Genecological studies on Japanese lawn grass (Zoysia japonica Steud.) with special reference to the seed propagation characteristics, 2: Seed productivity

In parallel with the previous study, seed productivity was investigated using the same materials described in the previous paper. The number of fertile seeds produced per unit area was estimated by multiplying the number of heading stems, the number of setting seeds per head, and fertility of seeds surveyed. Investigations were carried out in 1985 and 1986. Significant differences in fertile seed productivity were observed both between and within local populations. Statistically, 40 local populations were classified into four major groups, A-D. Group A, consisting of a Hokkaido population, showed an extremely large number of fertile seeds with about 600/100 square cm on average. In contrast, Group D, consisting of two populations from southernmost Kyushu, produced no seed at all. Between these extremes, Group B, consisting of five populations of Hokkaido and northernmost Honshu origin, produced 200-300 fertile seeds per 100 square cm on average. Group C. consisting of 32 residues, derived from a wide range of localities. From these, two further subgroups were distinguishable. They produced fertile seeds with 100-170 and below 50 per 100 square cm, respectively. Considering these groups and subgroups throughout, it can be concluded in general that northern Japan has the most clones with high seed productivity, followed by the clones of the central high mountain regions, whereas southern Japan has many clones with poor seed productivity. Among three components used for estimation of fertile seed productivity, heading stem density showed a particularly high correlation to the number of fertile seeds produced. Accordingly, this was believed to be the primary component contributing to fertile seed productivity. On the other hand, seed productivity observed in 1985 and 1986 showed a close correlation suggesting a fairly stable genotype-environment interaction in this trait under observation