The Florida citrus industry has seen a 90% decline in fruit production, following the first identification of huanglongbing (HLB) in 2005. Sweet orange (Citrus sinensis) cultivars make up a majority of the juice industry and are known to be susceptible to HLB; therefore, new tolerant or resistant cultivars or crop protection treatments need to be explored. Of the sweet orange cultivars released by UF Institute of Food and Agricultural Sciences, ‘OLL’ lines have shown some potential tolerance to this disease in cultivar field trials. High-throughput phenotyping revealed that nearly 14% of top performing trees across roughly 90 different research blocks in Florida, were accessions derived from the original ‘OLL’ tree. Of these trees, ‘OLL-8’ represents 11% of top performing trees across these different research blocks. This research explores the effects of different rootstocks in combination with the ‘OLL-8’ scion. Three UF rootstocks (‘UFR-2’, ‘UFR-4’ and ‘UFR-6) and three industry standard rootstocks (‘US-897’, ‘US-942’ and ‘Swingle’) were compared. For each rootstock, 12 mature trees, across three different blocks were compared across three different time intervals during the 2023 and 2024 ‘Valencia’ harvest seasons at a field trial in Lake Alfred, Florida. In 2024, the same 12 mature trees per rootstock were compared with trees that received oxytetracycline injections following the previous harvest season. Data was collected on juice quality variables including total soluble solids, titratable acidity in citric acid equivalents, sugar:acid ratio, pounds solids per box, percent juice, and color as well as on external fruit quality data parameters such as mass, diameter, length, and color. Data were analyzed to determine statistically significant differences among the different rootstocks evaluated. To determine differences in tree health, high-throughput phenotyping via drone flight occurred in December of 2023 and March of 2024 and included variables such as tree count, measurements of canopy area and volume, normalized difference vegetation index (NDVI), and normalized difference red edge index (NDRE). There was evidence for statistically significant differences for various traits among the rootstock combinations evaluated in this study.
