St. Cloud OLL Clone/Rootstock Demonstration Planting

Dr. Jude Grosser – Orie Lee – Dr. Bill Castle – Dr. Fred Gmitter
November 22, 2021 - Revised
July 22, 2020 - Posted
CREC Citrus Plant Improvement

St. Cloud OLL Clone/Rootstock Demonstration Planting - Description

At the suggestion of long-time cooperator, Orie Lee, a demonstration was planted to compare the performance of 8 OLL [Orie Lee Late] sweet orange clones on 18 rootstocks. Pathogen-free budwood was not available for most of the OLL clones at the time of tree propagation, thus, a permit was obtained from FL Department of Agriculture, Division of Plant Industry [DPI] to propagate the trees using budwood from the original OLL somaclone trees, located on the Lee property. The DPI permit limited this project to 2 acres, so it was designed with one, 2-tree, plot per scion/rootstock combination. Trees were planted in June 2013 with rootstocks in rows running in one direction with OLL clones in perpendicular rows. Propagation took place on the Lee property with the assistance of Briteleaf Nursery. Trees received standard imidacloprid treatments the first two years, but no psyllid control thereafter. Diaprepes weevils were observed in the trial block. By year 3, all trees in the trial showed HLB symptoms. Trees have received the Lee Groves standard 4 soluble dry fertilizer treatments per year, and since year 4 have received supplemental treatments of CRF (controlled release fertilizer) with an enhanced micronutrient package two times per year.

This small trial is remarkable for multiple reasons. The soluble solids being produced in the fruit across most of the scion/rootstock combinations are exceptionally high, and would be considered high for young trees even for trees before the HLB endemic. Yields of some combinations are also quite good, even though psyllid control has not been employed, and the grove is under high psyllid/HLB pressure. Finally, it is quite interesting that so many of the trees are testing negative by PCR for an active CLas infection, suggesting a positive effect from the combination of good genetics and constant enhanced micronutrient availability.

St. Cloud OLL Clone/Rootstock Demonstration Planting - Summary

• Location: St. Cloud Florida, Block 13-W
• Scions: 8 OLL (Orie Lee Late) somaclones
• Rootstocks: Swingle, Carrizo, x639 and 15 tetraploid rootstocks from the UF breeding program
• Date planted: June 2013
• Design: 
  
  
  • One, 2-tree, plot per scion/rootstock combination; rootstocks planted in east/west rows; OLL clones in perpendicular north/south rows
  • Spacing: 12.5 x 25 ft. or 140 trees/acre
• Data:
  • 2018/19: Yield, juice quality, cumulative Yield, PS/tree, HLB PCR Ct values
  • 2019/20: Yield, juice quality, cumulative Yield, PS/tree, HLB PCR Ct values
  • 2020/21: Juice Quality
    
    
    
• Trial status: ACTIVE

Acknowledgement and Publication

The authors acknowledge Mike Irey and the Southern Gardens Diagnostic Laboratory for running the PCR tests

Huang, L, J.W. Grosser, F.G. Gmitter, C.A. Sims and Y. Wang. 2020. Effects of Scion/Rootstock Combination on Flavor Quality of Orange Juice from Huanglongbing (HLB)-Affected Trees: A Two-Year Study of the Targeted Metabolomics.  J. Agric. Food Chem. 2020, 68, 10, 3286