Citrus dwarfing viroid: effects on tree size and scion performance specific to Poncirus trifoliata rootstock for high-density planting

Abstract

The term 'transmissible small nuclear ribonucleic acids' (TsnRNAs) describes well-characterised viroid RNA species that do not induce any pronounced disease syndromes in specific citrus hosts, but rather act as regulatory genetic elements modifying tree performance. The canopy volume (CV) of 13-yearold navel orange trees (Citrus sinensis) on Poncirus trifoliata rootstock treated with TsnRNA-IIIb (syn. Citrus dwarfing viroid) was reduced by 45% and 53.5% in standard-density (6 m × 6.7 m) or high-density (3 m × 6.7 m) plantings, respectively. The total yield of eight consecutive harvests was not affected significantly by the TsnRNA-IIIb treatments or the two planting densities. However, the yield per land surface unit (Y/LSU) was almost doubled (increased by 97.5%) for the high-density plantings over the standard-density plantings of the untreated controls. The Y/LSU of the TsnRNA-IIIb treated navel orange trees in the standard-density planting was reduced by 32.7%. The TsnRNA-IIIb treatment in both planting densities concentrated significantly more fruit production (approximately 60%) in the economically advantageous middle canopy height zone (0.6-2.4 m) in comparison with the untreated controls (35%). Fruit grade, size, appearance, organoleptic characteristics or time of maturation of the TsnRNA-IIIb dwarfed navel trees were not significantly different between the two planting densities and the controls. Fruit with higher commercial value was produced in the TsnRNA-IIIb dwarfed navel trees in the high-density planting by 3.9% and 4.6% over the TsnRNA-IIIb or controls in standard-density planting respectively. The increase in Y/LSU and fruit value for the TsnRNA-IIIb treated navel trees in the high-density plantings in combination with the reduced management cost of dwarfed trees could result in substantial higher profits for a commercial grove despite the higher establishment cost of high-density plantings.

Harnessed viruses in the age of metagenomics and synthetic biology: an update on infectious clone assembly and biotechnologies of plant viruses

“…Described almost 100 years ago, cross-protection has been applied to promote the health of crops, including cucurbits, papaya and citrus (Ziebell and Carr, 2010). Commercial use of viroids is approved in United States to induce desired dwarfing in citrus trees and increase yields per land surface unit (Vidalakis et al, 2011). Plant viruses have been used as herbicides to control invasive weeds by inducing lethal hypersensitive reactions (Harding and Raizada, 2015).…”

Viroid research and its significance for RNA technology and basic biochemistry

“…Careful monitoring may help to avoid such transmissions in the future. Locally restricted viroid infections, such as dwarfing of citrus trees for easier harvesting and less water consumption ( 187 , 188 ), will require exploration.…”

Grapefruit Production in Open Hydroponics System

“…Conversely, studies conducted prior to the HLB era in Florida have shown that grapefruit trees bear more fruit even when subjected to rigid tree size control at high-density planting [43]. Previous studies have also demonstrated that high-density plantings result in greater production per area [53,54] especially under HLB-endemic conditions [9,16]. New groves planted at higher densities in Florida can be more profitable than groves planted at low densities [7,14].…”