Publications des agents du Cirad


Detection, diversity and integration of yam badnaviruses

Seal S.E., Kenyon L., Lebas B., Muller E., Caruana M.L., Marchand J.L.. 2003. In : Advances in plant virology : A three day International conference at CIRAD, Montpellier, France on 29 September - 1 October 2003. Warwick : AAB, 1 p.. International Conference : Advances in Plant Virology, 2003-09-29/2003-10-01, Montpellier (France).

Yam plants are usually propagated through their tubers and this has resulted in the accumulation of viruses. Such infections currently paralyse yam germplasm movement worldwide and thus hinder international exchange of selected varieties. A study based at CIRAD (Montpellier) was carried out in 2001-2002 to tackle this problem by improving our knowledge of yam badnaviruses and the detection thereof. CIRAD and NRI's worldwide collections of yam samples were screened and 62 of 79 samples tested scored PCR-positive for badnavirus sequences with a general badnavirus primer pair. Confirmation of these infections was carried out through ELISA and immunosorbent electron microscopy (ISEM). The existence of PCR-positive, but ISEM/ELISA negative results suggested that some plants may contain integrated badnavirus sequences. To determine if viral sequences had integrated into yam host genomes, nucleic acid hybridisations were undertaken with yam badnavirus sequence probes. Autoradiographs indicated that one badnavirus probe hybridised to plant bands in some samples free from detectable badnavirus-particles. This result together with badnavirus sequence information obtained from the samples, revealed that integrated badnavirus sequences appear to be present in some yam species. Future collaborative research between CIRAD and NRI should determine if these sequences are dead integrants or activatable sequences that will pose a threat to yam germplasm health and movement. Analysis of 97 partial badnavirus RT-RNaseH sequences grouped them into 16 groups each sharing less than 80% nucleotide identity with the other groups. DNAs from single leaf samples often contained sequences belonging to more than one group. Near-identical sequences from samples from different countries and even continents suggest that recent international movement of badnavirus-infected yam tubers has occurred. (Texte intégral)

Mots-clés : dioscorea; virus des végétaux; variation génétique; séquence nucléotidique; germplasm; badnavirus

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