Four new SuperSour rootstocks for improved production of sweet orange in a Huanglongbing environment

Authors: Bowman, Kim

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2023
Publication Date: 11/28/2023
Citation: Bowman, K.D. 2023. Four new SuperSour rootstocks for improved production of sweet orange in a Huanglongbing environment. HortScience. 58(12), 1622-1625. https://doi.org/10.21273/HORTSCI17466-23.
DOI: https://doi.org/10.21273/HORTSCI17466-23

Interpretive Summary: Citrus production is severely reduced by infection of trees with Candidatus Liberibacter asiaticus, the causal agent of huanglongbing disease (HLB). The disease was first found in Florida in 2005 and has resulted in a sharp decline in Florida citrus production over the last 15 years. All commercial sweet orange cultivars are severely damaged by this disease, but some tolerant rootstocks may significantly improve health and productivity of infected trees. US SuperSour 2, US SuperSour 3, US SuperSour 4, and US SuperSour 5 are new citrus rootstock cultivars released by the U.S. Department of Agriculture as a result of breeding and selection of new hybrid rootstocks for superior performance in the HLB-endemic environment. Compared with other common citrus rootstock cultivars in Florida, sweet orange grafted on these four new rootstock cultivars produce trees that have superior tree health and superior production of good quality fruit. All four of the new hybrid rootstocks produce medium-sized trees when grafted with common commercial sweet orange and appear well-adapted to production in Florida.

Technical Abstract: Production of sweet orange, grapefruit, and mandarin is severely reduced by infection of trees with Candidatus Liberibacter asiaticus (CLas), the causal agent of huanglongbing disease (HLB). The disease is now endemic throughout Florida, which has resulted in a sharp decline in Florida citrus production over the last 15 years. All commercial sweet orange cultivars are severely damaged by this disease, with greatly reduced tree health, fruit productivity, and fruit quality. However, some rootstock cultivars exhibit significant tolerance, and greatly improve health and productivity of infected trees. US SuperSour 2, US SuperSour 3, US SuperSour 4, and US SuperSour 5 are new citrus rootstock cultivars released by the U.S. Department of Agriculture as a result of breeding and selection of new hybrid rootstocks for superior performance in the HLB-endemic environment. Compared with other common citrus rootstock cultivars in Florida, sweet orange grafted on these four new rootstock cultivars produce trees that have superior tree canopy health and superior production of good quality fruit. All four of the new hybrid rootstocks produce medium-sized trees when grafted with common commercial scions, and appear well-adapted to production in the commercial production region of Florida. The new rootstock cultivars are most effectively propagated by stem cuttings or micropropagation, and state certified plant material of the released rootstocks is available to Florida commercial nurseries. Information is provided to allow the four new hybrid rootstocks to be differentiated from other rootstocks in commercial use by visual or molecular methods.