Analysis QTL Of Soluble Sugar Concentration And Yield Components In Super Sweet Corn

Super sweet corn is one kind of sweet corn. Super sweet corn is characterized with sweet, waxy,tender and dulcet, had higher nourish and economic value, also known a fruit as well as vegetable, socalled "king of fruit". With the advances in the needs of the people, the better eating quality will berequired. These requirements in the quality of soluble sugar concentration, tenderness, and pericarpthickness have attracted a lot of scientist to improve the yield of super sweet corn. Conventional geneticstrategies have been employed to enhance eating quality. However it had limited efficiency to improvesuper sweet corn because of its lower breeding efficiency and long breeding period. Recent advances inDNA markers offer plant breeders a rapid and precise alternative approach to conventional selectionschemes to improve quantitative traits of quality.The genetic linkage map was constructed with1 450 SSR markers based on a super sweetpopulation consisting of 208 F₂ individuals from the cross Ji557(sh₂)×Ji165(sh₂), parents bred bySpecialty Corn Research Institute of Jilin Agriculture University. The objectives of the present studywere to identify QTLs of soluble sugar concentration and other traits, evaluate QTL effects with usingMapmaker/QTL. The work will do great help to fine mapping for QTL of kernel soluble sugarconcentration, map-based cloning of these genes, and marker-assisted selection in super sweet cornbreeding. The main results were as following:1. DNA polymorphism between mapping parentsA total of 121 polymorphism primer pairs were found among maize SSR primer pairs, and thepolymorphism primer pairs accounted for 26.9%. The polymorphism was higher between Ji557(sh₂) andJi165(sh₂). F₂ from Ji557(sh₂)×Ji165(sh₂) was an ideal mapping population.2. Trait performances of mapping parents and F_2:3 family linesThe seed of Ji557 had 6.38% for soluble sugar concentration, 13.8cm for ear length, 4.18cm forear diameter, 16.4 for row number, 1.11cm for kernel length, 0.62cm for kernel width, and 12.3g for100-kernel weight. The seed of Ji165 had 16.42% for soluble sugar concentration, 13.6cm for ear length,2.94cm for ear diameter, 12.6 for row number, 0.66cm for kernel length, 0.57cm for kernel width, and 6.2g for 100-kernel weight. The two mapping parents were markedly different in soluble sugarconcentration, ear diameter, row number, kernel length, kernel width, and 100-kernel weight.The soluble sugar concentration of 208 F_2:3 family lines ranged from 4.46% to 17.81, whit themean of 11.37%. Their ear length ranged from 6.5cm to 26.5cm, whit the mean of 14.75cm. Their eardiameter ranged from 2.12cm to 4.68cm, whit the mean of 3.78cm. Their row number ranged from 8 to22, whit the mean of 15.6. Their kernel length ranged from 0.61cm to 1.22cm, whit the mean of 0.91cm.Their kernel width ranged from 0.51cm to 0.92cm, whit the mean of 0.64cm. Their 100-kernel weightranged from 4.3g to 16.3g, whit the mean of 10.05g. For 7 traits of F_2:3 family lines, transgressivesegregation were observed falling beyond both Ji557 and Ji165.3. Linkage map of super sugar corn121 loci of SSR markers were employed to perform linkage analysis using the intraspecificpopulation F₂ of super sugar corn Ji557(sh₂)×Ji165(sh₂). 113markers were distributed into 10 linkagegroups, while 8 markers remained unlinkage. The linkage groups varied from 2.2cM to 65.3cM, withthe average distance about 13.02cM betweent two markers, and covered 1470.9Cm of the totalrecombination length of the super sweet corn. This is consistent with the maps previously reported. 25markers showed a distorted segregation from the expected ratio (1:2:1).4. QTL effects and origins of soluble sugar concentration and other traits in super sweetcornUsing Mapmaker/QTL, 11 QTLs were identified for soluble sugar concentration, explaining3.5-20.3% of soluble sugar concentration variance, collectively explaining 63.7% of the trait variance,SSC3 in the region of phi101049 marker was inferred as the major one, it explained 20.3% ofphenotypic variance.Five QTLs were identified for ear length, explaining 7.5-21.3% of ear length, collectivelyexplaining 33.9% of the trait variance, EL1 in the region of phi055 marker was inferred as the majorone.Four QTLs were identified for ear diameter, explaining 6.8-15.4% of ear diameter, collectivelyexplaining 45.3% of the trait variance.Three QTLs were identified for row number, explaining 4.7-14.8% of row number, collectivelyexplaining 25.2% of the trait variance.Seven QTLs were identified for kernel length, explaining 7.3-22.2% of kernel length, collectively explaining 47.6% of the trait variance, KL2 in the region of bnlg1953 marker and KL6 in the region ofphi059 were inferred as the major ones, they respectively explained 21.5% and 22.2% of phenotypicvariance.Four QTLs were identified for kernel width, explaining 5.9-17.8% of kernel width, collectivelyexplaining 48.5% of the trait variance.Five QTLs were identified for 100-kernel weight,, explaining 4.6-24.2% of 100-kernel weight,collectively explaining 63.6% of the trait variance, 100KW1 in the region of bnlg2077 marker wasinferred as the major one, it explained 20.2% of phenotypic variance.The region of umc2049 respectively effected ear diameter and kernel length. The region of phi093respectively effected kernel length and 100-kernel weight.5. QTL action modes of soluble sugar concentration and other traits in super sweet cornOf 11 QTLs associated with soluble sugar concentration, 2 QTLs(18.2%) showed additive effects,3 QTLs(27.3%) showed partially dominant effects, 3 QTLs(27.3%) showed dominant effects, 3QTLs(27.3%) showed overdominant effects. Four genetic effects all appear to play an important role incontrolling soluble sugar concentration.Among the traits of yield components, 5 QTLs(17.8%) showed additive effects, 13 QTLs(46.4%)showed partially dominant effects, 9 QTLs(32.1%) showed dominant effects, only 1 QTLs(3.6%)showed overdominant effects. That indicated dominant effects and partially dominant effects wereimportant to yield traits.