Tree tomato
(Cyphomandra betacea)

Botanical names: Cyphomandra betacea Cav.) Send., C. crasifolia (Ortepa) Kuntze, Solanum crassifolium Ortega, S. betacea Cav.
Common names: English: tree tomato, tamarillo; Spanish: tomate de árbor, berenjena, sachatomate, yuncatomate (Peru), limatomate, tomate de monte, tomate de La Paz (Bolivia, Argentina)
Family: Solanaceae

This is a native species of the Andes whose domestication and cultivation took place before the discovery of America. In spite of its age, no names are known in native languages.

Uses and nutritional value
Cyphomandra betacea is cultivated for its fruit which is a food resource and a potential raw material for the preserves industry. The peasants attribute to the fruit medicinal properties for alleviating respiratory diseases and combating anaemia. The tree tomato contains adequate levels of vitamins A, B6, C and E and iron.

The fruit is eaten raw or cooked. In all cases, the skin is removed as it has a bitter flavour. When ripe, the fruit is eaten raw as a fruit. More frequently it is eaten as a dessert of fruit in syrup. The whole pedunculated fruit is cooked for a short time in water so that the skin can be removed. Honey is then prepared with cinnamon and cloves, the peeled fruit is added and it is left to boil until it reaches a suitable consistency. ln the pre-ripe state, when the fruit takes on an orange colour, it is used in Peru to prepare a sauce together with Capsicum, pubescens R. & P., a variety of large green pepper. To prepare this, the fruit is lightly grilled, which facilitates removal of the skin (epicarp). It is then ground with a large green pepper and salt. This spicy sauce is eaten as an appetizer. In those areas of the sierra where tomato (Lycopersicon sp..) is not grown, tree tomato is used to prepare stews, thus replacing tomatoes.

Botanical description
Cyphomandra betacea is a small tree, growing 2 to 3 m in height, with a single trunk that is monopodial and branched at a height of 1 to 1.5 m into two or three branches. The same pattern of ramification is repeated on the branches. The leaves are cordiform, 17 to 30 cm long, 12 to 19 cm wide, subcarnose and lightly pubescent on the underside. There is a caulinar inflorescence opposite the leaf. The flowers are 1.4 cm long, the calyx persists on the fruit, the corolla is pinkish white and rotate-campanulate with reflexed apices, connivent stamens that are shorter than the corolla, yellow anthers and is dehiscent through two apical pores. The style emerges between the anthers. The fruit is 5 to 7 cm long, ovoid, glabrous, greenish yellow to orange in colur, with longitudinal markings, and the mesocarp is orange.

Phenology. Apparently no research has been done on the growth phases of this plant. Consequently, the following phenological description is an approximation and the result of field observations and information provided by peasants.

Propagation is most frequently by seed but can also be based on cuttings.

The plant's life is approximately three to four years and flowering begins eight to ten months after sowing in the permanent location. The flowering period begins at the same time as branching of the main stem. The first inflorescence is produced around the point of branching of the main stem and the following ones at the end of the branches, around their respective branching. Flowering is continuous and the number of inflorescences is directly proportionate to the plant's branching.

The plant is evergreen and constantly puts out leaves. However, the lower leaves later fall, leaving the main stem and lower part of the branches leafless.

Ecology and phytogeography
C. betacea grows best in regions with temperatures between 18 and 22°C and annual precipitations of 600 to 800 mm. These climatic characteristics occur in the Andes at average altitudes (1 800 to 2 800 m). Observations in family gardens show that the plants grow better in association with trees (e.g. Erythrina edulis, Juglans neotropica where a more humid microclimate has formed, with less soil dehydration and where the light is diffused. Tree tomato plants do not tolerate low temperatures (frost). High temperatures also affect flowering and fruiting, as do prolonged droughts.

C. betacea is cultivated sporadically from Mexico and the Antilles to Argentina. No wild populations are known and its domestication is presumed to be recent. Cultivation extends to subtropical areas such as New Zealand, where it is very advanced, southern Europe and tropical areas of other continents, India and Southeast Asia.

Genetic diversity
C. betacea is known only in the cultivated state. Populations display variability in the pigmentation of the young foliage and in the colour, shape and thickness of the fruit's mesocarp. Some of them have groups of silicose cells on the mesocarp, which lowers the quality of the fruit. According to growers, the yellowish green leaf colour is related to the production of yellowish fruit and the purple-green foliage with the production of orangey-red fruit. The shape of the fruit varies from subspherical to ovoid with a slightly pointed apex. Research on this aspect is necessary to elucidate the extent of variability and the phytogenetic relationship with wild species.

Related species. There are around 50 species of Cyphomandra which are found from southern Mexico to Argentina. C. bolivariensis and C. hartwegii are considered to be species related to the tree tomato. C. hartwegii produces edible fruit, is grown sporadically and has been used as grafting stock. Another species with edible fruit, C. cajanumensis or casana, originating from Ecuador, is cultivated in New Zealand.

Cultivation practices
Commercial cultivation of C. betacea is incipient, in spite of the fact that it is frequently grown in the gardens of rural and urban houses. In these gardens, very few plants (two to four) are grown for family consumption and only occasionally it is sold on local markets.

Cultivation techniques are based on propagation from seed and there are therefore two stages in cultivation:
Seed bed Seeds from ripe fruit are left to dry outside for ten to 15 days and are then put into a seed bed. They are left there for 30 days to germinate and reach 15 to 20 cm in height (with three or four leaves), at which point they are planted out in their final location.

Sowing. Since the plants are grown in gardens where there is no regular planting, no information is available on the depth of sowing, the distance between plants, tillage practices or crop protection.

Cultivation based on vegetative propagation is very rare. In Colombia, it is reportedly grown from cuttings which must be 20 to 30 cm in length and which take root 30 days after planting, at which stage they are thus suitable for planting out. In Cajamarca in Peru, one case of propagation from cuttings is known to have been carried out experimentally by a grower.

Prospects for improvement
Cultivation of C. betacea shows promise and should be the subject of research and experimentation in commercial crops which allow relevant technologies to be developed.

The limitations of C. betacea are determined by the traditional state of cultivation rather than by the plant's characteristics.

The present situation is characterized by:

· a lack of identification of cultivars;
· an absence of commercial cultivation techniques and plant management (plant regeneration and pruning techniques);
· cultivation limited to family gardens;
· the presence of mycotic diseases (Oidium sp.) and insect pests which attack the leaves.

It has been found that the species is not very stable in the characteristics obtained through selection, such as colour, size, sweetness of the fruit and yields. However, it should be recognized that those characteristics have been detected in cultivars developed outside the natural distribution area (New Zealand) where ecological factors may have had an influence.

The tree tomato's prospects are determined by the quality and diversity of use of its fruit. The most important and potentially exploitable is industrial processing of the fruit for preserves. This agro-industry would promote cultivation over larger areas and extend the market, while cultivars would be developed with bigger yields and better-quality fruit.

Lines of research
Intensive cultivation of C. betacea for industrial purposes involves carrying out various research studies aimed at achieving greater production. With this in mind. the following activities are recommended:

· Experimenting with vegetative propagation using hormones which accelerate rooting and activate buds; the results could bring forward the flowering period.
· Looking for techniques for pruning and activating dormant buds. Removal of apical dominance at an early age causes branching at lower altitude. After their second year, the plants have many dormant buds on the lower part of the branches and on the main stem which, when activated, would form new branches and increase production.
· Recognizing the genetic variability of the species within its natural geographical distribution as well as that of related species in order to select cultivars and try to obtain hybrids.
· Investigating floral biology and identifying the possible role of pollinating insects.