Rediscovered Orange Variety Offers Hope Against Citrus Greening Disease.

In a promising development for Florida’s citrus growers, scientists with the Agricultural Research Service (ARS) have rediscovered a sweet orange variety that may possess tolerance to citrus greening disease, also known as Huanglongbing (HLB). The disease, caused by the bacterium Candidatus Liberibacter asiaticus, has devastated the Florida citrus industry since its detection in 2005, reducing production by nearly 90%.

During a recent evaluation at the U.S. Horticultural Research Laboratory in Fort Pierce, Florida, researchers examined citrus trees with potential for commercial juice production. Their assessment led them to a notable discovery: a healthy sweet orange tree known as "Donaldson," located at the A.H. Whitmore Citrus Research Foundation Farm in Groveland, Florida. This variety is part of a USDA-ARS citrus collection that spans over a century of agricultural research.

According to research geneticist Matt Mattia, the Donaldson tree appeared remarkably healthy despite being surrounded by neighboring trees that were in severe decline or had died due to HLB. Interestingly, the tree tested positive for the presence of Candidatus Liberibacter asiaticus, suggesting that it may be tolerant to the disease rather than immune.

Historical records indicate that the Donaldson tree was planted more than 30 years ago—around the same time as the widely used Hamlin variety, which has suffered heavily from HLB. Both are early-season trees, typically producing fruit from December to January. Unlike Hamlin, which has long been used in commercial juice production, Donaldson remained confined to the research farm.

To determine the suitability of Donaldson for juice production, researchers conducted taste tests comparing juice blends made from both Donaldson and Hamlin oranges. While differences in flavor were noted, they were attributed to lower acidity levels in younger Hamlin trees. Overall, Donaldson juice was found to have good flavor and commercial potential.

Further research is ongoing to evaluate whether Donaldson’s apparent tolerance to HLB is long-lasting and whether it can be successfully cultivated on a broader scale. ARS scientists plan to partner with industry stakeholders to conduct field trials and investigate the genetic traits that may be responsible for the tree’s resilience.

Source:https://phys.org/news/2025-05-scientists-rediscover-orange-tree-variety.html

This is non-financial/medical advice and made using AI so could be wrong.