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Molecular studies on the sweet potato virus disease and its two causal agents

Kreuze, Jan (2002). Molecular studies on the sweet potato virus disease and its two causal agents. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae. Agraria, 1401-6249 ; 335
ISBN 91-576-6180-4
[Doctoral thesis]

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Official URL: http://www.vbiol.slu.se/tema/stress/VirologyGroup/...

Abstract

The studies presented in this thesis contribute to an increased understanding of the molecular aspects, variability and interaction of the two most important viral pathogens of sweet potato (Ipomoea batatas L): Sweet potato feathery mottle virus (SPFMV) and Sweet potato chlorotic stunt virus (SPCSV), which cause the severe sweet potato virus disease (SPVD) when co-infecting sweet potato plants. SPVD is the most important disease affecting sweet potato in Africa, and may be the most important virus disease of sweet potato globally. The coat protein gene sequences of several African SPFMV isolates were determined and compared by phylogenetic analyses. Results showed that East African SPFMV isolates were genetically distinct. They could furthermore be divided into two serotypes which differed in their ability to systemically infect the sweet potato cultivar Tanzania. The aetiology of SPVD was studied in sweet potato plants co-infected with SPFMV and SPCSV using nucleic acid hybridisation, bioassays, tissue printing and thin section immunohistochemistry. Resistance to SPFMV in East African sweet potato cultivars was found to be due to inhibition of virus replication rather than movement and resistance was suppressed by infection with SPCSV, resulting in a ca. 600-fold increase in titres of SPFMV. Furthermore, in SPVD affected plants SPFMV is detected outside of the phloem, whereas SPCSV is detected only inside the phloem, which suggests novel as yet unknown mechanisms how SPCSV synergises SPFMV. The genomic sequence of SPCSV was determined. It was composed of two RNA molecules (9407 and 8223 nucleotides), representing the second largest (+)ssRNA genome of plant viruses. The genomic organization of SPCSV revealed novel features for the genus Crinivirus, such as i) the presence of a gene putatively encoding an ribonuclease III-like protein, ii) near-identical, 208 nucleotides long 3’-sequences on both viral RNAs, and iii) the placement of the SHP gene at a new position on the genome of SPCSV relative to other closteroviridae. Northern analyses showed the presence of several sub-genomic RNAs, of which the accumulation was temporally regulated in infected tissues. The 5’-ends of seven sub-genomic RNAs were determined using a PCR based method, which indicated that the sgRNAs were capped.

Authors/Creators:Kreuze, Jan
Title:Molecular studies on the sweet potato virus disease and its two causal agents
Year of publishing :March 2002
Volume:335
Number of Pages:63
Papers/manuscripts:
NumberReferences
ALLI. Kreuze, J.F., Karyeija, R.F., Gibson, R.W. & Valkonen J.P.T. 2000. Comparisons of coat protein gene sequences show that East African isolates of Sweet potato feathery mottle virus form a genetically distinct group. Archives of Virology 145, 567-574 II. Karyeija, R.F., Kreuze, J.F., Gibson, R.W. & Valkonen, J.P.T. 2000. Two serotypes of Sweetpotato feathery mottle virus in Uganda and their interaction with resistant sweetpotato cultivars. Phytopathology 90, 1250-1255 III. Karyeija, R.F., Kreuze, J.F., Gibson, R.W. & Valkonen, J.P.T. 2000. Synergistic interactions of a potyvirus and a phloem-limited crinivirus in sweet potato plants. Virology 269, 26-36 IV. Kreuze JF, Savenkov EI, Valkonen JPT (2002) Analysis of the complete genomic sequence and subgenomic RNAs of Sweet potato chlorotic stunt virus reveals several new features for the genus Crinivirus. Journal of Virology 76, 9260-9270
Place of Publication:Uppsala
ISBN for printed version:91-576-6180-4
ISSN:1401-6249
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:H Protection of plants and stored products > H20 Plant diseases
Subjects:Not in use, please see Agris categories
Agrovoc terms:ipomoea batatas, sweet potatoes, plant diseases, potyviruses, viroses, molecular biology, east africa
Keywords:Sweet potato feathery mottle virus, Sweet potato chlorotic stunt virus, Ipomoea batatas, genetic variation, Crinivirus, Potyvirus, viral synergism, genome structure, expression strategy, virus resistance
ID Code:202
Department:?? 4062 ??
Deposited By: Jan Kreuze
Deposited On:24 Mar 2003 00:00
Metadata Last Modified:02 Dec 2014 10:02

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