Scientists peel back the ancient DNA of bananas and discover three "mysterious ancestors"

It is generally believed that bananas were first domesticated
by the people of the island of New Guinea 7,000 years ago.
However, the history of the domestication of bananas is complex, and their classification can also be hotly debated, as the boundaries between species and subspecies are often not clear
.

A recent study published in Frontiers in Plant Science suggests that this history is more complex
than we previously thought.
The results confirm that the genomes of today's domesticated breeds contain traces
of three other unknown ancestors.

Dr Julie Sardos, a French scientist at the International Centre for Biodiversity, said: "Here we show that most of the dioploid cultivated bananas today are from wild bananas (M.
Sardos).
acuminata) evolved and they are hybrids between different subspecies
.
At least three additional 'mysterious ancestors' were involved in the formation of this hybrid genome thousands of years ago, but have yet to be confirmed
.
”

Complex domestication history

It is believed that domesticated bananas were crossed by multiple parents, either M.
Different subspecies of acuminata (A genome) are either different but closely related
.
M.
acuminata appears to have evolved in the northern border region between India and Myanmar and has been present in Oceania for
about 10 million years.
To further complicate matters, domesticated species may have two sets (diploid), three sets (triploid), or four sets (tetraploids) chromosomes, and many are also wild species M.
Descendants
of the balbisiana (B genome).

Some recent small-scale studies have shown that although these situations are already complex, they may not be the whole story, as opposed to M.
Acuminata more distant ancestors may have also been involved in the domestication process
.
The new study not only confirms this result, but for the first time shows that these gene pools are common
in domesticated banana genomes.

Banana collection mission

The researchers collected 226 leaves from the Banana Germplasm Transfer Center in Belgium and performed DNA sequencing
.
Of these samples, 68 belonged to M.
Of the nine wild subspecies of acuminata, 154 belong to M.
Diploid domesticated varieties of acuminata, with 4 additional exotic wild varieties and hybrid varieties for comparison
.

The researchers first measured the kinship between cultivated bananas and wild bananas and established a "family tree" based on 39,031 single nucleotide polymorphisms (SNPs
).
They used a portion of these SNPs to analyze
their ancestors.
For the first time, they found traces of three other ancestors in the genomes of all domesticated samples, while no matching genes
have been found in the wild.

Mysterious ancestors

The mysterious ancestors of bananas may have been extinct long ago
.
Dr Sardos said: "But we personally believe that they still live somewhere in the wild, either because there is not much scientific research or there is no research at all, so it seems that they may be facing an existential crisis
.
" ”

Sardos et al.
have a good idea of where to go to find their ancestors: "Our genetic comparisons show that these mysterious ancestors either came from the region between the Gulf of Thailand and the western part of the South China Sea, from the region between northern Borneo and the Philippines, or from the island
of New Guinea.
" ”

Grow better bananas

What useful traits these mysterious ancestors contributed to the domestication of bananas is unclear
.
For example, the key feature of unisexual fruiting (i.
e.
, results without pollination) is thought to be inherited from M.
Acuminata, while bananas suitable for cooking have a large part of their DNA from M.
Acuminata banksii subspecies
.

Co-corresponding author Dr Mathieu Rouard of the International Centre for Biodiversity said: "It is important to identify the ancestors of cultivated bananas as it will help us understand the formation process and path of banana diversity observed today, which is a key step
in cultivating future bananas.
”

"Breeders need to understand the genetic makeup of currently domesticated diploid bananas in order to hybridize between different varieties, and this study is an important step
towards detailed characterization of multiple varieties.
"

Source text search

Hybridization, missing wild ancestors and the domestication of cultivated diploid bananas

Front.
Plant Sci.
, 07 October 2022