Research Of Functional Chromosome Segment Of Yield And Yield Components In Maize

Chromosome single-segment substitution lines (SSSLs) are powerfultools for detecting and precisely mapping quantitative trait loci (QTLs) and evaluating theaction of genes as single Mendelian factors. In our study, A set of chromosomesingle-segment substitution lines derived from two sequenced elite maize inbred lines wasconstructed used MAS. Each SSSL contained a single substituted chromosome segmentthat was derived from donor strain Chang7-2in the genetic background of the recipientZheng58strain. Based on those SSSLs, fifty-nine SSSLs, which covered31.47%of theentire maize genome, were used to identify the QTLs of maize yield and its components insix environments. Meanwhile, fifty-six heterotic lines derived from each SSSL andZheng58, which covered30.66%of the entire maize genome, were used to detectfunctional chromosome segment of heterosis in maize. The main results are as follows:108SSSLs, which included46uniquely substituted segments, were developed from anadvanced backcross procedure with the marker-assisted selection using the elite maizeinbred line Zheng58as the recipient and Chang7-2as the donor. The46substitutedsegments were unevenly distributed on ten maize chromosomes, and the substitutedsegment length ranged from2.7centimorgan (cM) to283.5cM with an average of66.0cM.The total length of the46substitution segments was3,035.2cM, which covered2,142.6cM (31.47%) of the entire maize genome.Through the phenotypic characterization of maize yield and its components in sixenvironments, a total of150QTLs were identified, including26,23,23,16,19,23,20QTLs for plant height, ear length, ear diameter, ear row number, kernel number per row,grain weight and100-kernel weight, respectively.108QTLs (72.00%) were detected indifferent environments. The major QTL of maize yield and its components with the samegene effect directions which detected in at least four environments, were qph-1-3, qph-2-2,qph-6-2, qearl-5-3, qearl-7-1, qearl-10-2, qeard-2-1, qeard-2-2, qeard-4-1, qeard-4-2,qrown-4-1, qgrwt-1-3, qgrwt-2-2, qgrwt-6-2and q100kw-5-3, respectively. In sixenvironments, many QTLs of multiple traits were identified on the substituted segments such as umc1703-umc1122-bnlg1556-umc1013, umc1635-umc1065, bnlg278-umc1680.The plant height of SSSL-Y7(one dwarf chromosome single-segment substitution linederived from a backcross procedure with ‘87-1’, as recipient, and ‘Zong3’ asdonor)were significantly shorter than the recipient parent of87-1in three differentenvironments, and the additive effect of the dwarf gene in SSSL-Y7was negative largerthan ten percent of the87-1, this results demonstrated that one major QTL that causedplant height dwarf might exist on the substitution segmentumc2151…umc1122…bnlg1556. The number of tall and dwarf plants in the F2population(SSSL-Y7×87-1) was found to be in accordance with the theoretical3:1ratio．A recessivegene derived from the donor parent Zong3was supposed to control the dwarf of plantheight. With the aid of SSR marker analyses, a new recessive dwarf gene was identified,designated as qph-1-3. The qph-1-3gene was located in the Bin1.07, flanked by the SSRmarkers MPH147and umc2396with the genetic distances of1.5cM and0.3cM,respectively. The other linked markers include MPH164、umc1222、MPH162and MPH9.These linked markers are in the order of MPH164-umc1222-MPH162-MPH147-qph-1-3-umc2396-MPH9.Through the phenotypic characterization and Over-standard heterosis analysis ofmaize yield and its components in four environments, a total of eighty-three QTLs ofheterosis were identified, including16,19,4,11,19,14QTLs for ear length, ear diameter,ear row number, kernel number per row, grain weight and100-kernel weight, respectively.Thirty-three QTLs (39.76%) were detected repeatedly. The major heterotic QTL whichdetected in at least three environments and the same gene effect directions, wereqhearl-5-1, qheard-2-3, qhkrow-1-2, qhkrow-2-1, qhkrow-5-2, qhgrwt-1-3, and qhgrwt-2-2,respectively. In four environments, the substituted segments such as umc1013-umc2029,umc1635-umc1065, bnlg278-umc1680，were identified many QTLs of multiple traits.These chromosomal regions will be focused in the further studies.