Quantitative Trait Loci Mapping for Plant Height, the First Branch Height, and Branch Number and Possible Candidate Genes Screening in Brassica napus L.

Abstract

Plant height, the first branch height and branch number are important agronomic traits in rapeseed. In our study, QTL mapping of plant height, the first branch height and branch number in Brassica napus was tested by using the high density SNP genetic map constructed from the high generation RIL population with the rapeseed 60 K chip array. The reference SNP genetic map contains 2795 SNP markers, covering 1832.9 c M with an average distance of 0.66 c M in B. napus genome. Totally, 24 putative QTLs were identified for plant height, the first branch height and branch number by using the complex interval mapping. The phenotypic variation was explained by individual QTL ranged from 5.00% to 15.26% for 11 QTLs of plant height, from 5.04% to 12.99% for seven QTLs of the first branch height, and from 5.95% to 8.14% for six QTLs of branch number. We collected 156 genes associated with plant height, 10 genes associated with the first branch height and 148 genes associated with branch number in Arabidopsis thaliana and searched the homology region of the QTL confidence interval E-value1E–20 to screen the possible candidate genes. We found 20 genes associated with plant height, three genes associated with the first branch height and 12 genes associated with branch number. The plant height candidate genes ATGID1B/GID1 B and WRI1 were found in QTL confidence interval on A07 and SLR/IAA14 and AXR2/IAA7 were found in QTL confidence interval on A08 in 2013 and 2014. The first branch height candidate gene PHT1;8 was found in QTLs q2013FBH-C05-1 and q2014FBH-C05-2 that had an overlapping con-fidence interval. Moreover, we found four genes associated with branch number that E-value from 0 to 3E–56 on A03 and C06, respectively.