ORIGINAL RESEARCH article
Front. Plant Sci.
Sec. Crop and Product Physiology
Volume 16 - 2025 | doi: 10.3389/fpls.2025.1614845
This article is part of the Research TopicFruit Trees Under Stress: Physiological, Biochemical, and Molecular MechanismsView all 6 articles
Novel Citrus Hybrids Incorporating Australian Lime Genetics: Development of HLB-Tolerant Citrus Rootstocks and Physiological Changes in 'Valencia' Sweet Orange Scions
Provisionally accepted
- University of Florida, Gainesville, United States
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Citrus greening disease, or Huanglongbing (HLB), represents the most destructive disease affecting citrus crops worldwide. All commercially cultivated citrus varieties are highly susceptible to HLB, and currently, no effective treatments exist. Several Australian limes have demonstrated significant HLB tolerance, making them promising candidates for developing HLB-tolerant rootstocks and scions through conventional breeding and biotechnological approaches. Herein, we report the successful development of HLB-tolerant citrus hybrids via integrating Australian lime genetics using traditional breeding methods and protoplast fusion techniques. To test the tolerance of those hybrids as rootstocks, the hybrids were clonally propagated via cuttings and divided into two groups: one grafted with CaLas-free 'Valencia' sweet orange budwoods and the other grafted with CaLasinfected 'Valencia' budwoods. The performance of these hybrids was compared to that of the Swingle rootstock, commonly used as a control. Total DNA was isolated from the 'Valencia' leaves at 6, 12, 18, and 24 months post-grafting to assess CaLas titers using quantitative PCR. After two years, significantly higher Ct values (ranging from 29.11 to 35.00) for CaLas were observed in 'Valencia' plants grafted onto the evaluated hybrids than in those grafted onto Swingle, which presented a Ct value of 22.25 ± 1.11. Compared with other hybrids, the mandarin (UF304) × finger lime hybrid (MFL1-98) and pummelo × finger lime hybrid (PFL2-61) exhibited improved graft-take, enhanced growth, and lower CaLas titers. Additionally, we analyzed the biochemical and molecular changes in the leaves of 'Valencia' grafted onto several Australian lime-derived hybrids. Biochemical analyses revealed significant alterations in chlorophyll content, starch accumulation, and levels of phenolic and flavonoid compounds. These results demonstrate the practical benefits of using Australian lime-derived hybrids as rootstocks to increase HLB tolerance in citrus, offering a promising approach for the sustainable management of HLB in commercial citrus production.
Keywords: Huanglongbing (HLB), Candidatus Liberibacter asiaticus, finger lime hybrids, Conventional breeding, Pummelo, rootstocks
Received: 19 Apr 2025; Accepted: 13 May 2025.
Copyright: © 2025 Mahmoud and Dutt. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Manjul Dutt, University of Florida, Gainesville, United States
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