RESEARCH TO IMPROVE THE YIELDS OF STALKED TOMATO PLANTS GROWN IN THE OPEN
The word 'yield' denotes that part of the total tomato produce, which is picked up to the end of the period of vegetation, as ripe fruits. Experience has shown that the 'yield' is gathered from the fruits up to the 5th cluster, that is why after the formation of the fifth inflorescence the tops of the plants are pinched out.
There is no statistically proved difference in the yields between the early and the later cultivars. The early ones produce a high average yield, while in the late variety, known as 'Dominator', a relatively large part of the fruits (26.4 per cen) remain green, for that reason they have not been included in the total yield. The medium early variety 'Apollo' and the slightly later variety 'Hellperle' are the most high-yielding cultivars. Their yields are with 16 respectively 19 per cent higher than those of the early cultivars. In accordance with these observations, the following recommendations for growing of stalked tomato plants in the German Democratic Republic can be given: for early production and tomato produce in climatically unfavourable areas, only early varieties should be cultivated. To obtain high yields the varieties 'Apollo' and 'Hellperle' should be grown in meteorologically favourable conditions. It should be borne in mind, however, that 'Hellperle' is more capricious in respect to climatic conditions than 'Apollo'.
With respect to the qualitative indices and the other requirements on the vegetable markets, a decisive factor and task to be solved in tomato breeding has been the increasing of their earliness. To a considerable extent this has been achieved by way of hybridization with Lycopersicon Pimpinellifolium. Thus, picking of ripe tomatoes has been hastened by 12 days in comparison to 'Bonner Beste', which has been the leading variety around the 1950's.
This improvement in the yields, however, should be considered only in connection with the early picking season. Table 1 indicates that towards the end of the growing period all tomato varieties yield a certain percentage of unripe fruits. While the green tomatoes of the early varieties amount to 10–15 per cent, the latter increase from 15 to 26 per cent in the medium early and the late ripening cultivars. The percentage of unripe tomatoes has even reached to around 50 per cent in years of particularly unfavourable meteorological conditions.
Table 2 illustrates the juxtaposition of the total yields, i.e. ripe and unripe tomato produce.