Phylogeography and population structure of the grape powdery mildew fungus, Erysiphe necator, from diverse Vitisspecies

Table 4 Population structure of Erysiphe necator by geographic region and host species.

Populations compared (sample sizes are in parentheses)	S _nn ¹	H _ST ¹
Eastern US (103) vs. introduced (43) populations	0.9182 (< 0.001)	0.0627 (< 0.001)
Within the eastern US
by geographic region northeast (59) vs. southeast (34) vs. central (10)	0.6856 (< 0.001)	0.0280 (< 0.001)
by geographic region on Vitis vinifera and vinifera hybrid hosts northeast (33) vs. southeast (15) vs. central (9)	0.6384 (< 0.001)	0.0396 (0.001)
by host agro-ecological habitat² cultivated (59) vs. wild (34) hosts	0.5733 (0.133)	0.0002 (0.407)
by host species within the northeast US V. vinifera (13) vs. vinifera hybrid (20) vs. V. labrusca (10) vs. V. riparia (8)	0.3532 (0.064)	0.0051 (0.333)
by host species within the southeast US including V. rotundifolia³ V. rotundifolia (5) vs. V. vinifera (11) vs. vinifera hybrid (4) vs. V. labrusca (3) vs. V. aestivalis (9)	0.3529 (0.008)	0.0857 (0.007)
by host species within the southeast US excluding V. rotundifolia V. vinifera (11) vs. vinifera hybrid (4) vs. V. labrusca (3) vs. V. aestivalis (9)	0.2552 (0.712)	-0.0179 (0.709)

¹The nearest neighbour statistic (S_nn) measures the proportion of times the most similar sequence ('nearest neighbour') is from the same population [67]. H_ST is a measure of population subdivision that estimates F_ST among haplotypes [68]. Significant differentiation between or among populations (α = 0.05) is shown in bold. P-values are in parentheses.
²Isolates from the central US were excluded because all but one were from cultivated species.
³A single isolate from V. riparia was excluded from the southeast population.

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