Frédéric Salmon

Radiotelemetry unravels movements of a walking insect species in heterogeneous environments.

The study of movements of individual organisms in heterogeneous environments is of primary importance for understanding the effect of habitat composition on population patterns. We developed a new experimental methodology to measure individual movements of walking insects, based on radiotracking. Our aims were to understand the link between habitat heterogeneity and moving patterns, and to characterize the movements with dynamic models of diffusion. We tracked individual movements of adults of Cosmopolites sordidus (Coleoptera: Curculionidae) with passive radio frequency identification (RFID) tags under different field management practices. Diffusion models based on recapture data indicated a subdiffusive movement of this species. Substantial variation was found between individual paths, but this variation was not sex dependent. Movement of released C. sordidus was affected by banana planting pattern and the presence/absence of crop residues but not by the presence of a cover crop between rows of bananas or by banana variety. These results show that the RFID technology is useful for evaluating the dispersal parameters of cryptic insects in heterogeneous environments.

Marker-assisted breeding of Musa balbisiana genitors devoid of infectious endogenous Banana streak virus sequences

Breeding new interspecific banana hybrid varieties relies on the use of Musa acuminata and M. balbisiana parents. Unfortunately, infectious alleles of endogenous Banana streak virus (eBSV) sequences are present in the genome of Musa balbisiana genitors. Upon activation by biotic and abiotic stresses, these infectious eBSVs lead to spontaneous infections by several species of Banana streak virus in interspecific hybrids harboring both Musa acuminata and M. balbisiana genomes. Here we provide evidence that seedy M. balbisiana diploids display diverse eBSV allelic combinations and that some eBSVs differ structurally from those previously reported. We also show that segregation of infectious and non-infectious eBSV alleles can be achieved in seedy M. balbisiana diploids through self-pollination or chromosome doubling of haploid lines. We report on the successful breeding of M. balbisiana diploid genitors devoid of all infectious eBSV alleles following self-pollination and on the potential of breeding additional M. balbisiana diploid genitors free of infectious eBSVs by crossing parents displaying complementary eBSV patterns. Our work paves the way to the safe use of M. balbisiana genitors for breeding banana interspecific hybrid varieties with no risk of activation of infectious eBSVs.

Green-life of pink banana (Musa spp., cv. Figue Rose Naine): determination of the optimum harvesting date.

Summary The context for the production of bananas for export is characterised by a wide range of transport-times between producer and importer countries, and by the use of a single cultivar of banana (Musa spp., AAA group, cv. Cavendish Grande Naine). We investigated the green-life of pink banana (Musa spp., AAA group, Red sub-group, cv. Figue Rose Naine) for the different physiological ages of banana fruit, measured in degree-days (°Cd). We measured the temperature threshold of pink banana (19.8°C) and showed that the green-life of pink banana decreased linearly with the physiological age of the fruit. Thus, we confirm the validity of the relationship between accumulated heat units during fruit growth and green-life that was previously established for Cavendish banana.We searched for the optimum physiological age (°Cd) for harvest, in order to ensure a green-life that fulfilled the requirements for transport and that maximised fruit weight. For Martinique, the optimum flowering-to-harvest interval was found to be 548°Cd, to ensure 25 d of green-life, as required for transport, and to maximise fruit size. We showed that fruit weight was not a good indicator on which to select bananas for harvest in order to ensure a particular green-life. This is the first time that guidance has been proposed for the transport and export of a non-Cavendish banana. These results may assist other producer countries that wish to diversify their banana exports by growing pink banana.

Evolution of the Banana Genome (Musa acuminata) Is Impacted by Large Chromosomal Translocations

Abstract Most banana cultivars are triploid seedless parthenocarpic clones derived from hybridization between Musa acuminata subspecies and sometimes M. balbisiana. M. acuminata subspecies were suggested to differ by a few large chromosomal rearrangements based on chromosome pairing configurations in intersubspecies hybrids. We searched for large chromosomal rearrangements in a seedy M. acuminata ssp. malaccensis banana accession through mate-pair sequencing, BAC-FISH, targeted PCR and marker (DArTseq) segregation in its progeny. We identified a heterozygous reciprocal translocation involving two distal 3 and 10 Mb segments from chromosomes 01 and 04, respectively, and showed that it generated high segregation distortion, reduced recombination and linkage between chromosomes 01 and 04 in its progeny. The two chromosome structures were found to be mutually exclusive in gametes and the rearranged structure was preferentially transmitted to the progeny. The rearranged chromosome structure was frequently found in triploid cultivars but present only in wild malaccensis ssp. accessions, thus suggesting that this rearrangement occurred in M. acuminata ssp. malaccensis. We propose a mechanism for the spread of this rearrangement in Musa diversity and suggest that this rearrangement could have played a role in the emergence of triploid cultivars.

Preharvest temperature affects chilling injury in dessert bananas during storage.

BACKGROUND The effect of temperature on chilling injury during fruit growth was studied in a new banana hybrid CIRAD925 in which seasonal variability in chilling susceptibility was observed when fruits were stored at 13 °C. RESULTS The relationship between the response to chilling (presence/absence) and the temperature during banana fruit growth was examined with a logistic regression model. An explanatory variable XN , P was defined as the mean temperature during a period, expressed in weeks, which began N week(s) after flowering and lasted P week(s). The model was calibrated with 143 bunches with a green life of 30 ± 5 days and validated with 156 bunches grown in six plots under different growing conditions. Chilling injury was best predicted by the mean temperature during the period beginning 1 week after flowering and lasting 5 weeks (X1,5 ). Above a mean temperature of 24.1 °C in the period concerned, banana fruits had a 95% probability of chilling injury at 13 °C. Below a temperature of 23.4 °C, banana fruits only had a 5% probability of chilling injury. CONCLUSION The results provide a tool to predict chilling susceptibility in banana fruit whatever the thermal conditions in tropical regions.