Citrus dwarfing viroid reduces canopy volume by affecting shoot apical growth of navel orange trees grown on trifoliate orange rootstock

I Lavagi-Craddock,G Vidalakis,T Kapaun,R Campos,C Lovatt,D Pagliaccia

doi:10.5070/c471045369

Abstract

Author(s): Lavagi-Craddock, I; Campos, R; Pagliaccia, D; Kapaun, T; Lovatt, C; Vidalakis, G | Abstract: Citrus dwarfing viroid (CDVd) infection of navel orange trees (Citrus sinensis (L.) Osb.) on ‘Rich 16-6’ trifoliate orange (Poncirus trifoliata (L.) Raf.) rootstock has been previously reported to reduce canopy volume by approximately 50%. We demonstrated that the reduction in tree size of CDVd-infected citrus resulted from a g20% reduction in the apical growth of individual shoots within the tree canopy. We also demonstrated that the reduced canopy volume of the CDVd-infected trees is a long lasting phenotype comparable to that of ‘Flying Dragon’ rootstock, which is known to reduce citrus tree size.

Highlights

At present, seven citrus viroids have been identified, and an eighth species awaits official recognition by the International Committee on Taxonomy of Viruses (Chambers et al 2018; Di Serio et al 2014)
The canopy volume of CDVdinfected trees was compared with the canopy volume of two types of controls planted on the same experimental block: (i) non-infected navel orange trees on ‘Rich 16-6’ trifoliate rootstock planted in 1998 and (ii) navel orange trees grown on trifoliate rootstock ‘Flying Dragon’, which is known to reduce tree size, planted in 1984 (Bitters et al 1979; Davies and Albrigo 1994; Roose 1986)
No previous study has looked in detail at the tree canopy growth patterns that collectively result in the dwarfing phenotype observed with Citrus dwarfing viroid (CDVd) infection

Summary

Introduction

Seven citrus viroids have been identified, and an eighth species awaits official recognition by the International Committee on Taxonomy of Viruses (Chambers et al 2018; Di Serio et al 2014). Citrus viroids are capable of inducing a range of symptoms in specific citrus hosts. CDVd typically induces mild symptoms such as tree stunting with reduced canopy volume as reported for Valencia and navel orange (C. sinensis (L.) Osb.) and clementine The CDVd infection of navel orange trees grafted on ‘Rich 16-6’ rootstock, planted in 1998, was reported to reduce tree canopy volume by approximately 50% after 13 years in the field (Vidalakis et al 2011). To evaluate the long-term CDVd effect on canopy volume, we measured the same 1998-planted CDVd infected navel orange trees after 20 years in the field. We discovered that CDVd reduced the tree canopy volume by more than 60% in comparison to the non-infected controls and by approximately 6% in comparison to the ‘Flying Dragon’ controls

Methods

Results

Conclusion