Status of Macrophomina phaseolina on Strawberry in California and Preliminary Characterization of the Pathogen

Figures & data

Table 1. Susceptibility of strawberry cultivars to toothpick crown inoculation with a California isolate of Macrophomina phaseolina.

Cultivar	Disease severity of strawberry inoculated with M. phaseolina^z		Disease severity of strawberry inoculated with sterile toothpick^z
	4 weeks	8 weeks	4 weeks	8 weeks
Albion	4.0	5.0	1	1
Camarosa	4.2	5.0	1	1
Diamante	4.9	5.0	1	1
Seascape	2.9	4.2	1	1
Ventana	3.9	5.0	1	1
LSD (P = 0.05)	0.8	n/s^y	n.a.^x	n.a.

^zNumbers represent mean values of disease severity where 1 = no symptoms; 2 = only lower older leaves were wilted, chlorotic, and/or necrotic; 3 = less than 50% of the foliage was wilted, chlorotic, and/or necrotic and included symptomatic younger foliage; 4 = more than 50% of the foliage was wilted, chlorotic, and/or necrotic; 5 = complete plant collapse and death.

^yn/s = no significant difference among cultivars at P = 0.05.

^xn.a. = not applicable. Sterile toothpick control plants were not included in the statistical analysis.

Table 2. Pathogenicity of strawberry and non-strawberry Macrophomina phaseolina isolates to strawberry (cv. San Andreas).

Isolate	Original host	Mean disease severity^z	Recovery of M. phaseolina
11-9	Strawberry	3.2	Yes
11-12	Strawberry	1.2	Yes
11-15	Strawberry	3.0	Yes
11-16	Strawberry	1.0	n.t.^x
11-17	Strawberry	1.3	Yes
11-18	Strawberry	3.3	Yes
11-20	Melon	1.0	n.t.
11-23	Melon	1.0	n.t.
13-1	Thyme	1.0	n.t.
13-9	Melon	1.0	n.t.
13-14	Apple	1.0	n.t.
LSD (P = 0.05)	—	0.34	—
Sterile toothpick	—	1.0^y	n.t.

^zNumbers represent mean values of disease severity where 1 = no symptoms; 2 = only lower older leaves were wilted, chlorotic, and/or necrotic; 3 = more than 50% of the foliage was wilted, chlorotic, and/or necrotic; 4 = complete plant collapse and death.

^ySterile toothpick control plants were not included in the statistical analysis.

^xn.t. = plants were symptomless and were not tested for M. phaseolina.

Table 3. Susceptibility of cover crops and strawberry to root inoculation with two isolates of Macrophomina phaseolina recovered from strawberry.

Plant	Root inoculation treatment	Number of plants with foliar dieback/ total plants	Number of plants with discolored roots/ total plants	Roots colonized with Macrophomina/ total roots tested
Vicia faba	Isolate 08-12	0/18	8/9	0/30
(fava bean)	Isolate 08-17	0/18	5/9	0/30
	Sand-cornmeal	0/18	0/9	n.t.^z
Sinapis alba	Isolate 08-12	0/45	0/9	1/30
(mustard)	Isolate 08-17	0/45	0/9	0/30
	Sand-cornmeal	0/45	0/9	n.t.
Avena sativa	Isolate 08-12	0/45	0/9	0/30
(oat)	Isolate 08-17	0/45	0/9	0/30
	Sand-cornmeal	0/45	0/9	n.t.
Secale cereale	Isolate 08-12	0/45	0/9	0/30
(rye)	Isolate 08-17	0/45	0/9	0/30
	Sand-cornmeal	0/45	0/9	n.t.
Vicia sativa	Isolate 08-12	0/45	0/9	0/30
(vetch)	Isolate 08-17	0/45	0/9	0/30
	Sand-cornmeal	0/45	0/9	n.t.
Fragaria ×	Isolate 08-12	8/10	9/9	5/20
ananassa	Isolate 08-17	6/10	9/9	4/20
(strawberry)	Sand-cornmeal	0/10	0/9	n.t.

^zn.t. = sand-cornmeal treated control plants were not tested for M. phaseolina.

Figure 1. Unweighted pair group method with arithmetic mean (UPGMA) cladogram calculated in NTSYS showing the relationship among isolates of Macrophomina phaseolina for 65 simple sequence repeat (SSR) markers.