Table 1. Ectomycorrhizal (EM) colonization, vitality index and root density of P. × canescens.

	EM colonization [%]		Vitality index [%]		Root density [g l −1]
	2009	2010	2009	2010	2009	2010
	F = 2.1939	F = 1.1465	F = 2.3565	F = 1.9684	F = 6.783	F = 0.9578
	p = 0.04758*	p = 0.3462	p = 0.0342	p = 0.0735	p<0.001	p = 0.4697
WT	71±5.4 a	99±0.4 a	85±4.9 ab	96±1.2 a	0.503±0.168 bc	0.962±0.321 a
CCR L5	64±7.3 a	99±0.6 a	89±5.1 ab	98±0.6 a	0.543±0.205 c	0.896±0.299 a
CCR L7	73±10.2 a	100±0.0 a	79±5.9 ab	92±2.3 a	0.104±0.039 a	0.739±0.246 a
COMT L9	82±4.8 a	99±0.4 a	76±5.2 ab	95±1.5 a	0.133±0.047 ab	0.652±0.217 a
COMT L11	75±4.1 a	100±0.1 a	91±2.5 a	94±1.9 a	0.384±0.128 c	0.862±0.287 a
CAD L18	86±1.7 a	99±0.3 a	86±5.0 ab	96±1.3 a	0.497±0.166 c	0.774±0.258 a
CAD L21	64±5.9 a	100±0.2 a	91±2.3 ab	97±1.1 a	0.447±0.149 c	1.146±0.382 a
CAD L22	58±8.2 a	99±0.4 a	67±8.8 b	91±2.8 a	0.256±0.090 abc	0.689±0.230 a

Root density was determined as root mass per liter of soil volume. Significant differences are indicated by different letters (ANOVA, followed by TukeyHSD, p≤0.05). Values indicate mean ± SE, (n = 7–9). CCR, COMT and CAD refer to transgenic poplar lines with suppressed activities of cinnamoyl coenzyme A reductase, caffeic acid O-methyl transferase, and cinnamyl alcohol dehydrogenase, respectively. *no significant differences were detected by TukeyHSD.