GEOGRAPHIC-VARIATION IN SEED DORMANCY AMONG POPULATIONS OF ECHINOCHLOA-CRUS-GALLI

In 1991-1993, we investigated the incidence of seed dormancy in 25 loc al populations of barnyard grass, Echinochloa crus-galli (L.) P.Beauv. , in the western Czech Republic. The percentage of germination after 4 months after:ripening of dry seeds at 25 degrees C varied between 0.0 and 83.6%. Although there were significant annual differences in the percentage of germination at some localities, typical proportions of d ormant seeds persisted over 3 years at field sites where the seed bank was not disturbed. One-way ANOVA (using data from 14 cultivated or ab andoned fields) revealed that 73.0% of variance in seed dormancy incid ence could be attributed to the effect of locality (P < 0.001). Incide nce of dormancy was not con-elated with mother plant stature (dry abov e-ground biomass, number of tillers, maximal stem height) nor seed mas s. There was a significant correlation (r(2) = 0.403, P < 0.005) betwe en dormancy incidence at natural localities in 1991 and in F-1 offspri ng sown at experimental grounds at Praha-Ruzyne in 1992. The results i ndicate that heredity is important in maintaining local variation in s eed dormancy, probably favoured by the self-pollinating reproduction o f barnyard grass.