Wild plants growing in backyards or forest edges can act as hidden carriers of citrus greening disease. A recent international study led by Universitas Gadjah Mada (UGM) revealed that Murraya sumatrana, a plant native to Indonesia, can naturally host Candidatus Liberibacter asiaticus (CLas), the bacterium causing huanglongbing (HLB), one of the most destructive citrus diseases.
The findings were published in the April 2024 edition of the Q1 journal Plant Disease titled “Natural Infection of Murraya paniculata and Murraya sumatrana with ‘Candidatus Liberibacter asiaticus’ in Java.”
For the first time, the study confirmed that M. sumatrana can be naturally infected by CLas, the bacterium responsible for HLB, which is transmitted by the Asian citrus psyllid (Diaphorina citri).
Over a year, the research team collected samples from various Murraya species growing in Yogyakarta, Purworejo, and Bogor Botanical Gardens.
They combined classical botany with chloroplast DNA and ITS analysis to confirm species identification and tested for CLas using polymerase chain reaction (PCR) and real-time PCR.
The results showed four accessions of M. paniculata (commonly known as orange jasmine, an ornamental plant) and three M. sumatrana (Javanese orange jasmine) accessions contained CLas.
Professor Siti Subandiyah from the UGM Faculty of Agriculture, the project’s lead researcher, is expanding our understanding of HLB’s epidemiological cycle in tropical ecosystems.
“We need to start paying attention to wild or uncultivated plant species that coexist with citrus crops. Murraya sumatrana, which is widespread in Indonesia, is susceptible to this pathogen and may transmit it to cultivated citrus plants via insect vectors,” she said on Thursday, Apr. 17, 2025.
- sumatrana often grows in secondary forests, yards, and conservation areas. When infected, it shows no clear symptoms, making it a likely undetected disease reservoir. Left unmanaged, it could accelerate HLB spread to citrus farms and the horticultural industry.
Moreover, the Asian citrus psyllid, the main vector of the disease, is known to breed rapidly on young shoots of Murraya plants. Its population increases during the dry season and can easily migrate to nearby citrus trees.
Field observations revealed that M. paniculata and M. sumatrana growing near citrus orchards and on the UGM campus hosted significant populations of this insect.
“This is a wake-up call that controlling HLB should not only focus on cultivated citrus. We must also monitor surrounding landscapes, including hedges, wild shrubs, and ornamental plants in city parks,” she emphasized.
However, Professor Subandiyah clarified that detecting the pathogen in M. sumatrana does not mean the plant should be eradicated. Instead, an ecosystem-based management approach is needed.
Regular maintenance, vector monitoring, and quarantine measures for plant movement in and out of HLB-prone zones should be strengthened.
“We do not recommend removing the species. Rather, we need to understand its ecological role and manage it wisely,” the professor asserted.
This study highlights how classical botany and molecular biotechnology can synergize. Species identification was not limited to leaf shape, flowers, fruits, seeds, or plant height but was genetically validated using chloroplast and ITS DNA sequencing.
This approach provides a robust scientific basis for distinguishing morphologically similar species, especially between M. paniculata and M. sumatrana.
These two species are frequently mistaken for one another in field identification, despite their distinct roles as hosts for pathogens, which significantly impact plant quarantine policies, disease risk management, and the movement of plants in the horticultural trade, particularly ornamental plants.
Disease control policies can be more targeted and effective with more accurate species identification.
The research was supported by the Indonesian Endowment Fund for Education (LPDP) through a scholarship awarded to Ayu Lestiyani, a doctoral student in Biotechnology at UGM’s Graduate School (SPs UGM).
The Australian Centre for International Agricultural Research (ACIAR) under project SRA No: HORT/2023/193 and the Student Mobility Program from Tokyo University of Agriculture provided additional support for international collaboration and her dissertation.
Sample collection also involved Bogor Botanical Gardens staff, who assisted the research team in the field.
Professor Subandiyah hopes the research will serve as a foundation for developing a more comprehensive, landscape-based HLB control strategy.
“If we only focus on citrus groves and ignore the surrounding vegetation, it’s like patching one hole while leaving another wide open,” she concluded.
This discovery not only broadens our understanding of HLB’s disease cycle but also reminds us that native plants, though seemingly harmless, can play significant roles in plant disease dynamics.
With a scientific approach integrating molecular taxonomy and field ecology, UGM researchers once again demonstrate how academic research can have a tangible impact on national food security.
Furthermore, integrated national and international research collaborations are crucial to achieving broader and more meaningful solutions to agricultural challenges.
Author: Triya Andriyani
Post-editor: Lintang Andwyna
Photograph: M. sumatrana research team