| A polyhaploid plant of Agropyron tsukushiense
var. transiens Ohwi found in a state of nature S. SAKAMOTO National Institute of Genetics, Misima, Japan A. tsukushiense var. transiens, a common weed growing in fields and along road - sides, is widely distributed in Japan, China, Manchuria and Korea. This species is hexaploid (2n = 42). 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 specimens of the species and had slender spikes, 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 disomic (2n = 42) and the other a monsomic (2n = 41). 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 A. tsukushiense var. transiens strains, and the crossing success amounted to 1.0 1.6%. Chromosome pairing at MI of PMCs of the polyhaploid and the monosomic is shown in Table 1. Of 442 cells observed in the polyhaploid, in 83% 21I and in 14% 1II ( terminal pairing ) + 19I were observed. In the majority of cells chromosome pairing in the monosomic was 20II + 1I. This result indicates that A. tsukushiense var. transiens is an allohexaploid whose genome constitution comparises three different genomes. |