Multi-site survey of the activation of eBSV OL1 and GF7 infectious alleles in a population of French Clair plantains derived from vitroplants. [P.43]

Banana streak viruses (BSV) are mealybug-transmitted badnaviruses. The genomes of interspecific banana varieties, including plantains, harbor infectious alleles of endogenous BSV sequences (eBSV), whose activation by abiotic stresses leads to spontaneous BSV infections. In Guadeloupe, activation of infectious alleles OL1 and GF7 is the main source of infections by BSOLV and BSGFV, respectively, in banana interspecific varieties, including widely cultivated French Clair plantain. The first multi-site survey of the activation of eBSV infectious alleles is being carried out in Guadeloupe. It focuses on infectious alleles OL1 and GF7. Nine experimental plots with 222 to 376 French Clair plants each were designed and deployed throughout Guadeloupe's south Basse Terre area at altitudes ranging from 15 to 300m. Planting material originated from two batches of vitroplants. Activation of OL1 and GF7 infectious alleles are monitored by immuno capture PCR (IC-PCR), using a polyclonal antiserum and BSOLV- or BSGFV-specific primers. Indexings were performed on vitroplants at the end of the weaning stage, prior to planting, on a 1:10 sampling. They showed that cell culture resulted in 12% and 15% activation levels for OL1 infectious allele for each batch of vitroplants, respectively. Activation levels of infectious allele GF7 was only 1% for both batches. These results confirm previous observations made on other AAB plantains. Indexings were also performed on all plants of the nine plots at the end the flowering stage. Activation levels varied between plots, from 0.3 to 6% for infectious allele OL1, and from 0% to 3% for infectious allele GF7. Overall, only one infected plant displayed leaf symptoms and no visible impact of BSV infections on plant growth and fruit production was noted. Activation rates will be monitored again at the end (flowering stage) of the second cycle. This experiment helps formulating a BSV risk management strategy