Volume 48, Issue 2 e12230
NEW DISEASE REPORT
Open Access

First report of a 16SrII-A subgroup ‘Candidatus Phytoplasma aurantifolia’-related strain associated with Celosia argentea in Taiwan

H. M. Mejia

H. M. Mejia

Institute of Biochemistry, National Chung Hsing University, Taichung, Taiwan

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Y.-C. Chiu

Y.-C. Chiu

Institute of Biochemistry, National Chung Hsing University, Taichung, Taiwan

Doctoral Program in Microbial Genomics, National Chung Hsing University and Academia Sinica, Taichung, Taiwan

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Y.-K. Chen

Y.-K. Chen

Department of Plant Pathology, National Chung Hsing University, Taichung, Taiwan

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P.-Q. Liao

P.-Q. Liao

Institute of Biochemistry, National Chung Hsing University, Taichung, Taiwan

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J.-Y. Yang

Corresponding Author

J.-Y. Yang

Institute of Biochemistry, National Chung Hsing University, Taichung, Taiwan

Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan

Advanced Plant and Food Crop Biotechnology Center, National Chung Hsing University, Taichung, Taiwan

Correspondence:

J.-Y. Yang, Institute of Biochemistry, National Chung Hsing University, Taichung 402, Taiwan. Email: [email protected]

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First published: 22 November 2023

Celosia argentea (family Amaranthaceae), commonly known as plumed cockscomb or silver cockscomb, is a tropical flower used ornamentally (Varadharaj & Muniyappan, 2017). In September 2021, a C. argentea plant with obvious proliferation of branches and loss of general flower characteristics, symptoms often associated with phytoplasma infection (Namba, 2019), was found in Fengan Road (23°47'10.5″N, 120°14'46.1″E), Mailiao, Yunlin County, Taiwan (Fig. 1a & b). Healthy C. argentea has alternate lanceolate leaves, whereas the diseased plant had shortened internodes and was abnormally branched with scattered misshaped leaves (Fig. 1c). Healthy C. argentea flowers have dense erect spikes and purple pigments, whereas the diseased plants had an altered flower structure (Fig. 1d).

Details are in the caption following the image
Samples of healthy and diseased Celosia argentea collected in Mailiao, Yunlin, Taiwan: (a), diseased C. argentea (arrowhead) obseved in Fengan Road, Mailiao, Taiwan; (b), healthy plant with normal flower and branch structures (left) and diseased plant (right) displaying witches’-broom symptoms (arrowhead); (c), healthy (left) and diseased (right) sample;.and (d), healthy (left) and diseased (right) flowers (arrowhead).

Diseased leaves were examined under a transmission electron microscope which revealed a dense accumulation of pleomorphic organisms, 200–800 nm in size, in the phloem (Fig. 2), consistent with previous descriptions of phytoplasmas in other plant species (Trivellone & Dietrich, 2021). Genomic DNA was extracted from diseased samples and then subjected to nested PCR using universal primers P1/P7 and R16F2n/R16R2 for the detection of the conserved 16S rRNA gene (International Plant Protection Convention, 2016). Uninfected and Echinacea purpurea witches’ broom phytoplasma-infected Catharanthus roseus were used as a negative and positive control, respectively. As expected, a 1.2 kb DNA fragment was amplified from diseased samples and the positive control.

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Transmission electron micrograph of phytoplasma cells in leaf veins of diseased Celosia argentea. Sieve element has a dense accumulation of pleomorphic organisms. CW, cell wall; Ph, phytoplasma; SE, sieve element; arrowheads indicate phytoplasma cells.

The P1/P7 primer pair-amplified DNA fragment was sequenced and deposited in GenBank (Accession No. OM690618) as a partial sequence of the 16S rRNA gene of C. argentea witches’ broom phytoplasma. The sequence was identical to ‘Ca. P. aurantifolia’ strain NTU2011 (AMWZ00000000.1) and shared 99.93% identity with a 16SrII-A type phytoplasma isolate (L33765), both are associated with peanut witches’ broom disease in Taiwan (Gunderson et al., 1994; Chung et al., 2013). A phylogenetic tree was constructed using MEGA-X software based on the 16S rRNA gene of phytoplasma strains identified in Taiwan. The tree demonstrated the close relationship of this phytoplasma to other 16SrII phytoplasmas reported in Taiwan (Fig. 3). An iPhyClassifier-based virtual RFLP analysis showed that the virtual RFLP pattern derived from C. argentea witches’ broom phytoplasma 16S rRNA gene sequence is identical (similarity coefficient 1.00) to the reference pattern of 16Sr group II, subgroup A (L33765) supporting its inclusion in the 16SrII-A subgroup. To the best of our knowledge, this is the first report of phytoplasma disease in C. argentea associated with a ‘Ca. P. aurantifolia’-related strain (16SrII-A) in Taiwan and globally.

Details are in the caption following the image
Phylogenetic tree based on the R16F2n/R16R2 fragment of the 16S rRNA gene of phytoplasma strains identified in Taiwan. The C. argentea witches’ broom phytoplasma identified in this study is marked in red. Acholeplasma laidlawii served as an outgroup.

ACKNOWLEDGEMENTS

Helen Mae Mejia was supported by Department of Science and Technology - Science Education Institute. This work was financially supported (in part) by grants-in-aid from the National Science and Technology Council (111-2313-B-005-014-MY3) and the Advanced Plant and Food Crop Biotechnology Center from the Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education in Taiwan.