Genomic Evaluation of Early-Season Sweet Oranges to Understand the Mechanism of HLB Tolerance
This study focused on early-season sweet orange trees that survived for several years under endemic HLB conditions in a Florida grove, initially planted as Hamlin-type citrus. Although CaLas infection levels were similar to those of declining trees, these surviving trees maintained canopy vigor, fruit retention, and juice quality suitable for commercial use. Physiological analysis revealed significantly higher levels of chlorophyll and carotenoids. Some trees labeled as Hamlin exhibited traits, such as seed counts, that were similar to those of the Parson Brown sweet orange. Whole-genome sequencing and SNP analysis uncovered substantial hidden genetic diversity, grouping the trees into two distinct sections - Hamlin type and Parson Brown type.