Fine Mapping Of Major QTLqTBN2-2 For Tassel Branch Number In Chromosome 2 Of Maize

Reasonable tassel structure is very important for coordination of tassel developmen and increase in grain yield,and the number of tassel branches is the main factor of determining the size of tassel.This study used the maize inbred lines3237 which had a more obvious difference in the number of tassels and R18 as parents to construct a near isogenic line,finding fine mapping of the main QTL for the number of tassels on the chromosome 2.Laying the foundation for cloning of key genes which affecting tassel branching in chromosome 2 of maize.The main results were as follows:1.The F₁ was obtained from the maize inbred line 3237 with tassel branch number 0-2and the maize inbred line R18 with more than 9 tassel branch numbers.F₁ selfed to obtain F₂.From the F₂ population,the single plant with less than 2 branches was selected and backcrossed with R18 to obtain BC₁F₂.From the BC₁F₂ population,single plants with a number of tassels less than 2 were selected and backcrossed with R18 to obtain BC₂F₂.From the BC₂F₂ population,single plants with less than 2 tassels were selected and backcrossed with R18 to obtain BC₃F₂.The BC₄F₂ segregating population was obtained from the BC₃F₂population by selecting individuals with less than 2 tassel branch numbers and backcrossing with R18 and selfing.Ten InDel markers were used to map QTLs for number of tassel branches in the BC₄F₂ population and a QTL locus was identified between the markers v4hr2-185158820-v4r55r2-187149880 and named QTLqTBN2.2.30 SSR and InDel markers were used to identify the genotypes of BC₄F₂ populations,andthesingleplantsA17thatwereheterozygousforthemarker v4hr2-185158820-v4r55r2-187149880 and the rest of the R18 genetic background were selected.The A17 single plant was selfed to obtain a BC₄F₃ near-isogenic lineage population.Eight InDel markers were used to identify QTLs for number of tassels in BC₄F₃ populations.AQTLwasmappedbetweenv4hr2-136149280-v4hr2-179168740and v4hr2-185158820-v4r55r2-187149880.Named QTLqTBN2-1 and qTBN2-2,respectively.3.Using the markers v4hr2-185158820 and v4r55r2-187149880 to identify the seeds of the heterozygous BC₄F₃ inbreds that were selfed.166 exchanged individuals were selected;5InDel markers were used to encrypt the target region,8 key exchanged plant genotypes were identified,and QTLqTBN2-2 was finely mapped to the marker v4hr2-185158820-v4chr2-185387180.It is 228kb.