The Citrus Budwood Program through the Florida Department of Agriculture is currently increasing stock of early-season orange varieties for expedited advancement into nursery production: Donaldson, Parson Brown, Carney’s 2 and 3, and Roble. Each of these varieties has shown some measure of HLB tolerance or HLB resistance and are being rushed towards production to help bolster the industry.
The Donaldson Sweet Orange is a lost gem from the early years of the Florida Citrus industry that was recently rediscovered on the Whitmore Foundation Farm. Although the tree is visibly infected with HLB, the fruit load is normal and the fruit drop is more consistent with healthy, uninfected trees. As for the fruit itself, the quality is very good, seeming to be a true sweet orange. As of this writing, the Donaldson tree is not yet available commercially. Nurseries are still building their stock before making the tree available because of its recent rediscovery.
Parson Brown/Carney #2 and #3
Carney’s #2 and #3 are improved selections of Parson Brown. The Parson Brown orange was first identified in 1875 but fell out of favor due to being seedier and having a lower yield than other popular varieties at the time. However, a small number of trees persisted, which still produced normal-sized fruit with minimal fruit drop, despite being infected with HLB. Genetic research is being conducted into the Parson Brown stock to help determine why it is tending to be more HLB resistant. The working theory is that the upregulation of the PR1 gene is elevated in Parson Brown trees, which adds to systemic acquired resistance, or SAR.
Parson Brown trees are distinct in a grove, as they tend to grow tall and upright, as opposed to most other citrus varieties which tend to have a shorter and rounder canopy.
Brought from Spain sometime after 1851 and first planted near Tampa, the Roble sweet orange shares much in common with the Parson Brown, both in terms of fruit quality and the early growth. The Roble is not recommended to be grafted onto Swingle or other trifoliate hybrid type rootstocks, due to previously observed declines. Today, Roble has demonstrated less fruit drop for an early orange compared to other early orange varieties.
Currently, there is a shortage of early season oranges and an excess of late season Valencia. The expedited early orange program will help the industry balance production. The industry commends Senator Ben Albritton, DPI, Florida Department of Citrus, and Florida Citrus Mutual for developing and implementing this concept.