Morphogenetic response of the endangered species Aztekium ritteri (Cactaceae) co-cultivated in vitro with Agrobacterium rhizogenes

Effects on callus overproduction in cultures of shoots and calli of Aztekiu m ritteri were evaluated following co-cultivation with Agrobacterium rhizog enes strain LBA-9402. In vitro produced shoots and callus pieces were cultu red on MS medium supplemented with L2 vitamins, 1 mg/l 6-benzylamino-purine + 0.05 mg/l l-naphthaleneacetic acid, with or without bacterial inoculatio n. Callus overproduction was inhibited in co-cultivated shoot cultures, whi le noninoculated shoot cultures produced large amounts of callus. The trans formed nature of the inoculated shoots was confirmed by the transient GUS g ene expression. Large sections of inoculated callus were killed by the bact erium. This technique is useful to control callus overproduction in the mic ropropagation of Aztekium ritteri and other members of the Line B. Stromboc acti.