Kosuke YAMASHITA
Biological Laboratory, Kyoto University, Kyoto, Japan
Various RT-types induced by X-rays in Einkorn wheats, Triticum aegilopoides and T. monococcum, were analyzed for their chromosome constitution, and a series of RT- types involving all 7 chromosomes from a to g was established. Subsequently, all the possible combinations of rings and pairs have been realized by successive crosses among them (Yamashita, 1951 and elsewhere). This is the situation in Oenothera, except for the balanced lethal mechanism.
In the meantime, however, considerable progress has been made in the linkage analyse for induced mutations, and 2 lethal genes, lethal-1 and -2, have been located on the d- and f-chromosome respectively (Yamashita, 1953). Consequently, crosses have been made in an attempt to combine these lethal genes into a ring complex, according to the plan which is as follows.
The final crosses were made in the 1955 season and the permanent RT-heterozygosity should be maintained in the plants, with a ring of 6 chromosomes, due to the balanced lethal mechanism as in the case of Oenothera.