Several peanut (Arachis hypogaea L.) breeding lines in the Florida program were highly variable even after constitution from single plant selections after 21 generations of assumed self-pollination. To assess potential causes of this variability a 3-yr study was conducted to determine outcrossing using Krinkle as a genetic marker. There was a significant year by genotype interaction in this study. Two breeding lines with Virginia botanical types averaged almost 1.5% outcrossing, and in 1990 more than 3% of the progeny from these lines were the result of outcrossing. The breeding line Valencia 803 averaged nearly 8% outcrossing, and a second Valencia type, F623, averaged over 4%.

The differences in outcrossing among these four lines did not appear to be related to floral morphology, pollen viability, or stigma receptivity, although delayed anther dehiscence may have contributed to the higher outcrossing in Valencia 803.