COMPETITION BETWEEN DIPLOID AND DERIVATIVE AUTOTETRAPLOID DACTYLIS-GLOMERATA L FROM GALICIA - IMPLICATIONS FOR THE ESTABLISHMENT OF NOVEL POLYPLOID POPULATIONS

The competitive ability of a tetraploid, and its morphologically indis tinguishable progenitor diploid Dactylis glomerata L., from Galicia (S pain), was tested in a two-year study, using isolated plants and the s ame individuals grown at two densities (16 and 36 plants per pot, resp ectively). Inverse linear regression equations were used to quantify t he response of the different ploidy levels (hereafter cytotypes) to de nsity. For the diploids, inter-cytotype competition coefficients were significantly higher than intra-cytotype coefficients. The substitutio n rate increased from 1.8 in the first year to 3.9 in the second year, when most of the diploids failed to flower and some died. The competi tive superiority of the tetraploids was associated with higher mean ti ller weight, particularly in the mixed cultures. The tetraploids also had heavier seeds and faster leaf production in early spring, and they flowered earlier than the diploids. Several of these differences betw een cytotypes appear to be due to differences in ploidy level and may play a major role in the establishment of the tetraploids in Galician pastures, where competition is high.