Embrapa Cassava & Fruits Research with citrus aim at obtaining somatic hybrids, particularly rootstocks, better adapted to the Brazilian tropical cultivation conditions than the varieties currently in use. The main objectives are the selection of genotypes tolerant to drought and aluminum toxicity, tolerant/resistant to Phytophthora foot rot and citrus tristeza virus, besides being well adapted to high planting densities. The following varieties have being used as protoplast sources: Cleopatra, Sunki and 'Swatow' mandarins, Rangpur lime selections Santa Cruz and Santa Bárbara, Volkamer lemon and Mazoe rough lemon, 'Hamlin' sweet orange selections CNPMF 04 and CNPMF 20, sour orange selections Common and Narrow Leaf, Troyer citrange, Citrus amblycarpa and Microcitrus papuana. The study focused on obtaining and cultivating embryogenic calli. Ovules taken from immature fruits were used in a modified MT culture medium, containing 50g.L-1 of sucrose and 500 mg.L-1 of malt extract, solidified with 7 g.L-1 of agar. In general, callus induction in the studied varieties was observed between the 6th and the 8th weeks of cultivation. In the Rangpur lime, 'Hamlin' sweet orange, Cleopatra and 'Swatow' mandarins and Troyer citrange, the percentage of callus formation was equal or superior to 50%. The Cleopatra mandarin stood out with a percentage near 70% of callus formation.
Embryogenesis; Citrus spp.; Poncirus trifoliata; Microcitrus papuana
