Volume 49, Issue 1 e12262
NEW DISEASE REPORT
Open Access

First report of a ‘Candidatus Phytoplasma trifolii’-related strain (16SrVI) associated with okra curled pod disease in Iran

S. Gharouni-Kardani

Corresponding Author

S. Gharouni-Kardani

Plant Protection Research Department, Khorasan Razavi Agricultural and Natural Resources Research and Education Center, AREEO, Mashhad, Iran

Correspondence

S. Gharouni-Kardani, Plant Protection Research Department, Khorasan Razavi Agricultural and Natural Resources Research and Education Center, AREEO, Mashhad, Iran. Email: [email protected]

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E. Taheri

E. Taheri

Plant Protection Research Department, Khorasan Razavi Agricultural and Natural Resources Research and Education Center, AREEO, Mashhad, Iran

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First published: 15 March 2024

Okra (Abelmoschus esculentus) is an important vegetable belonging to the family Malvaceae. Since April 2023 growers in Chenaran City (Razavi Khorasan province, Iran) have reported new and unusual symptoms in okra cultivated in greenhouses. The most common symptoms comprised bunchy top, progressive growth abnormalities, shortening of internodes, stunting, shoot proliferation, and wrinkled, curled or bent pods (Figure 1). The prevalence of the disease was c. 85%. This study was done to investigate the aetiology of the disease.

Details are in the caption following the image
Okra plants showing a) curled pod and b) shortening of internodes, stunting and shoot proliferation symptoms, compared with (c) healthy plant.

DNA was extracted from the leaf midribs of five diseased and three symptomless plants using a CTAB-based method (Zhang et al., 1998). Direct and nested PCR assays were performed using the universal phytoplasma primer pairs, P1/P7 (Deng & Hiruki, 1991) and R16F2n/R16R2 (Gundersen & Lee, 1996), respectively. Amplicons of the expected size were obtained from all five diseased plants. The sequence data were submitted to GenBank (Accession No. OR784662). No PCR products were obtained from the symptomless plants. A phylogenetic tree was constructed using the neighbour-joining method with MEGA-X software. To determine ribosomal group affiliation, the 16SrRNA gene sequences were analysed using iPhyClassifier software by virtual RFLP. The phylogenetic and virtual RFLP analyses revealed that the phytoplasma associated with okra curled pod disease belongs to the Clover proliferation group (16SrVI-A subgroup) (Figure 2).

Details are in the caption following the image
Phylogenetic tree generated using MEGAX by the neighbour-joining method (bootstrap analysis with 1000 replicates) based on partial 16S rDNA sequences (1247 bp) from the okra curled pod phytoplasma identified in this study (OR784662), and selected sequences retrieved from GenBank (accession numbers in parentheses). Acholeplasma laidlawii was used as the out-group.

These findings suggest that phytoplasmas are widening their host range in Iran. The 16SrVI group has been identified previously in Iran (Gharouni-Kardani et al., 2020). Different phytoplasmas associated have been reported to be associated with disease in okra in other countries. The 16SrXII and 16SrV groups were identified in okra in Mauritius (Gungoosingh-Bunwaree et al., 2011) and 16SrI group was reported in India (Kumar et al., 2012). To our knowledge, this is the first report of a ‘Candidatus Phytoplasma trifolii’ related strain causing okra curled pod disease in Iran and globally.