Huanglongbing as a Persistent Threat to Citriculture in Latin America

Abstract

Citrus commercial species are the most important fruit crops in the world; however, their cultivation is seriously threatened by the fast dispersion of emerging diseases, including Huanglongbing (HLB) citrus greening. HLB disease is vectored by psyllid vectors and associated with phloem-limited α-proteobacteria belonging to the Candidatus Liberibacter genus. Climatic change and trade globalization have led to the rapid spread of HLB from its origin center in Southeast Asia, causing a great economic impact in the main production areas, including East Asia (China), the Mediterranean basin, North America (the United States), and Latin America (Brazil and Mexico). Despite important advances to understand the HLB epidemiology, Candidatus Liberibacter genetics, psyllid vector control, the molecular citrus-Candidatus Liberibacter interaction, and the development of integral disease management strategies, the study areas have been mostly restricted to high-tech-producing countries. Thus, in this review, we provide an overview of the epidemiology, distribution, genetic diversity, management aspects, and omics analysis of HLB in Latin America, where this information to date is limited.

Keywords: Candidatus Liberibacter genus; HLB epidemiology; HLB management methods; Huanglongbing (HLB); Latin America.

Figure 1

Candidatus Liberibacter asiaticus infection cycle. (A) Acquisition by Diaphorina citri: The healthy insect acquires CLas by feeding on infected citrus plants, which are more attractive due to the high concentration of volatile organic compounds such as MeSA and β-caryophyllene. For D. citri to become infectious, it must undergo a latency period of 16–18 days. After this period, it can spread the disease from an infected citrus plant to a healthy one, with the first symptoms appearing 6 to 12 months after inoculation. CLas multiplies within the phloem [2,32,33,34,35,36,37,38,39]. (B) Long-distance spread: CLas can be transmitted over long distances through grafting from asymptomatic infected citrus trees and the movement of infected plant material [27]. This figure was created using BioRender. “https://BioRender.com (accessed on 19 March 2025)”.

Figure 2

Distribution of Huanglongbing (HLB) and detection of species of Candidatus Liberibacter in citrus and insect vector in Latin America from 2004 to 2022, EPPO Global Database information. This figure was created using MapChart “https://www.mapchart.net (accessed on 19 April 2024)”.

Figure 3

Genetic diversity of Candidatus Liberibacter asiaticus (CLas) strains from Brazil, China, Mexico, and the United States by double-locus analyses. (a) Distribution of TRN frequencies using repeat unit TACAGAA; (b) Distribution of TRN frequencies using repeat unit AGACACA. This graphic was performed using R Software (v4.3.2; R Core Team) with data published by [68,69,70,71].

Figure 4

Scheme of “Omics” approaches. Genomics, transcriptomics, proteomics, and metabolomics are the compressive analysis targeting genome, transcriptome, proteome, and metabolome, respectively, to elucidate the molecular regulation of different citrus phenotypes. The main instrumental tools used for each “Omic” approach are shown. This figure was created using BioRender. “https://BioRender.com (accessed on 8 November 2023)”.