Cytological and Electrophoretic Investigations of the Origin of ‘Callie’ Bermudagrass1

‘Callie’ bermudagrass (Cynodon dactylon var. aridus Harlan et de Wet) is a vigorous, robust form selected as an aberrant plant from a plot of PI 290814 bermudagrass (C. dactylon L. Pets.). Since Callie differed markedly from the original introduction, a cytological and electrophoretic investigation was undertaken in an attempt to determine how it originated. Callie and PI 290814 had a chromosome number of 2n=4x=36. Meiosis was regular in both plants and their chromosome pairing behavior was similar with primarily bivalent pairing. Pollen stainability in Callie was 46%. Seed set ranged from 1.0 to 3.2% in Callie and was 1.0% in PI 290814. Embryo sac development was normal and there was no evidence of ovule abortion in either plant. Thirtythree selfed progeny from Callie showed a considerable range in morphology and vigor, illustrating a high degree of heterozygosity. None were as large or vigorous as Callie, indicating an inbreeding depression after one generation of selling. Electrophoresis demonstrated qualitative differences in the water‐soluble proteins in leaf tissue of Callie and PI 290814. This eliminates mutation as a means of Caliie's origin. These findings suggest that Callie probably originated as a natural hybrid between PI 290814 and a giant, tetraploid form of C. dactylon var. aridus. Its size and vigor are probably the result of heterosis as well as characteristics from the pollen parent.