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Title: BUD HARDINESS AND DEACCLIMATION IN BLUEBERRY CULTIVARS WITH VARYING SPECIES ANCESTRY: FLOWERING TIME MAY NOT BE A GOOD INDICATOR OF DEACCLIMATION

Author
item Ehlenfeldt, Mark
item Rowland, Lisa
item RAJEEV, ARORA - IOWA STATE UNIVERSITY

Submitted to: International Society for Horticultural Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2001
Publication Date: 8/11/2002
Citation: Ehlenfeldt, M.K., Rowland, L.J., Rajeev, A. 2002. Bud hardiness and deacclimation in blueberry cultivars with varying species ancestry: flowering time may not be a good indicator of deacclimation. International Society for Horticultural Science Meeting.

Interpretive Summary:

Technical Abstract: Detached shoots of blueberry cultivars with varying percentages of species ancestry (V. corymbosum L., V. angustifolium Ait., V. ashei Reade, V. darrowi Camp) were assayed in mid-February to determine initial bud hardiness, and rates of deacclimation under constant temperature conditions. The LT50 of field-grown shoots of 'Weymouth', 'Bluecrop', 'Legacy', 'Ozarkblue', and 'Tifblue' were initially evaluated by controlled freezing in a glycol bath at temperatures from -1 degree C to -28 degrees C, followed by visual evaluation after a 24h incubation at 23 degrees C. Similar shoots were deacclimated at a constant temperature of 20 degrees C and batches were evaluated daily for 6 days. Cultivars with any amount of southern germplasm (V. ashei or V. darrowi) were less hardy (LT50 about 20-21 degrees C) than northern highbush cultivars (LT50 about -24 degrees C) which are composed primarily of V. corymbosum with small percentages of V. angustifolium. Cultivars with greater amounts of southern germplasm deacclimated more quickly and to a slightly less hardy level (LT50 about -12 to-14 degrees C) than did northern-adapted cultivars (LT50 about -15 degrees C). By 6 days, deacclimation appeared to plateau for all cultivars. 'Ozarkblue' is extremely late-flowering, and because of this would seem to be adaptable to northern climates, yet the data suggest bud swell and flowering time are poor measures of deacclimation. Deacclimation under fluctuating field conditions is currently being evaluated.