Differential sensitivity among Puccinia striiformis f. sp. tritici isolates to propiconazole and pyraclostrobin fungicides

Figures & data

Table 1. Effects on urediniospore germination rates by Puccinia striiformis f. sp. tritici isolates collected between 1968 and 2013, concentrations of Tilt or Headline fungicide and interaction determined using the Mixed Procedure.

	Tilt			Headline
Effect	Df^1	F value	Pr > F	df	F value	Pr > F
Isolate	7	37.5	<0.0001	7	33.6	<0.0001
Concentration	8	1083.3	<0.0001	9	1217.4	<0.0001
Isolate × concentration	56	13.8	<0.0001	63	9.2	<0.0001

¹ df, degree of freedom.

Table 2. Mean values of urediniospore germination rates in the treatments of Tilt at various concentrations for eight Puccinia striiformis f. sp. tritici (Pst) isolates collected from 1968 to 2013 in Washington State.

	Germination rate (%) treated with Tilt in relative concentration^1
Isolate	0	0.01×	0.02×	0.04×	0.08×	0.10×	0.15×	0.20×	1.0×
1968-31	97.5 a^2	96.8 ab	97.0 ab	96.2 ab	82.8 ab	75.2 ab	2.7 d	0 b	0
1972-7-5	96.3 a	91.9 c	92.8 b	93.0 ab	85.6 ab	82.1 ab	54.1 bc	8.6ab	0
1985-118	97.1 a	96.8 ab	96.8 abc	96.0 ab	79.0 ab	66.0 bc	5.8 d	0 b	0
1991-2	97.3 a	96.6 ab	96.6 abc	94.3 ab	70.5 b	42.5 c	2.3 d	0 b	0
2002-168	98.1 a	98.5 a	98.0 a	97.1 ab	95.2 a	94.1 ab	10.7d	0b	0
2012-116	96.8 a	95.6 b	93.7 b	91.9 b	77.5 ab	68.5 abc	34.8 c	0 b	0
2013-242-1	98.9 a	97.6 ab	98.1 a	98.9 a	97.7 a	98.0 a	96.9 a	16.9 a	0
2013-246	97.8 a	97.6 ab	96.3 abc	95.6 ab	93.1 ab	88.4 ab	67.9 b	0 b	0
P^3	0.1747	<0.0001	0.0032	0.04	0.0085	0.0002	<0.0001	0.0059	NA^4

¹ Concentrations were relative to the full concentration (1.56 mL L⁻¹) as 1.0× of Tilt labelled for use in fields.

² Means were separated by the Tukey test, and those followed by the same letter were not significantly different.

³ P, the probability value of analysis of variance for differences among the germination rates.

⁴ NA = not applicable.

Table 3. Mean values of urediniospore germination rates in the treatments of Headline at various concentrations for eight Puccinia striiformis f. sp. tritici (Pst) isolates collected from 1968 to 2013 in Washington State.

	Germination rate (%) treated with Headline in relative concentration^1
Isolate	0	0.00075×	0.001×	0.0015×	0.002×	0.003×	0.004×	0.006×	0.0075×	1.0×
1968-31	96.9 a^2	87.8 b	83.2 c	68.4 c	30.6 c	0.6 c	0 b	0 b	0	0
1972-7-5	96.4 a	95.7 a	90.8 bc	93.5 ab	92.4 ab	60.8a	25.0 a	3.1 a	0	0
1985-118	98.5 a	97.4 a	97.7 ab	96.9 ab	73.8 abc	34.6 b	14.1 a	0.5 ab	0	0
1991-2	97.6 a	96.4 a	96.4 ab	94.2 ab	93.1 ab	10.8 c	1.6 b	0 b	0	0
2002-168	98.0 a	97.7 a	98.4 ab	97.6 ab	60.8 abc	7.3 c	0 b	0 b	0	0
2012-116	97.5 a	98.5 a	97.9 ab	75.2 bc	48.2 bc	2.4 c	0 b	0 b	0	0
2013-242-1	98.3 a	99.0 a	99.1 a	98.7 a	99.2 a	38.4 b	0 b	0 b	0	0
2013-246	98.5 a	99.9 a	99.1 a	68.7 c	32.4 c	4.9 c	0 b	0 b	0	0
P^3	0.2117	<0.0001	<0.0001	0.0003	0.0002	<0.0001	<0.0001	0.0166	NA^4	NA

¹ Concentrations were relative to the full concentration (3.52 mL L⁻¹) as 1.0× of Headline labelled for use in fields.

² Means were separated by the Tukey test, and those followed by the same letter were not significantly different.

³ P, the probability value of analysis of variance for differences among the germination rates.

⁴ NA = not applicable.

Table 4. Effects on urediniospore germination rates by Puccinia striiformis f. sp. tritici isolates collected in 2014, concentrations of Tilt or Headline fungicide and their interaction determined using the Mixed Procedure.

	Tilt			Headline
Effect	Df^1	F value	Pr > F	df	F value	Pr > F
Isolate	30	10.1	<0.0001	30	29.6	<0.0001
Concentration	3	45 433.2	<0.0001	3	10 529.3	<0.0001
Isolate × concentration	90	7.8	<0.0001	90	25.6	<0.0001

¹ df, degree of freedom.

Fig. 1 (Colour online) Scatterplots of urediniospore germination rates of Puccinia striiformis f. sp. tritici isolates collected in 2014 tested with Tilt at concentrations 0.03× (a), 0.10× (b), and 0.15× (c) relative to the full concentration of Tilt (1.56 mL L⁻¹) treated as 1.00×. Refer to Table 1 for all isolate names. The dash line denotes the mean germination rate of the specific fungicide concentration treatment.

Fig. 2 (Colour online) Scatterplots of urediniospore germination rates of Puccinia striiformis f. sp. tritici isolates collected in 2014 tested with Headline at concentrations 0.0003× (a) and 0.003× (b) relative to the full concentration of Headline (3.52 mL L⁻¹) treated as 1.0×. Refer to Table 1 for the names of all isolates.

Table 5. Effects on the number of uredinia on seedlings and adult plants of wheat produced by Puccinia striiformis f. sp. tritici isolates, timings and concentrations of Tilt and Headline fungicides, and their interactions determined using the Mixed Procedure.

		Tilt			Headline
Test	Effect	df^1	F value	Pr > F	df	F value	Pr > F
Seedling	Isolate (I)	4	14.2	<0.0001	4	43.9	<0.0001
	Timing (T)	2	605.1	<0.0001	2	90.7	<0.0001
	Concentration (C)	5	269.1	<0.0001	5	347.9	<0.0001
	I×T	8	17.2	<0.0001	4	20.5	<0.0001
	I×C	20	11.0	<0.0001	20	5.7	<0.0001
	T×C	10	13.0	<0.0001	10	11.3	<0.0001
	I×T×C	40	5.5	<0.0001	20	2.4	0.0005
Adult-plant	I	4	21.3	<0.0001	4	19.3	<0.0001
	T	3	74.5	<0.0001	2	4.0	0.0202
	C	4	668.5	<0.0001	3	1988.9	<0.0001
	I*T	12	11.4	<0.0001	8	19.2	<0.0001
	I*C	16	6.0	<0.0001	12	9.7	<0.0001
	T*C	12	25.1	<0.0001	6	8.8	<0.0001
	I*T*C	48	5.2	<0.0001	24	9.9	<0.0001

¹ df, degree of freedom.

Fig. 3 (Colour online) Numbers of uredinia on seedlings of Avocet S wheat treated with Tilt at various concentrations relative to the full concentration of Tilt (1.56 mL L⁻¹) 1 day before (1 DBI) (a), on the same day (0 DAI) (b), and 3 days (3 DAI) (c) after inoculation with Puccinia striiformis f. sp. tritici.

Fig. 4 (Colour online) Disease severity on seedlings of Avocet S wheat treated with Tilt at different concentrations relative to the labelled full concentration of Tilt (1.56 mL L⁻¹) 1 day before (1 DBI) (a), on the same day (0 DAI) (b) and 3 days (3 DAI) (c) after inoculation with Puccinia striiformis f. sp. tritici isolates.

Fig. 5 (Colour online) Numbers of uredinia on seedlings of Avocet S wheat treated with Headline at various concentrations relative to the full concentration of Headline (3.52 mL L⁻¹) 1 day before (1 DBI) (a), on the same day (0 DAI) (b), and 3 days (3 DAI) (c) after inoculation with Puccinia striiformis f. sp. tritici.

Fig. 6 (Colour online) Disease severity on seedlings of Avocet S wheat treated with Headline at different concentrations relative to the labelled full concentration of Headline (3.52 mL L⁻¹) 1 day before (1 DBI) (a), on the same day (0 DAI) (b) and 3 days (3 DAI) (c) after inoculation with Puccinia striiformis f. sp. tritici isolates.

Fig. 7 (Colour online) Numbers of uredinia on adult plants of Avocet S wheat treated with Tilt at different concentrations relative to the labelled full rate of Tilt (1.56 mL L⁻¹) 1 day before (1 DBI) (a), on the same day (0 DAI) (b), 3 days (3 DAI) (c), and 7 days (7 DAI) (d) after inoculation with Puccinia striiformis f. sp. tritici.

Fig. 8 (Colour online) Disease severity on adult plants of Avocet S wheat treated with Tilt at different concentrations relative to the labelled full concentration of Tilt (1.56 mL L⁻¹) 1 day before (1 DBI) (a), on the same day (0 DAI) (b), 3 days (3 DAI) (c) and 7 days (7 DAI) (d) after inoculation with Puccinia striiformis f. sp. tritici isolates.

Fig. 9 (Colour online) Numbers of uredinia on adult plants of Avocet S wheat treated with Headline at different concentrations relative to the full concentration of Headline (3.52 mL L⁻¹) 1 day before (1 DBI) (a), on the same day (0 DAI) (b), and 3 days (3 DAI) (c) after inoculation with Puccinia striiformis f. sp. tritici.

Fig. 10 (Colour online) Disease severity on adult plants of Avocet S wheat treated with Headline at different concentrations relative to the labelled full concentration of Headline (3.52 mL L⁻¹) 1 day before (1 DBI) (a), on the same day (0 DAI) (b) and 3 days (3 DAI) (c) after inoculation with Puccinia striiformis f. sp. tritici.