Chromosomal numbers in parental and hybrid plants of the genus Echeveria

Echeveria is an American genus of approximately 127 species. This genus is distributed from southwest Texas to central and South America, Mexico being the country where most species are concentrated. Many of the species of this genus are cultivated as ornamentals for the beauty of their leaves and flowers. The objective of the present study was the determination of the chromosome number of: Echeveria chihuahuensis, Echeveria colorata, and the hybrids generated from some of these parental species: E. chihuahuensis × E. colorata. Methodology: roots of each of the study species were pre-treated in cold water for 24 h and fixed in Farmer's reagent. After two days the roots were hydrolyzed in 1 N hydrochloric acid and stained with Schiff's reagent. The preparations were made by the squash method and the best fields with metaphase stage cells were photographed for the chromosome count. Results: chromosome number found in E. chihuahuensis was 2n=52, Echeveria colorata 2n=54, the hybrid of these two species E. chihuahuensis × E. colorata 2n=50-52. It is advisable to use in situ fluorescent hybridization (FISH) to confirm the conformation the genome in hybrid plants.