New Disease Reports
New Disease Reports (2009) 20, 27.
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First report of a 16SrIX (Pigeon pea witches’ broom) phytoplasma associated with toria (Brassica rapa cv. toria) phyllody disease in India

M. Azadvar 1,2, V.K. Baranwal 1* and D.K. Yadava 3

*vbaranwal2001@yahoo.com

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Accepted: 16 Dec 2009

In October 2008, toria oilseed plants with symptoms of phyllody, virescence (Fig. 1), witches’ broom (Fig. 2), extensive malformation of floral parts, formation of bladder like siliques (Fig. 3) and flower sterility were observed in New Delhi, India . Incidence of the disease varied from 0.9% to 11% among 12 different lines of toria. A phyllody disease of toria was previously reported in Ludhiana district of Punjab state of India (Bindra & Bakhetia, 1967), but at that time the causal agent was believed to be sesamum phyllody virus.

In order to determine whether a phytoplasma was associated with toria phyllody, total DNA of symptomatic and healthy plants was isolated using the DNeasy kit (Qiagen GmbH,Hilden, Germany) and subjected to direct and nested PCR using universal phytoplasma specific P1/P7 primer (Schneider et al., 1995) and R16F2n/R2 primer pairs (Gundersen & Lee, 1996), respectively. Midrib and flower tissues from symptomatic toria gave amplification products of approximately 1.8 and 1.25 kb in direct and nested PCR reactions respectively. No amplification was observed from the healthy samples. The complete nucleotide sequence of the P1/P7 amplified fragment of the phytoplasma associated with toria phyllody disease was determined (GenBank Accession No. GU111554). Comparison of this sequence to other phytoplasma 16S rDNA sequences reported in GenBank using the BLAST tool revealed that the phytoplasma associated with toria phyllody shows maximum identity of 99 % to the rRNA gene sequence of Knautia arvensis phyllody (Y18052) from Italy and Khafr (Iran) almond witches’ broom phytoplasma (DQ195209) from Iran. It showed 98 % identity with Pigeon pea witches’ broom phytoplasma (AF248957) from the USA and ‘Candidatus Phytoplasma phoenicium’ (AF515636) from Lebanon and Iran . All these phytoplasmas belong to the Pigeon pea witches’ broom (PPWB) 16SrIX group of phytoplasma. This is the first report of the presence of a member of the 16SrIX group of phytoplasma in India and also the first report of its association with a brassica plant worldwide.

Figure1+
Figure 1: Toria plant showing phyllody and virescence symptoms
Figure 1: Toria plant showing phyllody and virescence symptoms
Figure2+
Figure 2: Witches’ broom symptoms associated with toria phyllody
Figure 2: Witches’ broom symptoms associated with toria phyllody
Figure3+
Figure 3: Formation of bladder like siliques, virescent flower stalks and pistil malformation associated with toria phyllody
Figure 3: Formation of bladder like siliques, virescent flower stalks and pistil malformation associated with toria phyllody

Acknowledgements

We thank the Head, Division of Plant Pathology, IARI for providing facilities.

References

  1. Bindra OS, Bakhetia DRC, 1967. A note on the natural incidence of sesamum phyllody virus disease in Brassica spp. At Ludhiana . Journal of Research Punjab Agricultural University 4, 406- 408.
  2. Gundersen DE , Lee IM, 1996. Ultrasensitive detection of phytoplasmas by nested PCR assays using two universal primer pairs. Phytopathologia Mediterranea 35, 144-151.
  3. Schneider B, Seemüller E, Smart CD, Kirkpatrick BC, 1995. Phylogenetic classification of plant pathogenic mycoplasmalike organisms or phytoplasmas. In: Razin R, Tully JG, eds. Molecular and Diagnostic Procedures in Mycoplasmology, Vol. I. San Diego, CA, USA : Academic Press, 369-380.
This report was formally published in Plant Pathology

©2009 The Authors