STAND DENSITY INFLUENCES OUTCROSSING RATE AND GROWTH OF OPEN-POLLINATED FAMILIES OF EUCALYPTUS-GLOBULUS

Using isozymes markers, we test BORRALHO and POTTS' (1996) hypothesis that poorer growth of open-pollinated (OF) families of Eucalyptus glob ulus grown from seed collected from less dense stands is a consequence of lower outcrossing rates. A significant relationship between stand density class and outcrossing rate was found, with outcrossing rates n ear one for families from closed forests. In support of BORRALHO and P OTTS' (1996) hypothesis, lower parental breeding values were generally associated with lower outcrossing rates. This is no doubt due to a hi gher proportion of less vigorous selfs within an OP family depressing mean growth relative to families where inbred progeny were virtually a bsent. It is suggested that the precision of predicting breeding value s with OP progenies may be improved by adjusting family performance fo r individual outcrossing rate.