Genotype and Media Effects on Callus Formation and Regeneration in Barley1

Abstract
The success of barley (Hordeum vulgare L.) cell and tissue culture research depends upon reliable callus culture and plant regeneration procedures. The objective of this study was to identify callus‐inducible genotypes, to evaluate media for effectiveness in promoting callus growth, and to identify genotypes capable of regenerating plants. Ninety‐one barley genotypes were evaluated for initiation and maintenance of callus growth. Forty‐five of the genotypes initiated callus, while 46 did not. Callus cultures were maintained by subculturing onto fresh media at monthly intervals. Genotypic variation was noted for longevity and rate of growth of callus cultures. Calli of several genotypes were maintained for more than 2 years. Murashige and Skoog's (MS) media promoted more callus initiation and provided better callus maintenance than media of Blaydes (B), Gamborg et al. (B5), Norstog (N), and Shenk and Hildebrandt (SH). Frequencies of callus initiation were high when either 0.5, 1.0, or 2.0 mg/L of 2,4‐D (2,4‐dichlorophenoxyacetic acid) were added to the media. There were significant genotype ✕ media interactions for callus initiation. Established calli were transferred to differentiation media to promote plant regeneration. Although there were genotypic differences in regeneration, the overall frequency was low (15%). Seventy percent of the regenerated plants were from calli of the cv. Akka and Wisconsin experimental selection X2387‐3.