Chilling requirement of strawberry June-bearer 'Opera'

‘Opera’ is a high yielding cultivar offering large firm fruit during the summer months on substrate culture. In order to optimise the quality and yield of developing plants it is important to have an understanding of the cultivar’s inherent chill requirement. The purpose of this trial was to investigate the effect of five different chill amounts on ‘Opera’ and determine the optimum for greenhouse production. Tray plants were exposed to either 350, 590, 830, 1070 or 1300 units of chill. Following the cold treatment plants were planted into substrate for production in the spring (March-May). Data on vegetative growth, fruit set, fruit size and yield were collected. Petiole and inflorescence extension growth was inadequate after 350 and 590 units of chill. After low amounts of chill were given ‘Opera’ was also characterized by a re-blooming period which resulted in a second harvest. Total yield was highest among plants which received 1070 chill units. There was, however, a trend which gave rise to significantly more ribbed and wedged shaped fruit as chill exceeded 1070 units. ‘Opera’ plants exposed to excessive amounts of chill were overly vegetative, exhibited lower yields and gave a notable delay in production. A significantly lower fruit number and higher average fruit weight was observed in plants which had received 1310 chill units. We conclude that ‘Opera’ plants receiving between 830 and 1070 chill units will deliver the highest yields and a good fruit quality.