| Karyotype analysis of seven D-nullisomic wheat lines
and their gigas plants T. OHTA Kihara Institute for Biological Research, Yokohama, Japan Seven D-nullisomic lines have been among the offspring of the pentaploid wheat hybrid between Triticum spelta and T. polonicum (MATSUMURA 1952). They are very dwarf, weak and are called a - g - dwarfs. In the progeny of the selfed dwarfs, so - called gigas plants having normal hight and vigor appeared unexpectedly. It was assumed that the appearance of the gigas plants was due to an increase in the number of chromosomes of A or B genome, which are homoeologous to the lacking D chromosomes. Among 21 chromosomes of the Dinkel wheat, two are Sat - chromosomes. According to KIHARA (1958), they are called Sat - 1 and Sat - 2 and are distinguishable by their shape and size. According to MORRISON (1953), chromosome I and X have satellites. Among MI chromosomes of a-g - gigas plants which are nulli - trisomic having 41 somatic chromosomes, the additional chromosome, homoeologous to the lacking a-g - chromosome respectively, is often a univalent. In the case of b - and c - gigas, the univalent is often, but not always, observed as satellited. However, the univalents of a -, d -, e -, f - and g - gigas have no satellite. Somatic chromosomes of seven nullisomic lines and their gigas plants have been examined with special reference to the Sat - chromosomes. Four chromosomes with a large satellite were observed in all nullisomic and gigas lines except the b - and c - gigas in which the number of Sat - chromosomes was increased. The b - and c - gigas, both of which are nulli - trisomic having 41 somatic chromosomes, have five chromosomes with large satellites. It is believed that SEARS' chromosome I or KIHARA'S Sat - 1 is supernumerary in b - gigas and chromosome X or Sat - 2 in c - gigas. |