Table 2.

Disease severity index (DSI_f) and disease incidence (DI_f, percentage of diseased plants) of clubroot visually assessed in early December 2018 and July 2019 on winter oilseed rape roots from each plot in field trials 2018/2019 at Simrishamn, Tomelilla, and Kumla for the clubroot-resistant cultivars cv. Mentor, cv. Alister, and cv. Archimedes and the susceptible Cultivar mix. Sites were selected based on field abundance (gene copies g⁻¹ soil) of Plasmodiophora brassicae DNA (Simrishamn 600,000; Tomelilla 370,000; Kumla 50,000).

	DSIf (0–100)					DIf (%)
Cultivar	Autumn 2018	July 2019		Both years		Autumn 2018	July 2019		Both years
Simrishamn
Cultivar mix	3.3	0.0		1.7		5.0	0.0		2.5
cv. Mentor	0.0	0.7		0.3		0.0	2.0		1.0
cv. Alister	0.0	0.0		0.0		0.0	0.0		0.0
cv. Archimedes	0.0	0.0		0.0		0.0	0.0		0.0
p-value	ns	ns		ns		ns	ns		ns
Coeff. of var. †	400	231		475		400	231		418
Tomelilla
Cultivar mix	0.0	0.0		0.0		0.0	0.0		0.0
cv. Mentor	0.0	1.0		0.5		0.0	1.0		1.5
cv. Alister	1.9	0.0		0.9		5.6	0.0		2.8
cv. Archimedes	0.0	0.0		0.0		0.0	0.0		0.0
p-value	ns	ns		ns		ns	ns		ns
Coeff. of var.	231	400		311		231	400		311
Kumla
Cultivar mix	22.5	27.5	a *	25.0	a	25.0	43.2	a	34.1	a
cv. Mentor	3.3	6.9	ab	5.9	b	7.5	10.9	ab	9.2	b
cv. Alister	5.8	1.7	b	5.1	b	7.5	8.0	ab	4.8	b
cv. Archimedes	6.7	5.3	b	3.8	b	6.7	2.0	b	7.4	b
p-value	ns	0.016		0.001		ns	0.025		0.004
Coeff. of var.	128	99		106		131	109		115

^† Coefficient of variation. * Different letters indicate significant differences according to Tukey’s HSD-test (p < 0.05).