Hybridization and tissue culture of Hordeum vulgare × Elymus canadensis

Canada wild rye (CWR, Elymus canadensis L.) is winter hardy, drought tolerant, and resistant to barley yellow dwarf virus. Crosses between CWR and barley (Hordeum vulgare L.) produce sterile F1 hybrids. The objectives of this study were to compare callus and regeneration response with different media, to assess the effectiveness of in vitro colchicine treatment, and to determine whether chromosome changes occurred in regenerated plants. 'Betzes' barley was crossed with CWR and hybrid plants were recovered using embryo rescue. Immature inflorescences of the hybrids were placed on Gamborg's B5 medium supplemented with two levels of sucrose and two levels of 2,4-dichlorophenoxyacetic acid (2,4-D) to initiate callus growth. Media were solidified with either agar or gellum gum. Beginning at 8 weeks, a portion of the calli was placed on medium containing 20 mg/L colchicine for 10 days to double the chromosome number. Callus initiation was significantly greater with media containing gellum gum than with agar and with 5 mg/L 2,4-D than with 20 mg/L 2,4-D. Plantlet regeneration response to media paralleled the callus response. Chromosome counts of 1864 regenerants showed that 12% had chromosome numbers other than the expected 2n = 21. Chromosome numbers in regenerants ranged from 7 to 44. There was no benefit to using colchicine in the media. Evidence of chromosome recombination was observed. A backcrossing program to barley was initiated using all regenerants, while concentrating on plants with 2n = 42, which had some restored female fertility.Key words: somaclonal variation, intergeneric hybridization, Canada wild rye.