| A new early ecotype of Agropyron tsukushiense
var. transiens OHWI S. SAKAMOTO National Institute of Genetics, Misima, Japan A.tsukushiense var. transiens (2n=42) is very common in Japan, growing in fields and along road-sides. An early ecotype of this species which differs in several characteristics from the common type was found as a swarm in idle lying paddy fields in the hilly vicinity of Misima. In comparison with the common type, plant height, first internode from the top, flag leaf and spike are shorter, the number of spikelets is much smaller but empty glume, lemma and palea are longer and all three are wider, the awn is shorter, the seed is longer and wider and much heavier; the flowering time is about 25 days earlier (Tab.1). Artificial hybrids between the early ecotype and the common type were easily obtained and the growth of the F1 plants was very vigorous. Out of the observed characters of F1, 74% were intennediate between the parents. At meiosis of F1 hybrid, tetravalent conjugation was observed in 14% of nuclear plates (163 plates observed). Pollen- and seed-fertility of F1 were lower than in both parents, but F1 was fairly fertile and the growth of F2 seedlings was very good. From the clear habitat segregation, the flowering tune differentiation and the genetic relationship between the two types, ecotypic differentiation must be assumed. The early ecotype was often found together with Astragas sinicus LINN. (Chinese milk-vetch) in paddy fields. The distribution of the early ecotype seems to follow that of Chinese milk-vetch. |