Nuclear DNA contents of meristematic root tip cells were determined in F1 hybrids between perennial teosinte and maize (Gaspé) and in its parents by microspectrophotometric measurements on 2C anaphase nuclei, at 560 nm. The DNA amounts of Gaspé, perennial teosinte and F1 are graphically demonstrated in Figure 1.

The nuclear DNA content, nuclear area and DNA density values were as follows:

Table.

The nuclear DNA content and DNA density were represented in arbitrary units and the nuclear area was represented in µ2.

Perennial teosinte had approximately 50 percent more DNA per 2C nucleus than Zea mays. Highly significant differences were found in DNA content between parents and with respect to the F1. For nuclear area significant differences were found between the F1 and Zea mays. The two parents did not differ in DNA density, but the F1 had more DNA density than both parents and significant differences were found. Close correlations were found between nuclear area, DNA density and DNA content:

Table.

The DNA content of F1 plants is higher than the DNA content of both parents. This fact is due to a higher DNA density, perhaps due to differential polynemy. The high DNA content in F1 plants was greater than expected. This fact leads us to suppose that amplification of DNA in F1 would explain this phenomenon, perhaps associated with heterosis shown by the hybrids.

Figure 1.

Ida Graciela Palacios

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