CN110777197A - Major QTL method for rapidly identifying cotton-related traits through compound BSA-seq - Google Patents

Abstract

The invention discloses a method for rapid identification of major QTLs of cotton-related traits by compound BSA-seq. The method utilizes sister line materials with similar genetic backgrounds, Zhongmiansuo 60 and varieties with excellent comprehensive traits, and Zhongmiansuo 60 with poor fiber quality. The 60 selected lines EZ60 as the female parent were crossed with R014121 in the common male parent to construct two F ₂ segregating populations each containing 1000 individual plants. The extreme materials were screened according to the relevant phenotypic data, and the fiber lengths of the two populations were constructed in total. A total of 6 groups of BSA mixed pools were obtained by using high-throughput resequencing technology, and the common segment (QTL) qFS-D02-1 of the two groups was obtained by screening, which is the main QTL, which is on the physical map. The interval is 3.15Mb. Therefore, multiplex BSA-seq can quickly identify relevant major loci, mine relevant genes, and lay the foundation for cotton genetic improvement.

Description

A major QTL method for rapid identification of cotton-related traits by multiplex BSA-seq

technical field

The invention belongs to the application field of biotechnology, and relates to the rapid identification of the main effect QTLs of upland cotton by multiple BSA-seq, which is the basis for the identification of the main molecules of cotton assisted selection.

Background technique

Cotton fiber is a trichome formed by the development of a single cell in the epidermis of the outer integument of the ovule. It is an ideal model material for the study of cell development, cell wall and cellulose synthesis. Initial stage, elongation stage, secondary wall thickening stage and mature stage. Quality traits such as cotton fiber strength are complex quantitative traits controlled by multiple genes and are easily affected by environmental factors. are negatively correlated, so the ability to genetically manipulate quantitative traits determines the efficiency of crop breeding. Traditional breeding methods require large populations, long periods, high costs, and poor predictability. Therefore, it is difficult to achieve simultaneous improvement of cotton fiber quality and yield by conventional breeding methods. In recent years, with the development of biotechnology, a new approach has been provided for the improvement of crop traits. Through molecular methods such as the localization of fiber strength and other related traits, molecular marker-assisted selection, and candidate gene screening and identification, cotton fibers can be accelerated. Quality improvement. The research on the genetic basis and molecular regulation mechanism of cotton fiber strength traits has been paid great attention at home and abroad, and important progress has been made in the research of genetic map construction, QTL mapping of fiber strength traits, and important gene cloning and functional identification.

In order to study the genetic mechanism of cotton fiber strength traits and use marker-assisted selection to improve fiber strength, a series of fiber strengths have been located on the basis of genetic linkage map construction in terrestrial and interspecific populations, marine and terrestrial populations, and other populations. Relevant QTL. Zhang et al. used the phenotypic data of the intraspecific (0-153×sGK9708) recombinant inbred line population in Upland cotton in 11 environments and a genetic map including 2394 SNP markers, and detected a total of 63 QTLs for fiber strength in a single environment. , 16 QTLs for multiple environmentally stable fiber strengths (Zhang et al. Construction of a high-density genetic map and its application to QTL identification for fiberstrength in Upland cotton. Crop Science, 2017, 57(2):774.); Ma et al. used the F ₁₄ recombinant inbred line population (RIL) to backcross the parent to construct a BC population, and detected 26 QTLs in this population, while 37 QTLs were detected in the recombinant inbred line population. Among them, only 7 QTLs could be detected in both populations (Ma et al.QTLsanalysis and validation for fiber quality traits using maternal backcrosspopulation in Upland cotton[J]. Frontiers in Plant Science, 2017, 8:2168) Liu et al. used the encrypted high-density genetic map including 2051 SSR markers and the fiber quality and yield phenotype data of the (CCRI35×Yumian 1) recombinant inbred line population in 6 environments, and detected a total of 113 yield and fiber phenotypes. Quality QTLs, of which 50 QTLs were detected in multiple environments or the QTL had an additive effect value greater than the environmental effect value (Liu et al. Enriching an intraspecifc genetic map and identifying QTL for fiber quality and yield component traits across multiple environments in Uplandcotton ( Gossypium hirsutum L.) [J].Mol Genet Genomics, 2017, 292(6):1281-1306); Diouf et al constructed a genetic map including 5178 GBS-SNP markers using the CCRI35×NHF _2:3 population, combined with A total of 110 QTLs were detected in the phenotypic data of 11 traits including fiber quality, of which 30 QTLs were detected in 2 environments (Diouf et al. QTL mapping of fiber quality and yield-related traits in anintra). -specific upland cotton using genotype by sequencing (GBS). International journal of molecular sciences, 2018, 19(2): 441); Tan et al. used Yumian No. 1 × Acala Maxxa recombinant inbred line population, through Cotton SNP80K chip, combined with SSR markers constructed a high-density genetic map of upland cotton, and obtained 27 QTLs related to fiber strength (Tan et al. Genetic Map Construction and Fiber Quality QTL Mapping Us ing the CottonSNP80K Array in Upland Cotton. Frontiers in Plant Science, 2018, 9:225.). Yu et al. constructed 146 BIL populations by backcrossing upland cotton and sea island cotton. There were 2 QTLs related to fiber quality detected in more than 2 environments, one related to fiber strength and one related to fiber uniformity ( Yu et al. 2013. Mapping quantitative trait loci forlint yield and fiber quality across environments in a Gossypium hirsutum×Gossypium barbadense, backcross inbred line population. Theoretical and Applied Genetics, 126(1):275-287); ₂ , F2 _:3 and TC, 5, 4 and 5 fiber quality QTLs were detected respectively (Yu et al.. Identification of quantitative trait lociacross interspecific F2, F2:3 and testcross populations for agronomic and fiber traits in tetraploid cotton. Euphytica, 2013, 191(3):375-389). Si et al. analyzed the genetic characteristics of upland cotton lint content and fiber quality using the upland cotton infiltration line under the background of sea island cotton. A total of 39 QTLs were detected, including 4 QTL clusters, of which 3 QTL clusters (fiber length, specific strength and boll quality) Heavy) introduced line reduces the quality and yield of sea island cotton (Si et al. Genetic dissection of lint yield and fiber quality traits of G. hirsutum in G. barbadense background[J]. Mol Breeding, 2017, 37(1):9). Jia et al. detected 36 QTLs related to fiber strength using recombinant inbred line populations between marine and terrestrial species (Jia et al. QTLdelineation for five fiber quality traits based on an intra-specific Gossypium hirsutum L. recombinant inbred line population. Moleculargenetics and genomics, 2018 , 293(4): 831-843). 42 fiber quality QTLs, including 15 fiber strength QTLs and 27 fiber micronaire values, were detected using the BC ₃ F ₂ , BC ₃ F _2:3 and BC ₃ F _2:4 introductory lines in the upland cotton background QTL (Wanget al. Advanced backcross QTL analysis of fiber strength and fineness ina cross between Gossypium hirsutum and G. mustelinum. Frontiers in PlantScience, 2017, 8:1848. Keerio et al. used SLAF-seq to analyze the 107 gradients of upland cotton and wool cotton. A total of 3157 high-quality SNP markers were obtained, including 30 QTLs related to cotton fiber quality and 44 QTLs related to yield traits (Keerio et al. QTL Mapping for Fiber Quality and Yield TraitsBased on Introgression). Lines Derived from Gossypium hirsutum × G. tomentosum [J]. International Journal of Molecular Sciences, 2018, 19(1):243.).

Pooled pool sequencing (BSA-seq): For the target traits of the study, select the parents with extreme differences in phenotype to construct pooled pools, perform DNA sequencing on the parents and extreme pooled pools, detect loci associated with traits, and quickly mine candidate genes Methods. As early as 1991, Michelmore et al. (1991) successfully screened three markers closely linked to the downy mildew resistance gene Dm5/8 in the lettuce segregated population by using the pooled pool analysis (BSA) method for the first time (Michelmore et al. of markers linked to disease-resistance genes by bulkedsegregant analysis: a rapid method to detect markers in specific genomic regions by using segregating populations. Proceedings of the National Academy of Sciences of the United States of America, 1991, 88: 9828); The BSA method of high-throughput sequencing technology, namely BSA-seq technology, has been successfully used for fine mapping and candidate gene identification of QTLs related to important agronomic traits in crops (Ogiso et al. Detection of novel QTLs qDTH4.5 and qDTH6.3, which confer late heading under short-day conditions, by SSR marker-based and QTL-seq analysis. Breeding Science, 2017, 67: 101.; Pandey et al. QTL-seqapproach identified genomic regions and diagnostic markers for rust and lateleaf spot resistance in groundnut (Arachis hypogaea L.). Plant Biotechnology Journal, 2017, 15: 927.; Shu et al. QTL-seq for rapid identification of candidate genes for flowering time in broccoli×cabbage. Theoretical and Applied Genetics. 2018, 101:1-12). BSA-seq technology can achieve efficient and accurate fine-mapping of QTL/key gene segments related to important crop traits, but in cotton, the fine-mapping reports are mainly related to quality traits. Chen et al. (2015) used BSA-seq technology to map the recessive infinite branch gene gb_nb1 between two SNP markers about 600 kb on chromosome 16 (Chen et al. Genetic mapping of the nulliplex-branch gene (gb_nb1) in cotton using next-generation sequencing. Theoretical & Applied Genetics, 2015, 128:539-547). Zhu et al. (2017) used Lu BSA-seq technology to fine-map the virescent-1 gene in bud yellow and successfully identified the candidate gene GhCHL1 (Zhu et al. Rapid mapping and cloning of the virescent-1 gene in cotton by bulked segregant analysis-next generationsequencing and virus -induced gene silencing strategies. Journal of Experimental Botany, 2017, 68: 4125). Marina et al. (2017) used BSA-seq technology to discover SNP loci that were completely linked to the Li trait, and obtained the ultrashort fiber Li1 gene after population verification. There are few reports on the mapping of QTLs related to quantitative traits such as cotton fiber strength using this technology. Zhang et al. (2015) constructed a genetic map of upland cotton chromosome 25 through BSA and SSR markers, and explored cotton fiber length, strength and QTL for micronaire value (ZhangZhen, Li Junwen, Muhammad Jamshed, et al. High Resolution Consensus Mapping of Quantitative Trait Loci for Fiber Strength, Length and Micronaire on Chromosome 25 of the Upland Cotton (Gossypium hirsutum L.). PLoS ONE, 2015,10 (8): e0135430). By using the segregated large population constructed by the sister line as the female parent, the retest BSA pool was constructed according to the related traits, and the consensus segment was quickly obtained by high-throughput resequencing technology, which was identified as a candidate QTL, which has not been reported yet.

SUMMARY OF THE INVENTION

Cotton fiber strength is positively correlated with length and negatively correlated with lint. Therefore, in combination with the correlation between traits, the present invention uses sister line materials with similar genetic backgrounds and common male parents to construct separate large groups, and select extreme materials for each trait. Construct a mixed pool of BSA with high trait value and low trait value, and use high-throughput sequencing technology to quickly obtain major QTL.

The technical scheme provided by the invention is as follows: the invention provides a method for rapid identification of major QTLs of cotton-related traits by compound BSA-seq: using sister line materials with similar genetic backgrounds, Zhongmiansuo 60, a variety with excellent comprehensive traits, and a relatively high fiber quality The poor China Cotton Research Institute 60 selected line EZ60 (hereinafter referred to as EZ60) (National Cotton Germplasm Mid-term Bank, National Germplasm Unified Bank No.: M116025, No. 38 Huanghe Avenue, Development District, Anyang City, Henan Province, zip code: 455000) and the common parent In this paper, R014121 (National Cotton Germplasm Medium-term Bank, National Germplasm Unified Bank No.: ZM115357) respectively constructs F ₂ segregating populations containing 1000 individual plants, which are ideal materials for the study of quantitative trait inheritance, which can effectively eliminate the genetic background in the population. Interference can improve the accuracy of gene mapping of complex agronomic traits. Cotton fiber strength is positively correlated with length and negatively correlated with lint. Therefore, combined with extreme materials with related traits, mixed pools were constructed respectively. A total of 60×medium R014121 F ₂ populations of China Cotton Research Institute were constructed. The fiber strength, fiber length and lint of the R014121 F ₂ population in EZ60×medium were mixed, with a total of 6 groups of mixed pools. Use high-throughput sequencing technology to quickly obtain major QTLs.

The method for rapidly identifying the main effect QTL of cotton-related traits by compound BSA-seq of the present invention comprises the following steps:

(1) Two hybrid combinations of upland cotton were constructed by using sister line materials with similar genetic backgrounds with excellent comprehensive traits and lines with poor fiber quality and their common male parents. Among them, Combination I: varieties with excellent comprehensive traits × male parent , Combination II: line with poor fiber quality × male parent, obtain F ₂ segregation population and F _2:3 , F _{2: 4} population each containing 1000 individual plants, and accurately identify F ₂ , F _2:3 , F _2:4 population phenotypic data;

(2) According to the characteristics that cotton fiber strength is positively correlated with length and negatively correlated with lint content, the F ₂ populations of varieties with excellent comprehensive traits × male parent and lines with poor fiber quality × male parent were screened for high-strength materials per plant, Low-strength single-plant material; longer-length single-plant material, shorter-length single-plant material; higher-lint single-plant material and lower-lint single-plant material, extract leaf genomic DNA;

(3) Mixing equal amounts of genomic DNAs of high-strength individual plants and low-strength individual plants; longer-length individual plants and shorter-length individual plants; higher-lint individual plants and lower-lint individual plants of the two populations , build six groups of BSA mixed pools;

(4) High-throughput resequencing technology was used to sequence the DNA of the mixed pools. The sequencing depth of each pool was 30 times that of cotton genomic DNA. The QTL-seqr software package was used to analyze the results. The results of the six groups of BSA mixed pools were the same. Points to a consensus segment qFS-chrD02-1, which is the major gene locus for upland cotton fiber strength.

The method for rapidly identifying the main QTL of cotton-related traits by compound BSA, specifically, in step (1), the variety with excellent comprehensive traits is China Cotton Research Institute 60, and the line with poor fiber quality is China Cotton Research Institute 60 The line EZ60 is selected, and the common male parent is Zhong R014121. Combination I: China Cotton Research Institute 60 × Zhong R014121, and combination II: EZ60 × Zhong R014121. A specific embodiment provided by the method of the present invention is as follows:

(1) Two crosses of upland cotton were constructed using sister line materials with similar genetic backgrounds, Zhongmiansuo 60 with excellent comprehensive traits, and EZ60 with poor fiber quality and common male parent Zhong R014121. Among them, Combination I: Medium Cotton Institute 60×ZhongR014121, Combination II: EZ60×ZhongR014121, 1000 individual F ₂ segregated populations were obtained, and the phenotypic data of F ₂ , F _2:3 and F _2:4 populations were identified;

(2) According to the characteristics that cotton fiber strength is positively correlated with length and negatively correlated with clothing fraction, the fiber high-strength materials and low-strength materials in the F ₂ group of 60×zhong R014121 of the China Cotton Research Institute were screened out respectively; Shorter materials; materials with higher lint content and 30 plants with lower lint content; fiber high-strength materials and low-strength materials in the F ₂ population of EZ60×medium R014121; materials with longer lengths and materials with shorter lengths; 30 plants with high material and 30 plants with low lint content; extract genomic DNA from leaves;

(3) The genomic DNAs of high-strength individual plants and low-strength plants of the two populations; longer-length individual plants and shorter-length individual plants; higher-lint individual plants and lower-lint individual plants were mixed in equal amounts, respectively. Build 6 groups of BSA mixed pools;

(4) High-throughput resequencing technology was used to sequence the DNA of each pooled pool. The sequencing depth of each pooled pool was 30× that of cotton genomic DNA. The results were analyzed using the QTL-seqr software package in R language. Six groups of pooled pools were used. The results collectively point to a consensus segment (QTL) qFS-chrD02-1 (FS indicates fiber strength, chrD02 indicates D02 chromosome, QTL) qFS-chrD02-1 indicates the first fiber strength-related QTL mapped on D02 chromosome ), which is the main gene locus of upland cotton fiber strength.

The present invention has the following advantages:

The application of the present invention is to use sister line materials with similar genetic backgrounds, Zhongmiansuo 60, a variety with excellent comprehensive traits, and a line EZ60 with poor fiber quality and a common male parent Zhong R014121 to construct F2 segregated populations containing 1000 individual plants respectively. Cotton fiber strength is positively correlated with length and negatively correlated with lint. Therefore, combined with extreme materials with correlated traits, mixed pools were constructed respectively, and the common segment (QTL) was quickly obtained by double BSA-seq technology.

The China Cotton Research Institute 60 and the line EZ60 used in the present invention are sister line materials with similar genetic backgrounds, and the F2 segregated population is constructed with _R014121 in the common male parent, ideal materials for studying the inheritance of quantitative traits, which can effectively eliminate the interference of genetic backgrounds in the population, It can improve the accuracy of gene mapping of complex agronomic traits.

The isolated population was constructed based on the sister line materials, combined with the duplex BSA-seq technology and RNA-seq data of the extreme materials between related traits to efficiently and accurately perform fine mapping of fiber strength qFS-D02-1. The method of the present invention is used in cotton quantitative trait QTL mapping Not yet reported, it is a first.

Description of drawings

Fig. 1 is the G-value value and SNP-index result of the 60× medium R014121F ₂ length extreme mixed pool of the present invention;

Fig. 2 is the G-value value and SNP-index result of the 60× medium R014121F ₂ intensity extreme mixed pool of the present invention;

Fig. 3 is the G-value value and SNP-index result of the extreme mixed pool of R014121 F ₂ length in EZ60× of the present invention;

Fig. 4 is the G-value value and SNP-index result of 60× middle R014121 F ₂ lint extreme mixed pool of China Cotton Research Institute of the present invention;

These shared peak profiles point to the D02 chromosome.

Detailed ways

The present invention is further illustrated below by the detailed description of specific embodiments:

The method for rapidly identifying the main effect QTL of cotton-related traits by compound BSA-seq of the present invention has the following specific steps:

(1) Breeding method and process of F ₂ population for rapid identification of major QTLs for cotton-related traits by multiplex BSA-seq: Upland cotton cultivar Zhongmian 60 and its selected line EZ60 bred by Cotton Research Institute of Chinese Academy of Agricultural Sciences were used respectively. As the female parent, R014121 of the boll material with excellent fiber quality cultivated by the Cotton Research Institute of the Chinese Academy of Agricultural Sciences was used as the common male parent. In the summer of 2015, the hybrid combinations were prepared at the experimental farm of the Cotton Research Institute of the Chinese Academy of Agricultural Sciences (Anyang, Henan), respectively, 2016 F ₁ was planted in Anyang in 2017, and an F ₂ population consisting of 1000 individual plants was planted in Anyang in 2017. After selfing, F _{2: 3} families were obtained, and 300 F _{2: 3} families of the combination of 60×Zhong R014121 of China Cotton Research Institute were selected respectively. As well as 200 F _2:3 families of EZ60×R014121 combination, and combined with Hainan for breeding in winter, one self-crossing boll was selected for each individual plant in the family, and F _2:4 was obtained by mixing. The F ₂ population was harvested according to a single plant, and the F _2:3 and F _2:4 were harvested according to the family. For related phenotypes (strength, length and lint), the extreme material phenotype data of F ₂ , F _2:3 and F _2:4 populations were comprehensively considered, and the single plant with consistent extreme phenotype was selected as the target material for Subsequent BSA-seq analysis.

In the present invention, the 60 selected lines of China Cotton Research Institute EZ60 and China R014121 are from the National Cotton Germplasm Mid-term Bank (Address: No. 38, Huanghe Avenue, Development District, Anyang City, Henan Province, zip code: 455000), and the national germplasm unified bank numbers are respectively : M116025, ZM115357.

(2) Take the leaf samples of the F ₂ population, and use the CTAB method to extract 1000 individual plants of the combination of CMI 60×Zhong R014121, 1000 individual plants of the combination of EZ60×Zhong R014121 and the three parents CMI 60, EZ60 as well as the DNA of R014121.

(3) Extract the DNA of the extreme individual plants screened in step (1), detect the integrity and concentration of DNA by agarose gel electrophoresis and NANODROP 2000, and set up mixed pools (China Cotton Research Institute 60) according to different characteristics of different groups. ×Middle R014121 F ₂ group medium fiber high-strength material, low-strength material; longer-length material, shorter-length material; higher lint material, lower lint material, a total of 3 groups of mixed pools; EZ60 × F of middle R014121 ₂ groups of fiber high-strength materials, low-strength materials; longer-length materials, shorter-length materials; higher lint materials, lower lint materials (a total of 3 groups of mixed pools), each DNA in the mixed pool is mixed in equal amounts , a total of 6 groups of mixed pools were constructed.

(4) High-throughput resequencing technology was used to sequence 6 groups of mixed pool DNA and three parental DNAs. BWA software was used to compare the sequencing data to the reference genome, and GATK software was used to detect SNP and INDEL sites.

(5) Using the QTL-seqr software package to analyze the results of step (4), the results of the six groups of pooled pools point to a common main site qFS-chrD02-1 (Figure 1), and its interval on the physical map is 3.15 Mb (Table 1), this segment also contains the major gene loci for upland cotton fiber length (Fig. 2, Fig. 3), and lint (Fig. 4).

Table 1 Screening common interval information

Note: The starting position, length and other information on the D02 chromosome corresponding to the common peak map, the smallest QTL start position is 17241605bp, the end position is 20388962bp, and the size is 3.15MB.

Claims (5)

1. a method for the rapid identification of the main effect QTL of cotton-related traits by multiple BSA-seq, is characterized in that comprising the following steps: (1) Two hybrid combinations of upland cotton were constructed by using sister line materials with similar genetic backgrounds with excellent comprehensive traits and lines with poor fiber quality and their common male parents. Among them, Combination I: varieties with excellent comprehensive traits × male parent , Combination II: line with poor fiber quality × male parent, obtain F ₂ segregation population and F _2:3 , F _{2: 4} population each containing 1000 individual plants, and accurately identify F ₂ , F _2:3 , F _2:4 population phenotypic data; (2) According to the characteristics that cotton fiber strength is positively correlated with length and negatively correlated with lint content, the F ₂ populations of varieties with excellent comprehensive traits × male parent and lines with poor fiber quality × male parent were screened for high-strength materials per plant, Low-strength single-plant material; longer-length single-plant material, shorter-length single-plant material; higher-lint single-plant material and lower-lint single-plant material, extract leaf genomic DNA; (3) Mixing equal amounts of genomic DNAs of high-strength individual plants and low-strength individual plants; longer-length individual plants and shorter-length individual plants; higher-lint individual plants and lower-lint individual plants of the two populations , build six groups of BSA mixed pools; (4) High-throughput resequencing technology was used to sequence the DNA of the mixed pools. The sequencing depth of each pool was 30 times that of cotton genomic DNA. The QTL-seqr software package was used to analyze the results. The results of the six groups of BSA mixed pools were the same. Points to a consensus segment qFS-chrD02-1, which is the major gene locus for upland cotton fiber strength. 2. The method for rapidly identifying the main QTL of cotton-related traits by compound BSA according to claim 1, characterized in that: in step (1), the variety with excellent comprehensive traits is China Cotton Institute 60, and the fiber quality is poor The line is EZ60, the 60-selected line of China Cotton Research Institute, and the common male parent is Zhong R014121. Combination I: China Cotton Research Institute 60 × Zhong R014121, and combination II: EZ60 × Zhong R014121. 3. The method for rapidly identifying the main effect QTL of cotton-related traits by compound BSA according to claim 2, is characterized in that: in step (1), 60 selected lines of China Cotton Research Institute EZ60, National Germplasm Unified Bank Number: M116025, China R014121 National Germplasm Unified Bank No.: ZM115357, all stored in the National Cotton Germplasm Mid-term Bank. 4. The method for rapidly identifying the main effect QTL of cotton-related traits by compound BSA according to claim 2, is characterized in that: in step (2), according to the characteristics that cotton fiber strength is positively correlated with length, and negatively correlated with lint, The fiber high-strength materials and low-strength materials in the F ₂ population of China Cotton Research Institute 60×Zhong R014121 were screened out respectively; materials with longer lengths and materials with shorter lengths; materials with higher lint and 30 materials with lower lint; EZ60 In the F ₂ population of ×middle R014121, fiber high-strength material, low-strength material; longer-length material, shorter-length material; higher lint material and lower lint material with 30 plants each; the leaf genomic DNA was extracted. 5. The method for rapidly identifying the major QTLs of cotton-related traits by compound BSA according to claim 2, wherein in step (3), the six groups of BSA mixed pools are respectively: China Cotton Research Institute 60×zhong R014121 In the F ₂ group, there are 3 groups of mixed pools of fiber high-strength materials and low-strength materials; longer-length materials and shorter-length materials; higher lint materials and lower lint materials; and EZ60×Middle R014121 F ₂ group Medium-fiber high-strength material, low-strength material; longer-length material, shorter-length material; higher lint material, lower lint material, a total of 3 groups of mixed pools.

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