Some causes of poor fruit set in Jucunda strawberries

Summary A study was made of the possible causes of poor fruit set occurring in the strawberry variety Jucunda. In experiments in which plants were exposed to different constant temperatures from the beginning of flowering it was found that fruit set in Jucunda was normal at temperatures of 17°C and higher, but decreased rapidly at lower temperatures to a very low level at 10°C. In other experiments, in which in each case the temperature treatments were started a different number of days before the begining of flowering, fruit set was always lower than in the experiments mentioned above, but here too the unfavourable effect of lower temperatures was quite distinct. The experimental results indicate that poor fruit set is Jucunda results from inadequate pollen production and that it will occur if temperatures during the period of flowering are below 17°C, and possibly also if temperatures at some time before flowering are higher than the normal temperatures prevailing in the field during that period.Fruit set in the variety Juspa which originated from a cross between Jucunda and the American variety Sparkle, showed sensitivity to temperatures before and during flowering which was identical, if less pronounced, with that of Jucunda. Thus it was confirmed that poor fruit set in Jucunda can be passed on to its progeny. The results of these experiments indicate under which conditions selection against poor fruit set can be effectively carried out in progenies derived from Jucunda.