Genetic Analysis Of Vitamin A And Vitamin E And Breeding By Molecular Marker-assisted Selection In Sweet Corn

Sweet corn is popular because of its abundant nutrients,including vitamins,amino acids and minerals.With the increase of consumption demand for sweet corn with high quality in China,Guangdong,which is a big province with sweet corn production and consumption,needs to constantly improve its breeding technology and cultivar's level to meet the diversified demands of the consumers,especially the varieties with high-quality nutritions and micronutriends are an important direction of future breeding in sweet corn.As important micronutrients,vitamin A and vitamin E are indispensable for human health and their biosynthesis and metabolism are controlled and regulated by a series of genes.However,the content of pro-vitamin A and vitamin E is low in promoting sweet corn cultivars.In order to improve the content of pro-vitamin A and vitamin E in sweet corn,47sweet corn inbred lines were screened by analyzing the variation of pro-vitamin A and vitamin E contents,and the haplotypes of key speed-limiting genes for pro-vitamin A synthesis were analyzed.For the abundant variation of vitamin E content in sweet corn,a F_2:3 families population was built to study the QTL associating with vitamin E content.BK-3 and SY999 were introduced from China Agricultural University to carry out molecular marker assisted selection breeding,one of them had high pro-vitamin A content with favorable allele at the site of lcy E and the other had high vitamin E content with favorable allele at the site of Zm VTE4.The main results of this study are as follows:1.Identification of pro-vitamin A and vitamin E content in sweet corn inbred lines.The content of pro-vitamin A ranged from 0.07 to 22.76?g/g in 47 sweet corn inbred lines,with an average of 3.28?g/g and a coefficient of variation of 1.44.These lines with higher pro-vitamin A content were A5,A37,A36,A6 and A8.The vitamin E content varied from18.50 to 99.17?g/g,with an average of 51.15?g/g and a coefficient of variation of 0.35.These lines with higher vitamin E content were A4,A5,A24 and A26.The content of pro-vitamin A and vitamin E increased linearly at 15-27 days after self-pollination in Notian 88,and they reached the maximum at 27 days after self-pollination.2.Haplotype analysis of the key genes for pro-vitamin A synthesis including PSY1,LCYE and crt RB1.The haplotype analysis of single gene showed that PSY1 was significantly correlated with total carotenoid content,LCYE was significantly correlated with?-carotene,pro-vitamin A and total carotenoid content,and crt RB1 was not correlated with carotenoids content.Combined haplotype analysis showed that the optimum haplotype combination was‘101110',and the contents of?-carotene,pro-vitamin A and total carotenoids were 3.17,15.16 and 68.30?g/g,respectively.3.QTL analysis of vitamin E content in sweet corn.A F_2:3 families populatin was built from two sweet corn lines with relative large difference in vitamin E content to map the QTLs associated with vitamin E.The genetic linkage map was constructed containing 136markers,including one candidate gene HPPD functional marker,and covering 10 linkage groups.The total length of the map was 2031.2 c M,and the average marker spacing was14.9 c M.A total of 11 putative QTLs were detected related to the contents of?-tocopherol,?-tocopherol,?/?-tocopherol and total vitamin E,which were located on chromosome 1,2,5,6 and 10,respectively.They could explain from 4.74 to 41.16%of the total phenotypic variation.Two major QTLs were detected on chromosome 1 and 5,one linked to HPPD functional markers,and the other was a new major QTL on chromosome 1.4.Marker-assisted selection breeding for lcy E allele in sweet corn.The functional marker 3'indel showed codominant between the donor parental line and 4 sweet corn lines and it was selected as the foreground marker.There were 61,61,60 and 61 polymorphic SSR markers for background selection,respectively.The comparison of agronomic traits between four BC₃F₃populations and their corresponding recipient parents were carried out by t-test.The results showed that most agronomic traits of the BC₃F₃populations were highly consistent with their cooresponding recipient parents.The introduction of favorable lcy E allele increased the contents of?-carotene,pro-vitamin A and total carotenoids.The?-carotene and pro-vitamin A contents increased by 1.54 and 1.69?g/g in the BC₃F₄populations,respectively.The increased ratio of pro-vitamin A reached 81.91%at the significant level of 0.01.10 excellent strains were screened out.Their average pro-vitamin A content was 3.95?g/g,and the increase rate was as high as 155.00%.5.Marker-assisted slection breeding for Zm VTE4 allele in sweet corn.The functional marker In Del118 showed codominant between the donor parental line and the 5 sweet corn lines and it was selected as the foreground marker.There were 71,73,73,74,and 70polymorphic SSR markers for background selection,respectively.The backcrossed populations were highly consistent with their cooresponding recipient parents in most agronomic traits including plant height,leaf number and grain number per row etc.The introduction of favorable Zm VTE4 allele significantly increased?-tocopherol,?-tocopherol and total vitamin E.The content of?-tocopherol increased by 3.29?g/g and the increased ratio was 62.71%,and the content of?-tocopherol increased by 17.25?g/g and the increased ratio was 79.64%.20 excellent strains were screened out.Their average vitamin E content was 61.88?g/g,and the increase rate was as high as 70.11%.In this study,the contents of pro-vitamin A and vitamin E were identified in 47 sweet corn inbred lines,the haplotypes of key genes for pro-vitamin A biosynthesis were analyzed,and the QTLs for vitamin E was mapped through constructing F_2:3 families population.Molecular marker-assisted selection(MAS)breeding was carried out through introducing dent corn lines with favorable lcy E allele and favorable Zm VTE4 allele and the content of pro-vitamin A and vitamin E of elite sweet corn lines were improved.The results laid the material foundation for further breeding of high pro-vitamin A and vitamin E in sweet corn.