Incidence, distribution, and genetic diversity of ‘Candidatus Phytoplasma luffae’-related strain (16SrVIII) associated with the cassava witches' broom (CWB) disease in the Philippines

Dolores, L.M.; Langres, Joanne A.; Pinili, Marita S.; Caasi-Lit, Merdelyn T.; Cortaga, Cris Q.; Retuta, Yron M.; Cueva, Fe M. Dela

doi:10.1016/j.cropro.2023.106244

Cited by 4 publications

(6 citation statements)

References 18 publications

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“…Symptom records do not indicate any striking difference between both dates. Nevertheless, it is important to mention that we cannot discard the involvement of additional pathogens in the development or severity of CWBD symptoms; a co-infecting phytoplasma is a possibility and sequence data suggest the occurrence of up to 4 different ribosomal groups of phytoplasma occurring in SEA 8 , 9 . In any case, previous conclusions based on the role of phytoplasma infection in the diagnostics and biology of CWBD, without confirming the correlation between symptoms and identity of the pathogen 8 , 19 , should be taken with caution.…”

Section: Discussionmentioning

confidence: 98%

“…In this work, we used a metagenomic approach to analyze the microbial content of plants affected by CWBD. This was prompted by the unexpected proportion of false positives obtained when detecting phytoplasma in diseased plants 9 , an observation that is reflected in a lack of data on the efficiency of phytoplasma detection in CWBD-affected plants 4 – 8 , 19 . As described earlier, using total DNA sequencing, we readily identified a fungus of the Ceratobasidium sp.…”

Section: Discussionmentioning

confidence: 99%

“…Cassava witches' broom disease (CWBD) was first reported in the Pacific Islands of Wallis and Futuna 3 , and remained largely unnoticed in SEA until 2010, when high incidences and significant fresh root yield reductions were reported in cassava fields of Vietnam, Cambodia, and Thailand 4 – 6 . Latest reports show that the impact of the disease is extended also in Lao PDR, Myanmar 7 and the Philippines 8 . In these reports, Candidatus phytoplasma asteris and luffae were identified in some of the affected plants.…”

Section: Introductionmentioning

confidence: 99%

“…In these reports, Candidatus phytoplasma asteris and luffae were identified in some of the affected plants. However, the percentage of diseased plants that are positive to phytoplasma (as detected by nested PCR and confirmed by sequencing) is generally not included 4 – 8 and on the contrary high percentages of false positives have been reported 9 . So far, there is no reliable molecular test for CWBD diagnostics.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the recent historically high cassava root prices and the expansion of CMD has seen considerable movement in cassava stems throughout the region (including across national borders) as farmers expand the production area and seek to access pathogen-free stem cuttings 13 . In the absence of a certified pathogen-free seed system, the region continues under constant threat from CWBD emergence 8 , 9 , reaching incidence levels where positive–negative selection strategies are becoming less viable, and the disease anticipated to lead to significant productivity declines and loss of economic value in forthcoming seasons.…”

Section: Introductionmentioning

confidence: 99%

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Ceratobasidium sp. is associated with cassava witches’ broom disease, a re-emerging threat to cassava cultivation in Southeast Asia

Leiva,

Pardo,

Arinaitwe

et al. 2023

Sci Rep

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Cassava witches' broom disease (CWBD) is a devastating disease of cassava in Southeast Asia (SEA), of unknown etiology. Affected plants show reduced internodal length, proliferation of leaves and weakening of stems. This results in poor germination of infected stem cuttings (i.e., planting material) and significant reductions in fresh root yields and starch content, causing economic losses for farmers and processors. Using a metagenomic approach, we identified a fungus belonging to the Ceratobasidium genus, sharing more than 98.3–99.7% nucleotide identity at the Internal Transcribed Spacer (ITS), with Ceratobasidium theobromae a pathogen causing similar symptoms in cacao. Microscopy analysis confirmed the identity of the fungus and specific designed PCR tests readily showed (1) Ceratobasidium sp. of cassava is strongly associated with CWBD symptoms, (2) the fungus is present in diseased samples collected since the first recorded CWBD outbreaks in SEA and (3) the fungus is transmissible by grafting. No phytoplasma sequences were detected in diseased plants. Current disease management efforts include adjustment of quarantine protocols and guarantee the production and distribution of Ceratobasidium-free planting material. Implications of related Ceratobasidium fungi, infecting cassava, and cacao in SEA and in other potential risk areas are discussed.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Ceratobasidium sp. is associated with cassava witches’ broom disease, a re-emerging threat to cassava cultivation in Southeast Asia

Leiva,

Pardo,

Arinaitwe

et al. 2023

Sci Rep

View full text Add to dashboard Cite

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Isolation, genome analysis and tissue localization of Ceratobasidium theobromae, a new encounter pathogen of cassava in Southeast Asia

Gil-Ordóñez,

Pardo,

Sheat

et al. 2024

Sci Rep

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In Southeast Asia (SEA) fastidious fungi of the Ceratobasidium genus are associated with proliferation of sprouts and vascular necrosis in cacao and cassava, crops that were introduced from the tropical Americas to this region. Here, we report the isolation and in vitro culture of a Ceratobasidium sp. isolated from cassava with symptoms of witches’ broom disease (CWBD), a devastating disease of this crop in SEA. The genome characterization using a hybrid assembly strategy identifies the fungus as an isolate of the species C. theobromae , the causal agent of vascular streak dieback of cacao in SEA. Both fungi have a genome size > 31 Mb (G+C content 49%), share > 98% nucleotide identity of the Internal Transcribed Spacer (ITS) and > 94% in genes used for species-level identification. Using RNAscope® we traced the pathogen and confirmed its irregular distribution in the xylem and epidermis along the cassava stem, which explains the obtention of healthy planting material from symptom-free parts of a diseased plant. These results are essential for understanding the epidemiology of CWBD, as a basis for disease management including measures to prevent further spread and minimize the risk of introducing C. theobromae via long-distance movement of cassava materials to Africa and the Americas.

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Status of Cassava Witches’ Broom Disease in the Philippines and Identification of Potential Pathogens by Metagenomic Analysis

Landicho,

Montañez,

Camagna

et al. 2024

Biology

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Cassava witches’ broom disease (CWBD) is one of the most devastating diseases of cassava (Manihot esculenta Crantz), and it threatens global production of the crop. In 2017, a phytoplasma, Candidatus Phytoplasma luffae (Ca. P. luffae), was reported in the Philippines, and it has been considered as the causal agent, despite unknown etiology and transmission of CWBD. In this study, the nationwide occurrence of CWBD was assessed, and detection of CWBD’s pathogen was attempted using polymerase chain reaction (PCR) and next-generation sequencing (NGS) techniques. The results showed that CWBD has spread and become severe, exhibiting symptoms such as small leaf proliferation, shortened internodes, and vascular necrosis. PCR analysis revealed a low phytoplasma detection rate, possibly due to low titer, uneven distribution, or absence in the CWBD-symptomatic cassava. In addition, NGS techniques confirm the PCR results, revealing the absence or extremely low phytoplasma read counts, but a surprisingly high abundance of fastidious and xylem-limited fungus, Ceratobasidium sp. in CWBD-symptomatic plants. These findings cast doubt over the involvement of phytoplasma in CWBD and instead highlight the potential association of Ceratobasidium sp., strongly supporting the recent findings in mainland Southeast Asia. Further investigations are needed to verify the etiology of CWBD and identify infection mechanisms of Ceratobasidium sp. to develop effective diagnostic and control methods for disease management.

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Incidence, distribution, and genetic diversity of ‘Candidatus Phytoplasma luffae’-related strain (16SrVIII) associated with the cassava witches' broom (CWB) disease in the Philippines

Cited by 4 publications

References 18 publications

Ceratobasidium sp. is associated with cassava witches’ broom disease, a re-emerging threat to cassava cultivation in Southeast Asia

Ceratobasidium sp. is associated with cassava witches’ broom disease, a re-emerging threat to cassava cultivation in Southeast Asia

Isolation, genome analysis and tissue localization of Ceratobasidium theobromae, a new encounter pathogen of cassava in Southeast Asia

Status of Cassava Witches’ Broom Disease in the Philippines and Identification of Potential Pathogens by Metagenomic Analysis

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