Tomatoes (section)

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tomatoes
Tomato (Solanum lycopersicum)

Tomato ( Solanum lycopersicum )

Systematics
Euasterids I
Order : Nightshade (Solanales)
Family : Nightshade family (Solanaceae)
Genre : Nightshade ( solanum )
Subgenus : Potato
Section : tomatoes
Scientific name
Solanum sect. Lycopersicon
( Mill. ) Compet.

The section of the tomatoes ( Solanum sect. Lycopersicon ) is part of the subgenus Potatoe within the genus of the nightshade ( Solanum ). It is assigned to 13 species that are native to western South America. The actual tomato ( Solanum lycopersicum ) came to Europe in the 16th century, is now cultivated worldwide and occasionally as a cultural refugee. For a long time, the species were placed in their own genus Lycopersicon , but current findings confirm that they belong to the nightshade.

description

Vegetative characteristics

Tomato plants are vigorous, herbaceous short-day plants that are usually annual , but sometimes also biennial or persistent . They reach a height of 1 to 2 m (rarely even 60 cm), they grow upright at first, later lying down or rarely climbing. The lavishly branched shoots can occasionally be up to 4 m long. The more or less succulent stem is hairless, stiff-haired or densely finely haired. The coat consists of mono- or multicellular nichtdrüsigen or provided with a single or multicellular glands head trichomes . Both stems and leaves are covered with raised stomata .

The leaves are unpaired to double pinnate and have no stipules . Two species have larger leaves that are 15 to 20 (rarely 10 to 30) cm long and 6 to 10 (to 15) cm wide. The leaves of the other species are 3 to 7 (to 12) cm long and 2 to 4 (rarely 1.2 to 6) cm wide. The partial leaves themselves are pinnate, (two) pinnate or entire. They usually come in two sizes on a plant: The larger are 2 to 6 (rarely 0.5 to 10) cm long, are in two to six pairs and are almost circular to ovoid or narrowly elliptical in shape. The smaller partial leaves are occasionally missing, if present they are 0.1 to 0.5 (to 2) cm long and often inserted between the larger ones. They are entire or almost entire, ovate to almost circular and sessile or have a short stalk.

Inflorescences and flowers

Inflorescence of Solanum chilense .

The flowers are in simple grape-shaped inflorescences , usually four to five, rarely up to ten flowers, on 1 to 1.5 cm long flower stalks that are bent like a joint in the middle or slightly above. The calyx is five to eight or ten parts, the individual sepals are not grown together almost to the base and about 1 cm long and 1 mm wide. A quarter to half of the lemon-yellow petals are fused together, lanceolate, pointed with bent-back corolla lobes. They are about 1 cm long or a little longer, hairless or, especially at the tip, more or less downy-haired. The five, eight or ten stamens share good time in the flowering stage in two or three groups, which almost unseated anthers are about 5 mm long. The stamens are almost completely fused together and form a tight ring at the base of the flower. The pollen is small with 20 to 27 µm, the pollen grain surface is reticulated. The stylus is slightly protruding, the ovary is hairless.

Fruits and seeds

The fruit is usually a three- to ten-chambered berry , which is often flattened, spherical. The colors of the ripe fruits vary between red, dark red-brown, reddish-yellow, yellow-greenish or whitish. The pericarp (fruit wall) is juicy with a shiny, hairless, or downy surface. During the development of the fruit, the calyx enlarges and the sepals bend back.

The fruits contain up to 250 ellipsoid-egg-shaped, flat seeds with a thick episperm , unique within the nightshade , which is surrounded by a layer of mucus. If this layer of mucus is removed or it dries up, the surface of the seeds appears to be covered with trichome-like hairs. However, these are pointed, elongated thickenings of individual cells of the outermost cell layer of the seed coat. The twisted embryo (seedling) has cotyledons (germ layers) that are almost as long as the rest of the embryo, the endosperm (nutrient tissue) surrounding it is relatively sparse.

Occurrence and locations

The natural range of the species of the section Lycopersicon extends over the west of South America . Most species colonize relatively dry locations, for example the Andes valleys , which are shaped by rain shadows , the high desert areas of the western Andean slopes and the extremely dry Loma formations near the Pacific coast of Peru and Chile. Occasionally, the species from high altitudes can also be found in lower-lying Huaycos (formations that arise from mud and stone avalanches during heavy rainfall). Solanum pimpinellifolium is also found in humid river valleys and in coastal habitats. The two species Solanum cheesmaniae and Solanum galapagense are endemic to the Galápagos Islands , so they only occur there.

The species known as the cultivated tomato Solanum lycopersicum is more strongly bound to moist locations than any other representative of the section. It grows wild in disturbed habitats in all parts of the tropical and temperate climate zones, but is rarely found there for several generations.

ecology

pollination

The blossoms of the tomatoes, like the blossoms of all other nightshades, are specialized in the so-called vibration pollination (buzz pollination) by bees. The insects vibrate with their indirect flight muscles in order to shake the pollen out of the anthers through resonance . Since nightshade flowers do not produce nectar , the pollen is the only incentive for the bees to visit the flowers. Since the protein and nitrogen content of the pollen is particularly high, it can serve as food for the larvae . Honey bees that visit the tomato blossoms do not get to the pollen by vibration pollination, but separate the anthers and thus steal the pollen. Also hoverflies visit the tomato flowers and looking with her proboscis into the flowers for nectar, but pollination by these visits is unlikely.

Predators and diseases

In total there are reports on 332 different butterfly species , for which the species in the section Lycopersicon are food plants. However, most of these observations come from cultivated tomatoes from the temperate zones around the world, only five of the butterfly species are also found in their natural range.

The types of dissection are susceptible to various pathogens. Fungal diseases, for example caused by Phytophthora or Cladosporium , occur; Various bacteria such as Ralstonia solanacearum (cause of tomato wilt ) attack the plants; by viruses such as tobacco mosaic virus or Pepinomosaikvirus diseases are triggered and roundworms (Nematoda) are among the pests. In various wild species resistance were detected against some of the diseases are so Solanum arcanum , Solanum neorickii and Solanum habrochaites against powdery mildew resistant in Solanum pimpinellifolium resistances are Cladosporium and other fungal diseases detected.

Systematics

External system

Within the nightshade ( Solanum ) the section Lycopersicon is classified in the subgenus Potatoe . By cladistic studies that both morphological as well as molecular were carried out level, it could be shown that the section is monophyletic. The relationships to closely related sections determined by these investigations are shown in the following cladogram:





Section of Lycopersicoides


   

Section Juglandifolia


   

Section Lycopersicon




   

Petota section



   

Etuberosum section



Internal system

There are 13 different types within the section:

Neolycopersicon group

Eriopersicon group

Arcanum group

Lycopersicon group

The cladistic relationships between the species have not yet been clarified beyond doubt. It is assumed, however, that Solanum pennellii is basal to all other species, the species is placed in a monotypical Neolycopersicon group. The four species of the Eriopersicon group mostly form branched inflorescences and green fruits. Three species with self-pollinating and unbranched inflorescences with green fruits are classified in the Arcanum group. Four species with red to orange colored fruits make up the Lycopersicon group.

Botanical history

Pre-Linnean history

The first description of the tomato imported from America by European botanists probably comes from Pietro Andrea Mattioli's work Di Pedacio Dioscoride Anazarbeo from 1544. This work is based on the works of the ancient author Dioscurides . The tomatoes are in it as a form of already known Dioscorides Mandrake shown. A French translation from 1572 put tomatoes close to eggplants , both of which are also said to belong to mandrake.

The oldest representation of a tomato plant comes from Leonhart Fuchs . Since it was never published, but only reached the Austrian National Library in Vienna with his unpublished manuscripts after Fuchs 'death, the date of creation cannot be precisely determined, but it must be between 1542 and Fuchs' death in 1560. The first published illustration of a tomato plant dates back to 1554 issued herb book by Rembert Dodoens . The oldest preserved specimen of a tomato plant also comes from the middle of the 16th century. It was collected by Ulisse Aldrovandi and is now kept in the herbarium of the Botanical Garden in Bologna .

The name of the tomatoes as Lycopersicon goes back to the Italian Luigi Anguillara . In 1561 he equated the tomatoes he knew about with a plant that the Greek scholar Galenus of Pergamon called λυκοπέρσιον ("wolf peach") long before the discovery of America.

Many pre-Linnéian botanists usually associated the tomato with the nightshade ( Solanum ) and often referred to it as “Solanum pomiferum” (“apple-bearing nightshade”) or with similar names. Joseph Pitton de Tournefort was the first botanist who separated the tomato from the remaining Solanum and led it under the name Lycopersicon . He differentiated the two groups according to the number of chambers in the fruit: he assigned plants with two-chamber fruits to the Solanum , plants with multi- chamber fruits to the Lycopersicon . He distinguished a total of nine different species within the Lycopersicon , one of which, however, probably belongs to the bladder cherries ( Physalis ) and another is probably identical to the Tamarillo ( Solanum betaceum ).

From Linnaeus to Wettstein

In the first edition of Species Plantarum (1753), Carl von Linné describes two types of tomatoes and assigns them to the nightshade as Solanum lycopersicum and Solanum peruvianum . Philip Miller contradicts this assignment in the edition of his "Gardener's Dictionary" published a year later and, not yet using Linné's binary system , lists tomatoes as Lycopersicon and adds the potato to this genus due to the structure of the fruit . In 1768 Miller introduced the binary nomenclature in his works and differentiated seven species within the genus Lycopersicon , including the potato and the Ethiopian eggplant ( Solanum aethiopicum ). In the 1806 edition of the "Gardener's Dictionary" published by Thomas Martyn after Miller's death , all species described by Miller as Lycopersicon are assigned to the Solanum .

In the period that followed, the tomato species were usually listed as a separate genus Lycopersicon , but some authors also assigned them to the Solanum . Among the most important works on tomatoes in the 19th century are the works of Dunal (1813, 1852), who recognized the genus Lycopersicon and describes several new species, as well as the revision of the nightshade family (Solanaceae) by Richard Wettstein (1895), in which he assign the tomatoes to the solanum .

From the middle of the 20th century

The first two extensive taxonomic studies of tomatoes come from CH Müller (1940) and LC Luckwill (1943), both of whom recognized the species as the genus Lycopersicon . Müller divided the genus into two sub-genera Eulycopersicon with two species and Eriopersicon with four species. It also describes a new species and several varieties and forms. Luckwill adopts Müller's classification of the subgenus, but recognizes five species within the subgenus Eriopersicon and sets up other infraspecific subdivisions. In the 1950s to the late 1970s, various papers on the taxonomy of tomatoes were published, often focusing heavily on the cultivated tomato. This is how concepts for the subdivision of the cultivated tomato were developed by Christian Lehmann (1954) at the Institute for Crop Plant Research Gatersleben (GDR) and by DD Brezhnev (Soviet Union, 1958, 1964).

In the USA, Charles Rick in particular was active in researching tomatoes for many decades. In addition to extensive breeding work, he created a taxonomic subdivision of tomatoes as the genus Lycopersicon based on the results of cross-breeding experiments . This division recognizes nine species and divides them into an Esculentum complex and a Peruvianum complex. A taxonomic treatment as the Lycopersicon section from 1990 by A. Child differentiates 11 species in two subsections and three series, but also subdivides the species of the now independent Solanum sect. Lycopersicoides in the Lycopersicon section .

A phylogenetic analysis of wild tomato species and their relatives carried out by Jeffrey Palmer and Daniel Zamir in 1982 is one of the first studies to use molecular biological methods on plants. From 1993 it could be shown by further molecular biological investigations that the tomatoes are to be assigned to the genus of nightshade ( Solanum ) and there to the subgenus Potatoe from a phylogenetic point of view . In addition, a total of three new species were described through intensive studies of herbarium specimens and expeditions through the distribution area up to 2008. These new findings made it clear that the previous taxonomic concepts were no longer tenable. A corresponding revision of the tomato section was published in June 2008 by Iris Peralta , David Spooner and Sandra Knapp . They recognize - as shown above - thirteen species in three groups of species and a separate species.

swell

  • Iris E. Peralta, David M. Spooner, Sandra Knapp: Taxonomy of Wild Tomatoes and their Relatives (Solanum sect. Lycopersicoides, sect. Juglandifolia, sect. Lycopersicon; Solanaceae) . Systematic Botany Monographs, Volume 84, The American Society of Plant Taxonomists, June 2008. ISBN 978-0-912861-84-5
  • Armando T. Hunziker: The Genera of Solanaceae . ARG Gantner Verlag KG, Ruggell, Liechtenstein 2001. ISBN 3-904144-77-4 . Pages 320-326.
  • J. Francis Macbride: Flora of Peru. Solanaceae. Botanical Series, Field Museum of Natural History, Volume XIII, Part VB, Number 1, May 1962. Page 161.
This version was added to the list of articles worth reading on November 6, 2008 .