Genetic anomaly creates giant apples

Posted by Nicole Eckersley on 8th July 2010

Gala and Grand Gala apples - Peter HirstA genetic glitch in some Gala apple trees, which stops cells from dividing, has been found to result in apples which are almost double the size of their normal counterparts.

Peter Hirst, a Purdue University associate professor of horticulture, found that the apples with the anomaly – called Grand Galas – produced fruit that were around 38% heavier, with a 15% greater diameter, than regular Galas.

“It’s never been found in apples before,” Hirst said. “This is an oddball phenomenon in the apple world.”

Hirst is trying to understand what causes the difference in the size of apples – for instance, why Gala apples are so much larger than crabapples.

“There is real incentive for fruit growers to increase the size of their apples,” Hirst said. “At 125 apples per bushel, a grower gets 8 cents per apple. But if they have larger apples – 88 per bushel – the price more than doubles.”

“The way the Grand Gala was found was that someone in an orchard full of Gala trees noticed that one branch had different-sized apples than the rest of the tree. They grafted new trees from this branch to started a new tree,” Hirst said. “These are just chance events.”

Normally, a larger apple has more cells than its smaller counterparts, but the Grand Gala has the same number. A phenomenon called endoreduplication causes each cell in a Grand Gala to grow larger instead of splitting into two cells.

The Grand Gala fruit has the same core size, so the added size and weight is in the meat, or cortex, of the fruit. Hirst said they’re also crunchier and tend to taste better.

Hirst’s study found that one or more of a handful of genes is likely responsible for the endoreduplication. And while it may be possible to isolate those genes and find ways to increase the size of other apples, Hirst said it’s unlikely.

“You won’t see Grand Galas in the grocery store,” Hirst said. “Consumers like shiny, perfect-looking apples. Grand Galas are slightly lopsided. They’re good eating apples, but the end product isn’t something that consumers are used to seeing at the store.”