Seedless fruit
Encyclopedia
A seedless fruit is a fruit
developed to possess no mature seed
s. As consumption of seedless fruits is generally easier and more convenient, they are considered commercially valuable.
Most commercially produced seedless fruits have been developed from plants whose fruits normally contain numerous relatively large hard seeds distributed throughout the flesh of the fruit.
s are usually defined (in a botanical sense) as mature ovaries
containing seeds
.
Seedless fruits can develop in one of two ways: either the fruit develops without any fertilization (parthenocarpy
), or pollination
triggers fruit development, but the ovules or embryos abort without producing mature seeds (stenospermocarpy
). Seedless banana and watermelon fruits are produced on triploid plants, whose three sets of chromosome
s prevent meiosis
from taking place and thus the plants cannot produce fertile gamete
s. Such plants can arise by spontaneous mutation or by hybridization between diploid and tetraploid
individuals of the same or different species. Some species, such as pineapple
and cucumber
, produce seedless fruit if not pollinated, but do produce seeded fruit if pollination occurs.
Lacking seeds, and therefore the capacity to propagate via the fruit, the plants are generally propagated vegetatively from cuttings, by grafting
, or in the case of bananas, from "pups" (offsets
). In such cases, the resulting plants are genetically identical clone
s. By contrast, seedless watermelons are grown from seeds. These seeds are produced by crossing diploid and tetraploid lines of watermelon, with the resulting seeds producing sterile triploid plants. Fruit development is triggered by pollination, so these plants must be grown alongside a diploid strain to provide pollen.
One disadvantage of most seedless crops is a significant reduction in the amount of genetic diversity
in the species. As genetically identical clones, a pest or disease that affects one individual is likely to be capable of affecting every clone of that individual. For example, the vast majority of commercially produced bananas are cloned from a single source, the Cavendish
cultivar
, and those plants are currently threatened worldwide by a newly discovered fungal disease to which they are highly susceptible.
Triploid plants with seedless fruits can also be produced using endosperm
culture for the regeneration of triploid plantlets from endosperm tissue via somatic embryogenesis
.
s, grapes and banana
s. Additionally, there are numerous seedless citrus
fruits, such as orange
s, lemon
s and lime
s.
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
developed to possess no mature seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s. As consumption of seedless fruits is generally easier and more convenient, they are considered commercially valuable.
Most commercially produced seedless fruits have been developed from plants whose fruits normally contain numerous relatively large hard seeds distributed throughout the flesh of the fruit.
Biology
The term "seedless fruit" is biologically somewhat contradictory, since fruitFruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
s are usually defined (in a botanical sense) as mature ovaries
Ovary (plants)
In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...
containing seeds
SEEDS
SEEDS is a voluntary organisation registered under the Societies Act of India....
.
Seedless fruits can develop in one of two ways: either the fruit develops without any fertilization (parthenocarpy
Parthenocarpy
In botany and horticulture, parthenocarpy is the natural or artificially induced production of fruit without fertilization of ovules. The fruit is therefore seedless. Stenospermocarpy may also produce apparently seedless fruit, but the seeds are actually aborted while still small...
), or pollination
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
triggers fruit development, but the ovules or embryos abort without producing mature seeds (stenospermocarpy
Stenospermocarpy
Stenospermocarpy is the biological mechanism that produces seedlessness in some fruits, notably many table grapes. In stenospermocarpic fruits, normal pollination and fertilization are still required to ensure that the fruit 'sets', i.e...
). Seedless banana and watermelon fruits are produced on triploid plants, whose three sets of chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s prevent meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....
from taking place and thus the plants cannot produce fertile gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s. Such plants can arise by spontaneous mutation or by hybridization between diploid and tetraploid
Ploidy
Ploidy is the number of sets of chromosomes in a biological cell.Human sex cells have one complete set of chromosomes from the male or female parent. Sex cells, also called gametes, combine to produce somatic cells. Somatic cells, therefore, have twice as many chromosomes. The haploid number is...
individuals of the same or different species. Some species, such as pineapple
Pineapple
Pineapple is the common name for a tropical plant and its edible fruit, which is actually a multiple fruit consisting of coalesced berries. It was given the name pineapple due to its resemblance to a pine cone. The pineapple is by far the most economically important plant in the Bromeliaceae...
and cucumber
Cucumber
The cucumber is a widely cultivated plant in the gourd family Cucurbitaceae, which includes squash, and in the same genus as the muskmelon. The plant is a creeping vine which bears cylindrical edible fruit when ripe. There are three main varieties of cucumber: "slicing", "pickling", and...
, produce seedless fruit if not pollinated, but do produce seeded fruit if pollination occurs.
Lacking seeds, and therefore the capacity to propagate via the fruit, the plants are generally propagated vegetatively from cuttings, by grafting
Grafting
Grafting is a horticultural technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together. This vascular joining is called inosculation...
, or in the case of bananas, from "pups" (offsets
Offsets
In botany and horticulture Offset is a term used to describe a small virtually complete daughter plant that has been naturally asexually produced on the mother plant. They are clones , meaning that they are genetically identical to the mother plant. In the plant nursery business and gardens they...
). In such cases, the resulting plants are genetically identical clone
Cloning
Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...
s. By contrast, seedless watermelons are grown from seeds. These seeds are produced by crossing diploid and tetraploid lines of watermelon, with the resulting seeds producing sterile triploid plants. Fruit development is triggered by pollination, so these plants must be grown alongside a diploid strain to provide pollen.
One disadvantage of most seedless crops is a significant reduction in the amount of genetic diversity
Genetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
in the species. As genetically identical clones, a pest or disease that affects one individual is likely to be capable of affecting every clone of that individual. For example, the vast majority of commercially produced bananas are cloned from a single source, the Cavendish
Cavendish banana
The Dwarf Cavendish banana is a banana cultivar originally from Vietnam and China. It became the primary replacement for the Gros Michel banana in the 1950s after crops of the latter were devastated by the Panama disease. The name 'Dwarf Cavendish' is in reference to the height of the pseudostem,...
cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...
, and those plants are currently threatened worldwide by a newly discovered fungal disease to which they are highly susceptible.
Triploid plants with seedless fruits can also be produced using endosperm
Endosperm
Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This makes endosperm an important source of nutrition in human diet...
culture for the regeneration of triploid plantlets from endosperm tissue via somatic embryogenesis
Somatic Embryogenesis
Somatic embryos are mainly produced in vitro and for laboratory purposes, using either solid or liquid nutrient media which contain plant growth regulators . The main PGRs used are auxins but can contain cytokinin in a smaller amount. Somatic embryogenesis is a process where a plant or embryo is...
.
Varieties
Common varieties of seedless fruits include watermelonWatermelon
Watermelon is a vine-like flowering plant originally from southern Africa. Its fruit, which is also called watermelon, is a special kind referred to by botanists as a pepo, a berry which has a thick rind and fleshy center...
s, grapes and banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....
s. Additionally, there are numerous seedless citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
fruits, such as orange
Orange (fruit)
An orange—specifically, the sweet orange—is the citrus Citrus × sinensis and its fruit. It is the most commonly grown tree fruit in the world....
s, lemon
Lemon
The lemon is both a small evergreen tree native to Asia, and the tree's ellipsoidal yellow fruit. The fruit is used for culinary and non-culinary purposes throughout the world – primarily for its juice, though the pulp and rind are also used, mainly in cooking and baking...
s and lime
Lime (fruit)
Lime is a term referring to a number of different citrus fruits, both species and hybrids, which are typically round, green to yellow in color, 3–6 cm in diameter, and containing sour and acidic pulp. Limes are a good source of vitamin C. Limes are often used to accent the flavors of foods and...
s.