Tag Archives: watermelon

New genetic research effort aims to make watermelons tastier, more resilient

If you like watermelons, this team has big news for you.

Image credits Aline Ponce.

A new research effort aims to pave the way towards new and improved watermelons. The study took a comprehensive look at the genomes of all seven watermelon species to create a database that plant breeders can use to produce tastier, plumper, and more resistant watermelons.

The Better Melon

“As humans domesticated watermelon over the past 4,000 years, they selected fruit that were red, sweet and less bitter,” said Zhangjun Fei, a faculty member at Boyce Thompson Institute and co-leader of the international effort.

“Unfortunately, as people made watermelons sweeter and redder, the fruit lost some abilities to resist diseases and other types of stresses.”

Back in 2013, Fei co-led the creation of the first watermelon reference genome. This database was built from an East Asian cultivated variety ‘97103’. That variety, and likely the watermelon you’re imagining right now belongs to the Citrullus lanatus species, i.e. the sweet fruit with a juicy red interior.

However, Fei explains that there are six other wild species of watermelon that have pale, hard, bitter fruits, but possess other desirable qualities — such as a higher resilience against man-made climate change. Introducing the genes that generate such qualities into cultivated watermelon varieties can help make the fruits tastier, better able to grow in diverse climates, as well as more resistant to pests, diseases, and other factors. But, in order for us to get there, we first need to know which genes these are.

In order to find out, the team started with the reference genome Fei worked on in 2013, and created an improved version. The previous work relied on short-read sequencing technologies, Fei explains, while the newer one uses long-read sequencing technologies, allowing for “a much higher quality genome that will be a much better reference for the watermelon community.”

Next, the group sequenced the genomes of 414 watermelons across all seven species. By comparing these genomes both to the new reference genome and to each other, they were able to determine the evolutionary relationship of the different watermelon species.

“One major discovery from our analysis is that one wild species that is widely used in current breeding programs, C. amarus, is a sister species and not an ancestor as was widely believed,” Fei said.

Modern watermelon cultivars were domesticated by breeding out the fruits’ bitterness while increasing their sweetness, size, and reddening their flesh. Over the past few hundred years, the fruits kept becoming sweeter, but also improved in regards to flavor and crispiness of texture. The team identified several regions of the watermelon genome that could be leveraged to continue improving these qualities in cultivars.

“The sweet watermelon has a very narrow genetic base,” says Amnon Levi, a research geneticist and watermelon breeder at that U.S. Department of Agriculture, one of the study’s co-authors. “But there is wide genetic diversity among the wild species, which gives them great potential to contain genes that provide them tolerance to pests and environmental stresses.”

The team also published an accompanying paper analyzing 1,175 melons, including cantaloupe and honeydew varieties. The researchers found 208 genomic regions that were associated with fruit mass, quality, and morphological characteristics, which could be useful for melon breeding.

The paper “Resequencing of 414 cultivated and wild watermelon accessions identifies selection for fruit quality traits” has been published in the journal Nature Genetics.

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How Nigerian music can help you choose ripe watermelons

When it comes to picking ripe watermelons, no method is fail-proof — but everyone has their own methods. Either by closely looking at it, tapping it, or simply taking a chance and picking the first watermelon you come across, we all have our ways of picking one. But a Nigerian researcher (and vocalist) believes traditional music can help in this endeavor.

In the scorching summers of my childhood, watermelons were a staple. The food markets were stacked with giant watermelon pyramids, sellers were shouting out their wares trying to woo customers. How do you pick a watermelon? I don’t even recall who taught me, but I was always a proponent of flicking the watermelons. You flick it with your nail and listen to the sound — if there’s a deep, almost echoing sound, it’s good. Otherwise, keep looking. Most days, it worked — some days, it didn’t. I never really understood why, and to be honest, I never thought too hard about it — but Nigerian researcher Stephen Onwubiko did.

Onwubiko, who is also a classically trained vocalist, has teamed up with physicist Tracianne Neilsen, from Brigham Young University in Utah and music researcher Andrea Calilhanna from the University of Sydney in Australia to quantify the watermelon-drumming phenomenon. The team analyzed the frequency spectrum of a Nigerian traditional drum, the igba.

An igba is cylindrical in shape and is between 70 and 75 centimeters long, and is widely available in Nigeria. Essentially, Onwubiko is working with watermelon sellers and consumers, training them to use an igba and recognize the sounds of a ripe watermelon. Of course, this involved a lot of trial-and-error in detecting the best watermelons. The similarities between the igba and ripe watermelons were remarkable.

“The sounds of ripe and unripe watermelons are heard in traditional music. An African drum pattern is made from the same two sounds,” said Neilsen.

Ultimately, the team hopes to develop a mathematical model involving the sounds, improving the efficiency (which is currently at 60%).

It’s a neat way in which we can use sounds to make a minor improvement in our lives. Onwubiko believes there are many such situations in such day-to-day situations, we just need to be on the lookout for them.

“Most people don’t have much idea about the noises around them or how they affect them,” Onwubiko said. “Everyday experiences, even decision-making, are influenced by the sounds around us.”

Sounds are an integral part of all cultures Calilhanna also points out.

Neilsen will present the findings at the 177th Meeting of the Acoustical Society of America, which takes place May 13-17, at the Galt House in Louisville, Kentucky. Results have not yet been peer-reviewed.