The University of Minnesota apple breeding program, which gave the world the Honeycrisp apple in 1991, is on a mission to develop apple varieties that will give consumers a consistently enjoyable apple eating experience. A multitude of traits contribute to eating quality, including the appearance of the fruit (e.g., color, shape and free of blemishes), fruit texture (crispness, juiciness, firmness), sweetness, tartness, aroma and flavor. In addition, qualities such as how long a variety will maintain its quality in storage, disease resistance and production traits need to be considered by plant breeders when developing a new variety. Apple breeding is therefore a time- and resource-intensive process. It can take 20-30 years to develop a new apple variety!
Located about one mile west of the Minnesota Landscape Arboretum entrance on Highway 5 near the Arboretum’s AppleHouse, the Horticultural Research Center (HRC) is the home of the University’s apple breeding program. The HRC’s vast landscape features acres of research orchards with apple trees in various stages of evaluation.
Seeds are the foundation of the apple breeding program
Each seed is a child (i.e., an offspring) of the apple variety it came from (its mother) and pollen from its father; therefore, each seed is genetically unique. For example, a seed from a Honeycrisp apple is a child of Honeycrisp and therefore will likely share some characteristics of Honeycrisp but will not be identical to Honeycrisp.
In the apple breeding program, seeds are produced through a process called controlled hybridization, which simply means that plant breeders control what pollen goes on what flowers. In the spring, research staff put pollen from the tree of one variety onto the flowers of another variety after months of planning and reviewing decades’ worth of data.
Horticultural Research Center staff member Winford McIntosh pollinates flowers of breeding parents to generate seeds. Photo by Kate Scapanski
The seeds are collected in the fall and germinated the following spring. About 5,000 new seedlings are propagated into the orchard each year. The challenge for breeding program staff is to identify which offspring, out of the thousands produced, have inherited the right combination of their parents’ characteristics. In other words, the apple breeding program team is looking for a needle in the proverbial haystack.
Apple breeding program staff taste thousands of apples each fall
Starting at the end of July until about the end of October, the breeding program team tastes fruit from thousands of seedling trees. Most fruit ranges in quality from mediocre to disgusting. The tasting process inevitably involves a lot of spitting. Most trees that are evaluated are discarded at the end of the year. Of the 2,000-5,000 trees evaluated in a year, only about 10 are determined to be promising enough to be selected for further testing.
Trees selected for further testing are propagated via grafting, which allows horticulturists to produce clones of a given tree. Selected trees are called “advanced selections,” and these will undergo testing for several years. Testing includes extensive evaluation of eating quality at harvest and after cold storage; determination of susceptibility to diseases, insect pests and other disorders; and evaluation of winter hardiness.
(Left) Young apple seedlings growing in the greenhouse at the Horticultural Research Center. (Right) Project staff Kate Scapanski, David Bedford and John (Jack) Tillman evaluate the fruit of an advanced selection. Photos by Sarah Kostick
After several years of testing, most advanced selections will be discarded from the breeding program. Only a handful of selections will become new varieties. Relatively recent apple varieties released by the apple breeding program include SweeTango®, First Kiss®, Triumph® and Kudos®. What could be next?
Learn more about the University’s apple breeding program and explore the University’s apple releases from the last 100 years on the Minnesota Hardy website.
Cover photo by David Hansen