Karyotype analysis in almond

Abstract

Knowledge of karyotype relationships is an important prerequisite for effective plant genetic and breeding studies. In Prunus species, karyotype analysis has been reported mainly from apricot and peach for mitotic cells from root tips or meiotic cells from flower buds,. Studies on Prunus karyotyping are frequently reported in diverse publications often having limited readership. In this study, different methods for the preparation of metaphase chromosomes have been evaluated using almond root tips. By modifying and updating these methods, an improved technique for counting chromosomes in almond has been developed. Root tips were first placed in cold water for 4 hours at 0°C, and treated with 0.2% colchicine for 3–4 hours at 5°C. They were then fixed in: 6 methanol, 3 propionic acid and 2 chloroform; for 24 hours at 5°C, and stored in ethanol (70%). Root tips were hydrolyzed in 1N HCl at 60°C for 20 minutes then stained in acetic acid orcein (45%) for 2 hours. Results allow the identification of almond chromosomes in the different stages of the mitosis. This technique has been successfully applied to other Prunus species including peach and apricot, utilizing either root tips or pollen mother cells.