Supporting Information (SI) Appendix - Proceedings of the National ...

with very few exceptions. Sampling was carried out during bloom, so it was possible to verify
the flower sex. Moreover, they ensured that the sylvestris samples did not come from
populations growing adjacent to present-day vineyards or land known to be previously planted
with vinifera. We note, however, that despite the use of these criteria, it is impossible to rule out
the possibility of influence from cultivated vines. All sampling locations were at an altitude of
0-500m with environmental conditions typical for sylvestris: wetlands and forests with high
humidity, as well as the frequent presence of tree species such as elm, poplar, hawthorn,
hornbeam and oak on which sylvestris grow as lianas. Ed Stover also used similar standard
criteria and ensured that the 9 samples used here from Armenia and Georgia did not come from
populations growing adjacent to present-day vineyards or land known to be previously planted
with vinifera. Dr Stover collected samples in October and therefore could not confirm flower
sex. However, the vast majority of the vines was not bearing fruit and was therefore presumably
male. It is worth noting that results are at least consistent across sampling expeditions: samples
collected from similar geographic locations on different expeditions generally cluster together in
PC space (Figure 4, Figures S7-S9).
It is impossible to claim with absolute certainty that the samples we identify as sylvestris are
truly wild samples with no genetic input from cultivated grapevines. This is the case for any
study that makes use of sylvestris samples [e.g. 8,9]. While it is most common to make use of
morphological criteria exclusively, here we enhance the morphological criteria we have used to
identify sylvestris with genetic analyses.
To provide a visualization of the relationships among all of the samples used in the present
study, a PCA plot was generated using the 2958 LD-pruned SNPs on the set of unique vinifera
and sylvestris samples (Figure S7). Figure S7 shows that there is one exceptional sample,
indicated with an arrow, that is labeled as vinifera but clearly clusters among the western
sylvestris. This sample was donated to the USDA collection in 1983 by Dr Harold Olmo and is
labeled in GRIN as “Beli Potok” (DVIT 1841), a female vine likely of Serbian origin with
morphological characteristics that are consistent with it being sylvestris. Olmo’s “wild vinifera”
samples, indicated by black dots in Figure S7, are discussed below. From Figure S7, it is
apparent that the western sylvestris are relatively distinct and pull out along both PC1 and PC2.