Project Number: 5306-21000-015-07
Project Type: Specific Cooperative Agreement

Start Date: Jun 25, 2004
End Date: Jun 24, 2009

Objective:
Characterize and determine the chilling requirements in walnut (Juglans regia) germplasm at the National Clonal Germplasm Repository, Davis.

Approach:
Plant materials will be collected around Nov.1 2004 from walnut collection at the National Clonal Germplasm Repository, Davis. Efforts will be made in the first year to determine the range of chilling requirements by including reportedly low chill types (Early Erhardt and Placentia) and high chill types (Franquette and Mayette) along with a diversity of germplasm selected based on origin and leafing date. A minimum of 18 shoots of one meter length with terminal bud intact will be collected from each accession. Shoots will be placed in a humid environment at 5C similar to that used for graft wood storage. At initiation, and at 200 hour intervals thereafter, two shoots from each accession will be removed and placed in water in a lighted (16 hr photoperiod) growth chamber. Percent and location of bud break will be recorded at weekly intervals. Data will be analyzed based on number of chill units required to achieve 50% bud break within 4 weeks as well as speed of bud break over time. Bud break will be defined as separation of the bracts and visible expansion of the leaves. Depending on results, a correction for late leafing accessions may be required. Documents SCA with UC Davis.