The Truth About Apples

Oct 10, 2017

In this month’s Field Notes, Susan Knight of Trout Lake Station tells us about the genetics of apples and the real story behind Johnny Appleseed.

Before I ever got to college, I knew I wanted to be a biologist, in fact, a zoologist, or so I thought. I grudgingly signed up for a few plant classes, including plant taxonomy. Well, the professor wasn’t all that interesting, but I would have followed the teaching assistant anywhere. I was completely smitten… with the plants, of course.  My class focused on flowering plants, but I was surprised to learn that included maple trees and grasses.  Who knew they had flowers? Buttercups and roses, sure, but oak and birch trees? Not only that, but after that flower was pollinated (I did know about birds and bees), you got a fruit.  I learned that fruits are just a handy container for seeds, those little bits of genetic recombination needed for the plant to persevere

Apples are especially intriguing. Did you ever wonder why apple trees are always grafted, instead of being grown from seeds? Apple seeds are hard and brown, bitter and buried deep within the apple. But the apple is nutritious and attractive to animals. Animals eat the fleshy fruit along with the less digestible seeds and poop out the seeds some ways off. The seeds arrive in a new neighborhood, and right in the middle of a nice nutritious pile of poop, ready to start their new life.

In the wild, this is how a new apple tree would get its start, but a seed from a Macintosh or Honey Crisp would grow into a tree with apples that tasted nothing like the parent. In fact, it is very likely they would be just horrible. While all offspring vary from their parents, just as your kids are not clones of you, in apples, the seeds grow into trees that are just crazy different from the parent. Lucky for us, the apples we eat do not reflect the genetic variety of the seeds inside.  The apple is just a fleshy, sweet swelling of a part of the apple blossom, and its taste is not controlled by the genetic chaos of the seeds. So, it is the parent tree to whom we must be grateful for the tasty apple, not the unreliable seeds.

After growing thousands of varieties of apple trees from thousands of seeds, and taste-testing the apples, the best varieties have been identified. Now, we propagate favorite varieties by grafting a branch of a tree with known flavorful apples onto a sturdy trunk. Varieties can be propagated, or cloned, almost forever in this way.

In “A Botany of Desire”, one of my all-time favorite books, author Michael Pollan traces the history of John Chapman, better known as Johnny Appleseed. Johnny Appleseed was a very strange dude, but he really did spread all those apple trees throughout the expanding United States. However, he did not make any effort to graft the best tasting varieties. Instead, he planted apple seeds, and grew apple trees to sell to the steady stream of homesteaders heading west.  Because the trees came from random seeds, the apples would have been largely inedible.  But the homesteaders didn’t really care. What they wanted was a source of sweet fruit to make alcoholic cider.  Grapes didn’t grow well in the colonies back then, and apples were the only fruit sweet enough to ferment into alcohol.

Apples, of course, have been around for millennia, but where are their roots? Michael Pollan describes how a Russian botanist, Nikoli Vavilov, stumbled on a forest of apple trees in Kazakhstan in 1929. Vavilov quickly realized this was most likely the center of the genetic diversity of apples. You may remember an earlier Field Notes in which I discussed the disastrous Soviet repudiation of genetics under Joseph Stalin. Unfortunately, Vavilov, our erstwhile apple geneticist, was thrown into prison by Stalin for his untimely interest in genetics, where, unfortunately, he starved to death in 1943.  Not until the fall of the Soviet Union did Vavilov’s last student summon help from the west to help preserve the genetic diversity of the Vavilov’s wild apples, growing on land under threat of a real estate development. That western help came from a New York horticulturist who traveled to Kazakhstan and was amazed to see apple trees of incredible variety, some of them 300 years old and 50 feet tall.  He brought back as many apple seeds as he could, and planted them out in what amounts to an apple museum, or apple genetic seed bank in the Finger Lakes region of NY.

The apple-eating public now favors just a few varieties, and since they are cloned, they are especially vulnerable to diseases and pests. The New York orchard cultivating and preserving apple genetic diversity may save our apples for the future, so that another generation’s Johnny Appleseed will always have apples to grow, and for us to eat. 

For Field Notes, this is Susan Knight of UW-Madison’s Trout Lake Station.