Solanum lycopersicum, tomato

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cellular organisms - Eukaryota - Viridiplantae - Streptophyta - Streptophytina - Embryophyta - Bryophyta - Moss Superclass V - Bryopsida - Funariidae - Funariales - Funariaceae - Physcomitrella - Physcomitrella patens

Brief facts

• Together with eggplants, potatoes, and peppers it belongs to the Solanaceae (nightshade) family. Tomato is short-lived perennial usually grown as annual plant.
• The tomato is native to Central, South, and southern North America. The Incas and Aztecs began cultivating tomato plants as early as 700 A.D. In the mid-1500s, Spanish conquistadors carried tomato seeds back to Europe, where they gained popularity as a food item in Italy, Spain and Portugal. Thomas Jefferson was one of the first Americans to grow tomatoes at his Virginia home. By 1812, tomatoes were embraced by Louisiana and Maine cooks.
• The tomato is one of the most commonly grown fresh market vegetables. Tomato farm can harvest as much as 19,000-25,000 pound (10-13 tons) per acre. Harvesting tomatoes is very labor intensive. Cultivation, handling, and marketing costs combined can run as high as $4,500 per acre. However, because of high market demands, farming of tomatoes can be quite profitable.
• There are two types of tomatoes: determinate and indeterminate. Determinate tomatoes grow to a certain height, then flower and set their fruit within a short time. "Celebrity" is popular cultivar of determinate tomato.
  Indeterminate tomatoes continue to grow and produce flowers and fruits until killed by first frost or senesce naturally. The harvest from indeterminate varieties often extends over 2 or 3 months (this is why they are very good for home gardening). Yields are generally heavier than from determinate types. The plants need to be supported by stakes, cages, or trellises. One of popular cultivars of indeterminate varieties is "Better boy".
• Tomatoes' varieties (more than 4,000) are commonly divided into these categories:
  • Cherry: sweet small round tomatoes, usually eaten whole in salads ("Small Fry", "Super Sweet 100" cultivars)
  • Plum: pear-shaped, meaty, multi-purpose tomatoes, eaten fresh or processed ("Roma" cultivars)
  • Slicing: round or globe-shaped, multi-purpose tomatoes ("Celebrity", "Better Boy" cultivars)
  • Beefsteak: round, juicy, ideal for sandwiches ("Big Beef" cultivar)
  • Heirloom: old varieties of tomatoes whose seeds were passed from generation to generation; they are not hybrids like many modern tomatoes cultivars; they are popular because many gardeners believe that they have better flavor; they come in all shapes (often quite irregular), colors and sizes
  • Yellow/Orange: sweet tomatoes rich in vitamin C and potassium but lacking lycopene ("Jubilee", "Lemon boy", respectively)
• The FDA found no credible evidence to support an association between lycopene intake or consumption of tomato and a reduced risk of lung, colorectal, breast, ovarian, or endometrial cancer. The FDA found very limited evidence to support association between tomato consumption and reduced risk of prostate, ovarian, gastric, and pancreatic cancers.
• One cup of chopped tomato contains about 32 calories (3 calories from fat). Tomatoes are valued for their vitamin and antioxidant content.

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Tomato flower

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Developmental stages (life cycle)

Life Cycle Stages

Tomato is a short-lived perennial, grown as an annual (5-6 months).

• seed stage MeSH
  • dormant seed
  • germination MeSH under optimal conditions seed germination (emergence of radicle) takes from 5 to 10 days
• vegetative vegetative stage (from emergence until the first flower) takes about 10-12 weeks
  • seedling MeSH the seedling can be transplanted to the field 3 to 6 weeks after sowing
• reproductive
  • flowering a period between floral initiation and production of mature flower; this process takes about 2 weeks; during this period number of carpels and shape of the fruit are determined;
• fruit development
  • fruit set at fruit set, flower petals and anthers senesce and fall away and a pea-sized green fruit appears; from this point it takes typically 40-50 days for fruits to be harvestable
  • developing fruit the fruit is of light green color and very firm; an intensive cell division takes place but overall fruit's growth is relatively slow; takes about 2-3 weeks
  • green fruit the fruit is still green; its growth accelerated by cell expansion rather than the cell division; cells enlarge up to 20-fold; this period takes about 3-5 weeks; fruit almost reached its final size and is changing colors
  • breaker stage rapid chemical and structural changes that determine fruit aroma, color, texture, etc. begin; fruit just started to change coloration; tannish-yellow, pink, or red occupies no more than 10 percent of the surface of the fruit
  • turning stage from 10 to 30 percent of surface of the fruit is tannish-yellow, pink, or red
  • pink stage from 30 to 60 percent of the surface of the fruit, in aggregate, shows pink or red color
  • light red stage from 60 to 90 percent of the surface, in the aggregate, shows pinkish-red or red color
  • ripe more than 90 percent of the fruit reached its final coloration; typically it is uniform bright red or orange color; unusually for plants, the ripe tomato fruit accumulates large amount of carotenoid lycopene, as the pattern of gene expression occurring in green fruit during the fruit ripening

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Tomato fruit

• Botanically, the tomato is a berry (a simple fruit produced from a single ovary). However, in 1893, the U.S. Supreme Court declared it as a vegetable.
• Ovary is superior (is above the attachment of the petals, sepals and stamens, and is free from the receptacle) and with 2-9 compartments. Mostly self- but partly cross-pollinated. Bees and bumblebees are most important pollinators.
• The tomato fruit is ripening by climacteric mechanism (as opposed to non-climacteric). Climacteric ripening is accompanied by a peak in respiration and a concomitant burst of ethylene (important phytohormone). Exposure to exogenous ethylene accelerates ripening of green tomatoes. Other examples of climacteric fruits are apple, grape, banana, strawberries. Fruit ripening culminates in dramatic changes in color, texture, flavor, and aroma of the fruit flesh. Chloroplasts are transformed into chromoplasts, chlorophyll is degraded and carotenoids accumulate.
• The characteristic pigmentation of red tomato fruit is due to the deposition of lycopene, the predominant carotenoid found in tomato fruit, and beta-carotene, which are associated with the change from green to red as chloroplasts are transformed to chromoplasts.
• The characteristic flavor of tomato fruits results from the volatile compounds produced within the fruit during the ripening. Over 400 volatile compounds are found in tomato fruit. Among them seven are the most important contributors to the aroma: hexanal, hexenal, hexenol, 3-methylbutanal, 3-methylbutanol, methylnitrobutane, and isobutylthiazole.
• Although fruit-bearing crop species are taxonomically diverse, they share a common feature: fruit from domesticated species often are considerably larger than their wild progenitors. For example, the putative wild ancestor of the cultivated tomato bears fruit that contains only two locules and weighs just a few grams. By contrast, a single fruit of a modern cultivated tomato may contain many locules and weigh up to 1 kg, a nearly 1000-fold increase in weight.

Appendix 1: inflorescence in tomato and related nightshades

Lippman ZB, Cohen O, Alvarez JP, Abu-Abied M, Pekker I, Paran I, Eshed Y, Zamir D. The making of a compound inflorescence in tomato and related nightshades. PLoS Biol. 2008 November; 6(11): e288.

Solanaceae Inflorescences and Mutant Phenotypes
(A) Pepper plant showing single-flower inflorescence and mature fruit (inset).
(B) Tomato plant and inflorescence (red ring) showing zigzag growth (lower inset) and maturing fruits (upper inset).
(C) Branched inflorescence of the species S. crispum.
(D) Mutant, highly branched inflorescence of s in a mixed genotype with the wild tomato species S. pennellii.
(E) Mutant inflorescence of a second allele, s-multiflora, having flowers (blue arrows) mixed with cauliflower-like tissue.
(F) Mutant, branched an-classic inflorescence with cauliflower-like tissue in place of flowers.
(G) A weaker an allele with sepal and carpelloid tissue.
(H) Mutant, branched fa inflorescence (dashed box) with leaves in place of flowers.
Scale bars in (A, B, C, D, H), 5 cm; in insets (E, F, and G), 1 cm.

Inflorescence Variation in Domesticated Tomatoes Is Due To Independently Arisen Alleles of s
The s-classic allele was first described 100 years ago as a highly branched variety called "Wonder of Italy", and garden varieties resembling s remain popular for their aesthetic value and prolific fruit production. Six thousand domesticated varieties were screened for inflorescence variation and 23 lines exhibited highly compound inflorescences. Among the 23 lines, at least 15 represented distinct genetic backgrounds based on differences in fruit size, shape, color, and quantitative variation in branch number.
(A) Phenotypic variation from three distinct varieties is shown. Core Collection line 2064 (CC2064) was extremely compound as a result of more than 200 branching events, whereas CC944 and CC3381 branched less often, and CC3381 also developed leaves within the inflorescence.
(B) Variation in fruit size, shape, and color highlighting the different genetic backgrounds of the varieties with compound inflorescences. Varieties with names are indicated.
(C) Cleaved amplified polymorphic sequence (CAPS) PCR genotyping assay showing that all except one of 23 varieties with compound inflorescences carry the s-classic allele. CC5721 (white asterisk), which carries the identical lesion as s-classic, arose independently from a distinct progenitor line (see text for details). Controls were varieties with weak (5–10 branching events) or no branching. Rose Quartz Multiflora was confirmed by complementation test to be an allele of s, and arose independently as a result of a genomic rearrangement (Figure S3). Scale bar in (A), 1 cm.

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Appendix 2: tomato reproductive developmental landmarks

Xiao H, Radovich C, Welty N, Hsu J, Li D, Meulia T, van der Knaap E. Integration of tomato reproductive developmental landmarks and expression profiles, and the effect of SUN on fruit shape. BMC Plant Biol. 2009 May 7;9:49. PMID: 19422692

 

Flower Development Landmarks

(The timing of the landmarks described by Buzgo et al (2004) in S. pimpinellifolium accession LA1589)

Flower Development Landmarks	Days after flower initiation in tomato	Perianth organs	Ovary and ovule	Stamen and pollen
(1) Inflorescence formation and flower initiation	1	Flattened inflorescence apex becomes dome-shaped.
(2) Initiation of outermost perianth organs	2	Emergence of sepal primordia in a helical pattern.
(3) Initiation of inner perianth organs.	4	Simultaneous emergence of petal primordia in alternating positions to the sepals. Sepals overlay the floral meristem
(4) Stamen initiation	5	Sepals and petals elongate.		Simultaneous initiation of stamen primordia.
(5) Carpel initiation	6	Petals start curling over the stamens.	Carpel primordia arise.
	7		Central column that will form the locular cavities arise.	Central column that will form the locular cavities arise.
6) Microsporangia initiation	8		Central column continues to elongate. Carpels fuse at the apex of the ovary. Style initiation. Initiation of placental development.	Primary pariety cells develop into endothecium, middle layers and tapetum. Sporogenous layers visible.
(7) Ovule initiation	9		Ovule primordia begin to emerge from the placenta.	The two lobes of the anther and the locule are distinguishable, microsporocyte and tapetal cells are distinguishable. Binucleate tapetal cells.
(8) Male meiosis	10			Microsporogenesis. Microsporocytes or microspore mother cells undergo meiosis I and II and forming tetrads.
(9) Female meiosis	11		Megasporogenesis. Megaspore mother cell (meiocyte or megasporocyte) is visible. Meiosis I. The nucellus is small resulting in a tenui-nucellate ovule.
	12	Petals grow to the top of sepals.	The single integument begins to grow over the nucellus resulting in unitegmic ovules.	Callose wall surrounding the tetrads degrades releasing the microspores. Tapetum starts degenerating.
	13	Petals emerge from the sepals.	Petals emerge from the sepals.	Free microspores are being incased in a thick polysaccharide wall; tapetum degenerated.
	14	Onset of sepal opening.	Megagametogenesis and development of the embryo sac.	Microspores come vacuolated, and begins asymmetric mitosis.
	15			Bi-cellular pollen grain.
	16		Bi-cellular pollen grain.	The vegetative cell and generative cell are well distinguishable.
(10) Anthesis	19	Petal opening.

 

Fruit developmental landmarks

(Timing of the fruit landmarks in S. pimpinellifolium LA1589)

Fruit Development Landmarks	Days post anthesis	Fruit growth (Gillaspy et al 1993)	Embryo/seed development
(1) Anthesis	0	Mature ovary, phase I.	Mature gametes. Pollen is shed, which will land on the stigma and germinate. Pollen tubes growth through the style.
(2) Fertilization	1 - 2	End of phase I, beginning of phase II.	Fusion of sperm and egg nuclei.
(3) 4–16 Cell Stage Embryo	3 - 6	Phase II and III, cell division and elongation stage.	First embryo divisions.
(4) Globular Stage Embryo	6 - 10	Phase III, cell expansion stage.	Globular embryo.
(5) Heart Stage Embryo	10 - 12	Phase III, cell expansion stage.	Heart Stage embryo lasts approximately one day and occurs 10–12 dpa.
(6) Torpedo Stage Embryo	13 - 16	Phase III, continued fruit enlargement.	Torpedo Stage embryo lasts approximately one day and occurs 13–16 dpa.
(7) Coiled Stage Embryo	20	Phase III, continued fruit enlargement.	Cotyledon expansion and curl as they elongate. Embryo appears physically mature, but the seed is not yet viable.
	20 - 28		Seed maturation period.
(8) Seed germination	29 - 31	The fruit has reached the mature green stage. Fruit becomes sensitive to ethylene.	Seeds are becoming viable for germination.
(9) Fruit ripening	33 - 40	Ripening starts at the onset of the breaker stage. Changes in pigmentation are visible.	After ripening of seed.
(10) Ripe Fruit	40	Red ripe stage of tomato.

 

 

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References

• Tanksley SD. The genetic, developmental, and molecular bases of fruit size and shape variation in tomato. Plant Cell. 2004;16 Suppl:S181-9. Epub 2004 May 6. PMID: 15131251
• Bramley PM. Regulation of carotenoid formation during tomato fruit ripening and development. J Exp Bot. 2002 Oct;53(377):2107-13. PMID: 12324534
• Kavanaugh CJ, Trumbo PR, Ellwood KC. The U.S. Food and Drug Administration's evidence-based review for qualified health claims: tomatoes, lycopene, and cancer. J Natl Cancer Inst. 2007 Jul 18 PMID: 17623802
• Alexander L, Grierson D. Ethylene biosynthesis and action in tomato: a model for climacteric fruit ripening. J Exp Bot. 2002 Oct;53(377):2039-55. PMID: 12324528

Websites

• Wikipedia: Tomato
• Organic tomato production by Diver S., Kuepper G., and Born H. (ATTRA). 1999 (.pdf)
• Agrodok 17: Cultivation of tomato: production, processing and marketing by Naika S et al., 2005 (.pdf)

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