| Cotton possesses certain physical features,including leaf and stem trichomes that help plants deter damage caused by insect pests,and to some extent,from abiotic factors as well.Among those features,trichomes?pubescence?hold a special place as the first line of defense and a management tool against sucking insects of cotton.Different pests of cotton?whiteflies,aphids,jassids,and boll weevil?severely damage the yield and quality of the crop.Likewise,whiteflies,aphids,jassids,and other insect pests are considered as potential carriers for cotton leaf curl viruses and other diseases.Apart from incorporating mechanical mechanisms in cotton to deter pests,production of naturally pigmented cotton fibers holds a significant place in textile industry.The naturally colored cotton has grown in recent years because it may reduce pollution from dyeing process.However,there are several drawbacks of color cotton,i.e.less color variation,low lint yield,poor fiber quality,low marketing demand and lack of marketing facilities.Fiber quality traits are considered as complex quantitative traits having negative relationship with yield and fiber color.Therefore,genetic improvement in fiber quality of colored cotton is one of main challenges encountered by cotton breeders.Genotyping by sequencing?GBS?study was conducted to understand and explore the quantitative trait loci?QTLs?governing color fiber,leaf and stem hairy?pubescence?and fiber qualities.A total of 224 F2 individuals developed from an intraspecific cross?densely haired cotton?Liaoyang duomao mian?×hairless color cotton?Zong 128??and characterized phenotypically for leaf and stem pubescence and fuzz color in different environments.Here we identify and report significant QTLs?quantitative trait loci?associated with leaf and stem pubescence,fuzz color,and the response of plant under pest?aphid?infestation.Five consistent and stable QTLs for leaf,two QTLs for stem pubescence,three QTLs related to plant responses under aphid attack and six QTLs identified for fuzz color trait.Further,we identified putative genes colocalized on chromosome A06 governing mechanism for trichome development and host–pest interaction.To understand the mechanisms of fiber quality and fiber color,we used a RIL?F8?population previously developed through an intraspecific cross between Zong128?Brown parent?and white cotton?Liaoyang duomao mian?in varied environments.We detected a total of 51 QTLs related to lint and fuzz color and 24 QTLs were found consistent in at least two environments.Out of 24 QTLs,six were located on At sub-genome and 18 QTLs were located on Dt sub-genome.96 QTLs were identified for different fiber quality traits like fiber length?FL?,fiber strength?FS?,fiber elongation?FE?and fiber micronaire?MIC?.We identified 21 consistent QTLs across different environments.We also found clustered QTL region for fiber length and fiber micronaire on chromosome D12.This is most useful and interesting region to further explore and mine for candidate genes identification and manipulation.Our study provides a comprehensive insight into genetic architecture that can be employed to improve molecular marker-assisted breeding programs aimed at developing biotic?insect pests?resilient color cotton cultivars. |
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