There are hundreds of different apple varieties, each with its own desirable qualities. Cultivated for centuries, apple trees have been selected to yield fruits with flavors, sizes or colors as nutritional treats within many different cultures. According to Cornell University, modern Americans tend to forget about old-fashioned apple varieties and want apples with recognizable shapes and variety names (such as 'Red Delicious,' 'Granny Smith' or 'Fuji'). While all apples and crab apples are closely related species, they can be interbred to yield new apple varieties that are easier to grow.
Apple tree varieties are developed as mutations occur on older apple trees or breeders deliberately cross the pollen of apple trees with the hopes to create an apple that combines desirable characteristics of two apple trees. Therefore, all apple varieties have different genetic makeup (DNA). For example, the "Gala" apple was created in New Zealand in 1934, when the apple tree variety "Kidd's Orange Red" was crossed with a "Golden Delicious" tree. Interestingly, the "Golden Delicious" apple tree resulted from a random seedling tree that resulted from the "Grimes Golden" variety tree, around 1900.
Seeds from apple trees result from flowers that were pollinated and therefore will never have the exact same genetics as the parent plant. The shuffling around of the DNA of plants in subsequent generations can produce plants that humans may or may not like. For apples, humans tend to favor those trees that produce lots of fruits with little effort. Those that have large, delicious-tasting fruits will likely be favored over trees that barely produce fruits or have an unpleasant color, shape or flavor. When presented with a selection of apple varieties, these basic fruit features will help identify them. While all the fruit may be the same size or color, the flavor of the apple's flesh, acidity, softness or grittiness of the flesh or color can all be used to differentiate among the many varieties.
While the best sized or tasting apple fruits may be the most desirable features of certain apple varieties, the varying genes in apple trees can also lead to trees with different tolerances to insects, diseases, winter cold or soil types. Some trees may have mature fruits earlier in summer, making them better for regions with shorter growing seasons. For example, the apple variety "Stayman," dating to the 1870's, produces a tasty apple but isn't particularly vigorous in growth. Plant breeders have retained the quality of the apple fruit, but further selected features that are worthwhile in agricultural settings. Today, many "improved" varieties exist, such as "Early Red Stayman," "Red Stayman," "Scarlet Staymared," "Snapp Stayman," "Staybrite Stayman" and "Supreme Staymared."