Changes

*''Solanum'' ''lycopersicum'' L. (1753), *''Lycopersicon'' ''lycopersicum'' (L.) Karsten (1882).

*Tomato, love apple (En). *Tomate (Fr)

Tomato originated from the Andean region of South America, in the area now covered by parts of Bolivia, Chile, Ecuador, Colombia and Peru. The related species of cultivated tomato are native and widely distributed in this region. Archaeological and circumstantial evidence (diversity of types and culinary uses, abundance of local names) all suggest that tomato was domesticated in Mexico, outside its centre of origin, and that the most likely ancestor is the primitive cherry tomato ( ''L.'' ''esculentum'' var. ''cerasiforme'' (Dunal) Gray). Tomato was introduced into Europe in an already fairly advanced stage of domestication soon after the discovery of the New World. From there, it was taken to other parts of the world at various times: in the 17th Century to China, South and South-East Asia; and in the 18th Century to Japan and the United States. Although initially grown only as a curiosity in Europe because of its erroneous reputation as a poisonous fruit, tomato has now become one of the most important vegetables worldwide.

100 g of edible fruit portion contains approximately the following: water 94 g, protein 1.0 g, fat 0.2 g, carbohydrates 3.6 g, Ca 10 mg, Fe 0.6 mg, Mg 10 mg, P 16 mg, vitamin A 1700 IU, vitamin B₁0.1 mg, vitamin B₂0.02 mg, niacin 0.6 mg, and vitamin C 21 mg. The energy value is 80 kJ per 100 g. As may be noted, tomatoes are a good source of vitamins A and C. Both vitamins increase in quantity when the fruits are allowed to ripen on the vine. Immature fruits contain the alkaloid tomatine. The seeds contain 24% of a semi-drying edible oil. The 1000-seed weight is 2.5-3.5 g.

*Variable annual herb, up to 2 m tall or taller. *Taproot strong, to 0.5 m deep or more, often damaged at transplanting, and a dense system of lateral and adventitious roots. Stem solid, coarsely hairy and glandular. *Growth habit varies from indeterminate with stems several m long and prostrate when not supported, carrying an inflorescence every 3rd to 4th leaf, to determinate with several short and more erect stems with inflorescences (4-6 per stem) every second leaf and one terminating the shoot apex. *Leaves spirally arranged with a 2/5 phyllotaxy, imparipinnate, in outline 15-50 cm × 10-30 cm; petiole 3-6 cm long; major pinnae 7-9, opposite or alternate, ovate to oblong, 5-10 cm long, irregularly toothed and sometimes pinnatifid at base; a variable number of smaller pinnae occur between the larger leaflets; leaflets petiolate, covered with (glandular) hairs, producing a characteristic and species-specific odour. *Inflorescence cymose, normally with 6-12 flowers, but compound inflorescences with 30-100 flowers do occur; flowers regular, about 2 cm in diameter, pendent, bisexual, hypogynous, usually 6-merous; calyx tube short and green with pointed lobes, persistent and enlarging in fruit; corolla rotate, petals yellow, stellate, later reflexed and dropping off after pollination; stamens 6, anthers bright yellow, conically arranged, surrounding the style and prolonged into a sterile beak; superior ovary with 2-9 loculi and fleshy central placenta. *Fruit a berry, flattened, globular or oblate, smooth or furrowed, 2-15 cm in diameter, green and hairy when young, glabrous and shiny, red, pink, orange or yellow when ripe. *Seed flattened ovoid, 3-5 mm × 2-4 mm, up to 250 per fruit, light brown and hairy. *Germination is epigeal. Seedlings have a thin taproot and cordate cotyledons; the first leaves have few leaflets.

Dry seed (5.5% moisture content) will maintain a high viability (90-95% germination) after several years of storage at ambient (18-24°C24 °C) temperatures, provided the seeds have been extracted from fully mature fruits. Seeds germinate within 6 days after sowing at optimum soil temperatures of 20-25°C25 °C, and the first true leaf is formed one week later. About 7-11 leaves are usually formed on the main stem before the apex is transformed into a terminal inflorescence. The main axis is continued by the development of a new stem from the primary axillary bud in the leaf subtending the inflorescence. As the new shoot grows this leaf changes to a position above the inflorescence. The appearance is of continuous growth with internodal inflorescences, but it is actually sympodial. In indeterminate cultivars this process is repeated indefinitely with inflorescences every 3rd to 4th leaf and fruits maturing sequentially over a long period of time. In determinate types it is arrested after 4-6 inflorescences, when the primary axillary bud of the last leaf aborts and the next bud develops into a slower growing shoot with one leaf and a terminal inflorescence. Strong axillary bud development at the base of determinate plant types produces the bushy habit with several stems and a short period of prolific flowering followed by a period when fruit growth is dominant. In processing tomatoes, synchronization of fruit growth and ripening is such that once-over machine harvesting becomes possible.

* the esculentum complex, including ''L. esculentum'' , ''L. hirsutum'' Humb. & Bonpl., ''L. pimpinellifolium'' (Jusl.) Miller, ''L. chmielewskii'' Rick, Kes., Fob. & Holle, ''L. parviflorum'' Rick, Kes., Fob. & Holle, ''L. pennellii'' (Corr.) D'Arcy, and ''L. cheesmanii'' Riley;

* the peruvianum complex, including ''L.'' ''peruvianum'' (L.) Miller, and ''L.'' ''chilense'' Dunal.

* var. Within ''cerasiformeL. esculentum'' (Dunal) Gray, with fruits 1.5-3 cm in diameter;two botanical varieties are distinguished:

* var. ''cerasiforme'' (Dunal) Gray, with fruits 1.5-3 cm in diameter; * var. ''esculentum'' , with fruits > 3 cm in diameter.

* growth habit: indeterminate, semi-determinate and determinate (bush);

* fruit size: small round (cherry, 30 g; "Moneymaker", 80 g), medium-large round (120-150 g), beefsteak and ribbed (> 200 g);

* fruit shape: round, egg-shaped and elongated ("San Marzano") or flat ("Marmande");

* colour: red, pink, orange or yellow;

* utilization: for fresh market (direct consumption) or processing (high dry matter content and viscosity).

In South-East Asia, many farmers still use local cultivars (landraces). For example in West Java, "Gondol" is a popular highland tomato, possibly derived from a very ancient import of "San Marzano" and reputed for a good taste and a certain tolerance of late blight and other diseases. This cultivar has been replaced by Taiwanese hybrids which, in spite of an inferior taste, have become popular because of the high yield capacity combined with resistance to transport damage. The Indonesian cultivars "Ratna", "Intan" and "Berlian", selected from AVRDC lines with bacterial wilt resistance, have found some acceptance at lower elevations. The Thai cultivars "Seeda" and "Seedathip" are well adapted to the rainy season. It may be expected that in the coming decade landraces and local open-pollinated cultivars will be replaced by F₁hybrid cultivars.

Ideally, tomato requires a relatively cool, dry climate for high yield and premium quality. However, it is adapted to a wide range of climatic conditions. Tomatoes have been grown as far north as the Arctic circle (under protection) down to the hot and humid equator. The optimum temperature range for growth and development is 21-24°C24 °C. Prolonged exposure to temperatures below 12°C 12 °C can cause chilling injury. Mean temperatures above 27°C 27 °C severely impair growth and fruit set. Destruction of pollen and egg cells occurs when the maximum daytime temperature is 38°C 38 °C or above for 5-10 days. Fruit set is also generally poor if the night temperatures are above 21°C 21 °C during the few days before and after anthesis. Hot dry winds can also cause flower abortion. Light intensities below 1000 ft-candles retard plant growth and delay flowering. Tomatoes are not sensitive to daylength and set fruits in photoperiods ranging from 7-19 hours. 

Tomatoes can be direct-seeded or transplanted in the field. Relatively little seed-drilling or direct sowing into the field is practised in the humid tropics because of adverse growing conditions. In contrast, raising the young transplants in a special nursery enables growers to achieve great seedling uniformity and to check for early diseases and pests. Other advantages of transplanting are the smaller quantity of seed needed and reduced competition of weeds in the field. For raising transplants, 70-90 g of seeds are sown per 250 m²of seed-bed, which is sufficient to provide enough plants for one ha. Many farmers use banana leaf pots for plant raising. When direct-seeded, the sowing rate is about 500-1000 g of seeds per ha. Fertilizer at the rate of 40 g ammonium sulphate, 50 g superphosphate, 30 g potassium chloride and 2 kg compost per 1 m²of seed-bed area should be broadcast and worked into the seed-bed.

Tomatoes are attacked by many diseases and insect pests. Of about 60 pathogens that attack tomatoes, 15 are considered to be major diseases in the hot and humid tropics. Bacterial wilt ( ''Pseudomonas'' ''solanacearum'' ) has often been reported as the most serious handicap for tomato in the tropics. Bacterial spot ( ''Xanthomonas'' ''campestris'' p.v. ''vesicatoria'' ) is another serious disease. Long-term crop rotation is recommended to control bacterial wilt. There is no effective chemical control. Minimal infection has been reported when tomatoes are grown after lowland paddy rice. The most important control measures are a good drainage, a large dose of organic manure, and mulching in order to avoid rain damage to the roots. Bacterial spot is serious during the rainy season and is most noticeable on fruits but also causes damage to the foliage and stems. It is transmitted through the seed. Spraying with copper fungicides can control this disease fairly well except under heavy infection. Growing resistant cultivars is the best control method for both bacterial diseases but resistance is not universal owing to variable strains of the pathogens.

The most important fungal diseases of tomatoes in the tropics are early blight ( ''Alternaria'' ''solani'' ), black leaf mould ( ''Pseudocercospora'' ''fuligena'' ), late blight ( ''Phytophthora'' ''infestans'' ), leaf mould ( ''Cladosporium fulvum'' , syn. ''Fulvia fulvum'' ), powdery mildew ( ''Leveillula'' ''taurica'' ), southern blight ( ''Sclerotium'' ''rolfsii'' ) and target spot ( ''Corynespora'' ''casiicola'' ). Diseases such as ''Fusarium'' wilt ( ''F. oxysporum'' ) and ''Verticillium'' wilt ( ''V. dahliae'' ) are reported sporadically in the tropical highlands but they are not a problem elsewhere in the tropics. Some fungal diseases like late blight can cause 100% yield loss in the highland tropics where conditions are cool and moist. Spraying with chemicals such as maneb compounds can control most of the above fungal diseases in varying degrees. Field sanitation and proper rotation are also effective control measures. Planting resistant cultivars is the most effective and the cheapest control method, but resistance to late blight is not yet available. Local cultivars often are more or less tolerant of late blight.

Among the insects, the polyphagous tomato fruitworm ( ''Heliothis'' ''armigera'' ) is one of the most destructive, causing as high as 70% yield loss due to fruit boring. Synthetic pyrethroids sprayed at the rate of 50-100 g a.i. per ha can control this pest. Tomatoes should not be planted near other alternative hosts like maize and cotton.

Cotton aphid ( ''Aphis'' ''gossypii'' ) is a major pest during the dry season. It injures the plants by sucking the sap and by acting as a vector for the cucumber mosaic virus. Spraying with dimethoate and prothiophos is effective to control aphids. Several species of coccinelid beetles and syrphids also act as natural enemies, but they generally appear when the aphid population is already high. Whitefly ( ''Bemisia'' ''tabaci'' ) is a serious pest, not only because of its foraging on the tomato plants but also because it acts as a vector of the tomato yellow leaf curl virus. More recently thrips, especially ''Frankiniella occidentalis'' , has become a problem as it is the vector for tomato spotted wilt virus.

Root knot nematodes ( ''Meloidogyne'' ''incognita'' and other species) invade the tomato roots and cause galling. Yield losses due to direct infection and indirect losses due to predisposition or breakdown of resistance to other root diseases, such as bacterial wilt, are significant. Nematicides and other soil fumigants can effectively control nematodes but are expensive. The use of resistant cultivars is still the most cost-effective measure, although breakdown of resistance can occur at high temperatures and there is no resistance to ''M. hapla'' .

The storage life of tomatoes depends on the maturity stage at which they were harvested and on the desired quality of fruits. Quality is highest when completely ripe, whether artificially or on the vine. Ideally mature-green tomatoes should be stored for 7-10 days at 13-18°C 18 °C with 85-90% relative humidity so that they will ripen properly. Ethylene is sometimes used to rapidly and uniformly ripen mature-green tomatoes prior to shipping them to the market, but this adversely affects quality.

Tomato is one of the best-studied plant species, reflecting its great economic importance. Many important genetic traits have been discovered, evaluated and genetically localized in their respective chromosomes. Tomato has a prolifically marked genome, very useful in genetic and breeding research. Many useful traits have been incorporated by tomato breeders into modern-day cultivars, among which are high yield, disease resistance, improved quality for processing, and stress tolerance. Seeds of both standard (open-pollinated) and F₁hybrid cultivars are now available to tomato growers. New cultivars continue to be developed, offering improvements in one or more traits of interest. When tested in the South-East Asian countries the "international" hybrid cultivars often show disadvantages and weaknesses, which can only be amended by breeding work "in situ". Areas of continuing concern to tomato breeders in South-East Asia are disease resistance (bacterial wilt, ''Phytophthora'' and ''Alternaria'' ), tolerance to environmental stress (such as high temperatures, excess soil moisture due to high rainfall and problem soils, e.g. acid or saline soils), quality (for fresh-market consumption and for processing), and long shelf life (for long distance transport and longevity in storage). 

*R.T. Opeña & H.A.M. van der Vossen