Key Points:
- Genetic results confirm the genome of today’s domesticated varieties of bananas contain traces of three unknown ancestors.
- The mystery ancestors might be long since extinct, or either poorly described by science or not at all.
- Identifying the ancestors of cultivated bananas is a crucial step to breed bananas of the future.
Bananas are thought to have been first domesticated by people 7,000 years ago on the island of New Guinea from a cluster of four ancestors, either subspecies of the wild banana Musa acuminata, or distinct but closely related species.
Now, a study in Frontiers in Plant Science shows that the bananas history is more complex than though, with the genome of today’s domesticated varieties containing traces of three extra, unknown ancestors.
For the study, the authors sequenced the DNA in 226 extracts leaf extracts from the world’s largest collection of banana samples at The Alliance of Bioversity International and CIAT’s Musa Germplasm Transit Centre in Belgium. Among these samples, 68 belonged to 9 wild subspecies of M. acuminata, 154 to diploid domesticated varieties descended from M. acuminata, and 4 more distantly related wild species and hybrids as comparisons.
The researchers first measured the levels of relatedness between cultivars and wild bananas and made family trees based on the diversity at 39,031 single nucleotide polymorphisms (SNPs). They used a subset of these to statistically analyze the ancestry of each block. For the first time they detected traces of three further ancestors in the genome of all domesticated samples, for which no matches are yet known from the wild.
The mystery ancestors could long be extinct, but the researchers believe they are still living somewhere in the wild, either poorly described or not described at all—in which case they are probably threatened. Luckily, the study results gave researchers a clue as to where to start looking.
“Our genetic comparisons show that the first of these mystery ancestors must have come from the region between the Gulf of Thailand and west of the South China Sea. The second, from the region between north Borneo and the Philippines. The third, from the island of New Guinea,” the researchers said.
Which useful traits these mystery ancestors might have contributed to domesticated bananas is not known—yet.
“Identifying the ancestors of cultivated bananas is important, as it will help us understand the processes and the paths that shaped the banana diversity observed today, a crucial step to breed bananas of the future,” said second corresponding author Mathieu Rouard, from Bioversity International. “Breeders need to understand the genetic make-up of today’s domesticated diploid bananas for their crosses between cultivars, and this study is a major first step toward the characterization in great detail of many of these cultivars.”
Information courtesy of Frontiers.