Stability at the phosphoglucoisomerase (PGI/2) locus in Festuca arundinacea plants regenerated from cell suspension and protoplast culture

A study was made of the phosphoglucoisomerase (PGI/2) phenotype of plants regenerated from suspension and protoplast culture originating from a Festuca arundinacea (2n = 6x = 42) plant with distinct PGI/2 phenotype. Of the regenerated plants from suspension culture, 20 were abnormal in that they deviated from the PGI/2 phenotype of the donor plant. Among the abnormal plants two distinct isozyme variants absent in the original donor, which were probably the result of point mutations, were recorded. There was evidence of deletions of specific PGI/2 alleles. This was confirmed cytologically by the reduced chromosome number found in the relevant cell suspension derived plants. There was also evidence that an active allele had been transformed into a null allele. All the plants regenerated from protoplast culture had the same PGI/2 phenotype as the donor plant but were hyperpolyploid. The loss of activity of individual PGI/2 alleles in plants derived from protoplasts was masked by gene duplication because of their hyperpolyploid nature. A high degree of instability was identified in nonregenerating calli. It was thought that abnormalities in the nonregenerating calli were affecting their potential to regenerate plants.Key words: Festuca arundinacea, somaclonal variation, phosphoglucoisomerase (PGI/2), chromosome instability, point mutations.