ABSTRACT
Infectious alleles of endogenous banana streak viruses (eBSVs) are present in the genome of all banana interspecific cultivars, including plantains and cooking types. Activation of these infectious eBSV alleles by biotic and abiotic stresses leads to spontaneous infections by cognate viruses and raises concerns about their ability to promote outbreaks of banana streak viruses under field cultivation conditions. We undertook a comprehensive risk assessment study of infectious eBSV alleles of species BSOLV, BSGFV and BSIMV in banana interspecific cultivars in Guadeloupe, a tropical island of the Caribbean where bananas are grown for export and local markets. We carried out a prevalence survey of BSOLV, BSGFV and BSIMV species in a range of cultivars grown in Guadeloupe. Our results suggest that BSOLV and BSGFV infections arise from the activation of infectious eBSVs rather than vector-borne transmission and point to a correlation between altitude and infection rates in interspecific hybrids with AAB genotypes. We studied the dynamics of activation of infectious eBSOLV and eBSGFV alleles by tissue culture and field cultivation in a range of cultivars. We showed that tissue culture and field cultivation trigger distinct activation pathways, resulting in distinct activation patterns. We also showed that activation decreased over time during cell culture and field cultivation and that BSV infections arising from the activation of infectious eBSV alleles cause symptomless infections in the most cultivated plantain in Guadeloupe, French Clair. Overall, our study shows that the risk of BSV outbreaks resulting from the activation of infectious eBSVs in plantain originating from vegetative multiplication is negligible in Guadeloupe.
ABSTRACT
Chromosome rearrangements and the way that they impact genetic differentiation and speciation have long raised questions from evolutionary biologists. They are also a major concern for breeders because of their bearing on chromosome recombination. Banana is a major crop that derives from inter(sub)specific hybridizations between various once geographically isolated Musa species and subspecies. We sequenced 155 accessions, including banana cultivars and representatives of Musa diversity, and genotyped-by-sequencing 1059 individuals from 11 progenies. We precisely characterized six large reciprocal translocations and showed that they emerged in different (sub)species of Musa acuminata, the main contributor to currently cultivated bananas. Most diploid and triploid cultivars analyzed were structurally heterozygous for 1 to 4 M. acuminata translocations, highlighting their complex origin. We showed that all translocations induced a recombination reduction of variable intensity and extent depending on the translocations, involving only the breakpoint regions, a chromosome arm, or an entire chromosome. The translocated chromosomes were found preferentially transmitted in many cases. We explore and discuss the possible mechanisms involved in this preferential transmission and its impact on translocation colonization.
