[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.

[Objective] This study aims to investigate the effect of irrigation frequency and irrigation quota on the characteristics of temporal and spatial distribution of reproductive organs and yield of filmless cotton, so as to provide references for the irrigation system to the cultivation of filmless cotton in Southern Xinjiang. [Method] From 2020 to 2021, using Zhongmian 619 as the test variety, the single-factor random block design was adopted. In the field trial of the first year, treatments of 3 irrigation frequencies were set, including 4 times (W4), 6 times (W6), and 8 times (W8) irrigation during the flowering and boll-setting period. The corresponding irrigation interval of each treatment was 12 d，8 d and 6 d, respectively. In the second year, treatments of 4 irrigation frequencies were set, and the W7 treatment of 7 times irrigation with 7 days irrigations interval was included during the flowering and boll-setting period on the basis of the first year's experimental setup. The irrigation quota of all treatments of filmless cotton in two years were 69 mm per time, besides the last round of irrigation in W8 treatment which used 52.2 mm water. The cotton with mulching film was set as control (CK) with irrigation frequency of 8 times and irrigation quota of 45 mm per time during the flowering and boll-setting stage in both years. The plant architecture map of each cotton developmental stage was collected, and the actual yield and corresponding traits were evaluated. [Result] The statistical analysis of the boll formation rate at each fruit node was conducted on the horizontal and vertical directions during the boll-opening stage. The results showed that the number of bolls and the boll-formation rate of the upper fruit branches and peripheral bolls of W4 were lower than those of other treatments. And the boll number and boll-formation rate are similar in W6 and W8. In 2021, the number of bolls and the rate of boll formation in W7 were higher than those in W4, W6, and W8. The result of the shedding rate of bolls in the boll-opening period showed that the shedding rate of the peripheral bolls and the upper fruit branches were higher in two years, but the specific site of the shedding bolls and the shedding rate varies among treatments. The analysis of yield components showed that W7 had significantly higher number of bolls per unit area, higher boll weight, and higher seed cotton yield than W4, but were not significantly different from CK. And the water use efficiency of W7 was higher than that of W6 and W8. [Conclusion] Application of extreme high or low irrigation frequency and irrigation quota during the flowering and boll-setting period affect the number of bolls, spatio-temporal distribution of cotton bolls, shedding rate as well as boll weight of filmless cotton, which in turn affects yield. In this study, the W7 treatment can provide a reference for the designing of the irrigation system for filmless cotton production in Southern Xinjiang. In detail, the recommended irrigation frequency is 2 times in the squaring period with the irrigation interval of 10 days, 7 times irrigation in the flowering and boll-setting period with the irrigation interval of 7 days, and the irrigation quota in total is 573 mm.

[Objective] The aim of this study is to explore the elite gene/quantitative trait loci (QTL) resources of yield and fiber quality, and to provide useful information for developing cotton varieties with high yield and excellent fiber quality. [Methods] A superior chromosome segment substitution line MBI9626, and a high-yield and wide-adaptability upland cotton CCRI 36 were selected to construct a secondary segregation population BC₆F₂ which contained 152 individuals. And 109 selected simple sequence repeat(SSR) markers were used to genotyping parents and the population, and QTL mapping for yield and fiber quality traits was conducted based on genotype data and phenotype data. [Results] Genotyping resutts showed MBI9626 recovered to 94.8% of the genetic background of CCRI 36. A total of 28 QTLs related to yield and fiber quality traits were detected in BC₆F₂, BC₆F_2:3, and BC₆F_2:4 populations, which were distributed on 6 chromosomes. Among them, there are 16 QTLs related to yield, accounting for 2.25%-6.14% of the phenotypic variation, including 6 stable QTLs; 12 QTLs related to quality traits, accounting for 2.49%-12.30% of the phenotypic variation, including 2 stable QTLs. There were 19 newly discovered QTLs, including 5 stable QTLs. And 233 genes were identified in a QTL cluster with 6 QTLs on D3 chromosome. Based on gene ontology (GO) cluster and Kyoto encyclopedia of genes and genomes (KEGG) analysis and TM-1 transcriptome data, 6 candidate genes were screened to be involved in fiber development, namely GH_D03G1428、GH_D03G1466, GH_D03G1518, GH_D03G1570, GH_D03G1586, and GH_D03G1640. [Conclusion] Twenty-eight stable QTLs related to cotton yield and fiber quality were identified and would lay a solid foundation for fine mapping and cloning of candidates genes and marker assisted selection.

[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] 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.

[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.

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.