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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETIC IMPROVEMENT OF CITRUS

Location: Subtropical Insects and Horticulture Research

Title: Update on USDA advanced citrus scion selections for Indian River Citrus League

Authors
item Stover, Ed
item McCollum, Thomas
item Driggers, Randall
item Salvatore, James

Submitted to: River Ramblings: the newsletter of the Indian River Citrus League
Publication Type: Popular Publication
Publication Acceptance Date: May 1, 2013
Publication Date: May 5, 2013
Citation: Stover, E., McCollum, G., Driggers, R., Salvatore, J. 2013. Update on USDA advanced citrus scion selections for Indian River Citrus League. River Ramblings: The Indian River Citrus League Newsletter, May 2013, p.5.

Technical Abstract: In an effort to help maintain the Florida citrus industry, the USDA US Horticultural Research Laboratory (USHRL) citrus breeding team is working to make advanced selections available for limited testing earlier and more broadly than in the past to quickly identify material with commercial potential. Efforts are underway at USHRL to systematically test Huanglongbing (HLB) resistance/tolerance of all our new selections, but for now comments on resistance are based mainly on field observations. The amount of testing that has been done for these new selections varies greatly. In an effort to expedite evaluation of these new selections we will soon be engaging more broadly with growers. ‘US Early Pride’ was released as a cultivar in 2011 and is available for commercial planting. In addition to being a very early-maturing tangerine, ‘US Early Pride’ has shown considerable resistance to HLB in the field and in greenhouse studies, always being in the most-resistant category among cultivars tested. However, these studies have been ongoing only for a few years; long-term growth and productivity when exposed to HLB is uncertain. A number of citrus scion types have been in the “advanced selection” stage for the last 20 years and quite a bit of information is available for them. Unfortunately, like most citrus scions, a majority of these advanced selections appear to be quite susceptible to HLB and probably won’t merit interest of Indian River growers until other solutions are found for HLB control. However, there are a few tangerine types growing at our Ft. Pierce farm that seem to be quite HLB-tolerant. So far, they have normal growth, fruit set, and fruit quality despite blotchy-mottle symptoms and severe HLB pressure. Unfortunately our most advanced grapefruit-types have displayed HLB-susceptibility similar to true grapefruit. We do have a few newly selected grapefruit-like pummelo hybrids that seem to have better tolerance to HLB so far, but information is very limited. All sweet oranges are virtually genetically identical, being mutations of some original hybrid that arose many hundreds of years ago. As a result of this narrow genetic base, it is unlikely that an HLB-resistant sweet orange will be found. We now have five hybrids that look and taste like sweet oranges and some may offer improved tolerance to HLB compared to sweet orange. These new selections include an easy peeling “sweet orange” that has been very well received in taste tests. All are being tested for HLB response in greenhouse evaluations and have been put into field trials at our Ft. Pierce farm. It seems likely that some new hybrids may provide improved performance over standard varieties when HLB-infected, but this will require broad testing to quickly provide information to assist grower decisions. Beginning in spring 2014 and continuing into the future, there will be a modest number of trees available for grower trials. We look forward to your help in evaluating this material.

Last Modified: 9/10/2014
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