Scientists have developed a new genetic analysis method that uses “time stamps” hidden in DNA to trace the complex origins of the cultivated strawberry, revealing a far more complicated evolutionary history than previously understood.
Many major crops, including strawberry, wheat and cotton, have highly complex genomes formed through repeated hybridization and whole-genome duplication. These plants carry multiple sets of chromosomes from different ancestral species, making it difficult for scientists to reconstruct their exact origins, especially when some ancestor species are extinct or unknown.
A new study published in the journal *Horticulture Research* presents a genome-wide approach that helps untangle these complicated histories. The method analyzes patterns in long terminal repeat retrotransposons, a type of mobile DNA that leaves behind evolutionary signatures over time. By comparing similarities in these genetic elements across chromosomes, researchers can separate different ancestral genome groups and estimate when key genome-merging events took place.
When applied to the cultivated octoploid strawberry the approach revealed that its genome was formed through multiple rounds of ancient hybridization events. The analysis identified four distinct subgenomes and suggested that three major genome-merging events occurred between about 3.1 and 0.8 million years ago.
The findings also support links between parts of the strawberry genome and two wild species, ‘Fragaria vesca’ and ‘Fragaria iinumae’, while challenging earlier theories that suggested additional unknown ancestor species. Researchers say some of the missing contributors may be extinct or have not yet been identified.
Before testing the method on strawberry, scientists validated it using other well-studied crops such as teff and cotton, where it successfully separated known subgenomes and reconstructed their evolutionary timelines.
Researchers say the approach could have broad applications for other important polyploid crops. Better understanding of subgenomes may improve gene mapping, trait identification and plant breeding strategies, potentially helping to develop stronger and more productive crop varieties.
The study highlights how mobile DNA elements can act as evolutionary markers, allowing scientists to reconstruct genome history even without direct access to ancestral species.
Source: Daily Science