Somatic hybridization in the Gramineae: Saccharum officinarum L. (sugarcane) and Pennisetum americanum (L.) K. Schum. (pearl millet)

Somatic hybrid cell lines with embryogenic capacity were obtained by fusion of protoplasts isolated from an embryogenic cell line of sugarcane with inactivated protoplasts of an S-(2-aminoethyl)-L-cysteine (Aet-Cys)-resistant cell line of pearl millet. Initial selection for putative hybrids was performed by plating protoplast-derived microcolonies onto medium containing 300 mug of Aet-Cys per ml. Calli growing in the presence of Aet-Cys were screened with respect to their electrophoretic pattern of phosphogluconate dehydrogenase (6-phospho-D-gluconate; EC 1.1.1.44), a dimeric enzyme. The somatic hybrid calli showed both parental homodimer bands plus an intermediate heterodimer band. Somatic hybrid lines were characterized further by electrophoretic patterns of shikimate dehydrogenase (shikimate; EC 1.1.1.25) and arylesterase (aryl-ester hydrolase; EC 3.1.1.2). All cell lines expressed the nuclear genomes of both parents. Use of a maize ribosomal DNA probe allowed the identification of diagnostic ribosomal DNA fragments in Xba I digests of total DNA in both parents and the somatic hybrids. The somatic hybrid lines carried both sugarcane and pearl millet ribosomal DNA fragments. The somatic hybrid calli formed somatic embryos. The banding pattern of phosphogluconate dehydrogenase from the somatic embryos was similar to that of the somatic hybrid calli.