Rapid Movement of ‘Candidatus Liberibacter asiaticus’ on ‘Hamlin’ Sweet Orange and ‘Swingle’ Citrumelo Trunks

Abstract

Huanglongbing (HLB), caused by phloem-limited ‘Candidatus Liberibacter asiaticus’ (CLas), is the primary limiting factor of production in most citrus regions of the world. After infection, CLas is transported systemically throughout the phloem tissues following the source-sink movement. Split-root rhizoboxes and one-sided graft inoculation above the split trunk was used to understand if the vertical distance of the inoculum source and different anatomical structures (grafted or seedling trees) can affect the speed of the CLas movement, as well as the effects of the seasonality on these movements. The time for CLas to reach the roots was not affected by either distance of the inoculum source or tree type. The seasonal infection period appears to have an important effect on CLas movement. Trees inoculated in the summer had fast and uniform movement (first detection at 4 weeks after inoculation). Plants inoculated in the winter had a slow and uneven movement (first CLas detection at 14 weeks after inoculation). Our results indicate that summer and spring are the seasons of CLas down and lateral movement, but this is independent of the vertical distance of the inoculum source or anatomical structures of the plants. The findings from this study aid in the management of HLB in the field, as well as improve the methods for CLas detection. [Figure: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Keywords

• citrus roots
• HLB
• huanglongbing
• Liberibacter movement