Scientists find genetic markers for size, firmness, sweetness
By DAN WHEAT
PULLMAN, Wash. -- The Pacific Northwest cherry industry is making big steps in the development of what it calls "Big Jim," the ultimate cherry that's large, firm and has great flavor.
Genetic markers linked to genes that control cherry size, firmness and sweetness have been discovered by Michigan State University and Washington State University scientists.
It's exciting, said Cameron Peace, a WSU tree fruit molecular geneticist, because it will increase the efficiency of WSU's cherry breeding program and means the new cherry may be available for commercial production in 10 instead of 15 years.
"Big Jim is the target the industry has wanted for years, but getting there is like trying to pin the tail on the donkey, blindfolded," Peace said. "Now we can take the blindfold off and pin size, firmness and tastiness all at the same time."
In 2004, WSU began a new sweet cherry breeding program at its Prosser, Wash., research station, replacing a program that had lapsed.
Amy Iezzoni, professor of horticulture and a tart cherry breeder at Michigan State University in East Lansing, Mich., chose initial parent material and made the first crosses for WSU's new program.
In 2005, WSU hired a new cherry breeder, Nnadozie Oraguzie, a Nigerian native with a doctorate in plant breeding and genetics from New Zealand. Iezzoni still assists the program as a consultant.
She said she had been working toward identifying genetic markers for large cherries for a couple of years. This fall, she said, she found the marker, and Peace was able to find the same marker in cherry seedlings in Washington.
Certain genetic markers indicate large cells, which in turn means larger fruit, Peace said.
"We don't know the gene," he said. "We just have the DNA marker."
Peace confirmed Iezzoni's marker for large fruit, but also discovered it's a predictor of soft fruit, not a desirable trait.
Then he found another genetic marker for large but firm and sweet fruit.
Iezzoni said it's a rare find. Peace agreed.
"Its a very rare variance. It's amazing," he said. "Normally when these studies are done, large is always softness and smallest is firmest."
But he wasn't done. He discovered a DNA marker for self-fertility. A cherry with that trait needs no other variety nearby for pollination.
Oraguzie will cross seedlings with the DNA markers to try to find a selection that is large, firm, delicious and self-fertile, Peace said.
Great genetic diversity of cherry seedlings that Iezzoni established is of equal importance to the DNA in the process, he said.
A statistical analysis confirming the markers for size, firmness, sweetness and self-fertility was completed in early November.
"The science of genetics in cherries is finally on a roll," said Tom Auvil, a research horticulturist with the Washington Tree Fruit Research Commission.
"It appears every single cherry variety we grow commercially has a flaw we don't like," Auvil said.
Rainier is extremely sensitive to handling, bruising too easily, even from its own leaves in wind, he said.
Bing is low yielding and susceptible to mildew. Lapin and Sweetheart are self-fertile, but they pit and bruise.