The U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) is evaluating the Donaldson sweet orange as a possible replacement for the HLB-affected Hamlin orange in commercial juice production. Research is being conducted at the U.S. Horticultural Research Laboratory located in Fort Pierce, Florida, where researchers discovered the Donaldson variety at the A.H. Whitmore Citrus Research Foundation Farm in Groveland, Florida.
The Donaldson tree, part of the USDA-ARS citrus variety collection, has displayed exceptional health compared to nearby declining industry-standard trees. Matt Mattia, a USDA-ARS research geneticist, noted, "The Donaldson sweet orange tree stood out as being exceptionally healthy compared to the industry-standard trees that were planted close by and were in decline or had died." Despite testing positive for Candidatus Liberibacter asiaticus, scientists suggest that the Donaldson may have disease tolerance.
This variety has existed for over 30 years alongside Hamlin at the farm. Though Hamlin has historically been used for orange juice production, Donaldson has remained largely unused for commercial purposes. Taste tests demonstrated differences in OJ blends made with Donaldson and Hamlin, attributed to varying acidity levels from young Hamlin trees, as observed by researchers.
Further investigation aims to explore whether Donaldson trees maintain long-term HLB tolerance and can satisfy commercial production needs. Collaboration with industry and academic partners will focus on understanding the genetic mechanisms underpinning disease tolerance and evaluating performance in field trials. Detailed findings are available in the HortScience journal, published in collaboration with the University of Florida Institute of Food and Agricultural Sciences.
Source: Citrus Industry