Submitted to: Small Fruit Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2002
Publication Date: 7/1/2004
Citation: Spiers, J.M., Marshall, D.A., Braswell, J.H. 2004. Chilling requirement studies in blueberries. Small Fruit Reviews Vol. 3 no.314 p. 325-330.
Interpretive Summary: This study evaluated a method to more quickly determine chilling requirements of blueberries using a minimum number of plants. Floral buds on excised stems and plants were forced to bloom under greenhouse conditions. With sufficient chilling, floral bud development in excised stems without leaves closely mimics that of intact plants for a period of 3.5 weeks and reached at least stage 3, an easily identifiable floral stage. These results plus further studies should benefit research scientists by providing a quicker means to evaluate the chilling requirements of blueberries.
Technical Abstract: Two separate studies were initiated in January 1998 on 'Tifblue' rabbiteye (Vaccinium ashei Reade) and 'Magnolia' southern highbush (V. corymbosum L.) blueberry plants that had received > 500 chilling hours (<7°C). In each study, the terminal 2 flower buds from both excised stems and paired stems on plants were forced in a greenhouse (17° - 23°C and natural daylength) and rated for floral bud development. In 'Magnolia,' leaf removal from excised stems and intact stems resulted in an increased rate of floral bud development. After 7 days of forcing, excised stems with leaves removed showed no significant differences in floral bud development from intact plants with unabscised leaves. After 40 days of forcing, flower buds from all treatments had reached stage 3, an easily recognizable stage of development. With 'Tifblue,' stems with a 5 mm basal section removed weekly to retard vascular blockage did not differ in floral bud development from stems without basal pruning. Excised stems did not differ from matching intact stems for the first 3.5 weeks of forcing. At this time 'Tifblue' flower buds had reached 3.7 on the floral development scale. After =4.5 weeks of forcing in the greenhouse floral bud development ratings on excised stems were significantly lower than those on intact stems. These studies indicate that with sufficient chilling floral bud development in excised stems without leaves approximate that of intact plants for a period of 3.5 weeks and reach at least stage 3, an easily identifiable floral stage.