OUTCROSSING RATE IN CULTIVATED AUTOTETRAPLOID POTATO

Outcrossing rates in potato were measured in an open-pollination field experiment at a location in the Peruvian Andes. Embryo spot, a domina nt genetic seed marker, was used to measure outcrossing rate. The sour ce of the dominant marker, the donor, was interplanted among recipient clones lacking the marker (recessive genotype), for which outcrossing was to be measured. Eight out of the 17 clones tested were advanced b reeding clones which had wild species cytoplasm. Seven out of eight of these had outcrossing rates above 0.75, showing complete male sterili ty in one case and partial male sterility in six cases. Among the othe r clones tested, which were male-fertile, outcrossing estimates ranged from 0. 10 to 0.74. Wide variability in outcrossing rate in autotetra ploid potato suggests that it should be possible to select for higher outcrossing rate in production of open-pollinated true seed population s of potato for genetic or commercial purposes.