Cucurbit Genetics Cooperative Report 2:13 (article 8) 1979
Low Temperature Adapted Slicing Cucumbers Release
A. P. M. den Nijs
Institute for Horticultural Plant Breeding, Wageningen, The Netherlands
The Institute for Horticultural Plant Breeding (IVT) has since 1974 attempted to adapt slicing cucumbers for winter/spring glasshouse cultivation to lower temperatures. Fuel costs take a major share of total production expenses so that every reduction is very desirable. Selection was performed in poor light conditions in winter and early spring at temperatures of 20°C day, 15°C night. Root temperature, however, was maintained at 20°C throughout. This T-regime is about 5°C lower than usual and amounts to a savings of over 30% in fuel expenditures.
Few out of hundreds of varieties from all over the world tested grew well in the selection environment. The best growing varieties were crossed in a half diallel and progenies examined. The best plants were then selfed and intercrossed. Selection pressure was shifted from vegetative growth to growth and production (after pollination). After two more cycles of selection, a set of about 30 lines was developed that grow and produce well at the lower temperature and poor light conditions. At the lowered temperature, the best selections yielded during the first six weeks of harvest as much as leading varieties during the same harvest period at normal temperatures. Horticultural characteristics of the selections were acceptable, vine type being rather luxurious and flowering in many exclusively female. Besides, they are, at the low temperature, parthenocarpic.
Comparison of several lines and control varieties at both low and normal temperatures revealed that differences in vegetative growth between lines are correlated well in both environments, but fruit production varied widely. Some lines yielded well at both temperatures; most performed rather poor at normal temperature,
Possibilities for selection of high yielding lines at an early stage of growth appear to be meager. Correlations between seedling growth and later vegetative vigor were reasonably high, but fruit yield was rather unpredictable. Still, elimination of weak seedlings is justified.
Most lines yield fruits of acceptable size and shape, but some react to higher temperatures with strong elongation of especially side shoot borne fruits. Possibilities for exploiting observed variation in this character between the lines are still being studied. Thirty lines and crosses with leading varieties have been released to the Dutch private cucumber breeding companies for the exclusive use during the next five years.