In order to obtain basic data for future research in mutation breeding through "in vitro" technology in sweet orange cv. Pêra, gamma rays sensitivity of different types of explants was analyzed. After irradiation the following observations were carried out: response of explants, number of embryoids and adventitious buds, callus weight and rooting formation. Different results were obtained according the explant used. For irradiated nucellus, the dose was 20-40 Gy and for embryogenic callus 120 Gy is indicated. For irradiation of cotyledons originated from nucellar embryoids the use of 40 Gy of gamma rays was recommended.
gamma rays; Citrus sinensis Osbeck; nucellus; embryogenic callus; adventitious buds