May 7, 2004
From: British Soc. Plant Pathol., New Disease Reports [edited]

First report of Tomato leaf curl New Delhi virus affecting chilli pepper in Pakistan
M. Hussain, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan; S. Mansoor, (as for Hussain); S. Iram, (as for Hussain); Y. Zafar (as for Hussain); and R.W. Briddon, Department of Disease and Stress Biology, The John Innes Centre, Colney Lane, Norwich, NR4 7UH, UK.
Accepted for publication 15 Apr 2004.

Tomato leaf curl New Delhi virus (ToLCNDV), a bipartite begomovirus, infects tomato and watermelon crops in the Indian subcontinent (Padidam et al., 1995a; Mansoor et al., 2000). Chilli pepper, an important crop on the Indian subcontinent, often shows symptoms similar to tomato leaf curl, such as yellowing, leaf curling, reduction in leaf size and stunting. Since chilli and tomato crops overlap in the field, it is likely that chilli peppers may become infected with tomato begomoviruses.

To assess the presence of ToLCNDV in chilli pepper, symptomatic plant samples were collected from several locations in the Punjab Province, Pakistan. To confirm begomovirus infection, total DNA was isolated from leaf samples, resolved in agarose gels and blotted onto nylon membranes and probed with a radioactively-labelled probe of DNA A of ToLCNDV. The probe hybridised with bands in all samples collected from symptomatic plants, when the blot was washed at medium stringency.

To confirm infection of ToLCNDV, PCR was carried out using degenerate begomovirus DNA A primers and products were obtained from these samples. A nearly full-length clone of this DNA A product was partially sequenced and was found to share 95 percent sequence identity with DNA A of ToLCNDV. These results confirmed ToLCNDV
infection in chilli pepper in Pakistan. The DNA A positive samples were also tested by hybridisation using ToLCNDV DNA B as a virus-specific probe (Padidam et al., 1995b).

A positive signal was detected in 6 of 8 samples that were positive using the DNA A probe. The presence of ToLCNDV was further confirmed by PCR using specific primers for DNA B (Padidam et al., 1995), based on the movement protein gene of ToLCNDV (BC1F 5'-CACCATGGCAATAGGAAATGATGGTATGGG-3' and BC1R5'-AAGGATCCTCTTAATTTTTTGAATAAATTTGGC-3'). Use of these primers produced products of the expected size from all samples shown to be positive by hybridisation.

These results prove the occurrence of ToLCNDV in chilli pepper crops in Pakistan. Previous reports have identified the presence of distinct begomoviruses in chilli crops (Shih et al., 2003), but this is the first confirmed finding of ToLCNDV.

References

Mansoor S, Khan SH, Hussain M, Mushtaq N, Zafar Y, Malik KA, 2000. Evidence that watermelon leaf curl disease in Pakistan is associated with tomato leaf curl virus-India. Plant Disease 84, 102.

Padidam M, Beachy RN, Fauquet CM, 1995a. Tomato leaf curl geminivirus from India has a bipartite genome and coat protein is not essential for infectivity. Journal of General Virology 76, 25-35.

Padidam M, Beachy RN, Fauquet CM, 1995b. Classification and identification of geminiviruses using sequence comparisons. Journal of General Virology 76, 249-263.

Shih, SL, Tsai WS, Green SK, Khalid S, Ahmad I, Rezaian MA, 2003. Molecular characterisation of tomato and chili leaf curl begomoviruses from Pakistan. Plant Disease 87, 200.

[Tomato-infecting begomoviruses are particularly damaging to solanaceous crops. In the 1970's there were only 3 tomato-infecting begomoviruses in the Americas, but at present there are at least 14 new ones, of which 7 are distinct ToLCNDV species. Recombination or pseudorecombination are driving forces in the evolution of new
viruses, especially in tropical regions.

Disease management of ToLCV depends in part on preventing movement of Bt-infested plants (e.g.. tomato transplants) to virus-free areas, where the virus can become established and implementation of phytosanitary procedures.

Various control options include removal of infected plants (roguing) and removal or burial of infected crop residues and intercropping in combination with chemical insecticides and use of available resistant cultivars. Use of plastic UV-absorbing screening material to exclude Bt is another method. Genetic resistance to begomoviruses has been reported in some wild _Lycopersicon_ species such as _L. hirsutum_ and _L. peruvianum_ which might be transferred to tomato. In Pakistan, resistance to leaf curl virus has been incorporated into tomato and chili cultivars.

A useful reference: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-41582002000500001&lng=en&nrm=iso
- Mod.DH]