Horticultural attributes and root architectures of field-grown ‘Valencia’ trees grafted on different rootstocks propagated by seed, cuttings, and tissue culture

Authors: POKHREL, SAMEER - UNIVERSITY OF FLORIDA; MEYERING, BO - UNIVERSITY OF FLORIDA; Bowman, Kim; ALBRECHT, UTE - UNIVERSITY OF FLORIDA

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2020
Publication Date: 12/23/2020
Citation: Pokhrel, S., Meyering, B., Bowman, K.D., Albrecht, U. 2020. Horticultural attributes and root architectures of field-grown ‘Valencia’ trees grafted on different rootstocks propagated by seed, cuttings, and tissue culture. HortScience. 56(2):163–172. https://doi.org/10.21273/HORTSCI15507-20.
DOI: https://doi.org/10.21273/HORTSCI15507-20

Interpretive Summary: Huanglongbing (HLB), also known as citrus greening, is a devastating disease of citrus that is found in most citrus production areas. Considerable root loss can be observed in affected trees, so root architecture and fibrous root regeneration capacity are two important rootstock traits that can substantially influence the performance of trees under HLB endemic condition. Rootstock propagation is typically by seed, but due to the increased demand for some of the best performing cultivars, propagation by other methods is increasingly common. This research investigates the difference in root architecture and root growth in field-grown citrus trees of Valencia sweet orange on six different rootstocks propagated by seed, cuttings, and tissue culture. Trees were evaluated for their performance during the first two years after planting. Although differences were found among propagation methods for some of the variables measured, root growth parameters and scion performance were influenced more by the rootstock cultivar than by the method of propagation.

Technical Abstract: Huanglongbing (HLB), also known as citrus greening, is a devastating disease of citrus that is found in most citrus production areas around the world. The bacterium causing this disease resides in and damages the phloem, restricting the movement of photosynthates throughout the plant, eventually leading to tree decline. Considerable root loss can be observed in affected trees before disease symptoms are visible on the shoot system. Therefore, root architecture and fibrous root regeneration capacity are two important rootstock traits that can substantially influence the performance of trees under HLB endemic condition. Rootstock propagation is typically by seed, but due to the increased demand for some of the best performing cultivars, propagation by other methods is necessary. This research investigates the difference in root architecture and root growth in field-grown citrus trees of six different rootstocks propagated by seed, cuttings, and tissue culture. It also evaluates the performance of the ‘Valencia’ (Citrus sinensis) scion grafted on those rootstocks. The trial was conducted in Collier County, Florida. The experimental design was a randomized split-plot with rootstock cultivar as the main plot and their methods of propagation as subplot factors. Trees were evaluated for their performance during the first two years after planting and a subset of trees was excavated to observe root architecture, root biomass, and other root traits. Although differences were found among propagation methods for some of the variables measured, root growth parameters and scion performance were influenced more by the rootstock cultivar than by the method of propagation.