SELECTING LEMON PROTOPLASTS FOR INSENSITIVITY TO PHOMA-TRACHEIPHILA TOXIN AND REGENERATING TOLERANT PLANTS

Protoplasts isolated from an embryogenic callus line of 'Femminello si racusano' lemon [Citrus limon (L,) Burm, f.] were incubated with 0.5 m u M toxin of Phoma tracheiphila (Petri) Kanc, et Ghik., the pathogen o f the mal secco disease, which seriously damages most commercial lemon cultivars, Two toxin-tolerant cell lines were obtained, and plants we re regenerated from each line, The selected protoclones were tested fo r their tolerance by exposing callus and protoplasts to the toxin and detecting chitinase (a pathogenesis-related protein) among the intra- and extracellular proteins extracted from leaves of regenerated plants and suspension culture, respectively, The tolerance of the protoclone s in these tests was equivalent to the tolerant lemon cultivar Monache llo, and they were substantially more tolerant than their mother culti var Femminello siracusano.