Cytological Characteristics and Nuclear DNA Bouyant Densities of Corn, Teosinte, Tripsacum, and Corn‐tripsacum Hybrids1

Abstract

This study assesses the variability in buoyant density of nuclear DNA (nDNA) of corn and its relatives and the effect of several cytological phenomena on the demity of nDNA. The nDNAs of four Tripsacum L. spp., corn (Zea mays L.), annual teosinte (Z. mexieana [Schrad.] Kuntze), perennial teosinte (Z. perennis [Hitchc.] Reeves and Manglesdorf), and corn‐tripsacum hybrids were characterized for buoyant densities. Corn and perennial teosinte nDNA densities were similar but were significantly greater than those of tripsacum and annual teosinte. The latter two did not differ in densities. The corntripsacum hybrid densities resembled those of the higher parent. However small significant differences in parental base composition did not preclude hybridization. In all cases, and typical of grasses, nDNAs were resolved as single bands without satellites and with relatively high guanine and cytosine contents.Chromosome numbers of T. andersonii Gray, in ed., Guatemala grass, are reported for the first time (2n = 64). Chromosomal knob numbers of 12 Tripsocum accessions ranged from 0 to 40. One Tripsacum accession had 3 to 4 B chromosomes. The presence of chromosomal knobs and B chromosomes in tripsacums had no effect on the banding pattern and buoyant density of the nDNAs as determined by neutral CsCI analytical eentrifugation.Although similarities and significant differences in buoyant densities of nDNA were found among corn and its relatives, the value of these results for establishing genetic relationships is not clear.