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'Candidatus Phytoplasma asteris' Strains Associated with Oil Palm Lethal Wilt in Colombia
Elizabeth Alvarez1, Juan F Mejía2, Nicoletta Contaldo3
1Plant Pathology Program, International Center for Tropical Agriculture (CIAT), Cali, Valle del Cauca, Colombia.
Abstract:
The distribution of lethal wilt, a severe disease of oil palm, is spreading throughout South America. An incidence of about 30% was recorded in four commercial fields in Colombia. In this study, phytoplasmas were detected in symptomatic oil palm by using specific primers, based on 16S ribosomal DNA (rDNA) sequences, in nested polymerase chain reaction assays. The phytoplasmas were then identified as 'Candidatus Phytoplasma asteris', ribosomal subgroup 16SrI-B, through the use of restriction fragment length polymorphism (RFLP) analysis and sequencing. Cloning and sequencing of 16S rDNA from selected strains, together with phylogenetic analysis, confirmed the classification. Moreover, collective RFLP characterization of the groEL, amp, and rp genes, together with sequence data, distinguished the aster yellows strain detected in Colombian oil-palm samples from other aster yellows phytoplasmas used as reference strains; in particular, from an aster yellows strain infecting corn in the same country.
Insights
Lethal wilt disease in South American oil palms is caused by phytoplasmas. Researchers identified the specific pathogen,
Area of Science:
- Plant Pathology
- Molecular Biology
- Phytoplasmology
Background:
- Lethal wilt, a significant oil palm disease, is increasingly prevalent across South America.
- A high incidence of approximately 30% has been observed in Colombian commercial oil palm fields, indicating a serious threat to the industry.
Purpose of the Study:
- To detect and identify the causal agent of lethal wilt disease in symptomatic oil palm trees in Colombia.
- To characterize the identified phytoplasma and differentiate it from other known strains, including those affecting other crops in the region.
Main Methods:
- Phytoplasma detection in oil palm tissues using specific primers targeting 16S ribosomal DNA (rDNA) via nested polymerase chain reaction (PCR).
- Identification and sub-grouping using restriction fragment length polymorphism (RFLP) analysis and DNA sequencing of 16S rDNA.
- Phylogenetic analysis and RFLP characterization of additional genes (groEL, amp, rp) for strain differentiation.
Main Results:
- Phytoplasmas were successfully detected in symptomatic oil palms.
- The identified phytoplasma was classified as 'Candidatus Phytoplasma asteris', ribosomal subgroup 16SrI-B.
- Sequence and RFLP data confirmed the classification and distinguished the oil palm strain from a phytoplasma strain infecting corn in Colombia.
Conclusions:
- Phytoplasmas, specifically 'Candidatus Phytoplasma asteris' 16SrI-B, are the causative agents of lethal wilt in Colombian oil palms.
- This finding is crucial for understanding the epidemiology of the disease and developing targeted management strategies.
- The study highlights the importance of molecular techniques for accurate phytoplasma identification and strain differentiation in plant disease diagnostics.