Breeding Potential Of Six Flue-cured Tobacco Cytoplasmic Male Sterile Materials

In this study,6 cytoplasmic male sterile materials as entry and 6 flue-cured tobacco varieties as tester were crossed in incomplete diallel cross method to generate 36 hybrids.By randomized complete block design,botanic traits investigated were plant shape,leaf color and leaf shape.Agronomic traits measured were plant height,girth of stem,internode length,effective leaf number and yield.The resistance of disease investigated were tobacco mosaic virus,alternaria altemata,weather fleck and tobacco etch virus.Percent total sugar,percent reducing sugar,percent nicotine,percent chlorine,percent potassium and percent total nitrogen were evaluated on the cured leaves.The analysis of variance,heritability,genetic correlation,combining ability,biplot based on combining ability and heterosis were analyzed,which including agronomic traits,resistance of disease and conventional chemical composition.56 polymorphic primer pairs were selected from 280 tobacco SSR primer pairs,and were used to evaluate the genetic difference of 12 flue-cured tobacco materials.According to the genetic distance,the breeding potential of the parents and the heterosis of the flue-cured tobacco were discussed.The main results were as follows:1.The main agronomic traits were significant or extremely significant except the lug length,the upper singel leaf weight and the upper leaves yield.Only the general combining ability and the special combining ability effect of the internode length,length and width of cutter and the lower leaves yield reached significant or extremely significant.The conventional chemical composition were significant or extremely significant except chlorine in lower leaves.The general combining ability and the special combining ability effect reached significant or extremely significant except chlorine and potassium in lower leaves,total sugar,nicotine and potassium in cutters,nicotine in upper leaves.The incidence of TMV,TMV disease index and the incidence of weather fleck were significant or extremely significant.2.The broad sense heritability of the internode length,yield,total sugar,reducing sugar and nicotine in lower leaves,total nitrogen and chlorine in cutters,total sugar and reducing sugar in upper leaves were more than 50%;While the broad sense heritability of other traits were low.The narrow sense heritability of plant height,internode length,effective leaf number and chlorine in cutters were more than 40%;While the narrow sense heritability of other traits were below 40%.The length and width of cutter and upper leaves yield could be controlled by additive effects and non-additive effects,and additive effects could be the major genetic component for other agronomic traits.Nicotine could be controlled by additive effects,total nitrogen could be controlled by non-additive effects,and additive and non-additive effects could play a major role for total sugar,reducing sugar,chlorine and potassium.The resistance of alternaria altemata and weather fleck could be controlled by additive genes,the resistance of tobacco mosaic virus could be controlled by non additive effects,and the resistance of tobacco etch virus could be controlled by additive and non-additive effects.3.The correlation coefficients between agronomic traits were mostly positive correlation.There was a negative correlation between leaf position angle,plant height,internode length and yield,and other agronomic traits were positively correlated with yield.In different parts,the phenotypic correlation coefficient and genotype correlation coefficient of total sugar and reducing sugar were positive;The correlation coefficients between nicotine and total nitrogen were positive;There was a negative correlation between total sugar,reducing sugar and nitrogen compounds;And the correlation coefficients of other traits were positively correlated while some were negatively correlated.4.According to the results of general combining ability effect,PVH1452 could reduce the plant height,internode length,second leaf length,reducing sugar and total nitrogen in cutters,total sugar and reducing sugar in upper leaves;And could increase reducing sugar and nicotine in lower leaves,chlorine and potassium in cutters,nicotine and chlorine in upper leaves.ChuanYan 1 could reduce effective leaf number;And could increase singel leaf weight,reducing sugar in lower leaves,potassium in cutters,total sugar and reducing sugar in upper leaves.MS YunYan 85 could reduce leaf position angle,girth of stem,internode length,cutter width,singel leaf weight,nicotine in lower leaves,total sugar and reducing sugar in upper leaves and the resistance of TMV;And could increase reducing sugar in lower leaves.NC102 could reduce internode length,cutter width,second leaf width,total sugar and reducing sugar in lower leaves,chlorine and potassium in upper leaves;And could increase effective leaf number,yield,nicotine in upper leaves and the resistance of alternaria altemata.MS YunYan 87 could reduce cutter width,potassium in cutters,nicotine,chlorine and potassium in upper leaves;And could increase yield and total sugar in lower leaves,total sugar and reducing sugar in cutters,reducing sugar and total nitrogen in upper leaves.MS Y01 could reduce effective leaf number,yield,total sugar and reducing sugar in lower leaves,potassium in cutters,the resistance of alternaria altemata and weather fleck;And could increase leaf position angle,plant height,internode length,leaf width,total nitrogen in lower leaves,total nitrogen in cutters,total sugar,chlorine and potassium in upper leaves,the resistance of TMV and tobacco etch virus.5.The traits of significant of combining ability variance analysis were analyzed by biplot.There were only one heterosis group in internode length,four heterosis groups in cutter length,two heterosis groups in cutter width,and three heterosis groups in lower leaves yield.There were three heterosis groups in total sugar,reducing sugar and total nitrogen in lower leaves;And there were two heterosis groups in nicotine in lower leaves.There were two heterosis groups in reducing sugar in cutters,and four heterosis groups in total nitrogen and chlorine in cutters.There were two heterosis groups in total sugar in upper leaves,three heterosis groups in reducing sugar,total nitrogen and potassium in upper leaves,and four heterosis groups in chlorine in upper leaves.Parents are selected according to different breeding goals with reference to the heterosis groups and provide a theoretical basis for the future heterosis.6.The hybrid combinations of MS YunYan87×HongHuaDaJinYuan and MS YunYan87xJeYeHuang were better in agronomic characters,chemical composition and disease resistance.The genetic distance between MS YunYan87 and HongHuaDaJinYuan was 0.327,and that between MS YunYan87 and JeYeHuang was 0.375.The genetic distance is larger,and it may have strong heterosis.7.Genetic distance among the 12 flue-cured tobacco materials ranged from 0.065 to 0.452,with an average of 0.242;The average genetic distance between HongHuaDaJinYuan and JingYeHuang was the maximum(0.452),the average genetic distance between MS YunYan85 and MS YunYan87 and that between PVH1452 and NC102 were the minimum(0.065).The result of cluster analysis based on SSR markers showed that 12 flue-cured tobacco materials could be clustered into a big group,a small groups and two independent classes formed by a single flue-cured tobacco germplasm at the level of GD= 0.11,which were consistent with the actual genetic relationship of flue-cured tobacco.