Honeycrisp, introduced in 1991 by the University of Minnesota, set the standard for crispness, juiciness and upscale pricing. But for all its popularity, the apple is soft, quickly dissolving in the mouth. Its flavor is inconsistent and fades in long storage, and it is maddeningly difficult to grow.

Cosmic Crisp, a cross of Honeycrisp and Enterprise, is firmer but not too hard to bite, and much easier for farmers and packers to manage. Firmness is crucial because it helps apples keep longer, and supermarkets demand year-round availability.

Even more important for extended eating quality is acidity. It is low in the three leading Washington varieties — Red Delicious, Gala and Fuji — and drops in storage, leaving apples tasting flat. By contrast, Cosmic Crisp, which is high in both sugar and acidity, not only tastes great off the tree, but also retains a balanced flavor and crispness all year, even after weeks in a warm kitchen. That may not sound romantic, but it’s a game changer.

Cosmic Crisp, of course, is a commercial variety, with qualities far different from those of older varieties known as heirlooms. For example, it is only mildly aromatic compared with the best-flavored heirloom apples, which offer an added dimension of intensity and complexity akin to that of fine wines.

Dr. Evans, 49, grew up in England savoring highly aromatic Cox’s Orange Pippins, and loves that style of apple, but worries that it has to be harvested at optimal ripeness to fully develop its fragrance. “If you market something as highly aromatic and don’t deliver, you’re not going to get any repeat purchasers, are you?” she said.

Developing a new variety, from the initial cross to the store display, is a protracted and painstaking process. Dr. Evans uses the traditional method of applying pollen of one parent tree to the flowers of another, then planting the seeds of the resulting fruit, waiting five years for seedlings to bear, and evaluating tens of thousands of candidates for each eventual variety.