An improved media system for high regeneration rates from barley immature embryo-derived callus cultures of commercial cultivars

Improved plant regeneration from tissues of elite barley cultivars (Hordeum vulgare L.) will facilitate their genetic transformation. Significant improvements in green plant regeneration from tissues of `Morex' and `Harrington' were achieved by modifying iron and boric acid concentrations, and by adding 6-benzyl aminopurine (BAP) to the culture medium. The plant regeneration in response to various concentrations of eight micronutrients indicated that MS concentrations were appropriate for K[H.sub.2]P[O.sub.4], NaMo[O.sub.4], MnS[O.sub.4], KI, Co[Cl.sub.2], and ZnS[O.sub.4]. Increased [H.sub.3]B[O.sub.3] (0.75 mM) and decreased FeS[O.sub.4] (0.05 mM) improved green plant regeneration. The addition of 0.1 mg/L BAP to maintenance media resulted in an increase in regeneration. The effect of these changes, in combination with previously reported improvements, was assessed by comparing regeneration responses of eight cultivars and elite breeding lines on the improved media versus the original MS-based media. Green plant regeneration was improved for all tested lines and cultivars, from an average of two green plants to 29 green plants per Petri dish. Regeneration rates from all elite lines and cultivars on the improved media exceeded that of the highly regenerable `Golden Promise' on the original media, indicating that poor plant regeneration should no longer limit the transformation of modern North American cultivars.