PRO/PL> Sweet potato viruses - Spain

Wed Apr 7 11:28:50 CDT 2004

SWEET POTATO VIRUSES - SPAIN
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Date: 1 Apr 2004
From: ProMED-mail<promed at promedmail.org>
Source: American Phytopathological Society, Plant Disease Notes [edited]

1st Report of Sweet potato chlorotic stunt virus and Sweet potato feathery 
mottle virus Infecting Sweet Potato in Spain.

R. A. Valverde, Department of Plant Pathology and Crop Physiology, 
Louisiana State University, Baton Rouge, 70803; G. Lozano and J. 
Navas-Castillo, Estacion Experimental "La Mayora", CSIC, 29750 
Algarrobo-Costa, Malaga, Spain; and A. Ramos and F. Valdes, Departamento de 
Biologia Vegetal, Universidad de La Laguna, 38206 La Laguna, Tenerife, 
Spain. Plant Dis. 88:428, 2004; published on-line as D-2004-0203-02N, 2004. 
Accepted for publication 9 Jan 2004.

Sweet potato chlorotic stunt virus (SPCSV), family Closteroviridae and 
Sweet potato feathery mottle virus (SPFMV), family Potyviridae) are 
whitefly- and aphid-transmitted, respectively, which in double infections 
cause sweet potato virus disease (SPVD), a serious sweet potato (_Ipomoea 
batatas_ Lam.) disease in Africa (2). During the past decade, sweet potato 
plants showing symptoms similar to SPVD have been observed in most areas of 
Spain. Nevertheless, not much information is available about the identity 
of the viruses infecting this crop in Spain.

During the summer of 2002, sweet potato plants with foliar mosaic, 
stunting, leaf malformation, chlorosis, and ringspot symptoms were observed 
in several farms in Malaga (southern Spain) and Tenerife and Lanzarote 
(Canary Islands, Spain). Vine cuttings were collected from 21 symptomatic 
plants in Malaga and from 8 plants on Lanzarote and 6 on Tenerife. Scions 
were grafted to the indicator hosts, Brazilian morning glory (_I. setosa_) 
and _I. nil_ cv. Scarlett O'Hara. 3 weeks after graft inoculations, all 
plants showed various degrees of mosaic, chlorosis, leaf malformation, and 
stunting.

4 field collections (2 from Malaga, one from Tenerife, and one from 
Lanzarote) with severe symptoms on _I. setosa_ were selected for whitefly 
(_Bemisia tabaci_ biotype Q) transmission experiments. Acquisition and 
transmission periods were 48 h. _I. setosa_ was the acquisition host, and 
_I. nil_ was the transmission host. For each isolate, groups of 10 
whiteflies per _I. nil_ plant were used.

All _I. nil_ plants used as transmission hosts with the 4 field collections 
showed chlorosis and leaf malformation. Reverse-transcription polymerase 
chain reaction (RT-PCR) was performed on _I. setosa_ (grafted with the 4 
selected field collections) and _I. nil_ plants (from the 
whitefly  transmission experiments) with primers for the HSP70h gene of 
SPCSV. A 450-bp DNA fragment was obtained with all _I. setosa_ and _I. nil_ 
samples.

Sequencing of the 450-bp DNA from 2 samples from Malaga yielded a 
nucleotide sequence with 98 to 99 percent similarity to the HSP70h gene of 
West African SPCSV isolates. Foliar samples from _I. setosa_, originally 
grafted with the 21 vine cuttings, were used for nitrocellulose membrane 
enzyme-linked immunosorbent assay (NCM-ELISA) testing with antiserum 
specific to SPFMV-RC (provided by J. Moyer, North Carolina State 
University, Raleigh). Positive control was sap extract from _I. setosa_ 
that was infected with the common strain of SPFMV. Procedures for 
NCM-ELISA-ELISA were as described (4).

NCM-ELISA testing suggested that SPFMV was present in all samples. RT-PCR 
was conducted with degenerate primers POT1/POT2 (1). The nucleotide 
sequence that was amplified by these 2 primers spans part of the Nlb 
protein and part of the coat protein gene of potyviruses.

All samples yielded the expected 1.3-kb DNA. Sequencing of the RT-PCR 
products of 2 isolates from Malaga and sequence comparisons yielded 
nucleotide sequences with 97 percent similarity to 2 East African isolates 
(Nam 1 and Nam 3) of SPFMV (3).

These results confirm the presence of SPCSV and SPFMV in sweet potato in Spain.

References:
(1) D. Colinet and J. Kummert. J. Virol. Methods 45:149, 1993.
(2) R. W. Gibson et al. Plant Pathol. 47:95, 1998.
(3) J. F. Kreuze et al. Arch. Virol. 145:567, 2000.
(4) E. R. Souto et al. Plant Dis. 87:1226, 2003.

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ProMED-mail
<promed at promedmail.org>

[SPVD is considered the most damaging virus disease of sweet potato in 
Africa and may be the most serious disease in the crop worldwide. SPFMV is 
ubiquitous, whereas SPCSV has been reported only from Africa (Nigeria, 
Uganda, Kenya, Zaire), Asia (Taiwan, China, Indonesia, Philippines), 
America (USA, Brazil, Argentina, Peru) and Israel. The fact that both 
viruses are present in Spain indicates that SPVD can be expected to spread 
in the country.

Virus research at the International Potato Center in Peru is focused on 
SPVD because of its debilitating effect on resource-poor farms, especially 
in sub-Saharan Africa. Unfortunately, SPFMV-resistant cultivars originating 
from CIP were found to be susceptible to SPVD. Identification of genes for 
resistance to both SPCSV and SPFMV is a high priority. In China, using 
healthy planting materials resulted in yields that were 2-3 times greater 
than SPVD-infected plants. Similar results were obtained in African trials.

Additional references:
<http://ss.mykz.affrc.go.jp/Workshop/WS2000/proceedings/pdf/p014_salazar.pdf>
<http://cms2.gre.ac.uk/gre_research/Agriculture/Plant%20Health/Gibson%20R%20W1.doc>
<http://www.nri.org/work/sa-sweetpotatoes.htm>
  - Mod.DH]

[see also:
2001
----
Cucurbit yellow stunting dis. crinivirus - Portugal 20010529.1040]
.......................................dh/pg/dk

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