Relative DNA content of cells in Festuca Arundinacea and Dactylis Glomerata calli of different ages

Abstract

Experiments were conducted to determine changes in nuclear DNA content in cells of tall fescue ( Festuca arundinacea) and orchardgrass ( Dactylis glomerata) embryo-derived calli ranging in age from 3 to 24 weeks. Calli were induced and maintained on a modified Murashige-Skoog medium containing 22.6 μM of 2,4-dichlorophenoxyacetic acid. Calli were divided with one pieces being fixed in 3:1 ethanol: acetic acid and the other transfered too fresh maintenance medium at 3, 6, 9, 12, 18 and 24 weeks after initial plating of mature embryos. Fixed calli were processed through a cold hydrolysis technique and Feulgen stained. Stained callus pieces were squashed in 45% acetic acid and relative DNA contents were measured with a microscope cytophotometer. Results showed predominately 2C nuclei in calli of both species regardless of callus age. More cells with high DNA contents ( ≧4 C ) were found in orchardgrass than in tall rescue calli. The proportion of 2C cells increased with increasing callus age, especially in tall fescue. Cells of various sizes and shapes were observed in calli of both species and very large cells with small (2C) nuclei were common in callus tissue of all ages. The mitotic index was low and decreased with increasing callus age, especially in tall fescue. Nuclei with 2C4C, 4C8C, or less than 2C, amounts of DNA may be due to anuploidy.