Intertribal somatic hybridization between rapid cycling Brassica oleracea L. and Camelina sativa (L.) Crantz

Black spot, caused by Alternaria brassicae and A. brassicicola, is an impor tant disease in all Brassica oleracea vegetables. Sufficient resistance to the pathogen is not found within the species, nor in species that readily c ross to B. oleracea. Camelina sativa (false flax) is highly resistant to Al ternaria spp. and has, in addition, other desirable characters for the impr ovement of B. oleracea. Protoplast fusions were performed between rapid cyc ling B. oleracea (tribe Brassiceae), which has good regenerability, and C. sativa (tribe Sisymbrieae) by polyethylene glycol (PEG) treatment. The B, o leracea fusion partner was inactivated by treatment with iodoacetate. C. sa tiva has poor regenerability; hence, no pretreatment was needed for this sp ecies. The protoplasts were cultured using a feeder layer system. A total o f 2903 calli were isolated from the fusions. Fourteen of these initiated sh oots, i.e., 0.5% regeneration frequency. Approximately 110 shoots were exci sed from 6 of these calli and transferred to rooting medium. Rooted plantle ts grew vigorously in vitro and flowering was frequently observed. However, establishment of rooted shoots in soil was unsuccessful. Hybrid identity w as confirmed by intermediate shoot morphology, RAPD marker analysis, and fl ow cytometric estimation of nuclear DNA content.