QTL Mapping Of Maize Kernel Row Number,Tassel Branch Number And Leaf Canopy Structure Traits

Maize（Zea mays ssp.mays L.）is the largest grain crop in both plant area and production in China.It has a wide range of uses and plays an important role in protecting the food security.In maize production,maize yield is mainly composed of effective ear number per unit area,kernel number and grain weight.Dissecting the genetic basis of agronomic traits related to yield factors is of great significance to genetic improvement of maize and to promote high yield breeding in maize.In this study,we utilized maize inbred line Mo17 as recipient and teosinte MT1（Zea mays ssp.mexicana）as donor to construct advanced backcross populations,and fine mapping of the main KRN（Kernel Row number）QTL and main TBN（tassel branch number）QTL on chromosome 2 were performed.These results provided the basis for QTL cloning and molecular mechanism study of KRN and TBN.Meanwhile,by using one previously reported RIL population derived from elite inbred line B73 and waxy landrace inbred line SICAU1212,QTL mapping was performed to analysis the genetic basis of leaf angle,leaf width and leaf length,and provided a theoretical basis for ideal type breeding at different canopy levels.The main results are as follows:1.By screening the BC₃F₂ population of Mo17×MT1,we identified a chromosome segment substitution line‘729’which had significantly decreased KRN than the recipient Mo17.Two linkage KRN QTL on the short arm of chromosome 2was detected by using BC₃F_3:4:4 population derived from 729,which were named as qKRN2.1 and qKRN2.2.qKRN2.1 was located in the interval of 3 Mb by molecular marker M11 and M13,and qKRN2.2 was mapped a region of 8 Mb between M17 and M18.By constructing sub-NILs to analyze genetic effects of KRN QTL,it is found that when qKRN2.1 and qKRN2.2 both exists,KRN of Mo17 decreases by about 2.5rows.When qKRN2.1 exists alone,KRN decreases by about 1.0 row.When qKRN2.2exists alone,KRN also decreases by about 1.0 row.Meanwhile,a large BC₃F₅segregating population containing 1800 plants was used for fine mapping.28recombinant plants were obtained,and qKRN2.1 was then finely mapped to a 288 kb region by progeny test.This region contains 17 genes according to B73 referencegenome.2.Using BC₃F_3:4:4 population derived from 729,a main TBN QTL,qTBN2.1,was detected and located on the short arm of chromosome 2.Meanwhile individuals containing segment of qTBN2.1 was selected to backcross Mo17 two times,and then BC₅F₂ population was obtained.Using BC₅F_2:3:3 population for QTL mapping,qTBN2.1 was further mapped the interval between InDel-1 and InDel-9,LOD=45.9,PVE=64.0%,and the additive effect value was-1.51.76 recombinant plants were obtained by screening 2000 individuals from BC₅F₂ population.Through the progeny test in two environments of Yunnan and Sichuan,qTBN2.1 was precisely defined a⁵.5 kb interval of the B73 genome sequence,which contain only one gene.3.Through the RIL population derived from B73 and SICAU1212,QTL mapping were performed for leaf angle,leaf width and leaf length of eight leaves at different nodes utilizing single-environment analysis and joint mapping,15,27 and 16QTL associated with corresponding traits at eight nodes were detected,respectively.The individual effect of QTL ranged from 0.39%to 24.77%and the number of related leaf traits controlled by a single QTL varied from 1 to 8.For example,qLA2-1simultaneously controlled LA of all the eight nodes,and qLA2-2 only affected that of1stLA.The total phenotypic variation explained by all QTL identified for LA at eight nodes ranged from 15.69%（8thLA）to 51.73%（1stLA）.The number of QTL detected for LA at each nodes ranged from 4（7thLA）to 11（1stLA）.