Prevention of Floral Initiation in Highbush Blueberry with Gibberellins, Poster Board #203

Highbush blueberries (Vaccinium corymbosum L.) are an important horticultural crop, but are slow to establish in colder regions.  Preventing fruit production can hasten establishment by directing more energy towards vegetative growth.  Manual removal of floral meristems is effective, but labor intensive.  Gibberellins (GA), a class of plant hormones, have prevented floral initiation in highbush blueberries in previous studies.  Two field experiments were conducted to test the effectiveness of GA inhibitory properties.  The first experiment compared GA ₍₃₎ and GA ₍₄₊₇₎ at 400 mg/L, applied during three time periods from August through September, with cultivars “Aurora’, ‘Elliott’ and ‘Liberty’.  The second experiment tested GA ₍₄₊₇₎ at 200 mg/L or 400 mg/L, applied four times in 10 day intervals from July to August or September to October.  Other bushes were sprayed eight times from July through October.  Cultivars tested were ‘Aurora’, ‘Draper’, ‘Elliott’, and ‘Liberty’.  Floral meristems, flowers per inflorescence, and fruit were counted the year after treatments.  Floral meristem and fruit numbers were reduced by most GA treatments.  Multiple applications over a long time period reduced floral initiation by up to 78%.  The most effective treatment period was in late summer to early fall. Flowers per inflorescence were unaffected.  No differences in the form or rate of GA were observed.  Results suggest that floral initiation in young highbush blueberry plants occurs over a long time period and that multiple GA applications are needed to strongly inhibit floral initiation.   Further studies are needed to understand floral initiation patterns and determine why GA only provided partial inhibition of floral initiation.