Understanding the Mechanism Behind Lower Fruit Drop and Enhanced Huanglongbing Tolerance in the ‘Parson Brown’
Posted August 2025
Researchers: Manjul Dutt, Nabil Killiny, Tripti Vashisth, Lamiaa Mahmoud
Contact: Manjul Dutt, UF/IFAS CREC manjul@ufl.edu
Summary:
The early-season ‘Parson Brown’ sweet orange demonstrates enhanced tolerance to huanglongbing (HLB). This tolerance enables ‘Parson Brown’ trees to produce healthier fruit even when infected with HLB. Furthermore, ‘Parson Brown’ oranges are known for their lower rates of fruit drop, a common issue with HLB-affected sweet oranges. Several factors, including reduced callose deposition and starch accumulation in ‘Parson Brown’, may play a role in this observed tolerance. Additionally, preliminary results from fruit detachment force analysis indicate that fruits from ‘Parson Brown’ trees have significantly higher fruit detachment force than ‘Hamlin’, resulting in better fruit retention and less fruit drop. This combination of HLB tolerance and reduced fruit loss makes the ‘Parson Brown’ a promising cultivar for growers facing the challenges of HLB.
Take Home Message:
- ‘Parson Brown’ sweet oranges are more tolerant to HLB than ‘Hamlin’.
- ‘Parson Brown’ sweet oranges can retain fruit on the tree significantly better than ‘Hamlin’ under endemic HLB.
