SANITATION TRIALS FOR THE PRODUCTION OF VIRUS-FREE FIG STOCKS

Heat therapy, meristem tip culture in vitro and a combination of both techniques were used for obtaining fig (Ficus carica) plants free from some viruses associated with fig mosaic, a disease with a worldwide distribution. Source plants were two field-grown adult fig accessions from a germplasm repository of the University of Bari (Italy) that showed severe and mild symptoms of mosaic, respectively, and two symptomless fig seedlings grown under screen. Adult plants were infected by Fig mosaic virus (FMV), Fig latent virus 1 (FLV-1) and Fig badnavirus 1 (FBV-1). Seedlings were infected by FLV-1 and FBV-1. Progeny of explants subjected to meristem tip culture were still infected by FMV (93.8% elimination). This virus, however, was eradicated (100% sanitation) by shoot tip culture combined with heat therapy, or in vitro heat therapy. High sanitation rates from FLV-1 (81 to 100%) were also registered with all sanitation procedures employed, such as in vitro heat therapy alone (two cycles) or combined with tissue culture. By contrast, the DNA virus FBV-1 resisted all attempts of elimination, a behaviour that confirms indirectly its hypothesized integration in the fig genome.