PRO/PL> Tomato leaf curl virus, potato - India: first report

TOMATO LEAF CURL VIRUS, POTATO - INDIA: FIRST REPORT
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Date: 26 Sep 2003
From: ProMED-mail<[EMAIL PROTECTED]>
Source: British Society Plant Pathology, New Disease Reports, Vol 8: Aug 
2003 - Jan 2004 [edited]


Potato leaf curl - a new disease of potato in northern India caused by a 
strain of Tomato leaf curl New Delhi virus

K. S. Usharania, Plant Virology Unit, Division of Plant Pathology, Indian 
Agricultural Research Institute, New Delhi 110012, India; B. Surendranatha 
(as for Usharania); S.M. Paul-Khurana, Central Potato Research Institute, 
Shimla, 171001, India; I.D. Garg, (as for Paul-Khurana); and V.G. Malathia 
<[EMAIL PROTECTED]>)

Accepted for publication 1 Sep 2003.

A severe leaf curl disease has been observed since 1999 in potato (_Solanum 
tuberosum_) crops in northern India. Affected plants were severely stunted 
with apical leaf curl, crinkled leaves, and expressed conspicuous mosaic. 
Garg et al. (2001), using polyclonal antiserum to Indian cassava mosaic 
virus in IEM, detected a begomovirus associated with this disease.

Inoculum from a severely affected potato plant was sap-transmitted to 
_Nicotiana benthamiana_ [Nb] seedlings, in which it induced severe leaf 
distortion and stunting 15 days post inoculation. Meristem-derived 
plantlets of potato cv. Kufri Anand inoculated with sap from infected Nb 
leaves developed yellow mottling, mosaic, and leaf curl symptoms.

Double-stranded viral replicative DNAs were purified from infected potato 
and Nb plants and cloned at HindIII, BamHI, XbaI, and PstI sites in the 
vector pUC18. The clones at the XbaI and PstI sites had a unit genome 
length insert (approx. 2.7 kb) which hybridized with the viral replicative 
forms from the infected plants. The nucleotide sequence of the XbaI and 
PstI clones corresponded to the DNA A (Accession No. AY286316) and B 
(Accession No. AY158080) components of the causal begomovirus.

Comparison of the complete nucleotide sequence of DNA A revealed that it 
has 93-95 percent identity with that of ToLCV-NDe isolates and <75 percent 
identity with other Tomato leaf curl virus isolates and Potato yellow 
mosaic virus.

A whitefly-transmitted potato begomovirus has not been reported previously 
in India, probably as potato crops on the North Indian plains have been 
cultivated during winter months, when whitefly populations are low. 
However, in recent years, potato crops have been planted earlier, resulting 
in a sufficient buildup of whitefly populations that might have led to the 
emergence of a new potato disease.

The nucleotide sequence data indicate that the cause is a virus closely 
related to ToLCV-NDe which, unlike the strain infecting potato, is not 
sap-transmissible and is not known to infect potato naturally. Therefore it 
is likely that a new strain of ToLCV-NDe has emerged that infects potato, a 
new host.

This is the first observation of a begomovirus causing a severe disease of 
potato in India. We conclude that potato leaf curl disease is caused by a 
strain of Tomato leaf curl New Delhi virus (ToLCV-NDe).

Reference:

Garg ID, Paul-Khurana SM, Kumar S, Lakra BS, 2001. Association of a 
geminivirus with potato apical leaf curl in India and its immuno-electron 
microscopic detection. Journal of Indian Potato Association 28, 227-232.

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ProMED-mail
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[This piece is a good example of virus evolution at work. A 
whitefly-transmitted begomovirus originating in potato fields in Northern 
India is shown to be closely related to ToLCV-NDe. What is interesting is 
that the new virus is a relatively rare example of a sap-transmissible 
begomovirus. Based on genome sequence analysis, it is closely related to 
ToLCV-NDe but less closely related to other ToLCV isolates/strains. At 
least 3 other begomovirus strains/isolates have been reported from Asia. 
The one associated with cucumber yellow leaf curl disease in Thailand 
shares 95.6 percent nucleotide sequence similarity with the DNA-A of 
ToLCV-NDe, and pumpkin yellow vein mosaic virus is most closely related to 
the same virus. Recently a begomovirus in sponge gourd (_Luffa cylindrica_) 
from India is now considered to be a putative strain of ToLCV-NDe. Clearly 
new viral species continue to emerge in Asia. - Mod.DH]

[see also:
Tomato leaf curl, tomato - Australia 20030608.1413
2001
----
Tomato viruses - Tunisia 20010926.2349
Tomato leaf curl begomovirus, tomato - Greece 20010707.1307
Tomato leaf curl begomovirus, tomato disease - India (02) 20010402.0663
Tomato leaf curl begomovirus, tomato disease - India 20010331.0649]
.......................................dh/pg/mpp

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