Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2009
Publication Date: 9/1/2009
Citation: Garris, A.J., Cousins, P.S., Ramming, D.W., Baldo, A.M. 2009. Parentage Analysis of Freedom Rootstock. American Journal of Enology and Viticulture. Am. J. Enol. Vitic. 60(3):357-361.
Interpretive Summary: Rootstocks are widely used in vineyards to provide resistance to soil pests, adaptation to soil conditions, and mitigation of scion vigor. Rootstock breeding utilizes wild Vitis species as a source for these desirable traits. Freedom was released by the USDA in 1967 to provide protection in the vineyard against the root-knot nematode, a small, soil-inhabiting worm that feeds on the roots of susceptible grapevines, damaging the roots and reducing vine growth and yield. The parentage of Freedom is partially known: the female parent was the selection 1613-59 and the male parent was the selection Dog Ridge 5. Both 1613-59 and Dog Ridge 5 have known female parents (1613C and Dog Ridge, respectively), but their male parents are unknown. Identification of the male parents Freedom’s parentage is not merely an historical footnote; it also has implications for the continued use of Freedom in California vineyards. Resistance to nematodes is still important for California viticulture, but resistance to phylloxera, a root louse, is now of equal importance in some locales. Rootstocks with the European grape (V. vinifera) in their pedigree are considered risky because of possible phylloxera susceptibility from the European parentage. While Freedom is reported to be immune to some biotypes of Phylloxera, V. vinifera is in its background from 1613C, which is one eighth V. vinifera. If Freedom has a European grandparent, there is increased risk of a recessive phylloxera susceptibility allele in Freedom and its offspring. We used genetic markers to confirm that the pedigree of Freedom includes the expected maternal parent (1613-59) and maternal grandparent (1613C). Then we examined a set of candidate parents for evidence of paternity of 1613-59. The non-European rootstock 3306C was identified as the male parent of 1613-59 and therefore the grandparent of Freedom, partially resolving the amount of V. vinifera parentage in Freedom.
Technical Abstract: The rootstock Freedom has been widely deployed for nematode resistance in California vineyards. As the offspring of two open-pollinated parents, its risk of V. vinifera-derived phylloxera susceptibility is unknown. In order to determine the progenitors of Freedom, genetic profiles of candidate parents were analyzed with twenty-five microsatellite markers. Our results confirm that 1613-59 is the parent of Freedom and that 1613C is the parent of 1613-59. In addition, 3306C was identified as the pollen parent of 1613-59, but the pollen parent of Dog Ridge 5 could not be determined, indicating a potential 3 to 28% V. vinifera composition for Freedom.