase of nitrogen application rate. Through fitting analysis, it was found that the fitting curves of seed cotton yield under W1 treatment and that under W2 treatment intersected when the nitrogen application rate was 278.07 kg·hm^-2. [Conclusion] For the Southern Xinjiang region with water shortage, 450 m³·hm^-2 irrigation quota and 300 kg·hm^-2 nitrogen application rate are efficient water and nitrogen application modes for increasing water use efficiency and cotton yield and reducing emission of soil greenhouse gas under non-film drip irrigation condition.

[Objective] Frego bract can greatly reduce the attachment of bract to boll and help to reduce the percentage of trash of machine-harvested cotton. In this study, we aimed to fine mapping the frego bract fg gene in cotton, so as to provide reference for its cloning and breeding utilization. [Method] Two F₂ segregating populations were constructed by crossing Gossypium hirsutum T582 (as the female parent) with G. hirsutum TM-1 and G. barbadense 3-79, respectively. Population 1 (T582 × TM-1) included 370 individual plants, and population 2(T582 × 3-79) contained 2 667 individual plants. The developed Indel (insertion-deletion) markers based on the reference genomic data of TM-1 and 3-79 were used to fine mapping fg. Functional annotation and expression pattern analysis of genes within the mapped sequence were performed using cotton functional genomics and multi-omics data. [Result] Genetic analysis showed that frego bract is controlled by a single recessive gene. Based on the previous mapping result of fg gene, cotton fg gene was further mapped between molecular markers M3 and M4 on chromosome A03, with an interval size of 188 kb in this study. A total of fourteen annotated functional genes were predicted in the mapping region. Among them, Gh_A03G021700, Gh_A03G021900, Gh_A03G022600 and Gh_A03G022700 were highly expressed in sepal and epicalyx. [Conclusion] Frego bract fg gene was finely mapped on chromosome A03, with an interval size of 188 kb, and 14 candidate genes in the mapping interval were preliminarily analyzed, which lays the foundation for map-based cloning of this gene.

[Objective] The purpose of this study was to screen and identify a strain of highly efficient biocontrol bacteria against cotton Verticillium wilt, and to clarify its control mechanism, so as to provide technical support for the disease control. [Method] An endophytic bacterial strain EBV02 against Verticillium dahliae was screened in our laboratory, the species were identified by morphological, physiological, and biochemical characteristics and molecular biological analysis, and its control effect on cotton Verticillium wilt was determined by the indoor bacteriostatic test, greenhouse test, field test, and induced resistance test. The control mechanism of EBV02 was analyzed by measuring the burst of reactive oxygen species, accumulation of callose, and expression of defense-related genes in cotton leaves. [Result] EBV02 was identified as the Bacillus velezensis through morphological observation and molecular biological analysis. The results of confrontation culture and plate-to-plate culture showed that the inhibition rates of EBV02 on mycelium growth of V. dahliae Vd080 were 63.27% and 59.83%, respectively. The inhibition rates of EBV02 on Vd080 sporulation and microsclerotia germination were 31.90% and 45.95%, respectively. In the greenhouse experiment, the highest control effect of EBV02 on cotton Verticillium wilt was 68.33%, and could significantly promote the growth of cotton seedlings. In the field experiment, the control effect of EBV02 fermentation broth spraying on cotton Verticillium wilt was 37.25%. In addition, seed cotton yield and lint yield with EBV02 treatment by seed soaking, root irrigation and spraying of fermentation broth were significantly increased by 8.34% and 8.26%, 3.38% and 5.60%, 7.04% and 7.06%, respectively. In the induced resistance test, EBV02 induced the burst of reactive oxygen species and the accumulation of callose in cotton leaves. The results of gene expression showed that EBV02 induced upregulation of defense-related genes such as POD, PPO, PAL, PR10, and JAR1 in cotton leaves, which enhanced the resistance of cotton to V. dahliae. [Conclusion] EBV02 has a good biocontrol potential of inhibiting the growth of V. dahliae, activating the systemic disease resistance, enhancing the cotton resistance to Verticillium wilt, and increasing the yield in cotton.

The different resistance levels of different cotton varieties to Apolygus lucorum Meyer-Dür and the relationships between the number of cotton leaf pastels, the pigment gland points and their resistance to Apolygus lucorum Meyer-Dür were studied in the net room and laboratory. The results showed that the difference of the resistance of different cotton varieties to Apolygus lucorum Meyer-Dür was obvious. The number of cotton leaf pastels and the pigment gland points indicated very clear difference in different cotton varieties and different cotton growing stages. The number of the cotton leaf pastels in the front and the back and the total in the seedling stage indicated the negative linear correlation with the resistance to Apolygus lucorum. The number of pigment gland points in the leaf nervure of front and back and the total in the bolling stage indicated the positive linear correlation with the resistance to Apolygus lucorum. These results could provide the basis for the cotton resistant breeding and IPM to Apolygus lucorum.

[Objective] This study aims to set up a near infrared spectrum(NIR) calibration model for the protein content and oil content in fuzz cottonseed. [Method] In this study, the SPXY (sample set partitioning based on joint X-Y distance sampling) method was used to divide the 426 samples into 320 as calibration set and 106 as prediction set according to the ratio of 3∶1, and the model was optimized by combining spectral pretreatment methods such as multiplicative scatter correction and first derivative. Three methods, linear partial least square method (PLS), support vector machine (SVM), and random forest (RF) were used to build the NIR rapid determination models of cotton seeds protein content and oil content. The coefficient of determination (R²), root mean square error (RMSE), and residual prediction deviation (RPD) were used as the evaluation indexes of the models. [Result] The results showed that the SVM model and PLS model performed better in the calibration set with R² more than 0.8, but with R² less than 0.8 in the prediction set, indicating that the models were overfitting. While the RF model was very well trained on both the calibration set and prediction sets with R² more than 0.9. The R², predicted RMSE, and RPD of RF model were 0.945 9, 0.935 2, and 4.539 1 for protein content, and 0.909 7, 0.770 4, and 3.489 1 for oil content, respectively. [Conclusion] The prediction model based on RF method can be well applied to the NIR spectroscopy determination of protein content and oil content of fuzz cottonseed, which could replace the chemical method. The results of the study not only lay a foundation for the rapid and nondestructive evaluation of the nutritional quality of cotton seed for seed quality breeding, processing production and marketing, but also provide technical references for the nondestructive analysis of seeds of other crops.

[Objective] This study aimed to explore the optimal boll-setting period of summer direct seeding mode and suitable cultivars in the Yangtze River Valley by studying the relationship between the boll temporal distribution and yield of different cotton cultivars, so as to provide a theoretical basis for the promotion of this mode. [Method] The experiment was conducted in the farm of Huazhong Agricultural University in 2019 and 2020. A random block design was used with 3 cotton cultivars (JH116, ZD2040 and HM3097) from Southern region and 2 cultivars (Z425 and Z619) from Northern region. Plant-mapping was used to investigate boll temporal distribution; cotton growth stages, dry matter accumulation, yield and its components were also investigated. [Result] Under the summer direct seeding mode, the cotton growth period was about 90 in 2019. The peak squaring period is about 44-63 d after emergence, the peak boll-setting period is about 63-82 d after emergence, and the peak boll-opening period is about 92-118 d after emergence. In 2020, due to the high precipitation and the low temperature, cotton growth period was extended by 23-40 d, and the start time of rapid growth period of the number of buds, flowers and open bolls was delayed by 19 d, 17 d, and 34 d, respectively; seed cotton yield and lint yield decreased obviously. On average of the two years, the sink biomass and plant biomass of cultivar HM3097 at the plant removal stage were 9.6%-43.0% and 14.7%-54.3% higher than other cultivars, respectively, and its lint yield was 12.5%-22.6% higher than other cultivars. Correlation analysis showed that lint yield was significantly positively correlated with the initial time and the duration of rapid accumulation period of cotton boll number and sink dry matter accumulation. [Conclusion] Under summer direct seeding mode, the proportion of late summer bolls is the largest, followed by early autumn bolls. Cultivar HM3097 from Southern region is more suitable for cultivating in the Yangtze River Valley due to its better yield performance under different weather conditions.

[Objective] This study aimed to explore the cotton yield formation mechanism under strip intercropping in the Yangtze River basin, and to screen the cotton intercropping patterns that are suitable for mechanized cotton production and highly efficient and sustainable. [Method] Four intercropping patterns of cotton-chili (CCI), cotton-bean (CBI), cotton-peanut (CPI), and cotton-sweet potato (CSI) and monocropping cotton (MC) were set up, and the photosynthetic characteristics, dry matter accumulation and distribution, yield and yield components of cotton under different intercropping patterns were analyzed, and the cotton partial land equivalent ratio (PLER) and economic benefits under various patterns were calculated. [Result] The seed cotton yield of CCI and CBI treatment were 6 055.19 kg·hm^-2 and 6 495.81 kg·hm^-2, which were 2.36% and 9.81% higher than that of MC, respectively. The main reason for the yield increase was that boll number per plant under these two modes increased by 1.61% and 11.21%, compared with MC, respectively. Compared with MC, the boll number per plant of cotton under CPI and CSI treatments decreased by 2.18% and 8.98%, and boll weight of cotton under CPI and CSI decreased by 2.59% and 5.60%. At full boll setting period, the leaf area index of cotton in various intercropping modes showed the following order: CBI > CCI > CPI > MC > CSI, and the leaf area index of cotton in CCI and CBI treatment increased by 5.88% and 9.80% compared with MC, respectively. At flourishing flowering period, compared with MC, the SPAD value and net photosynthetic rate of cotton leaves of CCI, CBI and CPI treatments increased by 8.51%, 7.65%, 6.37% and 11.55%, 8.31%, 4.02%, respectively. The CCI, CBI, and CPI treatments had a positive effect on the photosynthesis of cotton leaves and further increased the total dry matter accumulation of cotton at the boll opening period by 9.71%, 7.58% and 6.14% compared with MC, respectively. Under the treatments of CCI, CBI, CPI, and CSI, the economic benefits increased by 0.62, 1.53, 0.38, and 2.33 times compared with that of MC. Cotton is in the dominant position in CCI, CBI and CPI treatments based on the proportion of cotton area and the PLER. [Conclusion] From the perspective of economic benefits of cotton fields, the economic benefits of the four intercropping modes are higher than that of monocropping cotton, among which the cotton-sweet potato intercropping mode has the highest economic benefit, which has certain feasibility in production. The cotton-bean intercropping mode has the highest seed cotton yield, followed by the cotton-chili intercropping mode.

[Objective] This study aims to monitor the chlorophyll content of cotton leaves by utilizing unmanned aerial vehicle (UAV)-based multispectral technology. [Methods] This study utilized multispectral images of cotton canopies obtained by UAV in southern Xinjiang and employed seven different machine learning methods to estimate the canopy chlorophyll content during the flowering and boll-setting stage which is the critical growth period of cotton. The seven methods include linear regression (LR)-based methods, i.e., simple linear regression, partial least squares regression (PLSR), ridge regression (RR), least absolute shrinkage and selection operator (LASSO) regression, support vector regression (SVR), K-nearest neighbors regression (KNNR), and random forest regression (RFR). [Results] The results showed that compared with the LR method, the RFR, SVR and KNNR can improve the accuracy of prediction model of chlorophyll content in cotton canopies, especially the RFR algorithm, which had the coefficient of determination of 0.742, root mean square error of 1.158 mg·L^-1, residual predictive deviation of 1.969 with the validation dataset. [Conclusion] The use of UAV-based multispectral images with the RFR machine learning method, exhibits the most outstanding performance to estimate the chlorophyll content of cotton leaves and provide essential technical support for precision management in cotton field.