The Importance of Long-term Variety Trials - The Millennium Block
Posted August 2025
Researchers: Flavia Tabay Zambon
Contact: Flavia Tabay Zambon, UF/IFAS IRREC f.zambon@ufl.edu
Summary:
Established in 2019-20 the robust Millennium Block presents a look at the requirement of patience and consistent funding for large variety trials. In the 20 acres, 5,500 trees are divided in four independent trials: trial 1 comprised of 18 scions and 3 rootstocks, a total of 54 combinations. Trials 2, 3, and 4 are rootstock trials where 31 rootstocks are grafted onto ‘Ray Ruby’ grapefruit, ‘Glen’ Navel and ‘UF-950’ mandarin. For the past three seasons, ‘UF 914’ has had consistently higher °Brix and requires canopy management to sustain the cluster of heavy fruits. A fortuitous finding is ‘Triumph’, one of the oldest Florida grapefruit, yielding over 200 boxes per acre (at 227 trees/acre) in 2023-24. In the 2024-25 season, however, Triumph only produced around 90 boxes, with the same fruit quality as the previous season. The excellent juice quality and golden flesh are key to returning this variety to the market. ‘Ray Ruby’ grafted onto ‘UFR-15’ has shown the highest yield among the 32 rootstocks tested, while a new rootstock, 2247 x 6070-02-2, and ‘UFR-11’ yielded the highest °Brix in 2023-24 and 2024-25, respectively. Glen Navels are not suitable for the Indian River Region environment, as fruit quality and yield were below industry standards. For the third year in a row, the mandarins never produced a harvestable crop. The trees bloom, set fruit, but none reach maturity. On an important note, no oxytetracycline (OTC) injections have been done at the Millennium Block.
Take Home Message:
- ‘UF-914’ produces good quality fruit despite huanglongbing (HLB).
- ‘Triumph’ grapefruit hybrid opens an opportunity to revisit historical material for HLB tolerance.
- Glen Navels are not suitable for the Indian River Region environment, as fruit quality and yield were below industry standards.
