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Alocasia macrorrhiza Represents a New Host of ‘Candidatus Phytoplasma asteris’-Related Strains Associated with Yellows Symptoms in China

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    Authors and Affiliations
    • Shao-Shuai Yu
    • An-Na Zhu
    • Wei-Wei Song
    1. Coconut Research Institute, Chinese Academy of Tropical Agricultural Sciences, Wenchang 571339, China

    Alocasia macrorrhiza, which belongs to the Araceae family, is an important landscape plant in China and has significant medicinal uses (Wu and Li 1979). In 2022, A. macrorrhiza displaying abnormal symptoms were found in Qionghai (19°7′56.29″N, 110°23′3.06″E), Hainan Island, China. The incidence of symptomatic plants was about 40% in the sampled areas. The abnormal symptoms included chlorotic ovoid leaves that turned yellow from green gradually, yellowing of mesophyll tissue, miniature leaves, and systemic wilting. The disease symptoms were suspected to be associated with phytoplasmas according to the protocols of phytoplasma identification. In order to identify the pathogen, 11 diseased samples and three asymptomatic samples were collected from an area of about 40 ha. Total DNA was extracted from 0.10 g of fresh plant leaf tissues using a CTAB DNA extraction method (Doyle and Doyle 1990). PCR amplifications were performed using the primers R16mF2/R16mR1 and fTuf1/rTuf1 (Lee et al. 1993; Schneider and Gibb 1997) specific for phytoplasma 16S rRNA and tuf genes, respectively. Target PCR amplicons were obtained from the DNA of 11 diseased samples but not from the DNA of the asymptomatic samples. The PCR products were cloned and sequenced by Shanghai Biotechnology (Guangzhou, China), and the obtained sequences were assembled, edited, and analyzed using the EditSeq program and DNAMAN version 6.0. The phytoplasma 16S rRNA and tuf gene amplicons were 1,336 and 930 bp in length, respectively. The sequences of all 16S rRNA and tuf amplicons in this study were identical. The sequencing data were deposited in GenBank with accession numbers OR466206 (16S rDNA) and OR513090 (tuf). According to the methods and protocols of phytoplasma identified and classification (Wei and Zhao 2022), the phytoplasma strain was described as A. macrorrhiza yellows (AmY) phytoplasma, AmY-hn strain. A BLAST search was conducted based on 16Sr RNA and tuf genes. The results showed that the strain AmY-hn had 100% 16Sr RNA sequence identity (1,336 bp out of 1,336 bp) with that of 16SrI-B subgroup phytoplasmas like onion yellows phytoplasma (OY-M; AP006628). AmY-hn had 100% tuf sequence identity (930 bp out of 930 bp) with that of 16SrI-B subgroup phytoplasmas like OY-M. RFLP profiles obtained with iPhyClassifier (Zhao et al. 2009) demonstrated that the AmY-hn strain was a member of the 16SrI-B subgroup with a similarity coefficient of 1.00 to the reference phytoplasma strain (AP006628). Separated phylogenetic analysis based on 16S rRNA and tuf genes obtained with MEGA 7.0 using the neighbor-joining method with 1,000 bootstrap value (Felsenstein 1985; Kumar et al. 2016) indicated that AmY-hn clustered into one clade with phytoplasma strains of OY-M and chinaberry witches’ broom (KP662119) with 100 and 87% bootstrap values, respectively. To our knowledge, this is the first report that a ‘Candidatus Phytoplasma asteris’-related strain belonging to the 16SrI-B subgroup infects A. macrorrhiza in China. The 16SrI-B subgroup ‘Candidatus Phytoplasma asteris’-related strains can spread outwards through the plant A. macrorrhiza. Thus, the findings in the study will be beneficial to the detection of phytoplasmas parasitic to this plant and the epidemic monitoring of the related diseases.

    The author(s) declare no conflict of interest.

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    Funding: This work was supported by the Hainan Provincial Natural Science Foundation of China (no. 323RC524).

    The author(s) declare no conflict of interest.