NITRATE-NONUTILIZING MUTANTS OF GIBBERELLA-ZEAE (FUSARIUM-GRAMINEARUM) AND THEIR USE IN DETERMINING VEGETATIVE COMPATIBILITY

Twenty-four single-spore isolates ofFusarium graminearum were obtained from scabby wheat seeds or glumes collected from 23 locations in Kansas in 1990. All isolates were sexually fertile and homothallic. Nitrate-nonutilizing (nit) mutants of each isolate were generated on a medium amended with 1.5% KCIO3. Of 378 mutants, 161 were able to utilize nitrite and hypoxanthine (nit1), 165 utilized hypoxanthine but not nitrite (nit3), 47 utilized nitrite but not hypoxanthine (NitM), and 5 appeared to be global nitrogen regulatory mutants similar to the previously describednnu mutant. Complementation was tested by pairingnit1 mutants of each isolate with either a NitM or anit3 mutant from each isolate on media containing nitrate as the sole nitrogen source. Complementation was more pronounced whennit1 and NitM mutants were paired. Mutants were only able to complement with other mutants from the same wild-type isolate. Therefore, each wild-type isolate belonged to a genetically distinct vegetative compatibility group. The genetic diversity suggests that sexual genetic recombination may be important in the field. © 1992 Academic Press, Inc.