Effect of temperature on aggressiveness of Plasmopara viticola f. sp. aestivalis and P. viticola f. sp. riparia from eastern Canada

Figures & data

Table 1. Analysis of variance of the effect of temperature on the zoospore release (empty sporangia) of two formae speciales of Plasmopara viticola

	Factor	Degree of freedom	Mean square	F-value	P(>F)
Empty sporangia %	Temperature	5	13766	80.73	<0.001
	Forma specialis	1	305	1.79	0.182
	Incubation time	4	39671	232.65	<0.001
	Temperature*forma specialis	5	759	4.45	<0.001
	Temperature*incubation time	20	1165	6.83	<0.001
	Forma specialis*incubation time	4	356	2.08	0.082
	Temperature*forma specialis*incubation time	20	246	1.44	0.100

Fig. 1 Effect of temperature and incubation time on zoospore release of Plasmopara viticola f. sp. riparia and P. viticola f. sp. aestivalis. Error bars represent the standard error (STD) of mean of empty sporangia

Table 2. Analysis of variance of the effect of temperature on the aggressiveness variables of two formae speciales of Plasmopara viticola during the infection, penetration and sporulation processes

Process	Aggressiveness variable	Factor	Degree of freedom	Mean square	F-value	P(>F)
Infection	Incidence	Temperature	5	3.59	183.50	<0.001
		Forma specialis	1	0.13	6.83	0.010
		Temperature*forma specialis	5	0.04	1.83	0.115
	Latency	Temperature	2	58.29	59.360	<0.001
		Forma specialis	1	22.53	22.940	<0.001
		Temperature*forma specialis	2	1.05	1.07	0.352
	Severity	Temperature	5	3439.00	156.95	<0.001
		Forma specialis	1	913.00	41.68	<0.001
		Temperature*forma specialis	5	185.00	8.45	<0.001
	Sporulation efficiency	Temperature	5	199178.00	194.23	<0.001
		Forma specialis	1	124125.00	121.04	<0.001
		Temperature*forma specialis	5	28152.00	27.45	<0.001
Penetration	Incidence	Temperature	5	1.334.00	21.27	<0.001
		Forma specialis	1	0.593.00	9.45	0.003
		Temperature*forma specialis	5	0.02	0.31	0.904
	Latency	Temperature	5	6.78	10.46	<0.001
		Forma specialis	1	13.70	21.13	<0.001
		Temperature*forma specialis	5	1.93	2.98	0.015
	Severity	Temperature	5	2322.00	78.84	<0.001
		Forma specialis	1	1661.40	56.41	<0.001
		Temperature*forma specialis	5	31.50	1.07	0.387
	Sporulation efficiency	Temperature	5	138480.00	65.18	<0.001
		Forma specialis	1	268165.00	126.21	<0.001
		Temperature*forma specialis	5	14752.00	6.94	<0.001
Sporulation	Incidence	Temperature	5	3.23	157.30	<0.001
		forma specialis	1	0.44	21.25	<0.001
		Temperature*forma specialis	5	0.06	3.00	0.015
	Latency	Temperature	3	19.91	17.61	<0.001
		forma specialis	1	17.53	15.50	<0.001
		Temperature*forma specialis	3	0.72	0.63	0.594
	Severity	Temperature	5	3100.80	171.87	<0.001
		forma specialis	1	809.40	44.86	<0.001
		Temperature*forma specialis	5	101.20	5.61	<0.001
	Sporulation efficiency	Temperature	5	183732.00	63.00	<0.001
		forma specialis	1	226264.00	77.58	<0.001
		Temperature*forma specialis	5	34821.00	11.94	<0.001

Table 3. Parameter estimates of the Gaussian models fitted to the aggressiveness variables (incidence, severity and sporulation efficiency) as a function of temperature for the two formae speciales, Plasmopara viticola f. sp. aestivalis (P.v. aestivalis) and P. viticola f. sp. riparia (P.v. riparia), during the infection and sporulation processes

Processes	formae speciales	Variable	R^2 (R^2adj)	a ^1 (S.E.)	X0 ^1 (S.E.)	b ^1 (S.E.)
Infection	P.v. riparia	Incidence	0.83	0.988a	20.442a	4.609a
			(0.82)	(0.057)	(0.302)	(0.296)
	P.v. aestivalis		0.87	1.125b	20.639a	4.878a
			(0.86)	(0.051)	(0.258)	(0.257)
	P.v. riparia	Severity	0.89	34.067a	20.577a	3.723a
			(0.88)	(1.824)	(0.252)	(0.219)
	P.v. aestivalis		0.93	50.181b	20.595a	4.365b
			(0.92)	(2.138)	(0.219)	(0.211)
	P.v. riparia	Sporulation	0.79	175.500a	18.970a	3.539a
			(0.78)	(11.812)	(0.283)	(0.272)
	P.v. aestivalis		0.95	354.900b	19.845a	4.165b
			(0.94)	(10.480)	(0.148)	(0.137)
Sporulation	P.v. riparia	Incidence	0.76	0.967a	19.509a	5.630a
			(0.75)	(0.058)	(0.392)	(0.396)
	P.v. aestivalis		0.83	1.111b	18.741a	6.444b
			(0.82)	(0.050)	(0.335)	(0.345)
	P.v. riparia	Severity	0.94	34.275a	20.512a	4.275a
			(0.93)	(1.337)	(0.198)	(0.188)
	P.v. aestivalis		0.94	47.492b	19.833a	4.754a
			(0.89)	(2.245)	(0.262)	(0.257)
	P.v. riparia	Sporulation	0.92	168.600a	19.6040a	3.010a
			(0.91)	(6.065)	(0.178)	(0.119)
	P.v. aestivalis		0.77	356.400b	19.423a	4.658b
			(0.76)	(23.092)	(0.352)	(0.346)

¹For each parameter, values with the same letter are not significantly different according to the Student’s t-test (P ≤ 0.05).

The Gaussian model was: $Y=aexp\left(-0.5{\left(\frac{X-X_0}{b}\right)}^2\right)$, where Y is the different aggressiveness variables, X is the temperature, X₀ is the optimal temperature, a is the asymptote and b is the dispersion around X₀.

Fig. 2 Effect of temperature on the latency of the two formae speciales, Plasmopara viticola f. sp. aestivalis (P.v. aestivalis) and P. viticola f. sp. riparia (P.v. riparia), (a) during the infection process, (b) during the penetration process, (c) during the sporulation process, and (d) during all three processes (the average of all three processes). Error bars represent the standard error of mean (STD) of the latency. For each temperature, values of bars with the same letter are not significantly different according to Tukey’s test (P ≤ 0.05)

Fig. 3 Representation of the Gaussian models of the effect of temperature on the aggressiveness of the two formae speciales, Plasmopara viticola f. sp. aestivalis (P.v. aestivalis) and P. viticola f. sp. riparia (P.v. riparia), during the infection process. (a) Incidence, (b) Severity and (c) Sporulation efficiency

Table 4. Parameters of the linear models (LM) of the effect of temperature on the aggressiveness of the two formae speciales, Plasmopara viticola f. sp. aestivalis (P.v. aestivalis) and P. viticola f. sp. riparia (P.v. riparia), during the penetration process

formae speciales	Variable	R^2 (R^2 adj)	β1 (S.E.)	β0 (S.E.)	β2 (S.E.)	Degrees of freedom (P-value)
P.v. riparia	Incidence	0.46	−0.418	0.143	−0.004	51
		(0.44)	(0.165)	(0.022)	(0)	(<0.001)
P.v. aestivalis		0.52	−0.180	0.131	−0.004	51
		(0.50)	(0.136)	(0.018)	(0)	(<0.001)
P.v. riparia	Severity	0.84	−27.231	6.700	−0.186	33
		(0.83)	(3.857)	(0.505)	(0.014)	(<0.001)
P.v. aestivalis		0.85	−26.124	7.700	−0.210	33
		(0.84)	(4.350)	(0.569)	(0.016)	(<0.001)
P.v. riparia	Sporulation efficiency	0.60	−127.544	28.931	−0.801	51
		(0.58)	(25.522)	(3.339)	(0.093)	(<0.001)
P.v. aestivalis		0.71	−227.395	56.524	−1.548	51
		(0.70)	(38.653)	(5.058)	(0.141)	(<0.001)

The linear regression model Y = β₀ + β₁X + β₂X², where Y is the different aggressiveness variables, and X is the temperature, β₀, β₁ and β₂ are the estimates.

Fig. 4 Representation of linear regression analysis of the effect of temperature on the aggressiveness of the two formae speciales, Plasmopara viticola f. sp. aestivalis (P.v. aestivalis) and P. viticola f. sp. riparia (P.v. riparia), during the penetration process. (a) Incidence, (b) Severity and (c) Sporulation efficiency

Fig. 5 Representation of the Gaussian models (GM) of the effect of temperature on the aggressiveness of the two formae speciales, Plasmopara viticola f. sp. aestivalis (P.v. aestivalis) and P. viticola f. sp. riparia (P.v. riparia), during the sporulation process. (a) Incidence, (b) severity and (c) sporulation efficiency

Table 5. Analysis of variance of the effect of temperature on the index of aggressiveness of the two formae speciales, Plasmopara viticola f. sp. aestivalis (P.v. aestivalis) and P. viticola f. sp. riparia (P.v. riparia), during infection, penetration, and sporulation and the global process

Process	Factor	Degree of freedom	Mean square	F-value	P (>F)
Infection	Temperature	2	15.62	22.81	<0.001
	Forma specialis	1	34.28	50.06	<0.001
	Temperature*forma specialis	2	2.13	3.10	0.054
Penetration	Temperature	5	46.95	27.50	<0.001
	Forma specialis	1	71.44	45.20	<0.001
	Temperature*forma specialis	5	2.09	1.22	0.304
Sporulation	Temperature	3	45.87	69.63	<0.001
	Forma specialis	1	72.59	110.19	<0.001
	Temperature*forma specialis	3	1.88	2.86	0.044
Global	Temperature	5	52.68	57.16	<0.001
	Forma specialis	1	61.85	67.10	<0.001
	Temperature*forma specialis	5	1.97	2.13	0.068

Fig. 6 Effect of temperature on the index of aggressiveness of the two formae speciales, Plasmopara viticola f. sp. aestivalis (P.v. aestivalis) and P. viticola f. sp. riparia (P.v. riparia), (a) during the infection process, (b) during the penetration process, (c) during the sporulation process and (d) during all three processes (the average of all three processes). Error bars represent the standard error of mean (STD) of the aggressiveness index. For each temperature, values of bars with the same letter are not significantly different according to Tukey’s test (P ≤ 0.05)