Relative amount of nuclear DNA in tetraploid wheats

KOZO NISHIKAWA and Yukihiro SAWAI

Faculty of Agriculture, Gifu University, Gifu, Japan

Triticum timopheevi is a species in which much interest of wheat cytogeneticists has arisen. Genome analysis, protein or enzyme analysis and microspectrophotometry of nuclear DNA content has been carried out by many workers, but origin of T. timopheevi remains still ambiguous.

TANAKA, et al. (1968) identified two types of T. araraticum, No.1 and No.2, based on the morphological characters. According to them, No.2 is cytogenetically more alike to T. timopheevi than No.1; the F₁ of the former with T. timopheevi is fertile, while that of the latter sterile.

The relative amount of nuclear DNA in tetraploid wheat measured by means of microspectrophotometry is given in Table 1. Among tetraploid wheat, Emmer (AABB) represented by three species including five varieties had the equal amount of nuclear DNA. While, two strains of T. timopheevi (AAGG) had the significantly less DNA than Emmer, that is the same result of REES and WALTERS (1965). Species or varieties with the same genome constitution have been proved to have the equal amoimt of nuclear DNA in polyploid wheat (REES and WALTERS 1965, NISHIKAWA and FURUTA 1968, 1969). In contrast to these previous findings, T. araraticum showed intraspecific difference in nuclear DNA content; namely T. araraticum No.1 had higher amdunt of DNA than No.2, the former being equal to Emmer and the latter to T. timopheevi. Since DNA values given in Table 1 were obtained from four separate sets of slides, another measurement was made so as to allow the direct comparison of DNA content among T. durum reichenbachii, T. araraticum No.1 and No 2, and T. timopheevi No.1. On each slides of those varieties or strains to be compared were placed side by side in order to subject them to the same Feulgen staining condition. The result supported the original measurement given in Table 1.

The present result in relation to nuclear DNA content agrees with cytogenetical examination of this species by TANAKA et al. that T. araraticum No.2 is closer to T. timopheevi than No.1.

(Received September 19, 1969)