Roughly 5,000 to 10,000 years ago, peanut plants underwent a trade-off: the modern peanut plant lost the genetic diversity and disease-resistance of its wild relative, but gained all the qualities that make peanuts the most loved nut in America.
While it doesn’t sound like a bad trade-off, wouldn’t it be better to have your peanuts and eat them too? That’s the idea behind recent work out of the University of Georgia that seeks to cross the wild species to create lines that can be breed with modern peanut plants.
While modern peanut plants are tetraploids, or plants with four sets of chromosomes, wild peanut plants only have two sets of chromosomes, referred to as diploid. This chromosome discrepancy makes it impossible to breed modern peanut plants with their wild relatives—at least without some human assistance.
“The wilds are ugly distant relatives that peanut does not want to mix with, but we do the match-making,” said Soraya Leal-Bertioli, senior research scientist and co-director of the Wild Peanut Lab at the University of Georgia.
The germplasm lines Leal-Bertioli created, with her colleague and husband David Bertioli, are called "induced allotetraploids," meaning they are made through a complex hybridization that converts the wild diploid species into tetraploids. This new line is resistant to early and late leaf spot—diseases that cost Georgia peanut producers $20 million a year—and root-knot nematode, a problem that few approved chemicals can fight.
Additionally, Ye (Juliet) Chu, a senior research associate in the university’s horticulture department, used five peanut relatives to created three new varieties that also show resistance to leaf spot. One of Chu’s is even resistant to tomato spotted wilt virus, a disease that can destroy an entire peanut crop.
Creating the first fertile allotetraploids is an ongoing challenge that has been years in the making. The game-changer for the researchers came once they were able to sequence the genome of the peanut.
Over 10 years ago, acknowledging the disease-resistant benefits of wild peanut plants, the researchers began the arduous task of sequencing the peanut crop. In 2014, their work came to fruition, with University of Georgia researchers and collaborators releasing the first peanut genome sequence.
“With genetic markers developed using the genome, breeders not only can tell that a plant has a desirable trait, they know what genome regions are responsible for that trait and can combine DNA profiling with traditional field selection to speed the complex process of developing a new variety,” explain the researchers.
Once the allotetraploids are fertile, plant breeders will be able to cross those lines with the modern peanut plant to achieve the holy grail—a crop that produces nuts the size and taste of current times but with wild species disease-fighting abilities.
The researchers’ latest work is published in the Journal of Plant Registrations, where they will continue to document the release of additional peanut germplasm with advantageous traits.
"In the past, we knew where we were going, but it was like everyone drew their own map," said Bertioli. "Now, it's like we have GPS. [Scientists] can tell each other, 'Here are my coordinates. What are yours?' And all the data is published."
Photo: Wild peanut variations in the lab of David Bertioli and Soraya Leal-Bertioli at the Center for Applied Genetic Technologies. Credit: Andrew Davis Tucker/UGA