S01 - Session P6 - Regulation of the axillary bud fate of woodland strawberry

Authors: Javier Andrés *, Julie Caruana, Zhongchi Liu, Timo Hytönen, Elli Koskela

The fate of the aerial meristems define the yield potential and adaptability of strawberry plants. The shoot apical meristem (SAM) maintains vegetative growth of the main crown until the SAM differentiates into a terminal inflorescense meristem. Axillary buds (AXBs), located in leaf axils, can remain dormant, or form either stolons or branch crowns. Stolons facilitate clonal propagation, which is a prerequisite for strawberry farming, while branch crowns directly affect yield potential by providing new SAMs that can produce inflorescences. Despite its implications to the strawberry industry, AXB fate regulation remains obscure. To understand the regulation of AXB fate, we performed controlled climate and growth regulator experiments on several woodland strawberry ( F. vesca L.) accessions, cultivars and transgenic lines. We discovered that AXB fate regulation depends on the position of the AXB within the plant and is directly regulated by environmental factors in addition to endogenous factors that depend on the SAM fate. Our results confirmed that the F. vesca GA20-oxidase4 ( FvGA20ox4 ) gene is required for stolon formation, and that its expression in AXBs is tightly regulated by photoperiod and temperature. In addition, we revealed that apical dominance inhibits branch crown formation from the youngest AXBs, but FvGA20ox4 can overrun apical dominance by inducing stolon formation.