Genetic Studies Reveal QTL for Onion Pungency

Candidate genes for onion pungency have been reportedly identified by researchers in New Zealand and the United States. The pungent flavor and aroma of onions have long been attributed to organosulfur compounds, but this is the first report of the identification of genomic regions affecting the trait that have no pleiotropic effects on bulb solids content.

The group of John McCallum analyzed progenies from a cross between onion varieties ‘W202A’ and ‘Texas Grano 438’. The researchers have identified a major quantitative trait locus (QTL) within two closely linked sulfur assimilation genes, named ferredoxin-sulfate reductase (SiR) and plastidic ATP sulfurylase (ATPS). These genes were found to control 30-50% of genetic variation in the storage and sweet onion pedigrees that they have analyzed.

McCallum and colleagues stated that the association of the two genes with pungency suggests that mutations in one of these genes may influence the observed variation. They further recommend that molecular markers within these pungency loci may provide a practical means to select for onions with lower pungency.

The abstract, with links to the full paper for subscribers, can be accessed at http://www.springerlink.com/content/u13n67u3037531uk/ .