| The planting area of maize has reached a critical value in China,at present,only by increasing the corn yield can meet the demand for corn in China.It is an important way to improve the yield of Maize by studying the genetic control mechanism of maize yield traits and using molecular marker assisted selection to breed new varieties.The number of rows per ear(ER),kernels per row(KR)and kernel weight per ear(EKW)were the important yield components of maize,the study and analysis on them is significant.In this study,four elite maize hybrids(Zhongdan No.2,Danyu13,Yedan No.2,Yedan13)from different periods were used to construct four F9 recombinant inbred lines,which contained 187,189,152 and 142 families respectively.The SNP molecular linkage maps were constructed respectively based on the four populations(pop.1,pop.2,pop.3 and pop.4)and the QTLs for corn ER,KR and EKW were identified by composite interval mapping.The main results are as follows:1.Four genetic linkage maps covering 10 chromosomes of maize and including3217,2765,2409 and 2241 SNP markers respectively were constructed.The maps spanned a total of 2822.3c M,2273 c M,1986.1 c M and 2753.3 c M with an average interval of 0.88 c M,0.82 c M,0.82 c M and 1.23 c M respectively.2.The analysis results for phenotype values of ER,KR and EKW of four RIL populations in three locations showed that the phenotype values of three traits of four populations in three points mostly in between those of the parents.The coefficients of variation of the phenotype values of four populations were all ER < KR < EKW.The difference of ER between the 3 sites was small,the difference of EKW was larger,and the difference of KR in between.The phenotype values of the three traits of the four populations in Hebi point were bigger than the corresponding populations in the other two locations;the phenotype values of the KR and the EKW of the four populations and the phenotype values of the ER of pop.2 populations in Zhoukou point were smaller than the corresponding populations in the other two locations;the phenotype values of the ER of three populations(pop.1,pop.3 and pop.4)in Xinxiang point were smaller than the corresponding populations in the other two locations.Three traits of four populations were all influenced by the environment,and the continuous genetic variation was presented at the 3 sites.The correlation analysis of the 3 traits showed that the EKW was influenced by the ER and the KR,and greatly influenced by KR.3.The QTL mapping for three traits of four populations in three sites were performed with composite interval mapping method.And 72 QTLs for ER,49 QTLs for KR and 40 QTLs for EKW were detected respectively.The contribution to phenotypic variation for a single QTL of each trait varied respectively 4.17%-19.65%,4.87%-21.81% and 5.74%-20.66%.For the same trait,six m QTLs expressing stably between different populations were identified.Each m QTL respectively contained QTLs detected on different populations,among which the m QTL3-2 on chromosome 3 included three ER QTLs detected on three populations,the m QTL4-1 and m QTL4-2 on chromosome 4 respectively contained three KR QTLs detected on two populations,the other three m QTLs respectively contained two QTLs.Among which two m QTLs controlling ER were mapped on chromosome 4 and chromosome 5,one m QTL controlling KR was mapped on chromosome 3.11 overlapping marker intervals were detected for the same trait of the same population in different environments,the QTLs located in this overlapping interval expressed stably in different environments.Among which the intervals1:197826785-1:198252968 and 1:13092472-1:15490989 on chromosome 1respectively contained three QTLs detected in three sites,the other nine intervals respectively contained two QTLs from two locations,among which three intervals controlling ER respectively located on chromosome 4,chromosome 9 and chromosome 10;three intervals controlling KR located on chromosome 3;three intervals controlling EKW respectively located on chromosome 3,chromosome 4 and chromosome 8.The stability QTLs explaining more than 10% of the phenotypic variation were the QTLs q3 h ER4-3?q3z ER4?q3x ER4-1?q2x ER9-1?q4z ER1-1 and q4 x ER1-1 which controlled the ER,q3 z KR3-1 which controlled the KR,q3 h EKW3-3 and q1 z EKW8-1 which controlled the EKW.The further study for these QTLs will be significant.Totally 14 m QTLs were detected for different traits,1 of which contained 5 QTLs,2 of which respectively contained 3QTLs and the other m QTLs each contained 2QTLs,the QTLs contained by these m QTLs may due to or gene close linkage.4.The analysis of QTLs detected on seven populations at different environments showed that,the numbers of ER,KR and EKW QTLs identified on the same population at different environments all have some differences.Analysis for QTLs identified on different populations in 3 sites showed that different populations have a great influence on QTL number of same trait and distribution on chromosomes.Which may be due to the parental differences of different populations,the different genetic background and the different adaptability to the environment;it may also be concerned with the number of markers of each population and the marker density on each chromosome.The results of this study have important significance for the further analysis of the genetic control mechanism on ER,KR and EKW and maize breeding. |
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