New Disease Reports (2005) 12, 12.

First report of the natural occurrence of Tobacco streak virus on blackgram (Vigna mungo)

D. Ladhalakshmi 1*, M. Ramiah 1, T. Ganapathy 1, M. Krishna Reddy 2, Salah Eddin Khabbaz 1, Merin Babu 1 and A. Kamalakannan 3

*ladasalam@yahoo.co.in

Show affiliations

Accepted: 02 Sep 2005

Blackgram (Vigna mungo; family Fabaceae) is an important pulse crop in India, Nepal, Bangaladesh and Myanmar. During kharif season (June-September 2002), a new disease was observed in the majority of the blackgram growing areas of India. Symptoms of the disease consisted of brown necrotic lesions on young leaves (Fig. 1A), with brown streaks on petioles and stems (Fig. 1B). In severe cases infected plants were found dead (Fig. 1C). Mechanical inoculation of plant sap from infected plants onto various plant species: Vigna unguiculata cv. 152 (Fabaceae), Nicotiana tabaccum (Solanaceae) (Fig. 2), Chenopodium amaranticolor (Chenopodiaceae) and Gomphrena globosa (Amaranthaceae), produced necrotic lesions on leaves and streaks on stems. Alternate hosts may also play role in disease epidemiology; since TSV infects many widely distributed weeds. For example, Parthenium hysterophorus probably plays a major role in the spread of TSV in peanut (Arachis hypogaea) (Prasada Rao et al., 2003).

Infected leaf samples of blackgram tested positive for TSV by DAC-ELISA (Bhat et al., 2001) using a specific polyclonal antibody (a gift from G. Cook, Plant Protection Research Institute, South Africa). Electron microscopic observations of negatively-stained preparations of purified virus from infected blackgram leaves revealed spheres with a diameter of 27 nm; consistent with TSV infection. RT-PCR tests of tissue from diseased blackgram plants using primers specific for the coat protein gene of TSV (Bhat et al., 2002) resulted in an amplicon of the expected size: approximately 700bp (Fig. 3). TSV infects a wide range of hosts in India (Prasada Rao et al., 2003). This is the first report of the natural occurrence of TSV on Vigna mungo.

Figure1a+Figure1b+Figure1c+
Figure 1: Symptoms associated with natural occurrence of Tobacco streak virus on blackgram: left, brown necrotic lesions on the young leaves; middle, brown streaks on the petiole and stem; right, petiole and stem necrosis of TSV infected plants.
Figure 1: Symptoms associated with natural occurrence of Tobacco streak virus on blackgram: left, brown necrotic lesions on the young leaves; middle, brown streaks on the petiole and stem; right, petiole and stem necrosis of TSV infected plants.
Figure2+
Figure 2: Necrotic rings on the leaf of Nicotiana tabaccum
Figure 2: Necrotic rings on the leaf of Nicotiana tabaccum
Figure3+
Figure 3: Agarose gel electrophoresis of RT-PCR products: lane 1, 100bp DNA ladder; lane 3, healthy; lane 4, infected urdbean sample
Figure 3: Agarose gel electrophoresis of RT-PCR products: lane 1, 100bp DNA ladder; lane 3, healthy; lane 4, infected urdbean sample

References

  1. Bhat AI, Anil Kumar, Jain RK, Chander Rao S, Ramiah M, 2001. Development of serological based assays for the diagnosis of sunflower necrosis disease. Annals of Plant Protection Science 9, 292-296.
  2. Bhat AI, Jain RK, Ramiah M, 2002. Detection of Tobacco streak virus from sunflower and other crops by reverse transcription polymerase chain reaction. Indian Phytopathology 55, 216-218.
  3. Prasada Rao RDVJ, Reddy AS, Reddy SV, Thirumala Devi K, Chander Rao S, Manoj Kumar V, Subramaniam K, Yellamanda Reddy T, Nigam SN, Reddy DVR, 2003. The host range of Tobacco streak virus in India and transmission by thrips. Annals of Applied Biology 142, 365-368.

This report was formally published in Plant Pathology

©2005 The Authors