1. Origin
2. Taxonomy and morphology
3. Economic importance and geographical distribution
4. Edaphoclimatic requirements
5. Vegetal Material
6. Growing techniques
6.1. Settings for planting
6.2. Pruning
6.3. Ridging up
6.4. Trellising
6.5. Shoot thinning
6.6. Leaf thinning
6.7. Blunting of inflorescences and fruit thinning
6.8. Fertigation
7. Soilless crop
8. Pests and illnesses
8.1. Pests
8.2. Illnesses
9. Alterations of fruits
10. Harvest
11. Post harvest
12. Nutritional value
13. Marketing

1. ORIGIN

During the sixteenth century in Mexico, tomatoes of different shapes, sizes and colours (red and yellow) were consumed, by then they had been brought and served as food in Spain and Italy. In other European countries, such as Germany, they were only used in pharmacy until the early nineteenth century. The Spanish and Portuguese tomatoes had spread to the Middle East and Africa, and from there to other Asian countries. From Europe also had spread to the United States and Canada.

2. TAXONOMY AND MORPHOLOGY

The tomato belongs to the Solanaceae family, whose scientific name is Solanum lycopersicum.

Family	Solanaceae
Genus	Solanum
Specie	S. lycopersicum
Scientific name	Solanum lycopersicum
Common name	Tomato

- Plant: Perennial shrub that is grown annually. It can develop in creeping, semi-erect or erect way. There are varieties of limited growth (determinate) and other unlimited growth (indeterminate).

- Root system: It consists of main root (short and weak), many powerful secondary roots and adventitious roots. If the primary root is sectioned transversely from outside to inside, it can be found the epidermis (where absorbent hairs specialized for water absorption and nutrients are located), the cortex and the central cylinder (set of vessels specialized in the transport of nutrients).

- Main Stem: Its axis is 2-4cm thick at its base, on which the leaves, side shoots (sympodial branching) and inflorescences develop. Its structure, from outside to inside, consists of: 1. epidermis, the hub of outward glandular hairs, 2. bark or cortex, whose outermost cells are photosynthetic and the innermost are collenchyma, 3. vascular cylinder and 4. medullary tissue. In the distal part is the apical meristem where new leaf and floral primordia develop.

- Leaf: Complexed and imparipinnate with stalked leaflets, lobed, serrated edge and covered with glandular hairs. The leaves are arranged alternately on the stem.

The mesophyll or parenchyma tissue is covered by an upper and lower epidermis, both without chloroplasts. The lower epidermis has a high number of stomata. Within parenchyma, the upper or palisade zone is rich in chloroplasts. The vascular upper parts of the leaf are prominent, especially on the underside, and consist of a main nerve.

- Flower: Perfect, regular and hypogynous with 5 or more sepals and 5 or more petals and are helically arranged at intervals of 135°. Equal number of stamens which alternates with petals forming a staminal cone that surrounds the gynoecium. The ovary may be bilocular or plurilocular.

Often, the main axis of the inflorescence branch out below the first formed flower resulting in a composite inflorescence which can reach up to 300 flowers. The first flower develops in the bud and the other are arranged laterally below the first, around the main axis. The flower is united to the floral axis through an articulated pedicel that contains abscission area, which is distinguished by a thickening with small groove caused by the reduction in thickness of the cortex. The inflorescences develop in the axils every 2-3 leaves.

- Fruit: bilocular o plurilocular berry that can reach a weight from a few milligrams to 600 grams. It consists of pericarp, placental tissue and seeds.

The fruit can be harvested by separating the pedicel abscission area, as in industrial varieties, which is undesirable the presence of the petiole. It can also be separated from the base of the peduncular region of the fruit.

3. ECONOMIC IMPORTANCE AND GEOGRAPHICAL DISTRIBUTION

Tomato is the most common vegetable in the world and has the highest economic value. Its demand is continuously growing and with it, its growing, production and trade. The annual increase in production in recent years is mainly due to the increase in production yield, and to a lesser extent, due to the increase in acreage.

Countries	Tomato production in 2010 (tonnes)
China	47 110 084
United States	12 858 700
India	12 433 200
Turkey	10 052 000
Egypt	8 544 990
Italy	6 024 800
Iran	5 256 110
Spain	4 312 700
Brazil	4 114 310
Mexico	2 997 640
Uzbekistan	2 347 000
Russia	2 049 640
Nigeria	1 860 600
Ukraine	1 824 700
Greece	1 406 200
Portugal	1 406 100
Morocco	1 277 750
Syria	1 156 300
Tunisia	1 100 000
Iraq	1 013 180

Source: FAOStat

As what is observed in the table above, Spain is one of the main producers of fresh tomatoes.

4. EDAPHOCLIMATIC REQUIREMENTS

The proper management of climatic factors together is essential for the proper functioning of the crop, since all are closely interrelated and the action of one affects the other.

- Temperature: It is less demanding than aubergine and pepper.

The optimum growth temperature ranges from 20-30°C during the day and between 1-17°C during the night. Temperatures higher than 30-35°C affect fruiting (ovules bad development) and plant development in general and the root system in particular. Temperatures below 12-15°C below also cause problems in the development of the plant.

At temperatures above 25°C and below 12°C, fertilization is defective or null.

Fruit ripening is strongly influenced by temperature in relation to both the earliness and the colouring, so that at temperatures near 10°C or above 30°C can cause yellowish tones on the fruit.

However, the temperature rates ​​described above are only indicative and for this reason, the interactions of temperature with other climatic parameters should be taken into account.

- Humidity: The optimum relative humidity ranges from 60-80%. Very high relative humidity favours the development of aerial diseases and fruit cracking and it also interfere with fertilization, because with high humidity, the pollens become more compact and some of the flowers are aborted. Fruit cracking may have its origin in excessive soil moisture or heavy irrigation after a period of water stress. Low relative humidity makes also difficult the attachment of pollen to the stigma of the flower.

- Light: reduced light can have an adverse effect on the processes of flowering and fertilization and also on the vegetative development of the plant.

At critical times during the growing season, it is crucial the interrelationship between day and night temperatures and luminosity.

- Soil: The tomato plant is not demanding regarding the type of soil, except with regards to the draining system. It prefers loose siliceous-clay soils rich in organic matter and texture. However, it develops perfectly in sanded clay soils.

With regard to pH, soils range from slightly acidic to slightly alkaline when they are sanded.

It is the species grown in greenhouse conditions which can better tolerate both soil and irrigation water salinity.

- Carbonic Fertilization: The contribution of CO₂ is to compensate the consumption of plants and ensures the maintenance of above average concentration of CO₂ in the greenhouse. Thus, stimulates photosynthesis and accelerates plant growth.

To assess the needs of CO₂ of greenhouse crop, it is needed to be done in various periods of the year a balance of losses from absorption by the plants, the air changes made ​​in the greenhouse and contributions provided by the soil to the atmosphere.

CO₂ enrichment in greenhouse depends on the quality, productivity and crop earliness. It should be taken into account that too much CO₂ causes damage due to stomatal closure, causing cessation of photosynthesis and burns.

The most commonly used devices in carbonic fertilization are burner of propane gas and devices which are used for CO₂ distribution.

In tomato crop, the optimum amounts of CO₂ are between 700-800ppm. In terms of net income, the type of greenhouse and the climate control system, etc. provide increases of about 15-25%.

5. VEGETAL MATERIAL

Main selection criteria:

- Characteristics of the commercial variety: plant vigour, fruit characteristics, disease resistance.
- Target market.
- Greenhouse structure.
- Soil.
- Climate.
- Quality of irrigation water.

Main types of fresh market tomatoes:

- Beef Type: vigorous plants until the 6th -7th clusters of fruits, from which it loses enough plant strength, coinciding with the development of the first clusters. It has large fruits and little consistency, early production and grouped and has an irregular pistil closure. The most important markets are the domestic market and abroad (USA).

- Marmande Type: less vigorous plants that produce 4-6 clusters of fruits. The fruit is known for its good taste and ribbed form, flattened and multilocular. It can vary depending on the growing season.

- Vemone Type: Thin and narrow-leaved plants, indeterminate frame size and very dense setting for planting. Fruit calibre L that has high degree of acidity and sugar which are induced by the farmer through water stress. Harvest is done when it starts to change its colour, and the shoulders are still green. They are varieties with poor resistance to diseases and are cultivated with great success in Sardinia (Italy).

- Moneymaker Type: Plants with generally indeterminate growth size. Calibre M and S fruits which are smooth, round and well-formed clusters.

- Cocktail Type: Very thin and indeterminate growth development. Its fruits weigh between 30-50 grams, round, usually with 2 locular cavities, sensitive to cracking and are mainly used for decoration of dishes. There are also pear-liked fruits which have the characteristics of a market tomato because of its consistency, soluble solids content and acidity, but their use is mainly in fresh. The application of a fungicide that stains the fruit in order to prevent commercial depreciation should be eradicated.

- Cherry Type: Vigorous plants with indeterminate growth development. It has small fruits and thin skins which are prone to cracking and are grouped in clusters from 15 to more than 50 fruits. They are sweet and have pleasant taste. There are cultivars that have red and yellow fruits. The objective of this product is to have a complete annual production cycle with homogeneous quantities. In any case, it is pursued a tomato resistant to viruses and cracking since this type of tomato is very sensitive to sudden changes in the temperature.

- Long Life Type: The introduction of the Nor and Rin genes is responsible for its long life, giving greater consistency and high conservation of the fruits in the market at the expense of its taste. Generally, fruit calibres L, M or S with smooth surface and uniform colour orange or red are wanted.

- Smooth Type: Varieties grown for domestic market and sold in breaker stage in Italy. They have lesser plant vigour than long life type.

- Cluster Type: Increasingly present in the markets. It is difficult to define what type of tomato is ideal for making clusters. Fruit calibre M with bright red colour and inserted in clusters, etc. are generally preferred.

6. GROWING TECHNIQUES

6.1. Settings for planting

The setting for planting is set based on the plant growth habit, which in turn depends on the cultivated commercial variety. The most frequently used settings for planting are 1.5 meters between lines and 0.5 meters between plants.

When it comes to medium-sized plants, it is common to increase the density of planting to 2 plants per square meter, with settings of 1m x 0.5m.

When plants are trellised with hangers, the lines must be "paired" in order to move the plants from one line to another to form an endless chain. Wide corridors should be left for the descent of hangers (about 1.3m) and a distance about 70cm between joint lines.

6.2. Pruning

It is a must for varieties with indeterminate growth habit. It is done 15-20 days after transplant, when the first side shoots appear. Stems and senescent leaves are removed, thus improving aeration of the stem crown and facilitate completion of the ridging. Also, the number of stems for each plant is determined.

It is frequent in pruning to leave 1 or 2 stems, although in Cherry type tomatoes, up to 3 and 4 stems are usually left.

6.3. Ridging up

The ridging consists of covering the lower part of the plant with sand after pruning (sanded floors). The purpose of this work is to enhance the formation of a greater number of roots.

There is another variant of ridging up which is performed by bending the plant until it touches the ground, after being slightly scraped. Then it is covered lightly with sand, leaving out the terminal bud and a couple of leaves.

6.4. Trellising

Trellising and tying the plants is a must in order to maintain them in an upright position; it will also improve general air circulation and will make it easier to take advantage of the sunlight and to undertake all the necessary care in relation with crop production (pruning, harvesting, etc.). This will benefit the final production, fruit quality and disease control.

Tying is usually done with polypropylene thread which is tied to the basal end of the plant (bundled, knotted or attached by loops) and to another wire located at a certain height thereof (1.8-2.4m above the ground). As the plant grows, it will be fastened or tied up to the stake until the plant reaches the wire. From this moment, there are three options:

1. Lower the plant by dropping the thread: This practice involves an additional cost of manual labour.

The clamping mechanism used in this system is called "Dutch" or "hanger". It is done by placing hangers with thread around them at the top and which drop gradually as the plant grows. The plant is clamped to the thread by clips.

In this way, the plant always develops vertically which permit it to receive maximum amount of light, thus improving and increasing fruit quality and production.

2. Leave the plant to grow and to gradually drop by the action of gravity.

3. Allow the plant to grow horizontally on the trellises. These trellises form grids along the crop line. The plant is tied to the trellis through the use of rings.

6.5. Shoot thinning

It consists of removing the axillary buds to improve the development of the main stem. It must be done as often as possible (weekly in summer-fall and every 10-15 days in winter) to avoid loss of photosynthetically active biomass and to avoid making wounds.

The cuts should be clean to prevent the possible occurrence of diseases. In delicate times, it is advisable to apply phytosanitary treatment with a fungicide-bactericidal healing, such as those derivatives of copper.

6.6. Leaf thinning

It is advisable to remove senescent leaves to facilitate aeration and improve fruit colour and eliminate infected leaves (should be removed immediately from the greenhouse) to avoid the source of inoculums.

6.7. Inflorescences and fruit thinning

Both practices become more important with the introduction of the tomato in cluster. They are done in order to homogenize and increase the size and quality of the remaining fruits.

In general, there are two types of thinning:

- Systematic thinning: It takes place on the clusters. A fixed number of fruit is allowed, eliminating mal-positioned immature fruits.
- Selective Thinning: It takes place on the fruits to satisfy certain conditions regardless of their position in the cluster. These can be deformed and small sized fruits and those which are damaged by insects.

6.8. Fertigation

In protected tomato crops, water supply and much of the nutrients, are usually carried out by drip irrigation depending on the growth stage of the plant and the environment in which it develops (soil type, climatic conditions, irrigation water quality, etc.).

In soil and sanded crops, setting the timing and amount of irrigation is basically determined by the following parameters:

- Voltage of ground water (matric tension), which can be determined by the proper management of tensiometers, being convenient to water before reaching 20-30cb.
- Soil type (field capacity, saturation rate).
- Evapotranspiration of the cultivar.
- Efficiency of Irrigation (flow uniformity of the droppers).
- Quality of irrigation water (the poorer the quality of water, the higher the salinity level is, and the volume of water needed to move the salts is higher).

Table 1. Media consumption (l/m2·day) of tomato crop in greenhouse
Source: Experimental Station "Las Palmerillas". Cajamar Foundation

MONTHS	AUG		SEP		OCT		NOV		DEC
Fortnights	1	2	1	2	1	2	1	2	1	2
A	1.63	2.95	3.68	3.80	4.21	3.39	2.40	2.04	1.94	1.55
B		1.48	2.75	3.04	3.51	3.39	2.40	2.04	1.94	1.55
C			1.38	2.28	2.81	2.83	2.40	2.04	1.94	1.55
D				1.14	2.11	2.26	2.00	2.04	1.94	1.55
E					1.05	1.70	1.60	1.70	1.94	1.55

MONTHS	JAN		FEB		MAR		APR		MAY
Fortnights	1	2	1	2	1	2	1	2	1	2
A	1.59	1.46	1.70	1.88	2.84	2.88	3.19	3.39	3.69	4.03
B	1.59	1.46	1.70	1.88	2.84	2.88	3.19	3.39	3.69	4.03
C	1.59	1.46	1.70	1.88	2.84	2.88	3.19	3.39	3.69	4.03
D	1.59	1.46	1.70	1.88	2.84	2.88	3.19	3.39	3.69	4.03
E	1.59	1.46	1.70	1.88	2.84	2.88	3.19	3.39	3.69	4.03

A: 1^st half of August transplantation.
B: 2^nd half of August transplantation.
C: 1^st half of September transplantation.
D: 2^nd half of September transplantation.
E: 1^st half of October transplantation.

Table 2. Media consumption (l/m²·day) of spring tomato crop in greenhouse
Source: Experimental Station "Las Palmerillas". Cajamar Foundation

MONTHS	DEC		JAN		FEB		MAR		APR		MAY		JUN
Fortnights	1	2	1	2	1	2	1	2	1	2	1	2	1	2
A	0.40	0.65	0.93	1.31	1.88	2.25	3.40	3.84	4.39	4.24	4.15	4.03	4.88	5.09
B		0.33	0.66	1.03	1.53	2.06	3.40	3.84	4.79	4.66	4.61	4.54	4.88	5.09
C			0.34	0.74	1.19	1.69	3.13	3.84	4.79	5.09	5.08	5.04	5.48	5.09
D				0.44	1.03	1.50	2.84	3.84	4.79	5.09	5.08	5.04	5.48	5.09

A: 1^st half of December sowing or transplantation.
B: 2^nd half of December sowing or transplantation.
C: 1^st half of January sowing or transplantation.

There is another technique which consists of removing the liquid phase of the soil by suction through a porous ceramic and subsequent determination of the electrical conductivity.

In sanded crops, watering frequency for an established crop is 2-3 times/week in winter, increasing to 4-7 times/week in spring and summer, with flows of 2-3l/pl.

In hydroponic crops, irrigation is automated and there are different systems to determine water needs of the crop. The most common is the use of demand-irrigation tray. The time and amount of irrigation depend on the physical characteristics of the substrate.

With regard to nutrition, it is important to take into account the ratios of Nitrogen/Potassium throughout the whole crop cycle, which is usually 1/1 from transplant to flowering and 1/2 or even 1/3 during harvest season. In cluster tomato the role of potassium in the ripening is even more essential.

The addition of nitrification inhibitors slows the oxidation of ammonium to nitrate, so that the ammonium is maintained longer in the ground, as this type of fertilizer affect the bacteria involved in this process. Thus, nitrogen is supplied gradually to the plant as it adapts to the needs of each crop throughout its period of development and thereby decrease nitrate wastage by leaching and denitrification. The opposite effect occurs with the addition of mineral fertilizers high in ammonium nitrogen.

Phosphorus plays an important role in rooting and flowering stages. It is crucial for the formation of roots and the size and quality of flowers. Sometimes its use is abused, seeking the shortening of internodes at early times when the plant tends to weaken. During winter, the supply of this element and magnesium must be increased in order to prevent serious deficiencies due to the cooling of the soil.

Calcium is another essential macro-element in the nutrition of tomato. With this apical necrosis is avoided (blossom end rot), usually caused by lack of calcium or calcium blockage usually caused by high salinity level or serious irregularities in water irrigation. Calcium also affects the elasticity of the cellular wall of the fruit. Thus, the proper supply of calcium favours the development of fruits with high calibre and prevents the occurrence of cracking.

Among the most important microelements in the nutrition of tomato is iron, which plays a major role in the colour of the fruit, and to a lesser extent, are manganese, zinc, boron and molybdenum.

At the time of fertilization, there is a very wide range of fertilizer applications in which no substantial differences are observed in the crop, given the fact that varied and contradictory application methods can be found in the same area with the same soil type and the same variety. However, in order not to make great errors, the total dose of fertilizer should not exceed above 2g/l, being advisable is to provide 1g/l for water conductivity of approximately 1ms/cm.

Methods in establishing nutritional needs:

- Based on the extraction of the crop, on which there are wide and varied bibliographies.
- Based on an "ideal" nutrient solution to which applications will be adjusted after conducting water analysis. This method is the one used in hydroponic crops, and for it to be carried out in ground or sanded crops, it requires the placement of suction probes to determine the composition of the soil solution through macro and micronutrients analyses, CE and pH.

The most widely used are simple fertilizers: in soluble solid form (calcium nitrate, potassium nitrate, ammonium nitrate, monopotassium phosphate, monoammonium phosphate, potassium sulphate and magnesium sulphate) and in liquid (phosphoric acid and nitric acid) due to its low cost and they allow easy adjustment of the nutrient solution. However, complex crystalline solid and liquid fertilizers also exist in the market that can be used alone or in combination with simple fertilizers, to keep the balance required at different stages of crop development.

The contribution of microelements, which had been largely neglected in the past, is vital for proper plant nutrition. There is a wide range in solid, liquid and mineral chelates form in the market, when it is necessary to promote the absorption of nutrients and the stability of the plant.

Iron chlorosis is characteristic of species that grow in limestone soils. Iron deficiency shortens the life cycle of plants, reduces yields and lowers the quality of the fruit. The ferric chelate is one of the best solutions to combat iron chlorosis, but have a high price. For this, the application of the chelate is to be reduced in order to reduce the cost and increase the profits

There are also numerous deficiency correctors both macro and micronutrient which can be applied through foliar or drip irrigation. Examples are aminoacids - for preventive and curative use, which help the plant at critical stages in its development or under unfavourable environmental conditions and other products (humic and fulvic acids, saline correctors, etc.) that improve environmental conditions and facilitate the assimilation of nutrients by the plant

Humic substances are complexed with most of the metals in the soil, increasing its availability in the plant. Amino acids also play an important role in nutrient uptake.

Carbonic fertigation is the use of carbonated water for irrigation. Carbonated water is obtained by injecting CO₂ under pressure into the main pipe. Upon dissolution of the CO₂ in the irrigation water, it produces carbonic acid which reduces the pH and produces various bicarbonates upon reacting with carbonates and other salts present in the water. Carbonated water then receives regular fertilizer for irrigation whose solubility increases in slightly acidic water.

Carbon fertilization accelerates plant growth, increases the production and quality of the fruit, due to carbon uptake (plants absorb naturally CO₂). For this technique to be effective, it is essential to adjust the amount of light and water intake of the plant.

To provide CO₂ to the irrigation system, it should be taken into account the pressure line of the irrigation water, the distance between the CO₂ injection point and the first dropper, water temperature, CO₂ diffusion system in the water and the amount of CO₂ per litre of water.

The use of carbonated water is profitable in tomato crops. The optimal dose is around 0.20g CO₂/l but increased fruit size is achieved with an approximated dose of 0.35g CO₂/l (Aguilera et al; 2001).

Advantages of carbonic fertigation:

- Acidifies the soil, modifying the solubility of micronutrients.
- Increase the quality and number of fruits.
- Promotes the dissolution of used fertilizers.
- Prevents and removes deposits in the irrigation network.
- Save fertilizers.
- Partially replaces the use of nitric acid.

Author: Infoagro