This time of year, pumpkins are everywhere. From jack-o-lanterns to pies, the round, orange fruit has become synonymous with Halloween and the fall season. Yet many of us forget that pumpkins didn't always look or taste the way they do now.
It was only after thousands of years of genetic selection that early North American farmers turned the wild and bitter ancient fruit into the noble and delicious pumpkin.
Today, the process of genetic selection is much faster and more efficient. Especially now that researchers from the Boyce Thompson Institute (BTI) and the National Engineering Research Center for Vegetables in Beijing have successfully sequenced the genomes of two major pumpkin species: Cucurbita maxima and Cucurbita moschata.
Feeding the 7.3 billion people on Earth is a serious issue, and genetic engineering is one of the most promising solutions. Currently, over 796 million people suffer from chronic undernourishment, and the effects of climate change will only make this number worse. Many scientists believe that genetically improved crops are one of our best ways to tackle drought, climate change, increased soil salinity, insects and pathogens.
Pumpkins are no exception.
"Pumpkins are used as a staple food in many developing countries and are cultivated all over the world for their culinary and ornamental uses," said Zhangjun Fei, a senior author of the paper from BTI.
That's because pumpkins are remarkably nutritious and are packed with high levels of carotenoids, proteins, minerals and vitamins. As such, there is a growing demand for the crop in the developing world. Today, two-thirds of the world's pumpkins, squash and gourds are produced in Asia alone.
With such a large portion of the world relying on pumpkins for nutrition, it is crucial that scientists like Fei preserve the crop for the future. Sequencing the pumpkin's genome is an important first step.
In the study, Fei and his team of researchers decided to sequence the genomes of two different pumpkin species with different but equally desirable traits. C. moschata was chosen for its resistance to disease and extreme temperatures, while C. maxima was chosen for its fruit quality and nutrition.
Sequencing a genome is no easy task, especially when Cucurbitas have relatively large genomes compared to other fruits and vegetables. Each of the 20 pairs of its chromosomes needs to be physically separated, before each strand of DNA can be sequenced individually. In comparison, a watermelon has 11 pairs of chromosomes and a cucumber has only 7.
Even still, genomic sequencing is only the first step. Now, scientists have to actually analyze the results.
Nevertheless, once the genomes are deciphered, Fei hopes to be able to link specific pumpkin genes to the outward traits they control. That way, the pumpkins of the future will have greater nutritional value and will be less susceptible to disease. They will also be far better prepared for the effects of climate change.
The hybrid of these two species, called 'Shintosa', already shows great promise. It has an even greater stress tolerance than its parent, C. moschata, and its roots are often used to provide a strong foundation for other crops like watermelon.
By analysing these genomes, researchers will be able to better understand why the extreme phenotypes of the Shintosa hybrid exist. Even better, they may be able to figure out how to replicate these advantageous traits in the future.
According to Fey, the results of their study will go a long way towards accelerating the breeding process for pumpkin improvement.
Who knows what pumpkins will look like in the future.
The research was published in Molecular Plant.