Long-day rather than autonomous control of flowering in the diploid everbearing strawberry Fragaria vesca ssp semperflorens

The environmental control of flowering in the perpetual-flowering (everbearing) diploid strawberry Fragaria vesca ssp. semperflorens cultivars 'Rugen' and 'Baron Solemacher' has been studied in controlled environments. Seed-propagated plants were exposed to 10-h short-day (SD) and 24-h long-day (LD) conditions at temperatures ranging from 9 degrees - 27 degrees C. The results revealed a quantitative LD response of flowering that increased in strength with increasing temperature, to become almost obligatory at 27 degrees C. Occasional runner formation was observed in SD at high temperature, conditions which were inhibitory to flowering, demonstrating that runnering ability is not completely lost in these genotypes. A comparison with the perpetual-flowering octoploid F X ananassa 'Elan', in one experiment, demonstrated an identical LD X temperature interaction in the two species. The results are discussed in relation to available information on the genetics of flowering habits in the two species. Since seasonal flowering types of F vesca and E X ananassa have also been shown to share a principally identical flowering response, controlled by SD and low temperature, it is concluded that a remarkably similar flowering control system is present in the diploid F vesca and the octoploid F. X ananassa. Despite the large genetic differences between the two species, and regardless of the origin of the cultivars, the seasonal flowering types are all SD plants, while their perpetual-flowering counterparts all appear to be LD plants. In both cases, there is a pronounced interaction with temperature; the photoperiodic responses increasing with increasing temperature, in both cases. This raises the question whether a common genetic flowering control system is present in both species.