Author
 |
DUNKLE, LARRY |
|
Submitted to: International Plant Protection Congress
Publication Type: Abstract Only Publication Acceptance Date: 4/20/2004 Publication Date: 5/11/2004 Citation: Dunkle, L.D. 2004. Two cercospora pathogens causing gray leaf spot of maize. International Plant Protection Congress. p. 368. Interpretive Summary: Technical Abstract: Gray leaf spot (GLS), a foliar disease of maize (Zea mays), is caused by two fungal pathogens, Cercospora zeae-maydis and an undescribed species. These two pathogens, referred to as C. zeae-maydis Group I and C. zeae-maydis Group II, respectively, are closely related based on commonly applied taxonomic criteria, cause identical GLS symptoms, and are equally virulent or aggressive on a range of maize hybrids. However, the pathogens can be distinguished by a variety of cultural and genetic characteristics. Isolates of Group I grow faster on all media tested and produce the photoactivated perylenequinone phytotoxin, cercosporin, on media deficient in nitrogen. Isolates of Group II grow more slowly and do not produce cercosporin in culture. The nucleotide sequences of the ITS region of rDNA and AFLP profiles of genomic DNA of the two groups differ sufficiently to suggest that they are different species, both of which are distinct from the related sorghum pathogen, C. sorghi. Isolates of Group I contain a degenerate, inactivated transposable element, designated Malazy, that is absent from isolates of Group II, suggesting that the two species diverged before the acquisition of the transposable element by Group I. Populations of each pathogen from different continents are remarkably similar based on AFLP profiles and other molecular data. Both groups occur sympatrically in North America and South America, but only Group II has been recorded in Africa and only Group I in a limited number of samples from China. |
