Nectarines

Podcast

Nectarines

Transcript

The origin of the fuzzless peach. I'm Bob Hirshon and this is Science Update.

Today's Why Is It? question comes from Karen Hopkin Of Somerville, Massachusetts. She thought the nectarine was a cross between the peach and the plum. But she was startled to hear that the nectarine may actually be some sort of mutant peach. She wants to know what's what.

Well, according to Wayne Sherman, a horticulturist at the University of Florida, the mutation theory wins out.

Sherman:
A nectarine is a mutation of peach from fuzzy skinned to no fuzzy skinned, or glaucoused from pubescence.

That means peaches and nectarines essentially have the same genes. A peach tree will produce peaches if it inherits the dominant, fuzz-producing gene. But it'll make nectarines if it gets the recessive, or hairless, version of the gene.

And Sherman says the gene does more than produce fuzz.

Sherman:
There are a number of factors that go along with the glaucous skin of the nectarine. Nectarines generally have more red color in the skin, more rounder shape, smaller size, more sugars, more acids, and more higher density.

If you've got a science question, call us at 1-800-Why-Isit. If we use it on the show, you'll get a free Science Update mug. For the American Association for the Advancement of Science, I'm Bob Hirshon.

Making Sense of the Research

Although living things have thousands of genes, it's remarkable what a difference a single gene can make. In this case, the gene separates peaches from nectarines. As Sherman explains, it affects not only the skin of the fruit but also its color, shape, size, and flavor.

This is a classic example of Mendelian genetics at work. Named after Gregor Mendel, the 19th-century monk who pinoeered genetic science, it's a phrase that scientists use to describe the simplest patterns of genetic inheritance.

Nectarines and peaches demonstrate the pattern of simple dominance. Like people, animals, and most other living things, nectarine and peach trees have two copies of every gene—one from each parent. (Yes, plants have parents; see the Science NetLinks lesson Plant Parents, linked below, for more details.) The peach version is dominant and the nectarine version is recessive.

In simple dominance, as long as one copy of the dominant gene is present, the dominant trait will be expressed (in other words, it will show up in the living thing). So if you have even one peach gene, you get a peach tree. You need two copies of the nectarine gene to get nectarines.

There are other patterns of inheritance besides simple dominance. In incomplete dominance, if you have one copy of the dominant gene and one of the recessive, the living thing will be a hybrid that differs from both the pure dominant and pure recessive version. Many other traits are non-Mendelian, which means that although they are inherited, they don't follow the simple patterns that Mendel first described.

It's important to note that although nectarines are a mutant version of the peach, that doesn't mean they're "genetically engineered." Genetically-engineered foods are grown from plants whose genes were deliberately altered in the laboratory at some point in time. Nectarines are all-natural mutants that originated in China over 2,000 years ago.

Now try and answer these questions:

1. What is a nectarine?
2. What does "simple dominance" mean? How does it relate to peaches and nectarines?
3. Which of the following would be possible, and why? Remember that each tree inherits one copy of the peach/nectarine gene from each parent.
   A) Cross two peach trees, get a peach tree
   B) Cross two peach trees, get a nectarine tree
   C) Cross a peach and a nectarine tree, get a nectarine tree
   D) Cross a peach and a nectarine tree, get a peach tree
   E) Cross two nectarine trees, get a peach tree
   (Click here for answers)
4. Some people (incorrectly) believe that the nectrarine is a genetic cross between a peach and a plum. Why do you think this is?

Going Further

MendelWeb is an educational resource for teachers and students interested in the origins of basic genetics, elementary plant science, and the history and literature of science.

Plants 1: Plant Parents and Plants 2: Plant Propagation are two related Science NetLinks lessons on plant reproduction.

The Origins of Fruit and Vegetables, by Jonathan Roberts (Universe Books, 2002: ISBN 0789306565), traces the history of many of the fruits and vegetables we grow today, and includes perspectives on their roles in art and culture.