The Rediscovery of ‘Donaldson’ Sweet Orange, a Variety That Has Potential for Use in Orange Juice

In Summer 2021, a comprehensive evaluation of germplasm for the US Department of Agriculture (USDA), Agricultural Research Service (ARS) citrus breeding program was conducted to assess all citrus scions that may have commercial potential for use in not-from-concentrate orange juice (NFCOJ) to support Florida’s citrus industry that has been ravaged by Huanglongbing (HLB), causing production losses of 90%. The ‘Donaldson’ sweet orange tree ( Citrus sinensis ) stood out as being exceptionally healthy compared with industry standards that were planted close by and were in decline or had died. The tree tested positive for the presence of Candidatus Liberibacter asiaticus ( C Las), the presumed causal agent of HLB, indicating that the tree may have tolerance to HLB, as that tree was planted more than 30 years ago. The fruit was displayed at a field day in Dec 2021; the healthy-looking tree attracted growers’ attention and generated a records search for information. This is the only mature tree growing at the USDA, ARS Whitmore Foundation Farm. The results show that ‘Donaldson’ is an early season sweet orange variety that matures from December to January in HLB endemic conditions and has juice as a potential substitute for the early season orange variety ‘Hamlin’, contributing to NFCOJ. HLB tolerance is difficult to assess from a single tree and the HLB tolerance of ‘Donaldson’ will be confirmed in multiple replicated plantings.