EAST LANSING, Mich. – Michigan State University (MSU) researchers have announced they have mapped out a genome of the Montmorency sour cherry, the dominant sour cherry tree in the United States.

The researchers published their findings in a recent issue of the journal Horticulture Research, pointing out the difficult breeding history of the variety, which has impacted the tree’s fertility and ultimately tree fruit yield. “This really gives us the information we need to understand things like bloom time, firmness, color and size,” said Charity Goeckeritz, a PhD candidate at MSU and co-author of the paper. “This genome really gives us a much more holistic picture of what we’re working with.”

Genomes contain all the genes and genetic instructions for an organism’s development. Sequencing it provides a map for researchers when they are trying to, for example, grow a cherry tree that will bloom later in the season. The process of mapping out the genome might also be described as putting the pieces of a puzzle together; Goeckeritz added that the genome might be best described as a blueprint.

In the journal article, the researchers reference the disastrous 2012 season, in which a series of very early and pronounced warm spells were followed by frosts, essentially destroying the fruit harvest that year. Early spring freezes are major contributors to crop loss in the temperate fruit tree industry, the article states.

 “We could use the genome to develop a cherry tree that blooms later in the season,” Goeckeritz said. “If we knew which genes have the traits that we want, then we can more efficiently breed them into new trees. It’s possible to manipulate the trees to delay bloom time, but it would also be possible to develop a tree that would be resistant to the cold, even with the tree blooming early.” The authors point out a systemic problem with the sour cherry tree, namely that the tree produces far less fruit than what the tree could support, although the Montmorency sour cherry tree is an exception to this rule. “However, even in crosses between two productive cultivars, the low fertility in the offspring is clear,” the article states.” For example, the article states, when two well known sour cherry types were crossed,  fruit yield and pollen germination were very low, at 6.8 percent and 6.6 percent respectively. Both these values are far below what is needed for a commercial crop, the article says. The authors conclude that breeding for higher fruit yield is a major but challenging goal for the MSU sour cherry breeding program.

“We think one of the reasons the cherry tree has low fertility is that it has such a complicated genome structure,” Goeckeritz stated. “The genome will also help with our understanding of this fertility problem.”  MSU PhD candidate Kathleen Rhoades is also a co-author of the paper, as well as MSU researchers Kevin Childs, Amy Iezzoni, Robert VanBuren and Courtney Hollender.