New Disease Reports
New Disease Reports (2009) 19, 23.
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First report of 'Candidatus Phytoplasma asteris' (16SrI group) associated with colour-breaking and malformation of floral spikes of gladiolus in India

S.K. Raj 1*, S.K. Snehi 1, S. Kumar 1, B.K. Banerji 2, A.K. Dwivedi 2, R.K. Roy 3 and A.K. Goel 3

*skraj2@rediffmail.com

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Accepted: 06 Apr 2009

Gladiolus is an important ornamental plant, grown in the floriculture industry in India. More than 100 cultivars are maintained at NBRI, Lucknow. During January-February 2008, gladiolus plants (cv. Pacifica) exhibited symptoms of severe leaf stripe, colour-breaking, yellowing and malformation of flower spikes with stunted growth, small-sized corms and poorly developed root system (Fig.1). The disease incidence was low (3.2%), however the severity of symptoms imposed a threat for neighbouring plants by rapid disease spread. Similar symptoms have been previously reported on gladiolus, associated with a 16SrI phytoplasma, ‘Candidatus Phytoplasma asteris’ (Kamińska et al, 1999; Pfleger & Gould, 2002). Therefore, a phytoplasma infection was suspected.

Total DNA was extracted from 100 mg of leaf, flower and corm of infected and healthy gladiolus and indexed by nested PCR using phytoplasma universal primers specific to the 16S rRNA gene: P1/P6 (Deng & Hiruki, 1991) and R16F2n/R16R2 (Gundersen & Lee, 1996). This yielded amplicons of ~1.2 kb in two out of two infected leaves (Fig. 2a) and leaf, flower and corm of one severely infected plant (Fig 2b), but not in the single healthy plant tested. Two amplicons from infected leaves were directly sequenced and consensus data deposited in GenBank (Accession No. FJ491455). BLAST analysis revealed the highest identity of 97% with members of group 16SrI, confirmed by phylogenetic analysis (Fig. 3); this suggests the occurrence of a possible new ‘Candidatus Phytoplasma’ species. This is the first report on the association of 16SrI group, ‘Ca. Phytoplasma asteris’ with a disease of gladiolus in India.

Figure1+
Figure 1: Naturally infected gladiolus exhibiting colour-breaking, yellowing and malformation of flower spikes (b) as compared to a healthy plant (a). Symptoms of corm reduced sized and poor root system (c).
Figure 1: Naturally infected gladiolus exhibiting colour-breaking, yellowing and malformation of flower spikes (b) as compared to a healthy plant (a). Symptoms of corm reduced sized and poor root system (c).
Figure2+
Figure 2: Nested R16F2n/R16R2 PCR products from two infected leaves (DL) (a), and leaf (L), flower (F), and corm (C) samples from a severely infected gladiolus (b). M: Lambda DNA marker, digested with EcoRI and HindIII (Genei Pvt. Ltd, India).
Figure 2: Nested R16F2n/R16R2 PCR products from two infected leaves (DL) (a), and leaf (L), flower (F), and corm (C) samples from a severely infected gladiolus (b). M: Lambda DNA marker, digested with EcoRI and HindIII (Genei Pvt. Ltd, India).
Figure3+
Figure 3: Phylogenetic relationships between the gladiolus phytoplasma and selected 'Ca. Phytoplasma' reference strains from GenBank using MEGA 4.0.
Figure 3: Phylogenetic relationships between the gladiolus phytoplasma and selected 'Ca. Phytoplasma' reference strains from GenBank using MEGA 4.0.

References

  1. Deng S, Hiruki D, 1991. Amplification of 16S rRNA genes from culturable and nonculturable mollicutes. Journal of Microbiological Methods 14, 53-61.
  2. GundersenDE, Lee IM, 1996. Ultrasensitive detection of phytoplasmas by nested-PCR assays using two universal primer pairs. Phytopathologia Mediterranea 35, 144-151.
  3. Kamińska M, Rudzińska-LangwaldA, Korbin M, 1999. Occurrence and identification of aster yellows related phytoplasma in Gladiolus in Poland. Acta Physiologiae Plantarum.
  4. Pfleger FL, Gould SL, 2002. Gladiolus diseases: Virus and Phytoplasma disease, University of Minnesota (http://www.extension.umn.edu/distribution/).
This report was formally published in Plant Pathology

©2009 The Authors