Project Number: 6618-21000-013-10
Project Type: Nonfunded Cooperative Agreement

Start Date: Sep 12, 2006
End Date: Sep 12, 2011

Objective:
The objective of this cooperative research project is to evaluate multiple citrus rootstock scion selections, developed by the U.S. Department of Agriculture (ARS), in replicated field trails in Arizona.

Approach:
Cultivar evaluation field trials of tree fruit crops (e.g. citrus) typically require 10-15 years. Selections are planted in replicated fields at a minimum of two locations for each region (i.e. Arizona) where commercial use of the cultivar might be proposed. Four to six years of fruit yield and quality data from trees at each location are required to accurately assess commercial potential. For rootstocks, replicated field trials generally cover 1-4 acres and include several common rootstocks for comparison with the new hybrids. Propagation of trees for field trials usually takes about 2 years. Meaningful assessments of rootstock performance must wait until tree health, tree size, fruit yield, and fruit quality data have been collected on trees at least through 8 years in the field. Promising selections, especially rootstock selections, may require additional testing to reconfirm field observations of particular importance (i.e. CTV resistance) or to assess traits not adequately evaluated by field testing. Greenhouse tests for tolerance of high pH, salinity, or nematodes would be highly desirable, if these factors were not present at the field test locations. For both scions and rootstocks viral indexing, followed by shoot-tip cleanup and re-indexing if necessary, is conducted prior to the release of budwood to the industry. If virus or viroid cleanup is necessary, an additional 2-4 years may be required.