Radiossensitivity of two propagules of citrus

Studies have shown that the radiossensitivity in plants varies depending on the varieties and the propagules used in mutagenic treatment. The purpose of this study was to evaluate the radiossensitivity of two types of propagules (buds and in vitro segments of epicotyl) in `Murcott` tangor, `Thomas` and `Fremont` mandarins and `Rangpur` lime (only in vitro segments of epicotyl) and to compare the gamma-rays sensitivity among propagules and among varieties. The following doses were used: 0, 10, 20, 30, 40 and 50 Gy of gamma-rays. The parameters shoot mortality and shoot height, for experiment of bud irradiation, and number of regenerated shoots per explant and percentage of responsive explants, for experiment of peicotyl segments irradiation were evaluated after 60 days. The mutagenic doses tested in buds caused significant reduction in shoot height of all varieties. In the experiment of irradiation of in vitro segments of epicotyl, only `Murcott` tangor and `Rangpur` lime showed significant reduction in the number of regenerated shoots per explant, due to the increase of mutagen doses. Results indicate that radiossensitivity of in vitro (segments of epicotyl) and in vivo (buds) propagules is variable depending on the variety. Also, in some cases the in vitro propagules are more sensitive, to irradiation and in other cases, there is no differential sensibility.