Browsing by Author "Dollet, M."

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    Genetic diversity among coconut varieties for susceptibility to Cape St Paul Wilt Disease
    (2008) Baudouin, L.; Dery, S.K.; Philippe, R.; Owusu Nipah, J.; Nkansah-Poku, J.; Quaicoe, R.N.; Arthur, R.; Dare, D.; Yankey, N.; Dollet, M.
    The CSPWDis the Ghanaian formof lethal yellowing disease (LYD) of coconut, caused by a phytoplasma and has been active in Ghana since 1932. The paper updates the results of screening trials conducted with 38 pure and hybrid coconut varieties since 1981. Although no variety was found totally resistant, a wide range of susceptibility level was observed: almost all SGD were still unaffected, while the local WAT had almost totally disappeared, additive values were calculated for the parental varieties and it was shown that, in the average, hybrids are slightlymore susceptible than predicted by a purely additive model. According to this genetic model, the SGD 9 VTT hybrid will be appreciably less susceptible than the MYD 9 VTT currently being used for replanting devastated farms in Ghana. Our results tend to confirm the general trend that cultivars from the Pacific group (especially the Dwarfs) are less susceptible than the Indo-Atlantic cultivars. Proposals are made to adapt planting material to the risk level. Genetic control can only be efficient if it is considered as a link in a chain of control measures involving the choice of a proper planting site, goodmanagement and early eradication of diseased trees.
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    Recent lethal yellowing outbreak: why is the Malayan Yellow Dwarf Coconut no longer resistant in Jamaica?
    (Springer-Verlag, 2008) Lebrun, P.; Baudouin, L.; Myrie, W.; Berger, A.; Dollet, M.
    In Jamaica, the Maypan, a hybrid of Malayan Yellow Dwarf (MYD) and Panama Tall coconut, previously considered highly resistant, is currently being devastated by an epidemic outbreak of lethal yellowing disease. There are several possible causes for this change. In this study, we checked that affected planting material in Jamaica is genetically the same as the material shown to be resistant. We compared the deoxyribonucleic acid (DNA) of MYD sampled in four locations in Jamaica with a reference DNA of the same cultivar collected in five different countries. The results of our analyses showed more variation at 34 simple sequence repeat loci in Jamaica than in the rest of the world providing clear evidence for the presence of about 16% of alleles that do not match the usual typical MYD genotype. These alleles appear to have already been present in the introduced germplasm. This rules out a possible cause of the new outbreak: The observed heterogeneity may have caused some loss of resistance but is insufficient to explain a massive outbreak of the disease
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    Recent lethal yellowing outbreak: why is the Malayan Yellow Dwarf Coconut no longer resistant in Jamaica?
    (2008) Berger, A.; Myrie, W.; Baudouin, L.; Lebrun, P.; Dollet, M.
    In Jamaica, the Maypan, a hybrid of Malayan Yellow Dwarf (MYD) and Panama Tall coconut, previously considered highly resistant, is currently being devastated by an epidemic outbreak of lethal yellowing disease. There are several possible causes for this change. In this study, we checked that affected planting material in Jamaica is genetically the same as the material shown to be resistant. We compared the deoxyribonucleic acid (DNA) of MYD sampled in four locations in Jamaica with a reference DNA of the same cultivar collected in five different countries. The results of our analyses showed more variation at 34 simple sequence repeat loci in Jamaica than in the rest of the world providing clear evidence for the presence of about 16% of alleles that do not match the usual typical MYD genotype. These alleles appear to have already been present in the introduced germplasm. This rules out a possible cause of the new outbreak: The observed heterogeneity may have caused some loss of resistance but is insufficient to explain a massive outbreak of the disease.
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    The spliced leader RNA gene array in phloem-restricted plant trypanosomatids (Phytomonas) partitions into two major groupings : epidemiological implications
    (2001) Dollet, M.; Sturm, N.R.; Campbell, D.A.
    The arbitrary genus Phytomonas includes a biologically diverse group of kinetoplastids that live in a wide variety of plant environments. To understand better the subdivisions within the phytomonads and the variability within groups, the exon, intron and non-transcribed spacer sequences of the spliced leader RNA gene were compared among isolates of the phloem- restricted members. A total of 29 isolates associated with disease in coconut, oil palm and red ginger (Alpinia purpurata, Zingibreaceae) were examined, all originating from plantations in South America and the Caribbean over a 12-year period. Analysis qf non-transcribed spacer sequences revealed 2 main groups, I and II ; group II could be further subdivided into 2 subgroups, IIa and IIb. Three classes of spliced leader (SL) RKA gene were seen, with SLI corresponding to group 1, SLIIa to group Ila, and SLIIb to group IIb. Two isolates showed some characteristics of both major groups. Group- specific oligonucleotide probes for hybridization studies were tested, and a multiplex amplification scheme was devised to allow direct differentiation between the 2 major groups of phloem-restricted Phytomonas. These results provide tools , for diagnostic and molecular epidemiology of plant trypanosomes that are pathogenic for commercially important flowers and palms.