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Cytological Karyotyping of Three Cochliobolus spp. by the Germ Tube Burst Method

April 2001 , Volume 91 , Number  4
Pages  354 - 360

Dai Tsuchiya and Masatoki Taga

Department of Biology, Faculty of Science, Okayama University, Tsushima-naka, 700-8530, Japan

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Accepted for publication 8 January 2001.

Cytological karyotypes with mitotic metaphase chromosomes were analyzed for Cochliobolus heterostrophus, C. carbonum, and C. sativus by the germ tube burst method (GTBM). Prior to karyotyping, procedures of GTBM suitable to Cochliobolus were established by examining several crucial conditions such as incubation period of conidia. The estimated chromosome numbers of C. heterostrophus and C. carbonum were n = 15 or 16 and n = 13 or 15 depending on the strains, respectively. In C. sativus, n = 15 was estimated. Morphological information of chromosomes including chromosome size and a threadlike-specific structure representing the nucleolar organizing region was also obtained. Our results for some standard strains are in agreement with previous estimates by pulsed field gel electrophoresis (PFGE) or PFGE coupled with restriction fragment length polymorphism genetic linkage analysis, but inconsistent with the previous estimates for other strains by conventional light microscopic cytology. Additionally, PFGE analysis of C. heterostro-phus strains indicated that chromosome number was not determinable solely by PFGE, which is hampered by comigration and clumping of DNA bands.

Additional keywords: genome , Northern corn leaf blight , Southern corn leaf blight .

© 2001 The American Phytopathological Society