Risk assessment of the activation of infectious alleles of endogenous banana streak viruses in Guadeloupe. [P.44]

Edible banana arose from combinations of species Musa acuminata, whose genome is denoted A, and M. balbisiana, whose genome is denoted B. The nuclear genome of all known diploid BB genitors harbors infectious alleles of endogenous Banana streak viruses (eBSV). Their activation by abiotic stresses leads to spontaneous infections by cognate viruses in diploid AB, triploid AAB and tetraploid AAAB interspecific hybrids. Banana streak viruses are naturally transmitted by several species of mealybug. A comprehensive risk assessment study of the activation of infectious eBSV alleles was undertaken in Guadeloupe. Firstly, a large scale prevalence survey was carried out for viral species BSOLV, BSGFV and BSIMV among the main cultivated banana types. Overall prevalence levels were low for BSOLV (0.85%) and BSGFV (0.99%). No sample was found infected by BSIMV. No impact of BSV in infected plants could be observed, with only one infected sample displaying typical BSV leaf streak symptoms. The comparison of prevalence levels monitored in AAB genotypes and in AAA genotypes suggests that BSOLV and BSGFV infections in AAB genotypes result preferentially from the activation of eBSV infectious alleles rather than from vector-borne transmission. Statistical analyses showed a positive correlation between prevalence levels and altitude. Secondly, the activation of eBSOLV and eBSGFV infectious alleles was monitored under field conditions over two production cycles in triploid plantains French Clair (AAB genotype) and Pelipita (ABB genotype), using a random block assay and plants originating from either cell culture or horticultural multiplication. Activation rates were significantly higher for infectious allele GF7 than for infectious allele OL1 and also higher in French Clair than in Pelipita. Results pointed to an influence of the mode of production of planting material on activation, and to an absence of impact of BSGFV and BSOLV infection on production.