Abstract
Ag. tsukushiense var. transiens, a weed growing in fields and along road-sides, is a very common hexaploid species (2n=42), widely distributed in Japan, China, Manchuria and Korea. In a valley of the hilly neighborhood of Misima, a spontaneous polyhaploid plant (2n=21) of the species was found. It was smaller than the hexaploid strains, but its tillering was very vigorous. In natural condition it yielded two seeds which were assumed to have been produced by pollination with the pollen of hexaploid plants growing in its proximity. The two seeds gave two plants, one a monosomic (2n=41) and the other a disomic (2n=42).
Pollen fertility of the polyhaploid, the monosomic and the disomic was 0.001, 28.5 and 78.5%, and seed fertility was 0, 53.3 and 76.6%, respectively. The polyhaploid was crossed by the disomic and by two hexaploid strains, and the crossing success amounted to 0.7-1.6%.
As to chromosome pairing at MI of PMCs, the polyhaploid showed 21I in 84% and 1II+19I in 14% of 442 cells observed. In the majority of cells chromosome pairing in the monosomic was 20II+1I. From the result it is concluded that Ag. tsukushiense var. transiens is an allohexaploid whose genome constitution comprises three different genomes. Summarizing the cytological studies of polyhaploids in Agropyron, the types of polyploidy in this genus are assumed to be various and complex.
