The rediscovery of ‘Donaldson’ Sweet Orange, a variety that has potential for use in orange juice

Authors: Mattia, Matthew; Plotto, Anne; BUZZI, GIANCARLO - University Of Florida; SHAHID, MUHAMMAD - University Of Florida; FAN, ZHEN - University Of Florida; Jeffries, Kristen; OLMEDO, GABRIELA - Orise Fellow; FREITAS, THAIS - US Department Of Agriculture (USDA); Bai, Jinhe

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2024
Publication Date: 2/18/2025
Citation: Mattia, M.R., Plotto, A., Buzzi, G., Shahid, M., Fan, Z., Jeffries, K.A., Olmedo, G., Freitas, T., Bai, J. The rediscovery of ‘Donaldson’ Sweet Orange, a variety that has potential for use in orange juice. HortScience. 60(3): 362–368. 2025. https://doi.org/10.21273/HORTSCI18351-24.
DOI: https://doi.org/10.21273/HORTSCI18351-24

Interpretive Summary: In summer of 2021, an evaluation of citrus trees for the USDA, ARS citrus breeding program was done to assess all fruiting citrus accessions 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 stood out as being exceptionally healthy compared to industry standards that were planted close by and were in decline or had died. The tree tested positive for the presence of the disease, indicating that the tree may have tolerance to HLB, as that tree was planted over 30 years ago. The fruit was displayed at a field day in December of 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 findings show that ‘Donaldson’ is an early season sweet orange variety that matures from December to January in HLB endemic conditions and has juice that could potentially be a substitute for the early season orange variety ‘Hamlin’, contributing to orange juice. HLB tolerance is difficult to assess from a single tree and the HLB tolerance of ‘Donaldson’ will be confirmed in replicated plantings.

Technical Abstract: In summer of 2021, a comprehensive evaluation of germplasm for the USDA, ARS citrus breeding program was done 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 to 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 (CLas), the presumed causal agent of HLB, indicating that the tree may have tolerance to HLB, as that tree was planted over 30 years ago. The fruit was displayed at a field day in December of 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 findings show that ‘Donaldson’ is an early season sweet orange variety that matures from December to January in HLB endemic conditions and has juice that could potentially be a 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.