The following essay is reprinted with the permission of The conversationan online publication covering the latest research.
Cranberries are a staple in American homes at Thanksgiving, but how did this swamp-dweller end up on holiday tables?
Compared to many valuable plant species that were domesticated for thousands of years, the cultivated blueberry (Vaccinium macrocarpon) is a young agricultural crop, just as America is a young country and Thanksgiving is a relatively new vacation. But as a plant scientistI have learned a lot about the ancestry of blueberries from their botany and genomics.
New to the plant breeding scene
Humans have cultivated sorghum for about 5,500 years, corn for about 8,700 years and cotton for about 5,000 years. By contrast, blueberries were domesticated about 200 years ago, but people were eating them before then.
Wild blueberries are native to North America. They were an important food source for Native Americans, who used them in puddings, sauces, breads and a high protein portable food called pemmican – a carnivorous version of an energy bar, made from a mixture of dried meat and rendered animal fat and sometimes sprinkled with nuts. some tribes I still make pemmican todayand even market a commercial version.
Cranberry cultivation began in 1816 in Massachusetts, where Revolutionary War veteran Henry Hall discovered that covering cranberry bogs with sand It fertilized the vines and retained water around their roots. From there, the fruit spread throughout the Northeast and Upper Midwest of the United States.
A flexible and adaptable plant
Blueberries have many interesting botanical characteristics. Like roses, lilies, and daffodils, cranberry flowers are hermaphrodites, meaning they Contains male and female parts.. This allows them to self-pollinate rather than relying on birds, insects, or other pollinators.
A blueberry flower has four petals that are shed when the flower blooms. This exposes the anthers, which contain the plant’s pollen. The flower’s resemblance to a bird’s beak earned the blueberry its original name, the cranberry”.”
When blueberries are not self-pollinating, they rely on bumblebees and honeybees to transport their pollen from flower to flower. They can also be propagated sexually, by planting seeds, or asexually, by rooting vine cuttings. This is important for growers because seed-based propagation allows for greater genetic diversity, which can translate into things like greater disease resistance or greater pest tolerance.
However, asexual reproduction is equally important. This method allows farmers to create clones of varieties that perform very well in their peat bogs and grow even more varieties of those high-yielding types.
Each blueberry contains four air bags, which is why they float when farmers flood swamps to harvest them. Air pockets also cause raw cranberries to bounce when dropped on a hard surface, a good indicator of whether they are fresh.
These bags serve a biological function: they allow the berries to float down rivers and streams to disperse their seeds. Many other plants disperse their seeds through animals and birds that eat their fruits and excrete the seeds as they move. But as anyone who has tried them raw knows, cranberries are very acidic, so they have limited wildlife appeal.
Reading blueberry DNA
Because blueberries are such a young crop, scientists already know this a lot about your genetics. the cranberry It is a diploid, meaning that each cell contains one set of chromosomes from the maternal parent and one set from the paternal parent. It has 24 chromosomes and its genome size is less than a tenth of the human genome.
Knowledge like this helps scientists better understand where potentially valuable genes might be located in the blueberry genome. And diploid crops tend to have fewer genes associated with a single trait, making growing them to emphasize that trait much simpler.
Researchers have also described the genetics of the wild relative of the cultivated blueberry, known as “small blueberry” (Vaccinium oxycocci). Comparing the two can help scientists determine where the cultivated blueberry’s agronomically valuable traits reside in its genome and where some of the small blueberry’s cold resistance might come from.
The researchers are developing molecular markers – tools to determine where certain genes or sequences of interest reside within a genome – to help determine the best combinations of genes from different blueberry varieties that can improve desired traits. For example, a breeder might want to make the fruits larger, firmer, or redder in color.
While humans have only grown blueberries for a short period of time, they have been evolving for much longer. They entered agriculture with a long genetic history, which included things like Whole genome duplication events and genetic bottlenecks.which together change which genes are gained or lost over time in a population.
Whole genome duplication events occur when the genomes of two species collide to form a new, larger genome, encompassing all the traits of the two parental species. Genetic bottlenecks occur when the size of a population is greatly reduced, limiting the amount of genetic diversity in that species. These events are extremely common in the plant world and can cause both gains and losses of different genes.
Analysis of the blueberry genome can indicate when it diverged evolutionarily from some of its relatives, such as huckleberry, cranberry, and huckleberry. Comprehension how modern species evolved can teach plant scientists how different traits are inherited and how to effectively improve them in the future.
Ripe at the right time
The close association of cranberries with Thanksgiving was at first simply a matter of practicality. Fresh cranberries are ready to harvest from mid-September to mid-November, so Thanksgiving falls within the perfect period to eat them.
Cranberry sauce was first described in stories from the American colonies in the 17th century and appeared in a cookbook first published in 1796. The sour flavor of the berries, which comes from high levels of various types of acidsmakes them more than twice as acidic as most other edible fruits, so they add a nice touch to a meal full of milder foods like turkey and potatoes.
In recent decades, the blueberry industry has diversified towards juices, snacks and other products looking for markets throughout the year. But for many people, Thanksgiving is still the time when they’re most likely to see cranberries in some form on the menu.