Cochliobolus sativus

The fungus Cochliobolus sativus is the teleomorph (sexual stage) of Bipolaris sorokiniana (anamorph) which is the causal agent of a wide variety of cereal diseases. The pathogen can infect and cause disease on roots (where it is known as common root rot), leaf and stem, and head tissue. C. sativus is extremely rare in nature and thus it is the asexual or anamorphic stage which causes infections. The two most common diseases caused by B. sorokiniana are spot blotch and common root rot, mainly on wheat and barley crops.

Identification

The mycelium of B. sorokiniana is usually deep olive-brown. New cultures produce abundant simple conidiophores, which may be single or clustered and measure 6–10 x 110–220 μm with septations. Conidia develop laterally from pores beneath each conidiophore septum. Conidia are olive-brown and ovate to oblong, with rounded ends and a prominent basal scar. They measure 15–28 x 40–120 μm and are 3- to 10-septate. Some may be slightly curved. Their walls are smooth and noticeably thickened at the septa.

The sexual state (C. sativus), when formed in culture, is in the form of black, globose pseudothecia 300–400 μm in diameter, with erect beaks 50–200 μm long. Asci are clavate and measure 20–35 x 150–250 μm. Ascospores are hyaline, uniformly filamentous, and spirally flexed within asci. They measure 5–10 x 200–250 μm and are 4- to 10-septate.

Host species

Agropyron cristatum¹, Allium sp. ¹, Alopecurus pratensis¹, Aneurolepidium chinense¹, Avena sativa¹

Bromus inermis¹, B. marginatus¹, B. willdenowii¹

Calluna vulgaris¹, Chloris gayana¹, Cicer arietinum¹, Clinelymus dahuricus¹, C. sibiricus¹, Cynodon dactylon¹, C. transvaalensis¹

Dactylis glomerata¹

Echinochloa crus-galli¹, Elymus junceus¹

Festuca sp. ¹

Guzmania sp. ¹

Hordeum brevisubulatum¹, H. distichon¹, H. sativum var. hexastichon¹, H. vulgare¹, H. vulgare var. hexastichon¹

Lablab purpureus¹, Linum usitatissimum¹, Lolium multiflorum¹

Pennisetum typhoides¹

Roegneria semicostata¹

Saccharum sp. ¹, Secale cereale¹, Setaria italica¹, Sorghum sp. ¹

Taraxacum kok-saghyz¹, Trisetum aestivum¹, Triticum aestivum¹, T. secale¹, T. turgidum subsp. durum, T. vulgare¹

Zea mays¹

Notes

1. USDA ARS Fungal Database

Geographical distribution

Cochliobolus sativus has a world-wide distribution.

Notes

1. USDA ARS Fungal Database 2. https://jukuri.luke.fi/bitstream/handle/10024/485232/mttraportti183.pdf

Main diseases

Common root rot (barley); Common root rot (wheat); spot blotch (barley); Spot blotch (wheat)

Spot blotch of wheat

This is most important disease in non-tradition wheat growing areas. The B. sorokiniana comes with Pyrenophora tritici-repentis and causes millions of tons of wheat loss each year. The symptoms are blotch as well as induced senescence due to premature chlorophyll losses Rosyara et al., 2007.

References

External links

• Index Fungorum
• USDA ARS Fungal Database
• Helminthosporium leaf blights: spot blotch and tan spot
• Diagnosis of Common Root Rot of Wheat and Barley