, 215:34 | Cite as

Identification of heat tolerance loci in broccoli through bulked segregant analysis using whole genome resequencing

  • Sandra E. BranhamEmail author
  • Mark W. Farnham


Most broccoli cultivars are sensitive to high temperatures during the early stages of floral development causing a severe decline of head quality or even complete lack of head formation under superoptimal crop production temperatures. Several heat tolerant lines have been developed in recent years but there have been few studies of the genetic basis of this complex, polygenic trait. A doubled haploid population of broccoli was evaluated for head quality across two summer field trials with the phenotypic extremes validated in two additional summer fields. Whole-genome resequencing of the bulked segregants was used for a quantitative trait loci (QTL)-seq analysis of heat tolerance. Two novel QTL, which differ from previously reported QTL, were identified. Nonsynonymous SNPs were found in a block of flowering time genes within QHT_C09.2 and may explain the significant negative correlation between time to head maturity and heat tolerance. Breeding further genetic gains in this complex, polygenic trait could be expedited through marker assisted selection and gene pyramiding using markers developed from the QTL identified herein.


Broccoli Heat tolerance Bulked segregant analysis QTL-seq Brassica oleracea 



This study was funded by the United States Department of Agriculture, Project No. 6080-21000-018-00 and the National Institute of Food and Agriculture, Project No. 2010-51181-21062. The authors would like to thank Zachary J. Stansell and David M. Couillard for their technical assistance.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

10681_2018_2334_MOESM1_ESM.png (645 kb)
Online resource 1 Scatterplots of the SNP-index for the heat sensitive bulk at 654,288 SNPs across nine chromosomes. The red lines represent the results of a sliding window analysis with a 1 Mb interval and a window size of 10 kb (PNG 645 kb)
10681_2018_2334_MOESM2_ESM.png (526 kb)
Online resource 2 Scatterplots of the SNP-index for the heat tolerant bulk at 654,288 SNPs across nine chromosomes. The red lines represent the results of a sliding window analysis with a 1 Mb interval and a window size of 10 kb (PNG 525 kb)
10681_2018_2334_MOESM3_ESM.csv (37 kb)
Online resource 3 Candidate genes based upon functional annotation of the significant SNPs that cause missense or nonsense mutations or were found < 1000 bp upstream of the start codon of the listed gene (CSV 36 kb)


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Copyright information

© This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2019

Authors and Affiliations

  1. 1.USDA-ARS, U.S. Vegetable LaboratoryCharlestonUSA

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