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Cephalosporium gramineum

By: Richard Bittner

A Class Project for PP728 Soilborne Plant Pathogens

Fall 2010

Introduction

Photo Courtesy Cereal Disease Encyclopedia HGCA

Cephalosporium stripe is a disease of winter cereals.  This disease is caused by the soil borne fungus Cephalosporium gramineum (sporodochial stage: Hymenula cerealis) (1).  In 1930 the pathogen was first reported in Japan on wheat and barley and then on wheat in North America in 1955 (2).  The pathogen is the only true vascular wilt pathogens on wheat.  Overall the distribution of the pathogen is very sporadic in wheat growing regions (3).  However, the disease can cause high yield loses when it occurs in a field.  The pathogen is favored by wet soils, root injury, and repeated cropping of small grains (2).

Host Range and Distribution

Cephalosporium gramineum is a major pathogen of wheat (Triticum spp.).  The pathogen also infects barley (Hordeum vulgare), rye (Secale cereal), oats (Avena sativa), triticale (Triticosecale), and numerous grasses such as Bromus, Poa, and Dacty (1,3).  Cephalosporium gramineum can be found in North America (Midwest and Northwest states), South Africa, Europe, and Japan.

Isolation

From Soil:  Combine 15 to 25 grams of soil and 100 ml of water in a container.  Mix the water and soil in a shaker for 15 min.  The liquid suspension is then dilution-plated on Cephalosporium gramineum semiselective medium (CGSM).  Incubate plates at 15ºC for 10-12 days (5).

From Host Tissue:  Surface sterilize plant tissue by dipping in 70% ethanol, remove excess ethanol by blotting with paper towels.  Place plant tissue in 1% NaOCl, 1 min for root tissue and 2 min for stem tissue.  Cut root and stem tissue into 1-2 cm-long pieces and place on CGSM.  Incubate plates at 15ºC for 10-12 days (5).

Cephalosporium gramineum semiselective medium (CGSM): Use half strength acidified corn meal agar (0.5 ACMA).  Add 0.5 mg dicloran, 1.0 mg tolclofos-methyl, and 0.5 mg of triphenyltin hydroxide per liter after autoclaving.  Also bring the medium pH to 4.0 using 1.25 ml of 25% lactic acid after autoclaving media (4).

Identification

The pathogen causing this disease has two spore stages.  Cephalosporium gramineum produce conidiophores which produce conidia during the parasitic phase (2).  In the fall a saprophytic phase develops on dead wheat tissue where the fungus produces a fruiting structure that consists of a cluster of short conidiophores which are woven together on a mass of hyphae known as a sporodochia.  The fungus in this saprophytic stage is then called Hymenula cerealis (2).  

Symptoms

 

Photo Courtesy Maloy, O. C. and Inglis, D. A.   Washington State University

In young plants disease symptoms of Cephalosporium stripe is first observed in the late winter or early spring as yellow stripes which extend the length of the leaf blade (2,3).  Yellow stripes may also appear on the stem and sheath.  The leaf tissue may also contain necrotic brown streaks which border the yellow stripe.  Diseased plants will appear stunted, ripen prematurely producing white heads, and seed will be shriveled (2,3).  In mature plants the disease can be identified by observing darkened vascular bundles and nodes.  When the node is cut length wise, the inner nodal tissue will be brown in color (2,3).

Ecology and Life Cycle  

Photo Courtesy Cereal Disease Encyclopedia HGCA

Cephalosporium gramineum can survive in infested crop material for 4 to 5 years (3).  The survival period of the pathogen can be enhanced by antibiotic production (3).  Cephalosporium gramineum is favored by excessive soil and surface water from October through December, injury to roots, low soil pH, and frequent planting of small grains (2).  Cool wet soils can also cause the pathogen to sporulate at a faster rate.  Cephalosporium gramineum enters susceptible plant roots through wounds (2).  These wounds can occur from heaving during freezing and thawing of soils (2,3).  Inside the root the conidia germinate and produce conidiophores.  A conidiophore is a specialized hypha which produces one or more conidia.  These conidia then move into the vascular system where they lodge and germinate in the nodes and leaves (1).  The pathogen causes wilting of the plant, because the vascular system becomes clogged preventing the movement of water throughout the plant (1).    

Selected References

1.    HGCA. 2010. Cephalosporium Leaf Stripe.  Online. Cereal Disease Encyclopedia HGCA.

2.    Lipps, P. E. 2010. Cephalosporium Stripe of Wheat. Online. Ohio State University Extension.            

3.    Maloy, O. C., and Inglis, D. A. 1993. Cephalosporium Stripe. Online. Washington State University.

4.    Specht, L. P., and Murray, T. D. 1989. Sporulation and survival of conidia of Cephalosporium gramineum as influenced by soil pH, soil matric potential, and soil fumigation. Phytopathology. 79:787-793.

5.    Stiles, C. M., and Murray, T.D. 1996. Infection of field-grown winter wheat by Cephalosporium gramineum and the effect of soil pH. Phytopathology. 86:177-183.