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Strawberries

 

Strawberries

For other species of strawberry, see Fragaria. For other uses, see Strawberry (disambiguation).
Garden strawberry
Fragaria × ananassa
Garden strawberries grown hydroponically
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Rosales
Family: Rosaceae
Subfamily: Rosoideae
Genus: Fragaria
Species: F. × ananassa
Binomial name
Fragaria × ananassa
Duchesne

Fragaria × ananassa (aroma is also widely used in many industrialized food products.

The garden strawberry was first bred in Brittany, France, in the 1750s via a cross of Fragaria virginiana from eastern North America and Fragaria chiloensis, which was brought from Chile by Amédée-François Frézier in 1714.[1]

Cultivars of Fragaria × ananassa have replaced, in commercial production, the woodland strawberry (Fragaria vesca), which was the first strawberry species cultivated in the early 17th century.[2]

Technically, the strawberry is an aggregate accessory fruit, meaning that the fleshy part is derived not from the plant's ovaries but from the receptacle that holds the ovaries.[3] Each apparent "seed" (achene) on the outside of the fruit is actually one of the ovaries of the flower, with a seed inside it.[3]

History

Main article: The breeding of strawberries


The first garden strawberry was grown in France during the late 18th century.[2] Prior to this, wild strawberries and cultivated selections from wild strawberry species were the common source of the fruit.

The strawberry fruit was mentioned in ancient Roman literature in reference to its medicinal use. The French began taking the strawberry from the forest to their gardens for harvest in the 1300s. Charles V, France's king from 1364 to 1380, had 1,200 strawberry plants in his royal garden. In the early 1400s western European monks were using the wild strawberry in their illuminated manuscripts. The strawberry is found in Italian, Flemish, German art, and English miniatures. The entire strawberry plant was used to treat depressive illnesses.

By the 1500s references of cultivation of the strawberry became more common. People began using it for its supposed medicinal properties and botanists began naming the different species. In England the demand for regular strawberry farming had increased by the mid-1500s. Instructions for growing and harvesting strawberries showed up in writing in 1578. By the end of the 1500s three European species had been cited; F. vesca, F. moschata, and F. viridis. The garden strawberry was transplanted from the forests and then the plants would be propagated asexually by cutting off the runners.

Two subspecies of F. vesca were identified; F. sylvestris alba and F. sylvestris semperflorens. The introduction of F. virginiana from Eastern North America to Europe in the 1600s is an important part of history because this species gave rise to the modern strawberry. The new species gradually spread through the continent and did not become completely appreciated until the end of the 18th century. When a French excursion journeyed to Chile in 1712, it introduced the strawberry plant with female flowers that resulted in the common strawberry that we have today.

The Mapuche and Huilliche Indians of Chile cultivated the female strawberry species until 1551 when the Spanish came to conquer the land. In 1765, a European explorer recorded the cultivation of F. chiloensis, the Chilean strawberry. At first introduction to Europe, the plants grew vigorously but produced no fruit. It was discovered in 1766 that the female plants could only be pollinated by plants that produced large fruit; F. moschata, F. virginiana, and F. ananassa. This is when the Europeans became aware that plants had the ability to produce male-only or female-only flowers. As more large-fruit producing plants were cultivated the Chilean strawberry slowly decreased in population in Europe, except for around Brest where the Chilean strawberry thrived. The decline of the Chilean strawberry was caused by F. ananassa.[4]

Cultivation

Strawberry cultivars vary widely in size, color, flavor, shape, degree of fertility, season of ripening, liability to disease and constitution of plant.[5] Some vary in foliage, and some vary materially in the relative development of their sexual organs. In most cases, the flowers appear hermaphroditic in structure, but function as either male or female.[6] For purposes of commercial production, plants are propagated from runners and, in general, distributed as either bare root plants or plugs. Cultivation follows one of two general models—annual plasticulture,[7] or a perennial system of matted rows or mounds.[8] A small amount of strawberries are produced in greenhouses during the off season.[9]

The bulk of modern commercial production uses the plasticulture system. In this method, raised beds are formed each year, fumigated, and covered with plastic to prevent weed growth and erosion. Plants, usually obtained from northern nurseries, are planted through holes punched in this covering, and irrigation tubing is run underneath. Runners are removed from the plants as they appear, in order to encourage the plants to put most of their energy into fruit development. At the end of the harvest season, the plastic is removed and the plants are plowed into the ground.[7][10] Because strawberry plants more than a year or two old begin to decline in productivity and fruit quality, this system of replacing the plants each year allows for improved yields and denser plantings.[7][10] However, because it requires a longer growing season to allow for establishment of the plants each year, and because of the increased costs in terms of forming and covering the mounds and purchasing plants each year, it is not always practical in all areas.[10]

The other major method, which uses the same plants from year to year growing in rows or on mounds, is most common in colder climates.[7][8] It has lower investment costs, and lower overall maintenance requirements.[8] Yields are typically lower than in plasticulture.[8]

A third method uses a compost sock. Plants grown in compost socks have been shown to produce significantly higher oxygen radical absorbance capacity (ORAC), flavonoids, anthocyanins, fructose, glucose, sucrose, malic acid, and citric acid than fruit produced in the black plastic mulch or matted row systems.[11] Similar results in an earlier 2003 study conducted by the US Dept of Agriculture, at the Agricultural Research Service, in Beltsville Maryland, confirms how compost plays a role in the bioactive qualities of two strawberry cultivars.[12]

Strawberries are often grouped according to their flowering habit.[5][13] Traditionally, this has consisted of a division between "June-bearing" strawberries, which bear their fruit in the early summer and "ever-bearing" strawberries, which often bear several crops of fruit throughout the season.[13] Research published in 2001 showed that strawberries actually occur in three basic flowering habits: short-day, long-day, and day-neutral. These refer to the day-length sensitivity of the plant and the type of photoperiod that induces flower formation. Day-neutral cultivars produce flowers regardless of the photoperiod.[14]

Strawberries may also be propagated by seed, though this is primarily a hobby activity, and is not widely practiced commercially. A few seed-propagated cultivars have been developed for home use, and research into growing from seed commercially is ongoing.[15] Seeds (achenes) are acquired either via commercial seed suppliers, or by collecting and saving them from the fruit.

Strawberries can also be grown indoors in strawberry pots.

Kashubian strawberry (truskawka kaszubska or kaszëbskô malëna)[16] are the first Polish fruit to be given commercial protection under EU law. They are produced in Kartuzy, Kościerzyna and Bytów counties and in the municipalities of Przywidz, Wejherowo, Luzino, Szemud, Linia, Łęczyce and Cewice in Kashubia. Only the following varieties may be sold as kaszëbskô malëna: Senga Sengana, Elsanta, Honeoye that have been graded as Extra or Class I.

Manuring and harvesting

Most strawberry plants are now fed with artificial fertilizers, both before and after harvesting, and often before planting in plasticulture.[17]

To maintain top quality, berries are harvested at least every other day. The berries are picked with the caps still attached and with at least half an inch of stem left. Strawberries need to remain on the plant to fully ripen because they do not continue to ripen after being picked. Rotted and overripe berries are removed to minimize insect and disease problems. The berries do not get washed until just before consumption. They are covered in a shallow pan and refrigerated when storing.[18]

Soil test information and plant analysis results are used to determine fertility practices. Nitrogen fertilizer is needed at the beginning of every planting year. There are normally adequate levels of phosphorus and potash when fields have been fertilized for top yields. In order to provide more organic matter a cover crop of wheat or rye is planted in the winter the year before planting the strawberries. Strawberries prefer a pH from 5.5 to 6.5 so lime is usually not applied.[19]

The harvesting and cleaning process has not changed substantially over time. The delicate strawberries are still harvested by hand.[20] Grading and packing often occurs in the field, rather than in a processing facility.[20] In large operations, strawberries are cleaned by means of water streams and shaking conveyor belts.[21]

Pests

Around 200 species of pests are known to attack strawberries both directly and indirectly.[22] These pests include slugs, moths, fruit flies, chafers, strawberry root weevils, strawberry thrips, strawberry sap beetles, strawberry crown moth, mites, aphids, and others.[22][23]

The caterpillars of a number of species of Lepidoptera feed on strawberry plants.

Diseases

Strawberry plants can fall victim to a number of diseases.[24] The leaves may be infected by powdery mildew, leaf spot (caused by the fungus Sphaerella fragariae), leaf blight (caused by the fungus Phomopsis obscurans), and by a variety of slime molds.[24] The crown and roots may fall victim to red stele, verticillium wilt, black root rot, and nematodes.[24] The fruits are subject to damage from gray mold, rhizopus rot, and leather rot.[24] To prevent root-rotting, strawberries should be planted every four to five years in a new bed, at a different site.[25]

The plants can also develop disease from temperature extremes during winter.[24] When watering strawberries, advice has been given to water only the roots and not the leaves, as moisture on the leaves encourages growth of fungus.[26]

Production trends

World strawberry production in tons[27]
Rank Country 2006 2007 2008 2009 2010 2011
1  USA 1,090,436 1,109,215 1,148,350 1,270,640 1,294,180 1,312,960
2  Turkey 211,127 250,316 261,078 291,996 299,940 302,416
3  Spain 330,485 269,139 281,240 266,772 275,355 262,730
4  Egypt 128,349 174,414 200,254 242,776 238,432 240,284
5  Mexico 191,843 176,396 207,485 233,041 226,657 228,900
6  Russia 227,000 230,400 180,000 185,000 165,000 184,000
7  Japan 190,700 191,400 190,700 184,700 177,500 177,300
8  South Korea 205,307 203,227 192,296 203,772 231,803 171,519
9  Poland 193,666 174,578 200,723 198,907 153,410 166,159
10  Germany 173,230 158,658 150,854 158,563 156,911 154,418
11  Italy 143,315 160,558 155,583 163,044 153,875 150,000
Total world 3,973,243 4,001,721 4,136,802 4,596,614 4,366,889 4,594,539

Domestic cultivation

Strawberries are popular and rewarding plants to grow in the domestic environment, be it for consumption or exhibition purposes, almost anywhere in the world. The best time to plant is in late summer or spring. Plant in full sun or dappled shade, and in somewhat sandy soil. The addition of manure and a balanced fertilizer aids strong growth. Alternatively they can be planted in pots or special planters using compost. Fibre mats placed under each plant will protect fruits from touching the ground, and will act as a weed barrier.

Strawberries are tough and will survive many conditions, but during fruit formation, moisture is vital, especially if growing in containers. Moreover, protection must be provided against slugs and snails which attack the ripe fruit. The fruit matures in midsummer and should be picked when fully ripe — that is, the fruit is a uniform bright red colour. The selection of different varietes can extend the season in both directions.[28] Numerous cultivars have been selected for consumption and for exhibition purposes. The following cultivars have gained the Royal Horticultural Society's Award of Garden Merit:-

Propagation is by runners, which can be pegged down to encourage them to take root,[35] or cut off and placed in a new location. Established plants should be replaced every three years, or sooner if there are signs of disease.

When propagating strawberries, one should avoid using the same soil or containers that were previously used for strawberry cultivation. After cultivating strawberries, rotating to another culture is advisable, because diseases that attack one species might not attack another.[36]

Uses

In addition to being consumed fresh, strawberries can be frozen, made into preserves, as well as dried and used in prepared foods, such as cereal bars.[37] Strawberries and strawberry flavorings are a popular addition to dairy products, such as strawberry-flavored milk, strawberry ice cream, strawberry milkshakes, strawberry smoothies and strawberry yogurts. Strawberries and cream is a popular dessert, famously consumed at Wimbledon. In Sweden, strawberries are a traditional dessert served at Midsummer Eve, 23 June.[38] Depending on area, strawberry pie, strawberry rhubarb pie, or strawberry shortcake are also popular. In Greece, strawberries are usually sprinkled with sugar and then dipped in Metaxa, a famous brandy, and served as a dessert. In Italy, strawberries have been used for other desserts, especially for making strawberry tiramisu, a special form of the original tiramisu and as a popular flavoring for gelato (gelato alla fragola).

Strawberry juice is a fruit juice made from strawberries. Strawberry juice or concentrate is added to cocktails, such as Minute Maid Strawberry Passion and CoolBest Strawberry Hill.

Strawberry pigment extract can be used as a natural acid/base indicator due to the different color of the conjugate acid and conjugate base of the pigment.[39]

Strawberries contain fisetin, an antioxidant that has been studied in relation to Alzheimer's disease and to kidney failure resulting from diabetes.[40] Strawberries are the fruit that contains the highest amount of this antioxidant.[41] Fisetin lessens the complications of diabetes.[41] Strawberries can also help with heart disease and strokes.[42] Strawberries have a dark skin that has many antioxidants that help with heart disease.[42]

Nutrition

Nutrition
Nutritional value per 100 g (3.5 oz)
Energy 136 kJ (33 kcal)
Carbohydrates 7.68 g
- Sugars 4.89 g
- Dietary fiber 2 g
Fat 0.3 g
Protein 0.67 g
Thiamine (vit. B1) 0.024 mg (2%)
Riboflavin (vit. B2) 0.022 mg (2%)
Niacin (vit. B3) 0.386 mg (3%)
Pantothenic acid (B5) 0.125 mg (3%)
Vitamin B6 0.047 mg (4%)
Folate (vit. B9) 24 μg (6%)
Choline 5.7 mg (1%)
Vitamin C 58.8 mg (71%)
Vitamin E 0.29 mg (2%)
Vitamin K 2.2 μg (2%)
Calcium 16 mg (2%)
Iron 0.41 mg (3%)
Magnesium 13 mg (4%)
Manganese 0.386 mg (18%)
Phosphorus 24 mg (3%)
Potassium 153 mg (3%)
Sodium 1 mg (0%)
Zinc 0.14 mg (1%)
Fluoride 4.4 µg
USDA Nutrient Database

One cup (236 g) of strawberries contains approximately 45 kilo-calories (188 kJ) and is an excellent source of vitamin C and flavonoids.[43][44][45]

This fruit is very low in saturated fat, cholesterol and sodium. It is also a good source of folate and potassium, and a very good source of dietary fiber, and manganese[46] One serving of about eight strawberries provides more vitamin C than an orange. The strawberry is among the top 20 fruits in antioxidant capacity.[47]

Allergy

Some people experience an anaphylactoid reaction to the consumption of strawberries.[48] The most common form of this reaction is oral allergy syndrome, but symptoms may also mimic hay fever or include dermatitis or hives, and, in severe cases, may cause breathing problems. Some research suggests that the allergen may be tied to a protein involved in the ripening of fruits, which was named Fra a1 (Fragaria allergen1). Homologous proteins are found in birch and apple, which suggests that people may develop cross-reactivity to all three species.

White-fruited strawberry cultivars, lacking Fra a1, may be an option for strawberry allergy sufferers. Since they lack a protein necessary for normal ripening, they do not produce the flavonoids that turn the mature berries of other cultivars red. They ripen but remain white, pale yellow or "golden", appearing like immature berries; this also has the advantage of making them less attractive to birds. A virtually allergen-free cultivar named 'Sofar' is available.[49][50]

Chemistry

Garden strawberries contain the dimeric ellagitannin agrimoniin which is an isomer of sanguiin H-6.[51][52]

Chemicals present in the fragrance of strawberries include; methyl acetate, ethyl acetate, methyl propanoate, isopropyl acetate, ethyl propanoate, methyl butyrate, (E)-2-pentenal, butyric acid, methyl isovalerate, 3-hexanone (IS), ethyl butyrate, n-hexanal, butyl acetate, methyl pentanoate, 2-methyl butanoic acid, isopropyl butanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, (E)-hexanal, (E)-2-hexen-1-ol, 1-hexanol, isoamyl acetate, 2-methylbutyl acetate, 2-heptanone, propyl butyrate, ethyl pentanoate, 2-heptanol, amyl acetate, (E,E)-2,4-hexadienal, methyl hexanoate, hexanoic acid, benzaldehyde, butyl butyrate, ethyl hexanoate, (Z)-3-hexenyl acetate, hexyl acetate, (E)-2-hexenyl acetate, isopropyl hexanoate, ethyl-2-hexenoate, d-limonene, amyl butyrate, furaneol, heptanoic acid, mesifurane, propyl hexanoate, linalool, nonanal, methyl octanoate, octanoic acid, ocimenol, benzyl acetate, ethyl benzoate, butyl hexanoate, ethyl octanoate, octyl acetate, alpha-terpineol, isoamyl hexanoate, nonanoic acid, octyl butyrate, ethyl decanoate, decyl acetate, octyl butyrate, ethyl decanoate, decyl acetate, octyl isovalerate, beta-farnesene, gamma-decalactone, alpha-farnesene, (E)-nerolidol, octyl hexanoate, decyl butyrate, gamma-dodecalactone.[53]

See also

References

Further reading

  • Khanizadeh, S. and J. DeEll. 2005. "Our Strawberries/ Les Fraisiers de Chez Nous ", A Description of Over 170 Strawberry Cultivars along with Regional Evaluation and Details Information Used for Plant Breeder’s Right Office. PWGSC, Publishing and Depository Services, Ottawa, Ont. 551p. ISBN 0-660-62338-2.
  • Hancock, J.F. (1999). Strawberries (Crop Production Science in Horticulture). CABI. ISBN 978-0-85199-339-3

External links

 
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  • data from GRIN Taxonomy Database
  • Strawberries (Fact Sheet) (Berry Health Benefits Network)
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