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Title: A TWO-STEP PRETREATMENT SIGNIFICANTLY ENHANCES SHOOT ORGANOGENESIS FROM LEAF EXPLANTS OF HIGHBUSH BLUEBERRY CV. BLUECROP

Author
item CAO, XIAOLING - USDA VISITING SCIENTIST
item Hammerschlag, Freddi
item DOUGLASS, LARRY - UNIVERSITY OF MARYLAND

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2002
Publication Date: 8/20/2002
Citation: Cao, X., Hammerschlag, F.A., Douglass, L. 2002. A two-step pretreatment significantly enhances shoot organogenesis from leaf explants of highbush blueberry cv. bluecrop. Hortscience. 37:819-821

Interpretive Summary: Highbush blueberry is a good candidate for using molecular techniques to improve this species because traditional breeding methods requires a very long-term effort. Increasing leaf regeneration efficiency is critical for the development of a transformation system using either Agrobacterium tumefaciens as a vector and/or the particle bombardment process. Only a few reports exist of shoot regeneration from leaf explants of highbush blueberry, and to date, researchers have been unsuccessful in developing high frequency regeneration for the commercially important cultivar, Bluecrop. The aim of the present study was to investigate the effects of growth regulator pretreatments, growth regulators in the shoot regeneration medium, and age of the explant source on shoot organogenesis from leaf explants of Bluecrop. A protocol was developed for high efficiency regeneration of cultivar Bluecrop that included several growth regulator pretreatments. This protocol makes it possible to use Bluecrop in gene transfer studies and will be of value to scientists interested in using biotechnology techniques to improve Bluecrop and other blueberry cultivars.

Technical Abstract: As part of a program to improve highbush blueberry (Vaccinium corymbosum L.) cultivars via tissue culture and genetic engineering techniques, studies were conducted to determine optimum conditions for high efficiency shoot regeneration from leaf explants of in vitro-propagated, commercially important, tissue culture recalcitrant `Bluecrop' shoot cultures. The effects of pretreatments, growth regulators and age of explant source on shoot organogenesis were investigated. A maximum of 98 percent shoot regeneration and 11 shoots regenerating per leaf explant occurred when explants of 2-week-old shoot cultures were incubated on pretreatment medium I containing 5 uM thidiazuron (TDZ) and 2.6 uM alpha-naphthalene acetic acid (NAA) for 4 days, next on pretreatment medium II containing 7 uM zeatin riboside and 2.6 uM NAA for 3 days, then on regeneration medium containing 1 uM TDZ for 6 weeks, and last on medium without growth regulators for 10 days. No shoot regeneration occurred if explants were incubated without exposure to pretreatments prior to incubation on regeneration medium. There were no significant differences in percentage of regeneration or the number of shoots regenerating per explant from leaf explants derived from either 1-,2-, or 3-week-old shoot cultures. Shoot production per explant on 1 uM TDZ was about three times that on either 0.5 uM TDZ or 20 uM zeatin riboside, and nine times that on 5 uM TDZ.