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Eumusae leaf spot

Scientific Name
Mycosphaerella eumusae
Scientific Author
Crous & Mour.
Taxonomy
Dothideomycetes, Capnodiales
Status
Exotic species - absent from Australia
Reliability
High
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Diagnostic Images

Defoliation caused by Eumusae disease
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for use contact bananathanga@rediffmail.com
Source
R. Thangavelu National Research Centre for Banana
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Diagnostic Images (7)
Diagnostic Notes

Symptoms

 

Mycosphaerella eumusae has similar leaf spot characteristics to M. fijiensis and M. musicola. Primary lesions are brown streaks that expand to form large brown spots. This stage of the disease is the most recognisable and can be used to distinguish between the three Mycosphaerella leaf spot diseases. As the disease progresses, spots become grey in the centre but keep a brown border (Crous & Mourichon 2002).

 

The fungus:

 

Leaf spots amphigenous, initially visible as faint brown streaks, developing into oval or elliptical light brown lesions with grey centres and dark brown borders, coalescing to form large, brown necrotic areas under favourable conditions. Grey spots and patches are visible in necrotic areas, and lesions are surrounded by a chlorotic yellow zone. Pseudothecia amphigenous, predominantly hypophyllous, black, subepidermal, becoming slightly erumpent, globose, up to 80 µm diam., apical ostiole 10–15 µm wide; wall consisting of 2–3 layers of medium brown textura angularis. Asci aparaphysate, fasciculate, bitunicate, subsessile, obovoid, straight or slightly incurved, 8-spored, 30–50 × 9–15 µm. Ascospores tri- to multiseriate, overlapping, hyaline, guttulate, thick-walled, straight, obovoid with obtuse ends, widest in the middle of apical cell, medianly 1-spetate or basal cell slightly longer than apical cell, tapering towards both ends, but with more prominent taper towards lower end, (11–)12–13(–16.5) × (3–)3.5–4(–4.5) µm. Spermogonia predominatly hypophyllous, subepidermal, substomatal, globose, dark brown, up to 75 µm diam. Spermatia hyaline, rod-shaped, 3–6 × 1–2 µm. Mycelium internal, pale brown, consisting of septate, branched, smooth hyphae, 1.5–2.5 µm wide. Caespituli sporodochial, subepidermal, substomatal, predominantly epiphyllous, grey, up to 100 µm wide. Conidiophores aggregated in dense fascicles arising from the upper cells of a brown stroma up to 70 µm wide; conidiophores subcylindrical, smooth, hyaline or pale brown below, 0–3-septate, straight to geniculate-sinuous, unbranched or branched below, 10–25 × 3–5 µm. Conidiogenous cells terminal, unbranched, hyaline, smooth, tapering to flat-tipped apical loci, proliferating sympodially, or 1–4 times percurrently near the apex, 10–20 × 3–4 µm; scars inconspicuous. Conidia solitary, subhyaline to pale olivaceous, thick-walled, smooth, subcylindrical, apex obtuse, base subtruncate, straight to variously curved, 3–8-septate, (18–)30–50(–65) × (2–)2.5–3 µm; hila inconspicuous (Crous & Mourichon 2002).

 

Notes:

 

Two other virulent Mycosphaerella leaf spot diseases of banana are known. M. fijiensis Morelet (anamorph: Pseudocercospora fijiensis (Morelet) Deighton; black Sigatoka) and M. musicola R. Leach (anamorph: Pseudocercospora musae (Zimm.) Deighton; Sigatoka disease).

The teleomorphic stages of the Mycosphaerella leaf spot diseases on banana are morphologically similar and cannot yet be used as a method of diagnosis (Carlier et al. 2000). The anamorphic forms are distinctive and can be used for morphologic identification (Crous & Mourichon 2002):

 

 

Morphology

P. eumusae

P. fijiensis

P. musae

Sporodochia

epiphyllous

hypophyllous

amphigenous

Conidiophores

 

 

 

septa

0 to 3

0 to 5

aseptate

colour

sub-hyaline to pale brown

pale brown

pale brown

shape

subcylindrical

subcylindrical

ampulliform

size

10-25 x 3-5 µm

16.5-62.5 x 4-7 µm

5-25 µm

conidiogenic loci

truncate ends

minutely thickened scars

lacking visible scars

Conidia

 

 

 

shape

subcylindrical

obclavate to cylindric-obclavate

cylindrical to cylindric-obclavate

septa

3 to 8

1 to 10; commonly 5 to 7

0 to 8; commonly 2 to 5

size

(18-)30-50(-65) x (2-)2.5-3 µm

10-120 x 2.5-5 µm

6.5-22 x 2.5-4 µm

Table: Anamorphic characteristics of Musa leaf spot fungi.

 

More Information
Author
Thangavelu R, Carlier J, Henderson J & McTaggart AR
Created
16/10/2007 02:24 AEST
Last Updated
16/10/2007 14:24 AEST
Citation
Thangavelu R, Carlier J, Henderson J & McTaggart AR (2007) Eumusae leaf spot (Mycosphaerella eumusae) Updated on 10/16/2007 2:24:03 PM Available online: PaDIL - http://www.padil.gov.au.
Image Use
Free for use under the Creative Commons Attribution 3.0 Australia License

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