Somaclonal variation from cultured immature embryos of sister lines of rye differing in heterochromatic content

Somaclonal variation occurred among rye plants regenerated from cultured immature embryos of five sister lines that differed in their content of telomeric heterochromatin. Variation was observed in morphology, chromosome number, and secalin seed storage proteins. Morphological variation was present in 9.7% of the regenerants and included albinism and variegation, which appeared in different frequencies among the lines. Chromosome variation occurred in 15.8% of the regenerants and included translocations, tetraploidy, and trisomy in addition to meiotic disturbances such as centromere misbehaviour and asyndesis. Some of the regenerated plants were mosaic for the structural and numerical chromosome aberrations. The nature of the chromosome variation also differed among the lines. A single variant in the 40K γ-secalins was detected. The occurrence of variation is discussed in relation to differences in morphogenetic response of the rye lines and to the genotypic component of instability in culture.Key words: somaclonal variation, immature embryo culture, rye heterochromatin, chromosome variation, secalins.&nbsp

Variation in telomeric heterochromatin in somaclones of rye

Somaclonal variation in telomeric heterochromatin was detected by in situ hybridization with the het 1 probe, which hybridizes to a 380-bp repeated sequence family. In a control cultivar, Gazelle, large blocks of signal were detected at the telomeres but not at the centromeres or the secondary constrictions. In the donor line, 7R - , labelling was restricted to small telomeric dots, confirming that the large telomeric blocks had been removed in selection of this line. In situ hybridization with the het 1 probe to chromosomes of selfed progeny from 50 plants regenerated from independent cultured immature embryos of the 7R - line revealed variant patterns for three regenerants. In the progeny of two regenerants, a new interstitial hybridization site was detected on the short arm of a submetacentric chromosome. This site was not at the nucleolus organizer. In the progeny of the third regenerant two changes were detected: an enlarged telomeric block on the long arm of an unidentified chromosome and an interstitial site on the long arm of chromosome 6. All three regenerated plants had shown normal morphology and meiotic behaviour. The identification of somaclonal variants in telomeric heterochromatin provides further evidence for variation in repeated DNA sequences in plant tissue culture