DISEASE NOTESOpen Access icon OPENOpen Access license

First Report on the Occurrence of ‘Candidatus Phytoplasma aurantifolia’ (16SrII-D) Associated With Virescence and Phyllody Disease of China Aster in India

    Affiliations
    Authors and Affiliations
    • S. Mahadevakumar , Molecular Phytodiagnostic Laboratory, Department of Studies in Botany, University of Mysore, Manasagangotri, Mysuru 570 006, Karnataka, India
    • V. Thorat , Microbial Culture Collection, National Centre for Cell Science, Pune 411021, India
    • Vandana Yadav , Department of Studies in Microbiology, University of Mysore, Manasagangotri, Mysuru 570 006, Karnataka, India
    • A. Yadav , Microbial Culture Collection, National Centre for Cell Science, Pune 411021, India
    • G. R. Janardhana , Molecular Phytodiagnostic Laboratory, Department of Studies in Botany, University of Mysore, Manasagangotri, Mysuru 570 006, Karnataka, India.

      China aster (Callistephus chinensis [L.] Nees.) is an important floriculture crop grown in Karnataka (India) for its beautiful cut flowers. Field surveys conducted in regions of Karnataka during 2014 to 2016 revealed that virescence and phyllody symptoms, suggestive of phytoplasma infections, were present on China aster plants. The disease incidence ranged from 28 to 34% in 78 ha of cultivated area surveyed. Affected young plants showed crown of small leaves with reduced internodes devoid of floral organs. Plants during postflowering stage turned green and floral parts were replaced by green leafy sepaloid structures. A total of 18 leaf and flower samples containing eight symptomatic for phyllody, eight symptomatic for virescence, and two asymptomatic samples were collected for molecular identification of the causal agent. Total genomic DNA from leaves and flowers of symptomatic and asymptomatic plants was extracted by using GenElute Plant Genomic DNA Miniprep Kit (Sigma-Aldrich, St. Louis, MO). From the genomic DNA, phytoplasma specific 16SrRNA gene fragment was amplified using phytoplasma specific universal primers, P1 (Deng and Hiruki 1991) and P7 (Schneider et al. 1995). Fragments of ∼1.8 kb amplicons were detected only in template DNA from symptomatic plants. These PCR products were purified and sequenced directly using 343R, 704F, 907R, and 1028F primers (Baker et al. 2003). The obtained 16S rRNA sequence (GenBank accession no. KX013259, 1,568 bp) was assembled and analyzed using EzTaxon databases (Kim et al. 2012) which showed 99.8% sequence identity with ‘Candidatus Phytoplasma australasia’ strain Carica papaya (Y10097) and 98.57% with Ca. P. aurantifolia strain WBDL (U15442). NCBI-BLAST search indicated that it shared 99% similarity with Ca. P. australasia strains (AB257291 and KP869129) and was identical to the members of 16SrII-D group phytoplasmas. In silico RFLP pattern of KX013259 analyzed by iPhyClassifier (Zhao et al. 2009) showed closest similarity with the reference strain WBDL (Y10097) with similarity coefficient of 1, which belonged to the 16SrII group, subgroup D. Based on the sequence similarity and virtual RFLP pattern, the phytoplasma associated with virescence and phyllody of China aster was found belonging to 16SrII subgroup D. There are reports on the association of different groups of phytoplasmas with China aster (16Sr-I, 16SrII-A, and 16SrIII-A) from different parts of the world, and association of 16SrII-D phytoplasma on different plant hosts (e.g., peanut, papaya, sesame, common bean, eggplant, tomato, parthenium) was recorded in India. However, 16SrII-D group phytoplasma causing phyllody and virescence on China aster has not been reported. To the best of our knowledge, this is the first report on association of phytoplasma (16SrII-D) with China aster. Phyllody and virescence adversely affect quality and quantity of China aster production because the affected plants remain stunted without bearing any floral organs which has the potential to cause economic losses.

      References: