Karyotype analysis of seven species in the genus Sorghum

Karyotype morphology including chromosome length, centromere position, arm ratio, secondary and tertiary constriction, and staining properties was analyzed for seven sorghum species belonging to three subgenera of the genus Sorghum. Species with only 10 chromosomes—S. versicolor, S. purpureo-sericeum, S. stipoideum, and S. intrans—all had long chromosomes that stained uniformly. The ranges of chromosome length in the seven species were as follows: S. bicolor, 2.27 to 5.60 .μm; S. halepense, 2.31 to 4.41 μm; S. nitidum, 1.63 to 3.33 μm; S. versicolor, 5.99 to 7.42 μm; S. purpuroosericeum, 6.96 to 8.44 μm S. stipoideum, 3.72 to 4.89 μm; and S. Intrans, 5.41 to 6.52 μm. Other characteristics such as variation in chromosome length within species, satellite number and size, constrictions, and centromere placements were used to differentiate the species. Chromosome morphology for species in subgenus Eusorghum were distinctly different from those in subgenera Parasorghum and Stiposorghum, whereas some similarities were found among species within each subgenus. The 40 chromosomes in S. nitidum appeared to belong to 10 sets of four.