Can chocolate-dipped strawberries be improved upon—genetically? Separate teams of researchers have sequenced the genomes of varieties of the two crops that make up this treat, finding key coding information that could help keep these sweets on dessert trays—and assist science in the meantime. Both studies were served up online December 26 in Nature Genetics (Scientific American is part of Nature Publishing Group).
The world's chocolate supply comes from the Theobroma cacao tree, whose seeds are extracted, fermented, dried and eventually turned into consumable cocoa products. But Central American-based blights threaten to take a big bite out of the 3.7 million tons of cocoa produced each year, most of which comes from relatively defenseless crops in West Africa. So researchers have been racing to decode the tree's genome in hopes of finding ways to genetically dial up resistance.
In September, researchers backed in part by candy maker Mars, Inc. published their version of the T. cacao genome online before submitting it for peer review. The new paper was sponsored in part by confectionary competitor Hershey.
The Nature study assessed the genetics of the Criollo variety of cacao, which is the source of much of the world's high-quality and dark chocolate products, which have been becoming increasingly popular among consumers. Unlike the other major cocoa variety, Trinitario, Criollos are much less productive plants and are more susceptible to disease.
The Criollo cacao genome "provides a major source of candidate genes for T. cacao improvement," noted the researchers, led by Xavier Argout, of France's Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD). Researchers identified genes involved in the production of flavonoids, aromas and terpenoids, some of which might be involved in plant defense against predation and infection.
Strawberries are their jam
Although strawberries might not currently face the same crop-wide threats as cacao trees, the researchers behind the wild or woodland strawberry (Fragaria vesca) genome explain that it has plenty to offer.
The F. vesca, once the main strawberry of choice among growers and eaters, has largely given way to a more mass-produced cultivated variety, Fragaria x ananassa. But the two share a close genetic history, the latter having been bred only 250 years ago. Nevertheless, F. vesca has not fallen out of favor with geneticists, an international consortium of whom selected F. vesca to be the genus' reference genome—owing in large part to its small size. It is the second-smallest known plant genome after laboratory favorite thale cress (Arabidopsis thaliana).
As a member of the group that also includes peaches, apples and cherries, F. vesca is "an attractive surrogate for testing gene function for all plants in the Rosaceae family," wrote the researchers, led by Vladimir Shulaev, of the University of North Texas' Department of Biological Sciences. "Its nearest relatives are high-value fruit crops with cumbersome polyploidy genomes…or large statured crops with long generation times and/or spatial requirements," they noted.
The genes found inside this juicy berry are "critical to valuable horticultural traits including flavor, nutritional value and flowering time" as well as disease resistance, the researchers wrote. And because many of these genetic signatures are likely similar in related, more genetically complex fruits, researchers will be able to "get access to all of these useful genes comparatively easily" in the wild strawberry, Daniel Sargent, of East Malling Research in the U.K. and coauthor of the paper, said in a prepared statement.
The researchers used a short-segment sequencing technique and have made the genome available free of charge.
Image courtesy of Wikimedia Commons