Comparative analysis of SIMILAR to RCD ONE(SRO)family from tetraploid cotton species and their diploid progenitors depict their significance in cotton growth and development

Background SRO(Similar to RCD1)genes family is largely recognized for their importance in the growth,develop-ment,and in responding to environmental stresses.However,genome-wide identification and functional characteri-zation of SRO genes from cotton species have not been reported so far.Results A total of 36 SRO genes were identified from four cotton species.Phylogenetic analysis divided these genes into three groups with distinct structure.Syntenic and chromosomal distribution analysis indicated uneven distribu-tion of GaSRO,GrSRO,GhSRO,and GbSRO genes on A2,D5 genomes,Gh-At,Gh-Dt,Gb-At,and Gb-Dt subgenomes,respectively.Gene duplication analysis revealed the presence of six duplicated gene pairs among GhSRO genes.In promoter analysis,several elements responsive to the growth,development and hormones were found in GhSRO genes,implying gene induction during cotton growth and development.Several miRNAs responsive to plant growth and abiotic stress were predicted to target 12 GhSRO genes.Organ-specific expression profiling demonstrated the roles of GhSRO genes in one or more tissues.In addition,specific expression pattern of some GhSRO genes dur-ing ovule development depicted their involvement in these developmental processes.Conclusion The data presented in this report laid a foundation for understanding the classification and functions of SRO genes in cotton.

Genetics of biochemical attributes regulating morpho-physiology of upland cotton under high temperature conditions

Background Cotton is a strategically important fibre crop for global textile industry.It profoundly impacts several countries’industrial and agricultural sectors.Sustainable cotton production is continuously threatened by the unpre-dictable changes in climate,specifically high temperatures.Breeding heat-tolerant,high-yielding cotton cultivars with wide adaptability to be grown in the regions with rising temperatures is one of the primary objectives of modern cotton breeding programmes.Therefore,the main objective of the current study is to figure out the effective breed-ing approach to imparting heat tolerance as well as the judicious utilization of commercially significant and stress-tolerant attributes in cotton breeding.Initially,the two most notable heat-susceptible(FH-115 and NIAB Kiran)and tolerant(IUB-13 and GH-Mubarak)cotton cultivars were spotted to develop filial and backcross populations to accom-plish the preceding study objectives.The heat tolerant cultivars were screened on the basis of various morphological(seed cotton yield per plant,ginning turnout percentage),physiological(pollen viability,cell membrane thermostabil-ity)and biochemical(peroxidase activity,proline content,hydrogen peroxide content)parameters.Results The results clearly exhibited that heat stress consequently had a detrimental impact on every studied plant trait,as revealed by the ability of crossing and their backcross populations to tolerate high temperatures.However,when considering overall yield,biochemical,and physiological traits,the IUB-13×FH-115 cross went over particularly well at both normal and high temperature conditions.Moreover,overall seed cotton yield per plant exhibited a posi-tive correlation with both pollen viability and antioxidant levels(POD activity and proline content).Conclusions Selection from segregation population and criteria involving pollen viability and antioxidant levels concluded to be an effective strategy for the screening of heat-tolerant cotton germplasms.Therefore,understanding acquired from this study can assist breeders identifying traits that should be prioritized in order to develop climate resilient cotton cultivars.

Genome-wide identification and analysis of the CNGC gene family in upland cotton under multiple stress conditions

Background The cyclic nucleotide-gated channel(CNGC)gene family plays a significant role in the uptake of both essential and toxic cations,and has a role in enhancing tolerance to various forms of abiotic stresses as well as the modulation of the heavy metal toxicity to plant through the absorption of heavy metals.Results A complete genome-wide identification and functional characterization of the cotton CNGC genes was carried out,in which 55,28,and 29 CNGC genes were identified in Gossypium hirsutum,G.raimondii,and G.arboreum,respectively.The protein encoded by the CNGC genes exhibited GRAVY value below zero,indicating their hydrophilic property.CNGC genes were unevenly distributed in 19 out of 26 chromosomes,in which the highest density were observed on Ah05,with 8 genes.High gene coverage was observed among the diploid cotton species,with CNGC genes mapped on all A chromosomes and on 11 out of 13 of D chromosomes.The majority of CNGC proteins were localized in the endoplasmic reticulum,nucleus,and plasma membrane.Gene expression analysis revealed the up-regulation of Gh_A01G0520(CNGC4)and Gh_D13G1974(CNGC5)across various forms of abiotic stresses.Moreover,down-regulation of Gh_A01G0520(CNGC4)and Gh_D13G1974(CNGC5)in CNGCs silenced plants caused the significantly reduced ability to tolerate drought and salt stresses.All CNGCs silenced plants were recorded to have significantly low content of antioxidants but relatively higher content of oxidant,including MDA and H_(2)O_(2).Furthermore,SPAD,CMS(cell membrane stability),ELWL(excised leaf water loss),SDW(shoot dry matter weight),and RDW(root dry matter weight)were all lower in CNGCs silenced plants compared with the wild type plants.Conclusion Significant reduction in antioxidant content and negative effects of physiological and morphological characters in CNGCs silenced plants has revealed the novel role of CNGC genes in enhancing cell integrity under abiotic stress conditions.These results provide vital information that will expand our understanding of the CNGC gene family in cotton and other plants,thus promoting the integration of these genes in the development of the environmental resilient plants.

Development of a core set of SNP markers for the identifi cation of upland cotton cultivars in China

Considering the advantages of single nucleotide polymorphisms（SNP） in genotyping and variety identification, the first set public SNP markers at Cotton Marker Database（http：//www.cottonmarker.org/） were validated and screened across standard varieties of cotton distinctness, uniformity and stability（DUS） test, aiming to obtain an appropriate set of core SNP markers suitable for upland cotton cultivars in China. A total of 399 out of 1 005 SNPs from 270 loci including 170 insertions-deletions（In Dels） were evaluated for their polymorphisms among 30 standard varieties using Sanger sequencing. As a result, 147 loci were sequenced successfully, 377 SNPs and 49 In Dels markers were obtained. Among the 377 SNP markers, 333 markers（88.3%） were polymorphic between Gossypium hirsutum and G. barbadense, while 164 markers（43.5%） were polymorphic within upland cotton. As for In Del markers, the polymorphic rate is relatively lower than that of SNP both between species and within species. The homozygous DNA locus ratio of 121 SNPs was higher than 86.2% while that of other 43 SNPs was less than 70%. Only 64 SNPs displayed completely homozygous genotypes among all of the detected upland cotton varieties with 100% homozygous DNA locus ratio. At last, a set of 23 pairs of core SNPs were achieved in view of avoidance of linkage, with polymorphism information content（PIC） values varying from 0.21 to 0.38 with an average of 0.28. Genotype characteristics and genetic diversity were analyzed based on the set of core markers, while 40 pairs of core simple-sequence repeats（SSR） primers comprised of 10 sets of four multiplex PCR combinations were also used for analysis based on fluorescence detection system. Comparison results indicated that the genetic diversity level was almost equal, while various varieties were significantly different from each other. Genetic relationship revealed by SSR markers is related to geographic source to a certain extent. Meanwhile clustering results analyzed by SNP markers are more consistent with kinship, which demonstrated that the screen strategy for core SNP marker is effective.

Effects of soil salinity on rhizosphere soil microbes in transgenic Bt cotton fields

With increased cultivation of transgenic Bacillus thuringiensis （Bt） cotton in the saline alkaline soil of China, assessments of transgenic crop biosafety have focused on the effects of soil salinity on rhizosphere microbes and Bt protein residues. In 2013 and 2014, investigations were conducted on the rhizosphere microbial biomass, soil enzyme activities and Bt protein contents of the soil under transgenic Bt cotton （variety GK19） and its parental non-transgenic cotton （Simian 3） cultivated at various salinity levels （1.15, 6.00 and 11.46 dS m-1）. Under soil salinity stress, trace amounts of Bt proteins were ob- served in the Bt cotton GK19 rhizosphere soil, although the protein content increased with cotton growth and increased soil salinity levels. The populations of slight halophilic bacteria, phosphate solubilizing bacteria, ammonifying bacteria, nitrifying bacteria and denitrifying bacteria decreased with increased soil salinity in the Bt and non-Bt cotton rhizosphere soil, and the microbial biomass carbon, microbial respiration and soil catalase, urease and alkaline phosphatase activity also decreased. Correlation analyses showed that the increased Bt protein content in the Bt cotton rhizosphere soil may have been caused by the slower decomposition of soil microorganisms, which suggests that salinity was the main factor influencing the relevant activities of the soil microorganisms and indicates that Bt proteins had no clear adverse effects on the soil microorganisms. The results of this study may provide a theoretical basis for risk assessments of genetically modified cotton in saline alkaline soil.

Mechanism of floral scent production in Osmanthus fragrans and the production and regulation of its key floral constituents,β-ionone and linalool

Sweet osmanthus(Osmanthus fragrans Lour.)is among the top ten most well-known flowers in China and is recognized as both an aromatic plant and ornamental flower.Here,manual sectioning,scanning electron microscopy,and transmission electron microscopy of sweet osmanthus petals revealed that large amounts of lipids are present inside the petal cells and on the cell surfaces.However,no secretory structures were observed.Instead,the petal cells protrude slightly outward,and the surfaces of the cells are adorned with highly regular brush-shaped hairs.The surfaces of the‘Yingui’petals possessed mostly curled and more numerous hairs,whereas the‘Dangui’petals possessed fewer brush-shaped and more sparsely arranged hairs.In addition,many granular substances were attached to the brush-shaped hairs,and the granules were denser on the hairs of the‘Yingui’petals compared to the hairs on the‘Dangui’petals.Furthermore,35 aromatic components in the‘Yingui’petals and 30 aromatic components in the‘Dangui’petals were detected via GC-MS.The main aromatic component of the‘Yingui’petals wasβ-ionone,whereas that of the‘Dangui’petals was linalool and its oxides.Transcriptome sequencing and qRT-PCR indicated that the highβ-ionone content in the‘Yingui’petals was due to the overexpression of CCD1 and CCD4 and that the high linalool content in the‘Dangui’petals was due to the overexpression of MECS,HDR,IDI1,and LIS1,which function upstream of the linalool synthetic pathway.In particular,the expression levels of CCD4 and LIS1 were upregulated by 5.5-and 5.1-fold in the‘Yingui’and‘Dangui’petals,respectively.One transcription factor(ERF61)was cloned and named,and the expression pattern of ERF61 in sweet osmanthus petals was found to be generally consistent with that of CCD4.Tobacco transformation experiments,yeast one-hybrid experiments,and electrophoretic mobility shift assays indicated that ERF61 binds to the CCD4 promoter and stimulates CCD4 expression,thereby regulating the synthesis ofβ-ionone in sweet osmanthus petals.

The biotypes and host shifts of cotton-melon aphids Aphis gossypii in northern China

Aphis gossypfi is a globally distributed species and therefore has a highly variable life cycle. Populations of A. gossypii in northern China exhibit greater genotypic diversity and a broader host range, yet the details of life cycles of different biotypes is still unclear. In this study, the Cytb and 16S gene regions of A. gossypfi collected from 5 common summer hosts and 4 primary hosts were analyzed. A total of 57 haplotypes were obtained from 1 046 individual A. gossyp# sequences. The sequence included 44 variable sites, 27 of which were parsimony informative sites and 17 of which were singleton variable sites. The most frequent 3 haplotypes were found in 896 individuals, representing a total of 85.7% of all individuals and 36 haplotypes were found in 1 individual. A neighbor-joining tree was constructed using 21 haplotypes that were found in more than 2 individuals. Considering the individual host plant, 5 biotypes were identified. Type 1 corresponded exactly to the cucurbit host-race and the other 4 biotypes were found as cotton host-races. Type 3 was the most abundant biotype in cotton fields in northern China.

Identification and expression analysis of group Ⅲ WRKY transcription factors in cotton

The WRKY proteins constitute a large family of transcription factors in plants containing highly conserved WRKYGQK sequences and zinc-finger-like motifs. To comprehensively study WRKY III genes in cotton, we analyzed the genome sequences of Gossypium hirsutum, G. raimondii and G. arboreum. According to the three genome sequences, 18 group III Gh WRKY genes were identified in G. hirsutum, 12 both in G. raimondii and G. arboreum. Phylogenetic and motif analysis showed that proteins with high similarities could be clustered together and had the same motif components. The ratios of non-synonymous（Ka） to synonymous（Ks） of the Gh WRKY to Gr WRKY or Ga WRKY were lower than 1, which indicated that group III WRKY genes in Gossypium species are under purifying selection. Expression analysis revealed that group III Gh WRKY genes expressed during fiber development and leaf senescence, and most of them could be induced by salicylic acid（SA）, jasmonic acid（JA）, ethylene, abscisic acid（ABA）, mannitol, and Na Cl both in roots and cotyledons. Our study gives a briefly introduction on cotton group III WRKY genes and implicates their potential function in cotton fiber development, leaf senescence and abiotic stresses.

Effects of plant density on cotton yield components and quality

Yield and ifber quality of cotton even varies within locules in a bol, but it is not clear how yield components and quality parameters are altered across seed positions of a locule （SPL）. A ifeld experiment was arranged in a split plot design with transgenic insect resistant Bt （Bacilus thuringiensis） cotton hybrid cultivar CRI75 and conventional cultivar SCRC28 as the main plots, and three plant densities （15000, 51000 and 87000 plants ha–1） as the subplots in 2012 and 2013 at Anyang, Henan Province, China. Cotton was hand harvested by node and fruiting position, and then seeds of the ifrst fruiting posi-tion bols from nodes 6–10 were separated by SPL. The effects of plant density on lint yield, ifber quality, especialy across SPL were determined. It was showed that plant densities of 51000 and 87000 plants ha–1 increased lint yield by 61.3 and 65.3% in 2012 and 17.8 and 15.5% in 2013 relative to low plant density （15000 plants ha–1）, however, no signiifcant differ-ence was observed between 51000 and 87000 plants ha–1. The number of bols （bol density） increased while bol weight decreased as plant density raised, and no signiifcant changes occured in lint percentage in 2013 but increased with plant density in 2012. The number of bols in upper nodes and distal fruiting positions, the number of seeds per bol, seed area （SA） and seed vigor index increased with decreasing plant density. Seed area was found to be greater from the base to the middle compared to the apex of a locule. Mote frequency （MF） increased as plant density increased, and ifber quality was the best at the middle of the locule regardless of plant density. As the number of ifbers per seed area is geneticaly determined, adjusting plant density to produce more seeds and greater seed area can be a potentialy promising alternative to improve lint yield in cotton. These ifndings might be of great importantance to cotton breeding and ifled management.

Cotton cultivation technology with Chinese characteristics has driven the 70-year development of cotton production in China

Since the founding of the People’s Republic of China in 1949,significant achievements have been made in cotton production in China.China has maintained its position as the world’s largest cotton producer for 33 years(1983–2015),with average annual increases of 3.5 and 3.9% in the unit yield and total output of cotton,respectively.Cotton production has played an extremely important role in the development of the national economy and the improvement of living standards.Although the cotton planting area has been reduced in recent years,the total output has remained relatively unchanged due to the continuous increase in the unit yield.China’s dominant position in global cotton production is undoubtedly attributed to the progress and development of cotton cultivation technology.Over the past 70 years,China has established a high-yielding and high-efficiency cotton cultivation mode that corresponds to its national conditions,including a large population and a limited land area.Furthermore,cotton cultivation technology is constantly being innovated and developed to keep pace with the times.In this paper,we review the development of cotton production and cultivation in China over the past 70 years,with a particular focus on the innovation and development of cotton cultivation technology with Chinese characteristics.This review is intended to provide guidance for the sustainable development of China’s cotton production in the future and to provide a reference for global cotton production.

Estimating light interception using the color attributes of digital images of cotton canopies

Crop growth and yield depend on canopy light interception （LI）. To identify a low-cost and relatively efficient index for measuring LI, several color attributes of red-green-blue （RGB）, hue-saturation-intensity （HSI）, hue-saturation-value （HSV） color models and the component values of color attributes in the RGB color model were investigated using digital images at six cotton plant population densities in 2012-2014. The results showed that the LI values followed downward quadratic curves after planting. The red （R）, green （G） and blue （B） values varied greatly over the years, in accordance with Cai＇s research demonstrating that the RGB model is affected by outside light. Quadratic curves were fit to these color attributes at six plant population densities. Additionally, linear regressions of LI on every color attribute revealed that the hue （H） values in HSI and HSV were significantly linearly correlated with LI with a determination coefficient （R2）〉0.89 and a root mean square error （RMSE）=0.05. Thus, the H values in the HSI and HSV models could be used to measure LI, and this hypothesis was validated. The H values are new indexes for quantitatively estimating the LI of heterogeneous crop cano- pies, which will provide a theoretical basis for optimizing the crop canopy structure. However, further research should be conducted in other crops and under other growing and environmental conditions to verify this finding.

Early ABA-stimulated maintenance of Cl^(−) homeostasis by mepiquat chloride priming confers salt tolerance in cotton seeds

Mepiquat chloride(MC)priming alleviates the effects of salt stress during seed germination in cotton(Gossypium hirsutum L.),but the mechanisms underlying its effects are unknown.We found that MC priming increases salt tolerance,as evidenced by marked increases in seed vigor and germination rates,and alleviated salt toxicity by reducing Cl^(−)accumulation in germinating seeds.Consistently,electrophysiological experiments revealed that the seeds with MC priming displayed superior Cl^(−)exclusion ability in the root apex.These beneficial effects of MC priming were abolished by the abscisic acid(ABA)-synthesis blocker fluridone under salt stress.MC priming induced an early response to acclimatization and stress,as indicated by rapidly increasing ABA content during initial exposure to salt stress.Transcriptome analyses revealed that MC priming induced an array of differentially expressed genes(DEGs)in germinating seeds.The most noticeable changes in germinating seeds were MC priming-induced increases in the expression of DEGs encoding components of ABA biosynthesis,ABA catabolism,and ABA signaling pathways under salt stress.MC priming also increased the expression of some DEGs encoding Cl^(−)ion transporters(e.g.CCC,SLAC1/SLAH1/SLAH3,CLC,and ALMT9)in germinating seeds.These results indicate that MC priming-induced ABA contributes to Cl^(−)homeostasis in tissues and acts as a positive regulator of salt tolerance via regulation of Cl^(−)transporters(particularly CCC and SLAC1/SLAH1/SLAH3).Taken together,these findings shed light on the molecular mechanism underlying MC-mediated tolerance to salt stress during seed germination.

Genetic structure,gene flow pattern,and association analysis of superior germplasm resources in domesticated upland cotton(Gossypium hirsutum L.)

Gene flow patterns and the genetic structure of domesticated crops like cotton are not well understood.Furthermore,marker-assisted breeding of cotton has lagged far behind that of other major crops because the loci associated with cotton traits such as fiber yield and quality have scarcely been identified.In this study,we used 19 microsatellites to first determine the population genetic structure and patterns of gene flow of superior germplasm resources in upland cotton.We then used association analysis to identify which markers were associated with 15 agronomic traits(including ten yield and five fiber quality traits).The results showed that the upland cotton accessions have low levels of genetic diversity(polymorphism information content=0.427),although extensive gene flow occurred among different ecological and geographic regions.Bayesian clustering analysis indicated that the cotton resources used in this study did not belong to obvious geographic populations,which may be the consequence of a single source of domestication followed by frequent genetic introgression mediated by human transference.A total of 82 maker-trait associations were examined in association analysis and the related ratios for phenotypic variations ranged from 3.04% to 47.14%.Interestingly,nine SSR markers were detected in more than one environmental condition.In addition,14 SSR markers were co-associated with two or more different traits.It was noteworthy that NAU4860 and NAU5077 markers detected at least in two environments were simultaneously associated with three fiber quality traits(uniformity index,specific breaking strength and micronaire value).In conclusion,these findings provide new insights into the population structure and genetic exchange pattern of cultivated cotton accessions.The quantitative trait loci of domesticated cotton identified will also be very useful for improvement of yield and fiber quality of cotton in molecular breeding programs.

Identification and screening of nitrogenefficient cotton genotypes under low and normal nitrogen environments at the seedling stage

Background： Large quantities of nitrogen （N） fertilizer applied to cotton cropping systems support high yields but cause adverse environmental impacts such as N20 emission and water eutrophication. The development of cotton cultivars with higher N use efficiencies suitable for low-N conditions is therefore important for sustainable production. In this study, we evaluated 100 cotton genotypes in 2016 for N use efficiency and related traits at the seedling stage. Methods： Sand culture experiment was conducted with low N levels （0.01 g.kg i） or normal N levels （0.1 g.kg i）. We investigated plant height, SPAD value （soil plant analysis development chlorophyll meter）, dry weight, N accumulation, N utilization efficiency, and N uptake efficiency. Through descriptive statistics, principal component analysis and heatmap clustering analysis, we confirmed the evaluation index system of N-efficient genotypes and the classification of N-efficient genotypes. Results： Significant differences were observed among N levels and genotypes for all agronomic traits and N levels. Coefficients of variation varied greatly and ranged from 6.7N28.8 and 7.4N20.8 under low-N and normal-N treatment, respectively. All traits showed highly significant positive correlations with each other, except SPAD value. The principal components under both N levels were similar, showing that total dry weight, aboveground dry weight, total N accumulation, and N uptake efficiency were important components. We confirmed these four traits as suitable screening indexes for low N tolerance. Based on the results of heatmap clustering and scatter diagram analysis of N efficiency value, 10 genotypes were found low-N tolerant, in which five varieties were inefficient under both low and normal N conditions, while four varieties were found efficient under low-N conditions but inefficient under normal-N conditions. Only one variety was efficient under both low and normal-N conditions. Meanwhile, 20 genotypes were identified as low-N sensitive ones, in which 19 genotypes were inefficient under low-N conditions but efficient under normal-N conditions, one variety was inefficient under both low and normal-N conditions. Conclusion： We preliminarily identified Kashi as a low-N tolerant and N-efficient cotton genotype, and CCRI 64 as a low- N sensitive and N-inefficient cotton genotype. Further studies should be carried out to verify the yield and heritability effect of specific genotypes in the field.

A review of the pathogenicity mechanism of Verticillium dahliae in cotton

Verticillium wilt,caused by the notorious fungal pathogen Verticillium dahliae,is one of the main limiting factors for cotton production.Due to the stable dormant structure microsclerotia,long-term variability and co-evolution with host plant,its pathogenicity mechanism is very complicated,and the interaction mechanism between pathogen and host plant is also unclear.So identification and functional analysis of the genes involved in the pathogenicity or virulence of this fungus will benefit to uncover the molecular pathogenic mechanism of V.dahliae.In this review,many multifunction genes covering microsclerotia development,pathogen infection,effector proteins,transcription factors,horizontal gene transfer and trans-kingdom RNA silencing have been summarized to provide a theoretical basis to deep understand the molecular pathogenicity mechanism of V.dahliae and promote to effectively control Verticillium wilt.Furtherly,these pathogenicity-related genes may be considered as targets for effective control of Verticillium wilt in cotton.

Efficacy evaluation and mechanism of Bacillus subtilis EBS03 against cotton Verticillium wilt

Background:In our previous study,a strain EBS03 with good biocontrol potential was screened out of 48 strains of cotton endophyte Bacillus subtilis by evaluating the controlling effect against cotton Verticillium wilt.However,its mechanism for controlling Verticillium wilt remains unclear.The objective of this study was to further clarify its con-trolling effect and mechanism against cotton Verticillium wilt.Results:The results of confrontation culture test and double buckle culture test showed that the inhibitory effects of EBS03 volatile and nonvolatile metabolite on mycelium growth of Verticillium dahliae were 70.03%and 59.00%,respectively;the inhibitory effects of sporulation and microsclerotia germination were 47.16%and 70.06%,respec-tively.In the greenhouse test,the EBS03 fermentation broth root irrigation had the highest controlling effect at 87.11%on cotton Verticillium wilt,and significantly promoted the growth of cotton seedlings.In the field experi-ment,the controlling effect of EBS03 fermentation broth to cotton Verticillium wilt was 42.54%at 60 days after cotton sowing,and the boll number per plant and boll weight in EBS03 fermentation broth seed soaking,root irrigation,and spraying treatments significantly increased by 19.48%and 7.42%,30.90%and 2.62%,15.99%and 9.20%,respec-tively.Furthermore,EBS03 improved the resistance of cotton leaves against the infection of V.dahliae,and induced the outbreak of reactive oxygen species and accumulation of callose.In addition,the results of real time fluorescent quantitative polymerase chain reaction(RT-qPCR)detection showed that EBS03 significantly induced upregulation expression level of defense-related genes PAL,POD,PPO,and PR10 in cotton leaves,enhanced cotton plant resistance to V.dahliae,and inhibited colonization level of this fungal pathogen in cotton.Conclusion:Bacillus subtilis EBS03 has a good biological defense capability,which can inhibit the growth and coloni-zation level of V.dahliae,and activate the resistance of cotton to Verticillium wilt,thus increase cotton yield.

Genetic Analysis of Earliness Traits in Short Season Cotton (Gossypium hirsutum L.)

Inheritance and interrelationship of phenotype and genotype of earliness traits were evaluated in a diallel analysis involving six early-maturing parents. Date of first square （DFS）, date of first flower （DFF）, date of first open boll （DFOB）, number of node first sympodial branch （NNFSB）, and harvested rate before frost （HRBF） as earliness traits of six parents, 15 F1 hybrids and 15 F2 progenies were investigated from 2005 to 2008. The experiment design was a randomized complete block design with three replications. Additive, dominance and epistasis effects were analyzed with ADAA （additive- dominance-epistasis） model. HRBF, DFF, and DFOB showed significant additive genetic variances. Heritability estimates ranged from 0.088 （HN, narrow sense） and 0.416 （HNE, environment interaction） for HRBF, to 0.103 （HN） and 0.524 （HNE） for DFF, and to 0.187 （HN） and 0.519 （H~） for DFOB. Dominance genetic effects for DFS, DFF, DFOB, and NNSFB were stronger than additive effects. Additive-by-additive epistatic effects for DFS, DFOB, and NNSFB were detected and affected by environment. Correlation analysis showed generally that HRBF had a significant negative genetic and phenotypic correlation with DFS, DFOB, and NNFSB; DFS had significant positive genetic and phenotypic correlations with DFF, DFOB, and NNFSB; significant positive genetic and phenotypic correlations were also detected between DFF and DFOB, DFF and NNFSB, DFOB and NNFSB. The results showed that the lower the node to the first fruiting branch and the shorter the plant, the earlier was the onset of squaring, flowering, and boll opening, the higher was the harvest rate before frost. Heredity of earliness traits among parents and their hybrids were also detected and parents A1, A2, Bl, B2, and B3 could be used to improve earliness traits of short season cotton cultivars.

Comparative performance of hybrid generations reveals the potential application of F_(2)hybrids in upland cotton

Background:The utilization of heterosis has greatly improved the productivity of cotton worldwide.However,a major constraint for the large-scale promotion of F_(1) hybrid cotton is artificial emasculation and pollination.This study proposed the potential utilization of F_(2) hybrids to improve upland cotton production through a comparative evaluation of hybrid generations.Results:Eight upland cotton varieties were analyzed and crosses were made according to NCII incomplete diallel cross-breeding design in two cotton belts of China.Variance analysis revealed significant differences in agronomic,yield,and fiber quality in both generations and environments.The broad-sense heritability of agronomic and yield traits was relatively higher than quality traits.Furthermore,the narrow-sense heritability of some traits was higher in F_(2) than in the F_(1) generation in both cotton belts.Overall,parental lines Zhong901,ZB,L28,and Z98 were observed with maximum combining ability while combinations with strong special combining ability were ZB×DT,L28×Z98,and ZB×851.The yield traits heterosis was predominant in both generations.However,the level of heterosis was altered with trait,hybrid combination,generation,and environment.Interestingly,L28×Z98 performed outstandingly in Anyang.Its lint yield(LY)was 24.2%higher in F_(1) and 11.6%in F_(2) than that of the control Ruiza 816.The performance of SJ48×Z98 was excellent in Aral which showed 36.5%higher LY in F_(2)and 10.9%in F_(2)than control CCRI 49.Further results revealed most hybrid combinations had shown a low level of heterosis for agronomic and fiber quality traits in both generations.Comparatively,ZB×DT and L28×Z98 showed hybrid vigor for multiple traits in both generations and cotton belts.It is feasible to screen strong heterosis hybrid combinations with fine fiber in early generations.In the two environments,the correlation of some traits showed the same trend,and the correlation degree of Anyang site was higher than that of Aral site,and the correlation of some traits showed the opposite trend.According to the performance of strong heterosis hybrid combinations in different environments,the plant type,yield and fiber traits associated with them can be improved according to the correlation.Conclusions:Through comparative analysis of variance,combining ability,and heterosis in F_(2)and F_(2)hybrids in different cotton belts,this study proposed the potential utilization of F_(2)hybrids to improve upland cotton productivity in China.

Genetic analysis of yield and fiber quality traits in upland cotton(Gossypium hirsutum L.) cultivated in different ecological regions of China

Background:Cotton is an important fiber crop worldwide.The yield potential of current genotypes of cotton can be exploited through hybridization.However,to develop superior hybrids with high yield and fiber quality traits,information of genetic control of traits is prerequisite.Therefore,genetic analysis plays pivotal role in plant breeding.Results:In present study,North Carolina II mating design was used to cross 5 female parents with 6 male parents to produce 30 intraspecific F1cotton hybrids.All plant materials were tested in three different ecological regions of China during the year of 2016-2017.Additive-dominance-environment(ADE)genetic model was used to estimate the genetic effects and genotypic and phenotypic correlation of yield and fiber quality traits.Results showed that yield traits except lint percentage were mainly controlled by genetic and environment interaction effects,whereas lint percentage and fiber quality traits were determined by main genetic effects.Moreover,dominant and additiveen vironine nt in teraction effects had more influence on yield traits,whereas additive and domi nance-e nviron ment interaction effects were found to be predominant for fiber traits.Broad-sense and its interaction heritability were significant for all yield and most of fiber quality traits.Narrow-sense and its interaction heritability were non-significant for boll number and seed cotton yield.Correlation analysis indicated that seed cotton yield had significant positive correlation with other yield attributes and non-significant with fiber quality traits.All fiber quality traits had signiflcant positive correlation with each other except micronaire.Conclusions:Results of current study provide important information about genetic control of yield and fiber quality traits.Further,this study identified that parental lines,e.g.,SJ48-1,ZB-1,851-2,and DT-8 can be utilized to improve yield and fiber quality traits in cotton.

The cotton mitochondrial chimeric gene orf610a causes male sterility by disturbing the dynamic balance of ATP synthesis and ROS burst

Plant cytoplasmic male sterility(CMS)is maternally inherited and often manifested as aborted pollen development,but the molecular basis of abortion remains to be identified.To facilitate an investigation of CMS in cotton,the complete sequence of cotton mitochondrial(mt)genome for CMS-D2 line ZBA was determined.The mt genome was assembled as a single circular molecule with 634,036 bp in length.A total of 194 ORFs,36 protein-coding genes,six r RNAs,and 24 t RNAs were identified.Several chimeric genes encoding hypothetical proteins with transmembrane domains were identified.Among them,a previously unknown chimeric gene,orf610a,which is composed of atp1 and a 485-bp downstream sequence of unknown nature,was identified.RT-PCR and q RT-PCR validation indicated that orf610a was expressed specifically in a sterile line.Ectopic expression of orf610a in yeast resulted in excessive accumulation of reactive oxygen species and reduction in ATP content,in addition to inhibition of cellular growth.Transgenic A.thaliana overexpressing orf610a fused with a mitochondrial targeting peptide displayed partial male sterility.Interaction between ORF610a and the nuclear-encoded protein RD22 indicated an association between ORF610a and pollen abortion.Positive feedback during transcriptional regulation between nuclear regulatory factors and the mt CMS gene may account for the male sterility of ZBA.