| As the largest grain crop in China,corn is also used as energy feed and industrial processing raw materials,and its yield directly affects the national food security.With the continuous improvement of people’s living standards and the increasing demand for corn,improving corn yield is the core problem of corn breeding for a long time in the future.The main components of corn yield include effective panicle number,grain weight and grain number per row.Cloning QTL,to control agronomic traits related to maize yield is not only helpful to analyze the genetic mechanism of traits controlled by genes,but also has important practical guiding significance for high yield breeding of maize.In this study,the key traits of yield were selected as the research objectives,and two parts of the research work were carried out: in the first part,Mo17 was used as the recipient parent and M1 as the donor parent in the laboratory,and the molecular marker was used to assist the selection.The single segment substitution lines constructed by continuous backcross and multiple generations were used to analyze the yield traits of maize by QTL mapping.In the second part,the BC3F2 single plant containing one of the major QTL on chromosome 2was selected in the laboratory,and the BC3F5 near-isogenic line was constructed by continuous inbreeding for fine mapping of the main QTL of panicle row number.The phenotypic identification of multiple environments was carried out by using recombinant homozygote,and the accuracy of the target region was confirmed by genotyping.Then we continue to construct the high generation backcross segregation population,screen the exchange individual plant,encrypt the mark,and reduce the target area.The main results are as follows:1.Ear traits of maize are important factors affecting yield and quality of maize,and they are quantitative traits controlled by multiple genes.Chromosome single segment substitution lines have become a new genetic material for identifying complex traits QTL because of their homogeneous genetic background.In this study,133 chromosome single segment substitution lines constructed with Mo17 as receptor and M1 as donor were used as experimental materials.The differences of panicle traits between single segment substitution lines and recipient parents were tested by single factor variance analysis.Identification of QTL.related to panicle traits in substitution fragments At the threshold of P ≤ 0.05,a total of 178 panicle traits related QTL,were detected to be unevenly distributed on 10 chromosomes of maize.Among them,61 rows per panicle were correlated,the additive effect value of a single QTL was-1.25 ≤ 1.9 rows,and the percentage of additive effect was-12.5% ≤ 19.0%.The additive effect value of single QTL was-0.21 ≤ 0.51 cm,and the percentage of additive effect was-2.1% and 5.1%,respectively.The additive effect value of single QTL was-1.45 ≤ 0.99 cm,and the percentage of additive effect was-12% ≤5%.The additive effect value of a single QTL was-4.39 ≤ 3.4 grains,and the percentage of additive effect was-12% ≤ 9%.The identification of maize yield trait gene loci and the study of their genetic effects can not only lay a foundation for the cloning and mechanism of maize yield trait genes,but also provide theoretical guidance for crop genetic improvement.2.On the basis of single segment substitution line,sub-NILs constructed by Mo17 and diploid ruminant M1 was used to localize QTL of ear number on chromosome 2 of maize.Using NIL-F2:3 population,a local linkage map was constructed to evaluate the genetic effect of the target region of QTL per panicle.Linkage analysis showed that there was a QTL,that controlled the number of rows per panicle on the short arm of chromosome 2 and named it q KRN2.1,.The phenotypic variation explained by the QTL was 10.8%.The synergistic allele came from the Mo17,MT1 allele,which reduced the number of rows per ear to about one row.In 2018,in Chongzhou,the progeny test was carried out by exchanging the self-bred progenies of a single plant.The number of rows per ear identified as linkage QTL q KRN2.1 was reduced to the interval of marker M23 and M27,and the physical distance was about 600 k.the number of rows per ear identified as linkage was reduced to the interval of marker M23 and M27. |
