At the existing trend of greenhouse tomato production, certain stages of the whole vegetation period and especially the development and flowering of a number of their inflorescences happen to be in November and December of the beginning of January, when the day is shortest, the intensity of the sunshine is weakest, and the relative humidity highest, due to which a part of the clusters do not develop or the flowers drop off.
The countries with highly developed greenhouse production of vegetables, such at The Netherlands, Great Britain, the German Federal Republic, etc., grow tomato varieties, the fruits of which have a regular form, an uniform colouring and are green back-free.
Such tomato fruits are readily accepted on the international vegetable markets.
These circumstances made it necessary to study certain foreign and Bulgarian tomato varieties in order to establish a suitable variety for the country's greenhouse tomato production.
Over 70 different varieties and hybrid combinations were studied in preliminary variety testing and assortment.
The following varieties and hybrid combinations were experimented: Break O'Day x Comet, Moneymaker, Moneydor, Moncladex, Allround, Spanish, Topcross, Maascross, Nemacross, Rivermoon, Eurocross BB, No 24, Eurocross B, Extase, Azes66A6. The chess-board order of variant distribution was used in 4 replications, the size of the planted area being 6.6 or 11.2 m2 in every replication.
In the 1965/1966 crop period, sowing took place on 9 December 1965, the transplanting in peat-cellulose pots on 5 January 1966, and the seedlings were planted on 15 February, in bands at distances 90 x 70/35 in greenhouses of the Venlo type.
In 1966/1967 and 1967/1968 sowing took place during the last ten days of August, transplanting on 12 September, again in peat-cellulose pots, and planting was carried out during the last ten days of September, in bands and the same spacing as in the 1965/1966 season.
During the period of seedling production the preparation of the soil in the greenhouse, and during the vegetation period, all undertakings were carried out in accordance with the requirements of the plants, which assured their normal development.
The formation of the growth and reproductive organs were closely followed-up, the yields of each picking were recorded; the percentage of the standard and non-standard production as well as the average weight of the fruits and certain other qualitative indices of the fruits were also registered.
During the period of the most abundant fruit-bearing an anonimous morphological and degustational evaluation was also carried out.
In 1965/1966 the regular picking of the fruits began towards the end of April and the beginning of May, and continued until 15 July, while in 1966/1967 and in 1967/1968 regular picking began towards the second half of December and continued until the end of June.
The fruits were harvested in their export ripeness.