Genetic variability for yield and fiber related traits in genetically modified cotton

Background:Cotton(Gossypium hirsutum L.)is grown for fiber and oil purposes in tropical and sub-tropical areas of the world.Pakistan is the 4th largest producer of cotton.It has a significant contribution in the GDP of Pakistan.Therefore,the present study was performed to assess the genetic variations and genetic diversity of yield and fiber quality traits in cotton and to analyze the associations present among them.Results:Analysis of variance exhibited significant variation for all studied traits except total number of nodes and the height to node ratio.The phenotypic coefficient of variation was higher than the genotypic coefficient of variation for all studied traits.Plant height,monopodial branches,total number of bolls,lint index,seed index,and seed cotton yield displayed high heritabilities in a broad sense with maximum genetic advanee.Correlation analysis revealed that seed cotton yield had a significant positive association with plant height,the nu mber of monopodial branches,the nu mber of sympodia I branches,ginning outturn(GOT),the number of bolls,seed per boll,seed index,uniformity index,the number of sympodial branches,reflectance,and seed index at the genotypic level while a significant positive relationship was observed with plant height,the number of sympodial branches,boll number,and GOT.Plant height,monopodial branches,GOT,boll weight,seeds per boll,and short fiber index exerted direct positive effects on seed cotton yield.The first 6 principal component analysis(PCs)out of the total fourteen PCs displayed eigenvalues(>1)and had maximum share to total variability(82.79%).The attributes that had maximum share to total divergence in eluded plant height,uniformity index,the nu mber of sympodial branches,seed per boll,GOT,seed cotton yield,and short fiber index.Conclusion:The genotype AA-802,IUB-13,FH-159,FH-458,and CIM-595 were genetically diverse for most of the yield and fiber quality traits and could be utilized for the selection of better performing genotypes for further improvement.

Cotton germplasm improvement and progress in Pakistan

Cotton(Gossypium spp.)contributes significantly to the economy of cotton-producing countries.Pakistan is the fourth-largest producer of cotton after China,the USA and India.The average yield of cotton is about 570.99 kg.hm^(−2) in Pakistan.Climate change and different biotic stresses are causing reduction in cotton production.Transgenic approaches have unique advantage to tackle all these problems.However,how to confer permanent resistance in cotton against insects through genetic modification,is still a big challenge to address.Development of transgenic cotton has been proven to be effective.But its effectiveness depends upon several factors,including heterogeneity,seed purity,diffusion of varieties,backcrossing and ethical concerns.Cotton biotechnology was initiated in Pakistan in 1992–1993 with a focus on acquiring cotton leaf curl virus(CLCuV)-resistant insect-resistant,and improving fiber quality.This review summarizes the use of molecular markers,QTLs,GWAS,and gene cloning for cotton germplasm improvement,particularly in Pakistan.

Insect resistance management in Bacillus thuringiensis cotton by MGPS(multiple genes pyramiding and silencing)

The introduction of Bacillus thuringiensis(Bt)cotton has reduced the burden of pests without harming the environment and human health.However,the efficacy of Bt cotton has decreased due to field-evolved resistance in insect pests over time.In this review,we have discussed various factors that facilitate the evolution of resistance in cotton pests.Currently,different strategies like pyramided cotton expressing two or more distinct Bt toxin genes,refuge strategy,releasing of sterile insects,and gene silencing by RNAi are being used to control insect pests.Pyramided cotton has shown resistance against different cotton pests.The multiple genes pyramiding and silencing(MGPS)approach has been proposed for the management of cotton pests.The genome information of cotton pests is necessary for the development of MGPS-based cotton.The expression cassettes against various essential genes involved in defense,detoxification,digestion,and development of cotton pests will successfully obtain favorable agronomic characters for crop protection and production.The MGPS involves the construction of transformable artificial chromosomes,that can express multiple distinct Bt toxins and RNAi to knockdown various essential target genes to control pests.The evolution of resistance in cotton pests will be delayed or blocked by the synergistic action of high dose of Bt toxins and RNAi as well as compliance of refuge requirement.