Etude des mécanismes génétiques impliqués dans l'expression des séquences EPRVs pathogènes des bananiers au cours de croisements génétiques interspécifiques
Inter-specific hybrids have, in the past few years, been shown to express symptom of Banana streak disease (BSD) that could not have originated from external sources of Banana streak virus (BSV). It was hypothesised that infections arose instead through a complex recombination pattern from viral sequences integrated into the Musa genome called BSV-OL Endogenous Pararetrovirus Sequences EPRVs. The aim of our study was to search for the genetic factor that activates EPRV expression during genetic cross hybridisation of two interspecific crosses - PKW (BB) x IDN 110 4x (AAAA) and P. batu (BB) x P. pipit 4x (AAAA)-. The study of the two FI progeny showed Mendelian segregation of the disease with half of the hybrids containing virus. The observation of BSV strain 01 EPRV segregation occurs in a homozygous state at Musa balbisiana genome only. Ten AFLP markers were selected in female M. balbisiana parents. The segregation analysis allowed a genetic map of the locus responsible of disease expression, BEL Banana streak virus expresses locus, to be proposed. These data indicate that a genetic mechanism is involved in BSV appearance, and suggest that a monogenic allelic system confers the role of carrier to the M. balbisiana parent. Two previously unidentified BSV strains in addition to BSV-Ol, have been detected in diseased hybrids: BSV-Imove (BSV-Im) and BSV-Gold Finger (BSV-GF) strains. The BSVOl and BSV-Im strains appeared in almost all diseased hybrids. In contrast, the BSV-GF strain was detected in only 49 percent of the diseased hybrids tested. The presence of BSVGF and BSV-Im EPRVs among parental and progeny genotypes, shows that the M. balbisiana genome contains at least two other pathogenic BSV EPRVs. Genetic analysis resulting from AFLP results showed that BSV-OL and BSV-Im EPRVs' expression depends on the same genetic factor, the BEL locus. Although the BSV-GF is not genetically linked to the BEL locus, the BSV-GF strain appearance and the activation of corresponding EPRV(s) seem to be subordinated to the BEL locus. So, the discovery of new BSV EPRVs linked to BEL locus suggests that BEL differs in nature from BSV EPRVs. Finally, we have investigated the regulation of EPRVs by investigating the “healthy” behaviour of M. balbisiana parents. A resistance to EPRVs expression has been demonstrated even when these parents are inoculated with BSV. Propositions as for the origin of integration mechanism of BSV are discussed.
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| Format: | thesis biblioteca |
| Language: | fre |
| Published: |
ENSAM
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| Subjects: | F30 - Génétique et amélioration des plantes, H20 - Maladies des plantes, Musa, virus des végétaux, hybridation interspécifique, gène, locus, résistance aux maladies, expression des gènes, ségrégation, Musa balbisiana, http://aims.fao.org/aos/agrovoc/c_4993, http://aims.fao.org/aos/agrovoc/c_5985, http://aims.fao.org/aos/agrovoc/c_26794, http://aims.fao.org/aos/agrovoc/c_3214, http://aims.fao.org/aos/agrovoc/c_24869, http://aims.fao.org/aos/agrovoc/c_2328, http://aims.fao.org/aos/agrovoc/c_27527, http://aims.fao.org/aos/agrovoc/c_6947, http://aims.fao.org/aos/agrovoc/c_4995, |
| Online Access: | http://agritrop.cirad.fr/509863/ http://agritrop.cirad.fr/509863/1/ID509863.pdf |
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