High frequency of cytogenetic aberration in transgenic oat (Avena sativa L.) plants

Cytological abnormalities were observed in transgenic oat (Avena sativa L. cv. GAF/Park-1) produced by microprojectile bombardment of mature seed-derived highly regenerative tissues. Of the plants from 48 independent transgenic lines examined, plants from only 20 lines (42%) were karyotypically normal (2n=6x=42) without detectable chromosomal aberrations; plants from 28 lines (58%) had chromosomal variation, i.e. aneuploids and structural changes. No significant difference in cytological aberration was observed between the two different culturing systems used for transformation: 57% chromosomal abnormalities in plants derived from D'BC2 medium (2.0 mg/l 2,4-D, 0.1 mg/l BAP and 5.0 &mgr;M cupric sulfate) used for tissue initiation and maintenance and 60% in plants from tissue initiated on D'BC2 and maintained on DBC3 (1.0 mg/l 2,4-D, 0.5 mg/l BAP and 5.0 &mgr;M cupric sulfate). Comparative differences in chromosomal status frequently occurred among plants regenerated from the same T(0) line. The most common cytological aberration in transgenic plants was aneuploidy, followed by deletion of chromosomal segments; no change in ploidy level was observed. In contrast, nontransgenic plants, regenerated from tissues comparable in age and culture media to that used for transgenic tissues, had a much lower percentage of karyotypic abnormality (0-14%). Our data indicate that some stress(es) imposed by the transformation process, e.g. osmotic treatment, bombardment and selection, leads to cytological variation in transgenic oat plants, an observation similar to that observed in our recent studies with transgenic barley plants.