Deoxyribonucleic acid and the ancestry of wheat

Abstract

Rees has suggested that data relating to the DNA content of nuclei may provide a further clue regarding the parental composition of allopolyploid plants like durum and bread wheats. From Rees's results it is clear that Aegilops speltoides is more likely to be the donor of the B genome of tetraploid wheat than the other members of the Sitopsis section of Aegilops. With the view of understanding: (a) the relationship between somatic chromosome length and DNA content; (b) the extent of variation in DNA content of different varieties and species of Triticum and Aegilops, we estimated the DNA content of mitotic prophase nuclei using a microspectrophotometer constructed on the two wave-length principle of Ornstein and Patau. We preferred prophase nuclei to interphase nuclei since inter-slide differences were less in the former. When prophase nuclei were used in measurements, we did not find chromatin diminution to the extent inferred earlier. Examination of chromosome-length and DNA content indicated a definite relationship between the two. The DNA values of Triticum and Aegilops species (Table 1), however, did not lend themselves to interpretations such as those which Rees could draw.