With Michigan paving the way for the cherry industry as the nation's leading tart cherry producer, Michigan State University researchers were interested in finding genes associated with tart cherry trees that assist with blooming later in the season.
College of Agriculture and Natural Resources assistant professor Courtney Hollender and Ph.D. graduate research assistant Charity Goeckeritz found there were many similarities and differences in DNA sequencing between tart cherry genomes and those of a related species: the peach.
“I wanted to find out in this population, this group of cherry trees that were siblings, what gene or genes they're controlling, whether it's late blooming or early blooming,” Goeckeritz said. “To do that, though, you sequence the siblings, the individuals and then you compare their DNA sequences. But usually ... you have to align it to a reference, first.”
Originally, Goeckeritz and Hollender analyzed the tart cherry genomes by comparing them to peach genomes. However, they had to adjust their approach when there weren't enough similarities between the two genomes.
When Goeckeritz mentioned her frustrations with the peach genome to her friends, one of them suggested and one of them suggested that they simply sequence the genome.
“10 years ago, that would have been a really crazy thing to pitch," Goeckeritz said. "But with the technology nowadays, it’s actually relatively easy.”
The two researchers teamed up with horticulture professor and the nation’s only tart cherry breeder Amy Iezzoni, along with a multitude of other MSU researchers to get the project going.
“We thought that this species was going to be equally a mix of the one parent and the other parent, which it typically is," Goeckeritz said. "But what we weren't expecting is that one of the parents is also a hybrid."
Hollender and Goeckeritz found the the parent hybrid was actually a mix of two species: ground and sweet cherries.
Each species contributed their respective species genomes to the tart cherry. With three species- the ground cherry, sweet cherry, and tarty cherry- having four sets of chromosomes each, the project became more complicated.
Goeckeritz said the resulting mix was "beautifully complex" and gives the tart cherry it's fun, flavorful characteristics.
“We identified what sequences belong to what genes, like prediction models, and then as you figure out what traits you have, you can identify this flavor, this color, this size is associated with these specific genes,” Hollender said. “And then you can use that knowledge in the breeding process.”
In simpler terms, Hollender said, this genome sequence will make breeding more efficient. She said once genes have been identified that are associated with the desired traits, a molecular tag can pinpoint where they are.
Goeckeritz said their genome can also help people breeding related species, such as peach, sweet cherry, pear and almond.
“If you've got a gene in tart cherry that does one function and you have a related species like peach, then it probably has a (similar) gene ... that does the same function in a slightly different way," Goeckeritz said. “If we know a lot about the function of the one in tart cherry, then potentially we could kind of extrapolate that and guess what (other genes) could do."
Hollender and Goeckeritz said the reason for their specific interest in late blooming comes from Michigan's susceptibility to spring frosts.
In the last 20 years, April and May frosts have largely contributed to killing off entire tart cherry crops. If they can cultivate cherries that bloom a little later, Goeckeritz said, the cherries are less likely to be killed off.
“It's like cold avoidance,” Goeckeritz said. “We’re trying to avoid the cold, as opposed to breeding for cold resistance.”
Now that Goeckeritz and Hollender know what the genome looks like and consists of, as well as how it behaves, they may have the potential to increase fertility.
Then, Goeckeritz said, they can hopefully select trees that are better at meiosis and consequently more fruitful.
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