Effect of sugar alcohols, antioxidants and activators of systemically acquired resistance on severity of bacterial angular leaf spot (Xanthomonas fragariae) of strawberry in controlled environment conditions

Figures & data

Table 1.  Effect of acetylsalicyclic acid (ASA), acibenzolar-S-methyl (ASM), α-tocopherol, mannitol and α-tocopherol plus mannitol on the density of angular leaf spot lesions on ‘Honeoye’ strawberry leaves

Treatment	Concentration (mM)	Lesion density^a
Water (control)		2.11 (4.32)
ASA	10.0	2.50 (5.66)
ASM	0.17	−0.63 (0.65)
α-tocopherol	20.0	1.11 (2.16)
Mannitol + α-tocopherol	50.0 + 20.0	−1.30 (0.41)
Mannitol	50.0	−2.00 (0.25)
d.f.		64
LSD0.05		0.95
P		< 0.001
^aLog2 lesions cm^−2 (back transformed lesions cm^−2).

Table 2.  Effect of increasing concentrations of either acibenzolar-S-methyl (ASM) or mannitol alone and in combination on the density of angular leaf spot lesions on ‘Honeoye’ strawberry leaves

Treatment	Concentration (mM)	Lesion density^a
Water (control)		3.33 (10.1)
ASM	0.04	−1.24 (0.42)
ASM	0.08	−1.50 (0.35)
ASM	0.17	−2.14 (0.23)
ASM	0.33	−2.63 (0.16)
Mannitol	1.9	−0.17 (0.89)
Mannitol	5.6	−1.61 (0.33)
Mannitol	16.7	−2.39 (0.19)
Mannitol	50.0	−3.33 (0.10)
d.f.		111
LSD0.05		0.57
P (linear)		< 0.001
P (ASM × Mannitol)		> 0.05
^aLog2 lesions cm^−2 (back transformed lesions cm^−2).

Table 3.  Effect of acibenzolar-S-methyl (ASM), fosetyl-Al, and the sugar alcohols, mannitol, glycerol and glucitol alone and in combination with ASM or fosetyl-Al on the density of angular leaf spot lesions on ‘Honeoye’ strawberry leaves

Treatment	Concentration (mM)	Lesion density^a
Water (control)		2.33 (5.03)
ASM	0.17	0.11 (1.08)
Fosetyl-Al	12.4	0.19 (1.14)
Mannitol	50.0	−0.93 (0.53)
Glycerol	100.0	2.55 (5.86)
Glucitol	100.0	2.10 (4.29)
d.f.		41
LSD0.05		1.20
P		< 0.001
P (ASM or Fosetyl-AL × Sugar alcohol)		> 0.05
^aLog2 lesions cm^−2 (back transformed lesions cm^−2).

Table 4.  Effect of mannitol, ascorbic acid, benzoic acid, citric acid and dimethylsulfoxide alone and in combination with mannitol on the density of angular leaf spot lesions on ‘Honeoye’ strawberry leaves

Treatment	Concentration (mM)	Lesion density^a
Water (control)		4.06 (16.7)
Mannitol	50.0	−0.27 (0.8)
Ascorbic acid	1.0	3.74 (13.4)
Benzoic acid	1.0	4.49 (22.5)
Citric acid	5.0	4.53 (23.1)
Dimethylsulfoxide (DMSO)	1.0	3.83 (14.2)
Mannitol + ascorbic	50.0 + 1.0	−0.03 (1.0)
Mannitol + benzoic	50.0 + 1.0	0.15 (1.1)
Mannitol + citric	50.0 + 5.0	−0.93 (0.5)
Mannitol + DMSO	50.0 + 1.0	0.69 (1.6)
d.f.		59
LSD0.05		1.31
P		< 0.001
P (Mannitol × antioxidants)		> 0.05
^aLog2 lesions cm^−2 (back transformed lesions cm^−2).

Table 5.  Effect of four sugar alcohols on the density of angular leaf spot lesions on leaves of 16 strawberry cultivars

	Lesion density^a
Cultivar	Control	Mannitol	Ribitol	Glucitol	Inositol	Means
Mira	2.40 (5.3)	3.20 (9.2)	1.00 (2.0)	2.43 (5.4)	2.33 (5.0)	2.27 (4.8)
Seneca	3.77 (13.7)	−2.43 (0.2)	3.50 (11.3)	3.60 (12.1)	4.74 (26.7)	2.64 (6.2)
Sparkle	3.97 (15.6)	0.73 (1.7)	2.48 (5.6)	3.23 (9.4)	3.43 (10.7)	2.77 (6.8)
Glooscap	4.46 (22.0)	0.53 (1.4)	1.4 (2.7)	0.95 (1.9)	1.77 (3.4)	1.82 (3.6)
Kent	4.68 (25.6)	−1.25 (0.4)	3.35 (10.2)	4.58 (24.0)	4.87 (29.3)	3.25 (9.5)
Cavendish	4.68 (25.7)	0.81 (1.8)	4.76 (27.1)	2.87 (7.3)	2.03 (4.1)	3.03 (8.2)
Jewel	4.80 (27.9)	−2.41 (0.2)	4.10 (17.1)	2.80 (7.0)	3.75 (13.4)	2.61 (6.1)
Honeoye	4.85 (28.9)	−0.23 (0.9)	3.60 (12.3)	4.40 (21.1)	4.11 (17.3)	3.35 (10.2)
Cabot	4.90 (28.9)	−3.14 (0.1)	2.63 (6.2)	2.62 (6.2)	3.57 (11.8)	2.12 (4.3)
Annapolis	4.96 (31.1)	−0.69 (1.6)	3.90 (14.9)	4.39 (21.0)	3.03 (8.1)	3.39 (10.5)
Brunswick	5.12 (34.9)	−3.35 (0.1)	1.82 (3.5)	1.80 (3.5)	4.10 (17.2)	1.90 (3.7)
Bounty	5.14 (35.2)	0.06 (1.0)	2.98 (7.9)	3.23 (9.4)	4.33 (20.1)	3.15 (8.9)
Veestar	5.17 (36.0)	3.40 (10.6)	2.60 (6.1)	2.64 (6.2)	3.39 (10.5)	3.44 (10.9)
Evangeline	5.18 (36.3)	−1.40 (−0.4)	2.89 (7.4)	3.65 (12.6)	2.77 (6.8)	2.62 (6.1)
Sable	5.25 (38.0)	1.58 (3.0)	3.98 (15.8)	3.75 (13.5)	4.81 (28.1)	3.87 (14.7)
Micmac	5.42 (42.7)	2.53 (5.8)	4.09 (17.1)	4.40 (21.1)	3.55 (11.7)	4.00 (16.0)
Means	4.67 (24.2)	−0.04 (1.1)	3.07 (8.4)	3.21 (9.7)	3.53 (12.0)	2.89 (7.4)
	Cv	Sugar alcohol	Cv × sugar alcohol
d.f.	552	552	552
LSD0.05	0.65	0.37	1.46
P	< 0.001	< 0.001	< 0.001
^aLog2 lesions cm^−2 (back transformed lesions cm^−2).

Fig. 1. Mannitol treated strawberry ('Honeoye') leaf (left) compared with a water-treated control (right). Both plants were challenge inoculated with Xanthomonas fragariae 48 h after treatment and incubated in a humid chamber for 40 days. Individual lesions have coalesced in the control.

Fig. 2. Molecular structure of two similar sugar alcohols, mannitol and glucitol.