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 Diversity,Population Structure,and Genome-Wide Association Study of Seven Agronomic Traits in 273 Diverse Upload Cotton Accessions

Upland cotton(Gossypium hirsutum)is the most important plant producing natural fibers for the textile industry.In this study,we first investigated the phenotypic variation of seven agronomic traits of 273 diverse cotton accessions in the years 2017 and 2018,which were from 18 geographical regions.We found large variations among the traits in different geographical regions and only half of the traits in either years 2017 or 2018 followed a normal distribution.We then genotyped the collection with 81,612 high quality SNPs.Phylogenetic tree and population structure revealed a diverse genetic structure of the core collection,and geographical diversification was an important factor,but account for part of the variances of genetic diversification.We then performed genome-wide association study for the seven traits in the years 2017 and 2018,and the average values of each trait in the two years,respectively.We identified a total of 19 significant marker-trait associations and found that Pollen Ole e 1 allergen/extension could be the candidate gene associated with the fall-off cotton bolls from the last three branches.In addition,large variations were observed for the heritability of traits in the years 2017 and 2018.These results provide new potential candidate genes for further functional validation,which could be useful for genetic improvement and breeding of new cotton cultivars with better agronomic performances.

Genome-wide association study of micronaire using a natural population of representative upland cotton(Gossypium hirsutum L.)

Background: Micronaire is a comprehensive index reflecting the fineness and maturity of cotton fiber.Micronaire is one of the important internal quality indicators of the cotton fiber and is closely related to the value of the cotton fiber.Understanding the genetic basis of micronaire is required for the genetic improvement of the trait.However,the genetic architecture of micronaire at the genomic level is unclear.The present genome-wide association study(GWAS)aimed to identify the genetic mechanism of the micronaire trait in 83 representa:tive upland cotton lines grown in multiple environments.Results GWAS of micronaire used 83 upland cotton accessions assayed by a Cotton 63 K Illumina Infinium single nucleotide polymorphism(SNP)array.A total of 11 quantitative trait loci(QTLs)for micronaire were detected on 10 chromosomes.These 11 QTLs included 27 identified genes with specific expression patterns.A novel QTL,qFM-A12–1,included 12 significant SNPs,and GhFLA9 was identified as a candidate gene based on haplotype block analysis and on strong and direct linkage disequilibrium between the significantly related SNPs and gene.GhFLA9 was expressed at a high level during secondary wall thickening at 20∼25 days post-anthesis.The expression level of GhFLA9 was significantly higher in the low micronaire line(Msco-12)than that in the high micronaire line(Chuangyou-9).Conclusions: This study provides a genetic reference for genetic improvement of cotton fiber micronaire and a foundation for verification of the functions of GhFLA9.

Genome-wide identification,characterization,and expression analysis of aluminum-activated malate transporter genes(ALMTs)in Gossypium hirsutum L.

Aluminum-activated malate transporters(ALMT)are widely involved in plant growth and metabolic processes,including adaptation to acid soils,guard cell regulation,anion homeostasis,and seed development.Although ALMT genes have been identified in Arabidopsis,wheat,barley,and Lotus japonicus,little is known about its presence in Gossypium hirsutum L.In this study,ALMT gene recognition in diploid and tetraploid cotton were done using bioinformatics analysis that examined correlation between homology and evolution.Differentially regulated ALMT genetic profile in G.hirsutum was examined,using RNA sequencing and qRT-PCR,during six fiber developmental time-points,namely 5 d,7 d,10 d,15 d,20 d,and 25 d.We detected 36 ALMT genes in G.hirsutum,which were subsequently annotated and divided into seven sub-categories.Among these ALMT genes,34 had uneven distribution across 14/26 chromosomes.Conserved domains and gene structure analysis indicated that ALMT genes were highly conserved and composed of exons and introns.The GhALMT gene expression profile at different DPA(days post anthesis)in different varieties of G.hirsutum is indicative of a crucial role of ALMT genes in fiber development in G.hirsutum.This study provides basis for advancements in the cloning and functional enhancements of ALMT genes in enhancing fiber development and augmenting high quality crop production.