An apple is a sweet, edible fruit produced by an apple tree (Malus domestica). Apple trees are cultivated worldwide and are the most widely grown species in the genus Malus.
Of the many Old World plants that the Spanish introduced to Chiloé Archipelago in the 16th century, apple trees became particularly well adapted. Apples were introduced to North America by colonists in the 17th century, and the first apple orchard on the North American continent was planted in Boston by Reverend William Blaxton in 1625. The only apples native to North America are crab apples, which were once called "common apples". Apple cultivars brought as seed from Europe were spread along Native American trade routes, as well as being cultivated on colonial farms. An 1845 United States apples nursery catalogue sold 350 of the "best" cultivars, showing the proliferation of new North American cultivars by the early 19th century. In the 20th century, irrigation projects in Eastern Washington began and allowed the development of the multibillion-dollar fruit industry, of which the apple is the leading product.
The proverb, "An apple a day keeps the doctor away", addressing the supposed health benefits of the fruit, has been traced to 19th-century Wales, where the original phrase was "Eat an apple on going to bed, and you'll keep the doctor from earning his bread". In the 19th century and early 20th, the phrase evolved to "an apple a day, no doctor to pay" and "an apple a day sends the doctor away"; the phrasing now commonly used was first recorded in 1922. Despite the proverb, there is no evidence that eating an apple daily has a significant health effect.
In 2010, an Italian-led consortium announced they had sequenced the complete genome of the apple in collaboration with horticultural genomicists at Washington State University, using 'Golden Delicious'. It had about 57,000 genes, the highest number of any plant genome studied to date and more genes than the human genome (about 30,000). This new understanding of the apple genome will help scientists identify genes and gene variants that contribute to resistance to disease and drought, and other desirable characteristics. Understanding the genes behind these characteristics will help scientists perform more knowledgeable selective breeding. The genome sequence also provided proof that Malus sieversii was the wild ancestor of the domestic apple—an issue that had been long-debated in the scientific community.
The enzyme, polyphenol oxidase, causes browning in sliced or bruised apples, by catalyzing the oxidation of phenolic compounds to o-quinones, a browning factor. Browning reduces apple taste, color, and food value. Arctic Apples, a non-browning group of apples introduced to the United States market in 2019, have been genetically modified to silence the expression of polyphenol oxidase, thereby delaying a browning effect and improving apple eating quality. The US Food and Drug Administration in 2015, and Canadian Food Inspection Agency in 2017, determined that Arctic apples are as safe and nutritious as conventional apples.
World production of apples in 2017 was 83.1 million tonnes, with China producing 50% and Europe including Turkey producing 17% of the total (table). Other significant producers each with 3–5% of the world total were the United States, Turkey, and Poland.