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First Report of ‘Candidatus Phytoplasma australasia’ (16SrII Subgroup D) Associated with Virescence of Chia (Salvia hispanica) from India

    Affiliations
    Authors and Affiliations
    • Josna Joy1
    • A. S. Savitha2
    • S. Mahadevakumar3
    • K. Ajithkumar4
    • M. Mahesh5
    • M. Y. Sreenivasa1
    • Lakshmi Devi1
    1. 1Department of Studies in Microbiology, University of Mysore, Manasagangotri, Mysuru 570006, Karnataka, India
    2. 2Department of Plant Pathology, College of Agriculture, University of Agricultural Sciences, Raichur 584104, Karnataka, India
    3. 3Botanical Survey of India, Andaman and Nicobar Regional Centre, Haddo 744102, Port Blair, India
    4. 4AICRP on Linseed, Main Agricultural Research Station, University of Agricultural Sciences, Raichur 584104, Karnataka, India
    5. 5Department of Studies in Botany, University of Mysore, Manasagangotri, Mysuru 570006, Karnataka, India

    Chia (Salvia hispanica L., Lamiaceae) is an important commercial and medicinal crop recently popularized in India and widely cultivated in Karnataka (Joy et al. 2022). During the field survey of chia crop diseases, characteristic virescence-like symptoms were observed at Main Agricultural Research Station, UAS, Raichur, as well as at the Mysuru and HD Kote region. The disease incidence ranged from 2 to 4% in an area of 30 ha. Typical symptoms associated with chia were malformed shoot and/or inflorescence axis with reduced floral parts and greenish florets. The stem axis became thick and flattened, and leaves were reduced toward the terminal region. A total of five phytoplasma suspected samples and five suspected healthy samples were used for identification purpose. The Plant Genomic DNA Miniprep Kit (Sigma-Aldrich, Burlington, MA) was used to extract the DNA from the five symptomatic and five asymptomatic samples, and the DNA was used as a template to amplify the phytoplasma-specific 16S rDNA gene using P1/P7 primers (Deng and Hiruki 1991; Schneider et al. 1995) followed by nested PCR using R16F2n/R16R2 primers (Gundersen and Lee 1996). The expected 1.25-kb amplicon was detected from the suspected symptomatic samples. Nested PCR products were purified and sequenced from both directions using the ABIX370 Genetic Analyzer (Applied Biosystems, Waltham, MA). The analysis revealed that all five sequences shared 100% identity with ‘Candidatus Phytoplasma aurantifolia’ (OM649850 and ON975012) and tomato big bud phytoplasma (EF193359). The in silico restriction fragment length polymorphism (RFLP) pattern of the F2n/R2 primed region of the 16S rDNA gene analyzed by using iPhyClassifier (Zhao et al. 2009) revealed that the sequence shared 98.72% nucleotide sequence similarity with a coefficient value of 1.00 to the reference strain RFLP pattern of 16Sr group II, subgroup D (witches՚ broom disease of lime; U15442). Based on 16SrDNA sequences and in silico RFLP analysis, the phytoplasma associated with the chia virescence was identified as a member of the 16SrII-D group. Further, the SecA gene was also amplified from the samples using the SecAfor1/SecArev3 primer pair (Hodgetts et al. 2008). All samples produced ∼400-bp products and sequenced as detailed above. Sequence analysis by BLASTn revealed 100% similarity to ‘Candidatus Phytoplasma australasia’ (MW020545) and the ‘Ca. P. aurantifolia’ isolate Idukki Kerala 1 (MK726369), both representing 16SrII-D group phytoplasma. The representative sequences (16Sr, PP359693 and PP359694; SecA, PP386558 and PP386559) were deposited in GenBank. Chia virescence phytoplasma belonging to ‘Ca. P. australasia’ has not been reported anywhere. The phytopathological studies associated with chia crop are very limited. Joy et al. (2022) reported the occurrence of foot rot disease caused by Athelia rolfsii. Several hosts are recorded to be associated with 16SrII D phytoplasma, which includes china aster, eggplant, and crotalaria (Mahadevakumar et al. 2017; Yadav et al. 2016a, b). Now, the wide occurrence of the phytoplasma in the area might have been transmitted by vectors. The occurrence of virescence is of great importance as it affects the overall yield, which reduces the market value. To our knowledge, this is the first report of a group 16SrII-D phytoplasma associated with chia virescence in India.

    The author(s) declare no conflict of interest.

    References:

    J. Joy and A. S. Savitha contributed equally to this work.

    The author(s) declare no conflict of interest.