Penn State researchers created a new family tree for Solanum plants, like tomatoes and eggplants, showing that fruit size and color evolved together. They found that fruit-eating animals were not the main reason for these changes. This study, published in New Phytologist, could help in breeding better crops.
João Vitor Messeder, a Penn State graduate student and lead author of the paper, said, “There are about 1,300 species in the Solanum genus, making it very diverse. Researchers have thought fruit-eating animals like birds and bats drove the evolution of Solanum fruits. However, the plant’s evolutionary history has been overlooked. We needed a better family tree to understand these relationships.”
Solanum plants produce fruits of various sizes and colors, from tiny to large, and black, purple, red, green, yellow, or orange. Humans and many animals, including birds, bats, and mammals, eat these fruits. Some Solanum plants are also grown for their flowers.
Researchers collected plant samples worldwide and sequenced their genes to build a detailed Solanum family tree. They compared 1,786 genes from 247 species, covering all major branches of the genus.
This comprehensive tree, the best so far, uses thousands of shared genes. New technology allowed us to resolve species relationships better, helping us understand the evolution of fruit colors and sizes.
Researchers improved the family tree for potatoes, tomatoes, and wild relatives. These findings could help improve crop traits like pest resistance or fruit size and color.
“If wild relatives of crops have desirable traits, we can use them for breeding better crops,” said João Vitor Messenger.
The study found that Solanum fruit color and size evolved together, with closely related species having similar fruits. Color changes often matched changes in size.
These results suggest that physiological and molecular mechanisms may keep fruit color and size evolution linked. While fruit-eating animals may influence diversification, we must consider all possibilities.
Researchers also clarified Solanum’s origin and diversification timeline using the oldest nightshade fossil and specific genes. They dated Solanum’s origin to about 53.1 million years ago, much earlier than previous estimates. This helps us understand the environment that influenced the plant’s diversification.
The Earth’s environment changed a lot over 30 million years. Knowing when Solanum originated helps to understand the conditions that influenced its diversification.
The team found that early Solanum had medium-sized green berries. Green and yellow fruits became more diverse around 14 million years ago, possibly influenced by bats, which dispersed the fruits and seeds as they evolved.
Next, researchers will study how modern animal-fruit interactions and specific genes relate to fruit color and size evolution.
In conclusion, a new family tree for tomatoes and potatoes shows that fruit color and size evolved together. This finding challenges previous beliefs about the role of fruit-eating animals in this process and could help improve crop breeding.
Journal reference:
- João Vitor S. Messeder, Tomás A. Carlo et al., A highly resolved nuclear phylogeny uncovers strong phylogenetic conservatism and correlated evolution of fruit color and size in Solanum L. New Phytologist. DOI: 10.1111/nph.19849.