SISTER-CHROMATID EXCHANGES IN CULTURED IMMATURE EMBRYOS OF WHEAT SPECIES AND REGENERANTS

Immature embryos of Triticum aestivum (ten cultivars and lines), T. du rum, T. dicoccum and T. monococcum were cultured in vitro on MS medium supplemented with 1 or 2 mg/l of 2,4-D and 20 or 30g/l of sucrose for 3 days and processed to score sister chromatid exchanges (SCEs) per c hromosome. Media components affect DNA replication from the start of t he culture. The SCE frequencies were dependent on the genotype and wer e not correlated with the degree of ploidy. They increased after doubl ing of the concentration of 2,4-D and/or sucrose, except in one cultiv ar of T. aestivum. The mean numbers were lower than observed in root m eristems of T. aestivum (two cultivars) and T. dicoccum. Immature embr yos of regenerants of T. aestivum (one cultivar) and T. durum demonstr ated variable SCE frequencies, which may have been caused by mutations in the parental cell cultures. In the T. aestivum embryos the lowest frequencies were found in regenerants obtained from explants with the highest frequencies.