Peach
The peach is a deciduous tree that bears edible juicy fruits with various characteristics. Most are simply called peaches, while the [|glossy-skinned, non-fuzzy varieties] are called nectarines. Though from the same species, they are regarded commercially as different fruits.
The tree is regarded as handsome and is planted in gardens for its springtime blooms in addition to fruit production. It is relatively short lived, usually not exceeding twenty years of age. Peaches were first domesticated and cultivated in China during the Neolithic period. The specific name persica refers to its widespread cultivation in Persia, from where it was transplanted to Europe. It belongs to the genus Prunus, which also includes the cherry, apricot, almond, and plum, and which is part of the rose family.
The peach is very popular; only the apple and pear have higher production amounts for temperate fruits. In 2023, China produced 65% of the world total of peaches and nectarines. Other leading countries, such as Spain, Turkey, Italy, the U.S., and Iran lag far behind China, with none producing more than 5% of the world total. The fruit is regarded as a symbol of longevity in several East Asian cultures.
Description
The peach is a deciduous tree or tree like shrub that may very rarely grow to as much as tall, but is more typically with large specimens reaching. The spread of the crown is similar to the height, ranging from. They do not produce suckers or have thorns. The root system is deep, with the roots continuing to grow during the winter season.Unlike apples, the size of peach trees is not generally controlled by dwarfing rootstocks in commercial orchards. A great variety of growth habits have been selected including columnar, dwarf, spreading, and weeping. In order to have a single trunk, trees must pruned and likewise the branches have a tendency to droop over time and must be trained to allow for access under the tree.
The bark on the trunk and branches is dark gray with horizontal lenticels. It becomes more scaly and rough as the tree becomes older. Twigs on peach trees have a smooth, hairless surface, the bark is usually red, but may be green on the sides not exposed to the sun. As they become older, branchlets weather to become gray in color. Twigs have true terminal buds at their ends.
Peach leaves are oblong to lanceolate, having sides nearly parallel until tapering at end and base or shaped like the head of a spear. The widest portion of the leaf is midway or further towards the leaf tip. Each leaf folds along the central rib of the leaf and is often also curved, usually long and wide, though occasionally they may be shorter. The surface of the leaves is smooth and hairless, but the leaf stem sometimes has glands. The edges of the leaves have serrated edges with blunt teeth. The teeth have a reddish-brown gland at the tip. Leaves are attached to the twigs by petioles, leaf stems. They are strong and measure 1 to 2 cm. They can also have one or more extrafloral nectaries.
Flowering
Flowers on peach trees are either solitary or in groups of two, usually blooming before the leaves begin to grow. They may range in shades from white to red, but having pink or red flowers 2–3.5 cm in width is typical of cultivars selected for their fruit. Trees grown as ornamentals also may have double flowers, semi-doubled flowers, or bicolored forms. Each flower has four or five petals and is somewhat cup-shaped with the petals curving to shelter the flower's center. Each flower will have 20 to 30 stamens and purple-red anthers at their ends. The single style is nearly as long as the stamens. The flowers are self-fertile and outcross at about 5%.The bloom period is in the early spring, often cut short by frosts, in February, March, April, or May depending on location. In New Zealand and the southern hemisphere, blooming occurs in August to October.
Fruit
Trees can begin producing fruit in the two or three years after sprouting. Because of the hardness of the seed casing, peaches are called stone fruits like the others in the Prunus genus, but are more formally called drupes. Fruits range in color from greenish white to orange yellow, usually with a blush of red on the side of the fruit most exposed to the sun. Their shape varies widely from a flattened sphere resembling a doughnut, egg-shaped, or a slightly compressed sphere usually with a seam on one side. A normal diameter for a fruit is between, but sometimes may be as small as or as large as.Image:Drupe fruit diagram.svg|lang=en|thumb|upright=1.25|Diagram of a peach, showing both fruit and seed
The flesh of the peach is quite variable in color from greenish-white to white to yellow to dark red. The texture can also differ from soft to stone hard.
The growth of the fruit is a double-sigmoid growth curve: a beginning quick period of development followed by a resting period of little growth, and then a second period of rapid maturation.
The seed of the peach is much larger and less round than the seeds of its closest fruit relatives. Unlike the pit of an almond, which is only pitted, the peach pit has a stony exterior which is both pitted and deeply furrowed.
Taxonomy
The peach tree was given the name Amygdalus persica by Carl Linnaeus in 1753 in his book Species plantarum. The accepted combination Prunus persica was published by August Batsch in 1801, though this was far from settled until the 20th century with many different placements of the peach and even divisions of nectarines and flat peaches into different species. The botanist Ulysses Prentiss Hedrick argued persuasively in 1917 that these differences are merely simple mutations and not species or even varieties beginning consensus towards the modern classification. This was supported by breeding experiments as early as 1906 showing the hairlessness of nectarines is a recessive trait, though sometimes alternative names continue to be used even in the 21st Century with Amygdalus persica being used as recently as 2003 in an authoritative scientific publication. More than 200 scientific names have been published that are considered synonyms of Prunus persica by Plants of the World Online. Though the majority of sources agree on its classification as Prunus persica, there is division on the correct author citation for the name. Most sources, such as POWO, World Flora Online, and the Flora of North America give August Batsch credit. However, a few sources such as World Plants maintained by the botanist Michael Hassler instead credit Jonathan Stokes with priority dated to 1812.Prunus persica is classified in Prunus with other stone fruits within the rose family, Rosaceae. The further classification into a subgenus or section is disputed. The work of Alfred Rehder, published in 1940, has been widely used to group the species of Prunus. Rehder based his system largely on that of Bernhard Adalbert Emil Koehne with the peach placed with the almond in subgenus Amygdalus because similarities in the rough and pitted stone. However, since 2000 studies of nuclear and chloroplast DNA have shown that the five subgenera accepted by Rehder are not more closely related to each other than to other species in Prunus. In 2013 Shuo Shi and collaborators published research where they proposed it be part of subgenus Prunus together with the plums and cherries, but in a section named Persicae, now corrected to Persica. However, these groupings are not yet widely accepted.
The greatest genetic diversity in peaches is found in China, where it is generally agreed to have been domesticated. The species is often thought to be a cultigen, a taxon that has its origins in cultivation rather than as a wild species.
The closest relatives of the peach are the Chinese bush peach, Chinese wild peach, the smooth stone peach. Though Charles Darwin speculated that the peach might be a marvelous modification of the almond, research into the divergence of peach relatives shows this not to be the case. The almond, while in the same genus, is confirmed to be a more distant relative.
In April 2010, an international consortium, the International Peach Genome Initiative, which includes researchers from the United States, Italy, Chile, Spain, and France, announced they had sequenced the peach tree genome. In 2013 they published the peach genome sequence and related analyses. The sequence is composed of 227 million nucleotides arranged in eight pseudomolecules representing the eight peach chromosomes. In addition, 27,852 protein-coding genes and 28,689 protein-coding transcripts were predicted.
Particular emphasis in this study is reserved for the analysis of the genetic diversity in peach germplasm and how it was shaped by human activities such as domestication and breeding. Major historical bottlenecks were found, one related to the putative original domestication that is supposed to have taken place in China about 4,000–5,000 years ago, the second is related to the western germplasm and is due to the early dissemination of the peach in Europe from China and the more recent breeding activities in the United States and Europe. These bottlenecks highlighted the substantial reduction of genetic diversity associated with domestication and breeding activities.
Though not a separate grouping genetically, nectarines are regarded as different fruits commercially. The difference is the lack of fuzz, the trichomes, on the skin of the fruits. Research into the cause of this trait found the transcription factor gene PpeMYB25 regulates the formation of trichomes on peach fruits. A mutation can cause a loss of function resulting in the changed fruit type.