Home • Cercospora zeae-maydis v1.0
Photo of Cercospora zeae-maydis v1.0
Symptoms of Cercospora zeae-maydis on corn plants (Department of Plant Pathology Archive, North Carolina State University, Bugwood.org)

Cercospora zeae-maydis is a haploid, ascomycete fungus that causes gray leaf spot disease of corn (Zea mays). This disease was first discovered in Illinois, USA, during 1925 but has increased greatly in occurrence and severity during the past 20 years and now is an economic threat in many corn-production areas worldwide. Greater occurrence and severity of the disease have been associated with increased use of minimum-tillage agriculture. Symptoms include elongated, rectangular leaf lesions, discoloration (chlorosis), and entire leaf blight caused by coalescing lesions that can reduce yields by more than 50% under disease-favorable conditions. Gray leaf spot is an important disease throughout the United States, and is economically significant in the Midwest and Mid-Atlantic regions. However, it also occurs in Central America, China, Europe, India, Mexico, the Philippines, Southeast Asia, and is particularly devastating in parts of South America and Africa. Effective management of gray leaf spot is essential to ensure a stable supply of food, feed and fuel from corn crops of the future.

Cercospora zeae-maydis belongs to the class Dothideomycetes, one of the largest groups of fungi, which includes numerous economically significant plant pathogens as well as non-pathogenic saprophytes and extremophiles. No species of Cercospora has a known sexual stage, but phylogenetic analyses have shown that all are closely related to the sexual genus Mycosphaerella in the order Capnodiales. Both Cercospora and Mycosphaerella are extremely large genera of plant-pathogenic fungi and infect a wide diversity of plants, including almost all major crops. In addition to maize, members of the genus Cercospora infect numerous other crops that are important for energy production, such as C. beticola on sugar beet, C. kikuchii and C. sojina on soybean, C. longipes on sugar cane, and C. sorghi on sorghum. Other related pathogens include Mycosphaerella graminicola on wheat, Dothistroma septosporum on pine trees and Septoria musiva on poplars. Recent phylogenetic analyses have shown that gray leaf spot is a disease complex caused by two very closely related species, C. zeae-maydis, which predominates in North America but also occurs worldwide, and C. zeina, which occurs in North America but predominates in Africa.

In addition to being a significant pathogen of a major bioenergy crop, C. zeae-maydis is interesting because it produces the non-host-selective toxin cercosporin. Ability to produce this toxin seems to have been acquired by a common ancestor of the genus Cercospora and may have facilitated a rapid adaptive radiation of numerous species onto different hosts. The toxin is activated by light and its production is regulated so that it is available to the fungus only when needed. Light receptors have been cloned from C. zeae-maydis, and it is one of very few plant pathogens in which photobiology is known to be important. The genome sequence of C. zeae-maydis will be very useful for understanding mechanisms of pathogenicity, toxin production and photobiology and will facilitate opportunities for comparative analyses of the Dothideomycetes.

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