Involvement of Endogenous Gibberellins in the Chilling Requirements of Strawberry (Fragaria×ananassa Duch.)

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Abstract
Plants of Fragaria ananassa Duch. cvs Tioga and Fresno were chilled in a cold store at—1°C for 2–8 months, after which they were transferred to short-day (SD) and long-day (LD)) growth chambers. Chilling promoted subsequent vegetative development, as expressed through leaf area, petiole length and stolon production, but inhibited the formation of inflorescences. Leaf area and petiole length responses appeared to be almost saturated by 2 months' chilling. The increase in stolon production and the reduction in inflorescence formation came into full expression with longer periods of chilling. Application of gibberellin A3 (GA3 to plants pre-chilied for 2 months had little effect on leaf area or petiole length but promoted stolon production and retarded the formation of inflorescences. AMO-1618 applied to plants pre-chilled for 4 months antagonized the chilling responses. The level of diffusible gibberellin-like substances from crown apices remained low during most of the chilling period but increased markedly after 6–8 months of chilling, when plants approached spontaneous sprouting in the cold store. Plants pre-chilled for 2 months had low levels of gibberellin-like substances which increased several fold upon transfer to the growth chambers. This increase was somewhat delayed in plants treated with AMO-1618. The role of gibberellins in the responses of strawberry plants to chilling is discussed.