Visual and Electronic Evaluations of Detached Strawberry Leaves Inoculated with Colletotrichum Species

Figures & data

FIGURE 1 Main effect due to Group (A) and Isolate (B) of detached strawberry leaves inoculated with two Colletotrichum fragariae (CF63 and CF75) isolates and one C. gloeosporioides (CG162) isolate. Within each variable, bars with different letters are significantly different at p < 0.05 according to Fisher's protected least significant difference test.

TABLE 1 Average Percent Lesion Area Corresponding to Each Value of the 0–5 Visual Scale for Each of Two Independent Raters and Their Average Disease Scores Following Inoculation of Detached Strawberry Leaves with Three Colletotrichum Species

	Rater 1		Rater 2		Average
Disease score	N ^z	% Lesion area ^y	N	% Lesion area	N	% Lesion area
0	335	0.6 e ^x	124	0.3 e	157	0.3 e
1	132	2.1 e	440	2.2 e	316	1.4 e
2	92	4.8 d	71	14.4 d	122	5.9 d
3	66	15.5 c	35	33.6 c	54	22.3 c
4	52	34.7 b	19	64.3 b	39	49.2 b
5	36	75.3 a	24	85.6 a	25	85.6 a
LSD		2.4		3.2		2.6
^zTotal number of leaves scored at each value of the disease scale.
^yAverage percent lesion area was determined from the percent lesion area of each of the leaves scored at each value of the 0–5 disease rating scale.
^xTreatments with the same letter are not significantly different according to Fisher's protected least significant difference (p = 0.05).

FIGURE 2 Average percent lesion area vs. disease score of 21 strawbery clones following inoculation with three isolates of Colletotrichum spp. Percent lesion area was calculated from computer image analysis of photographed leaves. Disease scores are based on visual ratings by two independent raters and the average of their ratings. Exponential trend lines were calculated from the disease scores of each of two raters and their average score.

TABLE 2 Average Percent Lesion Area and Average Disease Score for Two Raters for Each of 21 Strawberry Clones Following Inoculation of Detached Strawberry Leaves with Three Colletotrichum Species

Group	Clone	N ^z	Lesion area (%) ^y	Disease score ^x
MS	Pelican	38	2.1 e ^w	0.6 hi
MS	MSUS1362	34	2.2 e	0.6 i
MS	MSUS1145	33	4.4 de	0.7 ghi
MS	US438	31	4.6 de	0.9 fghi
MS	US159	39	5.4 de	0.9 fghi
Cultivar	Earliglow	34	5.6 de	1.0 defghi
MS	MSUS1229	33	6.1 de	0.9 fghi
MS	MSUS1230	37	6.7 cde	1.0 efghi
MS	MSUS1365	30	7.0 cde	1.2 cdefg
MS	MSUS478	32	7.3 bcde	1.1 defgh
MS	MSUS1105	32	8.8 bcde	1.5 bcd
MS	MSUS1196	34	9.3 bcde	1.1 defghi
MS	MSUS1078	32	9.4 bcde	1.1 cdefg
MS	MSUS1511	41	9.5 bcde	0.9 efghi
Cultivar	Ovation	31	9.5 bcde	1.7 abc
Cultivar	Allstar	34	11.2 bcde	1.4 bcdef
Cultivar	Jewel	33	12.8 abcd	1.8 ab
Cultivar	Selva	30	13.9 abcd	1.5 bcde
Cultivar	Seascape	33	16.2 abc	1.8 ab
Cultivar	Chandler	36	16.8 ab	1.9 ab
Cultivar	Honeoye	36	21.9 a	2.2 a
	LSD		9.5	0.5
^zTotal number of detached strawberry leaves inoculated with three Colletotrichum species.
^yBased on average percent lesion area, values ≤7.0% are resistant (bold), >12.0% are susceptible (italic), and >7.0–12.0% are intermediate.
^xBased on average disease scores, scores ≤1.2 are resistant (shown in bold print), those >1.5 are susceptible (shown in italics), and those >1.2–1.5 are intermediate.
^wTreatments with the same letter are not significantly different according to Fisher's protected least significant difference (p = 0.05).

FIGURE 3 Anthracnose leaf spot on strawberry leaves following inoculation with Colletotrichum gloeosporioides (A) and C. fragariae (B). Original photograph of a leaf inoculated with C. gloeosporioides (C) and the same photograph computer enhanced (D). Visual scores for this leaf were 3 (Rater 1) and 2 (Rater 2), and 2.5 (average). Computer analysis determined the percent lesion area to be 10.2% (color figure available online).