Location: Vegetable ResearchTitle: Quantitative trait loci mapping of heat tolerance in broccoli (Brassica oleracea var. italica) using genotyping-by-sequencing
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2016
Publication Date: 3/1/2017
Citation: Branham, S., Stansell, Z.J., Couillard, D.M., Farnham, M.W. 2017. Quantitative trait loci mapping of heat tolerance in broccoli (Brassica oleracea var. italica) using genotyping-by-sequencing. Theoretical and Applied Genetics. 130(3):529-538.
Interpretive Summary: Broccoli is one of the most economically important vegetable crops in the United States with a farm-gate value of more than 800 million dollars annually. Heat stress during the heading stages of crop development can have a negative impact on crop production reducing yield and quality of heads. Indeed, the likelihood of this environmental stress occurring in a given location or season is the primary factor limiting where and when the crop can be grown. Breeding heat tolerant broccoli cultivars could extend the growing season, expand production areas, and increase resilience to fluctuating temperatures but is limited by a lack of genetic knowledge. USDA scientists in Charleston, SC, evaluated a population of broccoli for its ability to tolerate high temperature stress during summer and used next generation sequencing to identify markers associated with resistance to heat damage in this population. Identified markers are of great interest to public and private broccoli breeders working to accelerate the development of heat tolerant broccoli cultivars.
Technical Abstract: Predicted rising global temperatures due to climate change have generated a demand for crops that are resistant to yield and quality losses from heat stress. Broccoli (Brassica oleracea var. italica) is a cool weather crop with high temperatures during production decreasing both head quality and yield. Breeding for heat tolerance in broccoli has potential to both expand viable production areas and extend the growing season but breeding efficiency is constrained by limited genetic information. A doubled haploid (DH) broccoli population (N=156) segregating for heat tolerance was evaluated for head quality in 3 summer fields in Charleston, SC, U.S. Multiple quantitative trait loci (QTL) mapping of 1,435 single nucleotide polymorphisms (SNPs) developed through genotyping-by-sequencing (GBS) identified 4 QTL and 1 positive epistatic interaction that explained 57.5% of variation in heat tolerance. The QTL identified here can be used to develop markers for marker-assisted selection (MAS) and to increase our understanding of the molecular mechanisms underlying plant response to heat stress.