QTL Mapping And Analysis For Plant Height-related Traits Of Maize In Different Density

Maize is a typical crop for food and feed.In the unit area,increasing the plant density can improve the yield of maize to the maximum extent,which can make a significant contribution to the grain security of our country.Plant architecture traits closely related to the yield are more sensitive response to density.The plant height and ear height,as two important and easy-measure traits of plant architecture,have a great effect on corn yield,density,lodging resistance,ecological adaptability and so on.Ear height-to-plant height ratio is an important parameter to judge whether the two traits is reasonable.In this study,the four sets of study populations comprised 840 RIL,were derived from the Yu82 × Yu87-1,Yu82 × Shen137,Yu87-1 × Zong3 and Yu537 A × Shen137 crossing,which were referred to as Pop.1,Pop.2,Pop.3 and Pop.4,respectively.Plant height-related traits contained by plant height(PH),ear height(EH),and the ear height-to-plant height ratio(EH/PH)were measured in two different plant densities,low(60,000 plants/ha)and high(120,000 plants/ha).We constructed high-density single nucleotide polymorphisms(SNP)linkage map to performQTL mapping in two different plant densities,which was used the composite-interval mapping method(CIM).Analysis the “consistency” plant height-related traits QTL through the element analysis method.The major results are as follows:1.The analysis of phenotypic traits related to the plant height-related from the four sets of RIL populations and five parents under high and low plant density treatments,demonstrated that the PH,EH,and EH/PH values for parent Yu82 were less than those obtained for Yu87-1 and Shen137.Parent Zong3 had shorter PH and EH and a lower EH/PH compared with Yu87-1,and the PH,EH,while EH/PH for Yu537 were less than those obtained for Shen137.Wide variations among the four sets of populations were observed to measure these traits,showing a pattern of continuous distribution around the mean and transgressive segregations that exceeded the high or low parent values.Taking the Yu82 × Yu87-1 population and the parents Yu82 and Yu87-1 as examples,higher plant density increased the average PH from 186.63 to 193.46 cm,average EH from 63.47 to 69.73 cm,and EH/PH from 0.34 to 0.36.Higher plant density of Yu87-1 increased the average PH from 190.23 to 200.94 cm,EH from 60.91 to 72.15 cm,and EH/PH from 0.32 to 0.36.Higher densities for Yu82 also increased PH from 178.21 to 179.31 cm,EH from 51.90 to 54.20 cm,and EH/PH from 0.29 to 0.30.2.Three thousand and seventy-two SNP markers,which covered all maize chromosome,were used to genotyping the four sets of study populations and parents.The four populations respectively contained 1,179,1,116,1,243,and 1,102 SNP markers.By using the software Jionmap 4.0 to construct four linkage maps,the results showed that the Pop.1 map had a total length of 1,873.02 c M with an average interval of 1.59 c M,the Pop.2 map had a total length of 1,839.75 c M with an average interval of 1.65 c M,the Pop.3 map hada total length of 1,863.00 c M with an average interval of 1.50 c M,and the Pop.4 map had a total length of 1,629.48 c M with an average interval of 1.48 c M.The integrated genetic map for the four RIL populations,including 2,439 SNP markers,was 1,933.74 c M long with an average interval of 0.79 c M3.A total of forty-two QTLs associated with plant height-related traits were identified in the four populations under the two-plant density conditions using composition-interval mapping.Thirteen QTLs were located in Pop.1,eight QTLs were located in Pop.2,twelve QTLs were located in Pop.3,and nine QTLs were located in Pop.4.Twenty-three QTLs were detected under the two-plant density treatments,and seven QTLs were identified only under the high plant density treatment.An individual QTL accounted for 5.23–23.38 % of the phenotypic variation,while 20 of the QTLs accounted for more than 10 % of the phenotypic variation.4.A total of 10 mQTLs were obtained from the consistency analysis of 42 QTLs mapped by the four populations of the three traits,of which,22 initial QTLs accounted for 52.38 % of the phenotypic variance observed,located on chromosomes1,3,4,5,7,9,10 and each mQTL contained 2-4 QTLs from different populations or traits.