Hybridization of cultivated Vitis vinifera with wild V. californica and V. girdiana in California

Authors: DANGL, GERALD - University Of California; MENDUM, MARY LOU - University Of California; YANG, JUDY - University Of California; WALKER, ANDREW - University Of California; Preece, John

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2015
Publication Date: 11/19/2015
Publication URL: http://www.ars-grin.gov/dav
Citation: Dangl, G.S., Mendum, M., Yang, J., Walker, A.M., Preece, J.E. 2015. Hybridization of cultivated Vitis vinifera with wild V. californica and V. girdiana in California. Ecology and Evolution. 5(23):5671-5684. doi: 10.1002/ece3.1797.

Interpretive Summary: The native wild grape species of northern California, Vitis californica Benth. (California wild grape), and V. girdiana Munson (desert wild grape) in southern California are under increasing pressure from loss of habitat and from interbreeding with the domesticated grapevine, V. vinifera L. For its first century, the V. vinifera invasion consisted of a single, clonally propagated cultivar, ‘Mission’, that was planted across much of the ranges of V. californica and V. girdiana; other V. vinifera cultivars were subsequently introduced. Nineteen microsatellite markers were used to characterize the genetic diversity within and among three species-based groups: 119 presumed V. californica vines, 26 presumed V. girdiana vines, and 45 domesticated V. vinifera cultivars. Thirty-five of the V. californica individuals were hybrids, primarily with V. vinifera. The non-V. californica domesticated parent was identified for 16 F1 hybrid vines. Eight of the F1 vines collected in remote areas had ‘Mission’ as one parent. ‘Mission’ has not been grown in these areas in ~100 years, suggesting a long generation time for established hybrid vines in the wild or clonal propagation by layering. Backcrosses were also found, showing that the genetic invasion persists into subsequent generations. Similar results were obtained for the smaller V. girdiana sample set. The 84 V. californica vines with no detectable introgression had weak structure and very low genetic variability. The widespread introgression of an already inbred native population across its range with a single, invasive, domesticated clone, and the long life and vigor of the resulting hybrids, is a rare form of invasion with unique implications. A preliminary strategy for preserving V. californica and V. girdiana would involve limiting new introductions of domesticated cultivars into remote areas where possible, finding, characterizing and preserving non-introgressed V. californica and V. girdiana individuals from across their respective ranges and using a regionally appropriate mix of such individuals when restoring native ecosystems in California.

Technical Abstract: The native wild grape species of northern California, Vitis californica Benth. (California wild grape), and V. girdiana Munson (desert wild grape) in southern California are under increasing pressure from loss of habitat and from interbreeding with the domesticated grapevine, V. vinifera L. For its first century, the V. vinifera invasion consisted of a single, clonally propagated cultivar, ‘Mission’, that was planted across much of the ranges of V. californica and V. girdiana; other V. vinifera cultivars were subsequently introduced. Nineteen microsatellite markers were used to characterize the genetic diversity within and among three species-based groups: 119 presumed V. californica vines, 26 presumed V. girdiana vines, and 45 domesticated V. vinifera cultivars. Thirty-five of the V. californica individuals were hybrids, primarily with V. vinifera. The non-V. californica domesticated parent was identified for 16 F1 hybrid vines. Eight of the F1 vines collected in remote areas had ‘Mission’ as one parent. ‘Mission’ has not been grown in these areas in ~100 years, suggesting a long generation time for established hybrid vines in the wild or clonal propagation by layering. Backcrosses were also found, showing that the genetic invasion persists into subsequent generations. Similar results were obtained for the smaller V. girdiana sample set. The 84 V. californica vines with no detectable introgression had weak structure and very low genetic variability. The widespread introgression of an already inbred native population across its range with a single, invasive, domesticated clone, and the long life and vigor of the resulting hybrids, is a rare form of invasion with unique implications. A preliminary strategy for preserving V. californica and V. girdiana would involve limiting new introductions of domesticated cultivars into remote areas where possible, finding, characterizing and preserving non-introgressed V. californica and V. girdiana individuals from across their respective ranges and using a regionally appropriate mix of such individuals when restoring native ecosystems in California.