An apple is an edible fruit produced by an apple tree (Malus domestica). The apple trees are cultivated worldwide and are the most widely grown species in the genus Malus. The tree originated in Central Asia, where its wild ancestor, Malus sieversii, is still found today. Apples have been grown for thousands of years in Asia and Europe and were brought to North America by European colonists. These apples have religious and mythological significance in many cultures, including Norse, Greek, and European Christian tradition.
Pritish Kumar in this post discusses Apple, its cultivation and the disease that causes harm to the apple plant. Read below:
Apples grown from seed tend to be very different from those of their parents, and the resultant fruit frequently lacks desired characteristics. Generally, apple cultivars are propagated by clonal grafting onto rootstocks.
An apple is a deciduous tree, generally standing 2 to 4.5 m (6 to 15 ft) tall in cultivation and up to 9 m (30 ft) in the wild. When cultivated, the size, shape and branch density are determined by rootstock selection and trimming method. The leaves are alternately arranged dark green-colored simple ovals with serrated margins and slightly downy undersides.
Blossoms are produced in spring simultaneously with the budding of the leaves and are produced on spurs and some long shoots. The 3 to 4 cm (1 to 1+1⁄2 in) flowers are white with a pink tinge that gradually fades, five petaled, with an inflorescence consisting of a cyme with 4–6 flowers. Central flower of the inflorescence is called the “king bloom”; it opens first and can develop a larger fruit.
The fruit is a pome that matures in late summer or autumn, and cultivars exist in a wide range of sizes. Commercial growers aim to produce an apple that is 7 to 8.5 cm (2+3⁄4 to 3+1⁄4 in) in diameter, due to market preference.
Many apples grow readily from seeds. However, more than with most perennial fruits, apples must be propagated asexually to obtain the sweetness and other desirable characteristics of the parent. This is because seedling apples are an example of “extreme heterozygotes”, in that rather than inheriting genes from their parents to create a new apple with parental characteristics, they are instead significantly different from their parents, perhaps to compete with the many pests.
Triploid cultivars have an additional reproductive barrier in that three sets of chromosomes cannot be divided evenly during meiosis, yielding unequal segregation of the chromosomes (aneuploids). Even in the case when a triploid plant can produce a seed (apples are an example), it occurs infrequently, and seedlings rarely survive.
Apples are self-incompatible; they must cross-pollinate to develop fruit. During the flowering each season, apple growers often utilize pollinators to carry pollen. Honey bees are most commonly used. Orchard mason bees are also used as supplemental pollinators in commercial orchards. Bumblebee queens are sometimes present in orchards, but not usually in sufficient number to be significant pollinators.
There are four to seven pollination groups in apples, depending on climate:
Group A – Early flowering, 1 to 3 May in England (‘Gravenstein’, ‘Red Astrachan’)
Group B – 4 to 7 May (‘Idared’, ‘McIntosh’)
Group C – Mid-season flowering, 8 to 11 May (‘Granny Smith’, ‘Cox’s Orange Pippin’)
Group D – Mid/late season flowering, 12 to 15 May (‘Golden Delicious’)
Group E – Late flowering, 16 to 18 May (‘Braeburn’, ‘Reinette)
Group F – 19 to 23 May (‘Suntan’)
Group H – 24 to 28 May (‘Court-Pendu Gris’ – also called Court-Pendu plat)
One cultivar can be pollinated by a compatible cultivar from the same group or close (A with A, or A with B, but not A with C or D).
Maturation and harvest
Cultivars vary in their yield and the ultimate size of the tree, even when grown on the same rootstock. Some cultivars, if left unpruned, grow very large—letting them bear more fruit, but making harvesting more difficult.
Depending on tree density (number of trees planted per unit surface area), mature trees typically bear 40–200 kg (90–440 lb) of apples each year, though productivity can be close to zero in poor years. Apples are harvested using three-point ladders that are designed to fit amongst the branches. Trees grafted on dwarfing rootstocks bear about 10–80 kg (20–180 lb) of fruit per year.
Commercially, apples can be stored for a few months in controlled atmosphere chambers to delay ethylene-induced ripening. Apples are commonly stored in chambers with higher concentrations of carbon dioxide and high air filtration. This prevents ethylene concentrations from rising to higher amounts and preventing ripening from occurring too quickly.
Pests and disease
Apple trees are susceptible to a number of fungal and bacterial diseases and insect pests. Many commercial orchards pursue a program of chemical sprays to maintain high fruit quality, tree health, and high yields. These prohibit the use of synthetic pesticides, though some older pesticides are allowed. Organic methods include, for instance, introducing its natural predator to reduce the population of a particular pest.