Genetic Analysis Of Ear Length,Plant Height And Ear Height And It’s Breeding Applications In Maize

Silage corn plays an important role in maintaining grain structural reform of the supply front and development of animal husbandry in China.However,there are some problems in silage maize production,such as lack of special silage varieties,lagging cultivation technology and insufficient harvesting machinery.Silage maize varieties are the basis of industrial development,but low biological yield and poor silage quality are two prominent problems in silage maize breeding.It is an important way to improve biological yield and silage quality by increasing ear length and plant height.Therefore,it is of great theoretical and practical significance to study the genetic law of important agronomic traits of ear length and plant height,not only to breed the special silage varieties with high quality and study molecular marker assisted selection,but also to analyze the molecular biological mechanism of low biological yield and low quality silage maize.In this study,new QTLs and candidate genes for ear length(EL),plant height(PH)and ear height(EH)were identified by linkage analysis with genome-wide association analysis(GWAS)with the four populations,which the F2:3 populations were constructed by Zheng58 and Chang7-2 included 255 lines,the four-way cross populations were constructed by D276,D72,A188,and Jiao51 included 277 lines,the RIL populations were constructed by BT-1 and N6 included 250 lines,and the GWAS populations include three subgroups.The main results are as follows:1)Five QTLs for EL were identified by F2:3 located in chromosome 1,2,3,4,5,and 9 QTL for EL were identified by four-way cross populations located in chromosome 1,2,3 and 5.Three stable QTL were both identified in the F2:3 and four-way cross populations,which were named qEL1,qEL2 and qEL5,of which qEL2 on Chr.2 was a new one.2)Three EL candidate genes,GRMZM2G383817,GRMZM2G161291 and GRMZM2G168371,were identified by linkage analysis with GWAS,which were involved in autin polarity transport,ear growth point development,cell proliferation and other development processes,respectively.The qRT-PCR results showed that the expression of GRMZM2G161291 and GRMZM2G168371 for the ears in the early stage of A188 were significantly higher than that of Jiao51,indicating that these two candidate genes might be related to ear length development.3)Cloning the sequences of GRMZM2G161291 and GRMZM2G168371 in long ear parent A188,short ear parent Jiao51,and other 15 long ear and 15 short ear inbred lines.The sequence lack of GRMZM2G161291 and a special genotype of GRMZM2G168371 were found associated with EL,which proved the functions of candidate genes.Two functional SNP markers were further developed for each of the two genes,and they were divided into three functional haplotypes respectively.4)Markers assisted selection(MAS)with conventional breeding,the elite silage maize inbred line Z05 with an increase of 1.8cm in EL compared to was bred from the inbred line Jiao51 improved by the QTL qEL2,and its silage maize hybrid Zhengdan 919 was bred and passed the regional testing of varieties in Henan province,and the biological yield increased by 6.2%and starch content increased by 2.8%compared with the check variety(CK)Yayu silage no.8,which improved the silage quality.5)Three QTLs for PH and six QTLs for EH were identified by F2:3 populations from the cross Zheng 58/Chang 7-2,and three QTLs for PH and nine QTLs for EH were identified by the RIL populations from the cross BT/N6.The three QTLs for PH and EH were stable QTLs with multipopulations on chromosome 1,5 and 6.The QTL on bin1.05/1.06 was verified by the NILs.6)21 and 20 significant SNPs for PH and EH were identified by GWAS based MLM model with PCA and Kinship.19 candidate genes were focused within 29 significant SNPs.These candidate genes were involved in kinase family and signal transport process.7)MAS with conventional breeding,the elite silage maize inbred line Z01 with an increase of 8.65cm in PH compared to was bred from the inbred line Zheng58 improved by the QTL qPH1-1,and its silage maize hybrid Zhengdan 901 was bred and passed the regional testing of varieties in Henan province.The PH of Zhengdan 901 increased by 8.3 cm compared with Zhengdan958,and the biological yield increased by 12.27%compared to CK.