Graft Compatibility Classification within Aurantioideae Based on Biometric Traits and the Anatomy of Graft Union

Abstract

Citrus relatives are a relevant source of valuable traits for use in citrus breeding, including resistance to diseases such as Huanglongbing (HLB). Resistant rootstocks may impact tree responses to HLB. This requires graft compatibility, which has been poorly investigated within the Aurantioideae. In this study, the biometric characteristics and the anatomy of the graft union of 86 scion/rootstock combinations were assessed. This comprised 18 genotypes/species and 8 genera from Citrinae, Balsamocitrinae, and Clauseninae subtribes sensu Swingle and Reece. Most graft combinations were found to be noncompatible. Phylogenetic proximity did not ensure successful grafting as, for example, Orange jasmine autografts failed, whereas some intergeneric grafts were successful (>60% of graft-take). Plant scion height was directly related to graft-take, but the correlation between the scion and rootstock stem diameters was not a reliable indicator of graft compatibility. Rangpur/Tabog, Tabog/Rangpur, Wampee/Rangpur, Wampee/Pomeroy, Wampee/Swingle, Pomeroy/Wampee, and Swingle/Wampee were the most compatible intergeneric graft combinations. Graft-take success for this was at similar levels to those of sweet orange grafted on common citrus rootstocks. The position as a scion or rootstock in the combination affected the performance and was specific to the genotypes tested. The lack of differentiation between xylem-derived calli and the accumulation of phenolic compounds at the graft union were clear anatomical and biochemical markers, respectively, of incompatibility for most Aurantioideae combinations. In the field, within a set of the ten most promising combinations, Hamlin/Rangpur (control) was the only one that became infected by ‘Candidatus Liberibacter asiaticus’. This was first observed 12 months after planting. Overall, the assessment of biometric traits and anatomy of the graft union allowed Aurantioideae genotypes to be divided into four clusters, with respect to their graft compatibility, as follows: fully compatible with high graft-take and plant growth; potentially compatible with high graft-take but lower plant growth; partially incompatible with lower graft-take and poor plant growth; and fully incompatible with a complete absence of graft-take.

The Effects of a New Citrus Rootstock Citrus junos cv. Shuzhen No. 1 on Performances of Ten Hybrid Citrus Cultivars

“…Currently, rootstock selection for citrus production prioritizes compatibility and resistance; limited information, however, addresses rootstock impacts on performance of scion cultivars [ 10 , 11 , 12 ]. Despite the wide citrus grafting use, certain extensively employed rootstocks might still display graft incompatibility in the orchard, with manifestation taking years [ 13 ]. For instance, swingle citrumelo ( Citrus paradisi × Citrus trifoliata ), noted for biotic stress tolerance and enhancing scion fruit quality, exhibits incompatibility with specific sweet orange clones ( Citrus sinensis ) [ 14 ].…”

Dissection of transcriptional events in graft incompatible reactions of “Bearss” lemon (Citrus limon) and “Valencia” sweet orange (C. sinensis) on a novel citrandarin (C. reticulata × Poncirus trifoliata) rootstock

“…The greater the genetic divergence between the grafting partners, the more complex the interactions become, increasing the likelihood of graft failure (Gautier et al, 2019). Additionally, as in the case of citrus, the compatibility between the grafting partners can also be influenced by their respective position relative to the graft union (Raiol-Junior et al, 2022). Certain genotypes exhibit higher compatibility when used as scions, while others demonstrate greater compatibility when used as rootstocks or as interstocks.…”

Genome-Wide Identification and Functional Analysis of the AP2/ERF Transcription Factor Family in Citrus Rootstock under Waterlogging Stress

“…The citrus plant is cultivated by grafting, which joins the rootstock to the scion [4]. Rootstock is the core source of resistance to various abiotic stresses [5][6][7][8]. However, little is known about the molecular responses to waterlogging stress in citrus, which is crucial for citrus rootstock breeding [5].…”