PLANT-REGENERATION AND CHROMOSOME INSTABILITY IN TISSUE-CULTURE OF ELYMUS-CANADENSIS X ELYMUS-TRACHYCAULUS F1-HYBRID

Callus was induced from pieces of immature inflorescence of a sterile F1 hybrid (2n = 4x = 28) between Elymus canadensis and E. trachycaulus on MS medium supplemented with 2 mg/L of 2,4-D. Calli were of two types: compact or soft. Regeneration occurred predominantly from the compact callus. Although some plantlets were obtained on the callus initiation medium, the frequency of regeneration increased considerably when the callus was transferred to an auxin-free MS medium. Deliberate aging of callus induced cytological instability and variation in chromosome number of the regenerants. Five of the 43 regenerated plants had deviant chromosome numbers, including an octoploid (2n = 8x = 56). Chromosome pairing in the octoploid plant suggests that it originated through chromosome doubling.