MITOCHONDRIAL-DNA VARIATION IN PLANTS REGENERATED FROM EMBRYOGENIC CALLUS-CULTURES OF CMS TRITICALE

The mitochondrial DNA (mtDNA) organization of primary hexaploid cytopl asmic male-sterile (CMS) triticale regenerants containing Triticum tim opheevi cytoplasm was analysed by hybridization experiments and compar ed with the mitochondrial genome organization of the corresponding reg enerants with maintainer cytoplasm. Callus cultures had been derived f rom immature embryos, and 623 triticale plants were regenerated via so matic embryogenesis after three to four subcultures. The chondriome of 159 regenerants was investigated with regard to somaclonal variation. Six different mitochondrial gene probes and four different restrictio n enzymes were used for Southern blot analyses by the non-radioactive digoxigenin labeling technique. Alloplasmic regenerants showed a gain or loss of hybridization signals up to a high percentage, while euplas mic ones revealed only minor variability with respect to band stoichio metries. In 24 cases rearrangements in the mtDNA were proved. We suppo se that recombination processes and selective amplification events are responsible for these findings.