Comparison of Stenocarpella maydis isolates for isozyme and cultural characteristics

Isolates of Stenocarpella maydis from seed companies and plant disease clin ics in the United States and the Republic of South Africa were assayed for isozyme polymorphisms and cultural variability. A low level of isozyme poly morphisms was detected in this collection of isolates. Isozyme polymorphism s were detected for cx-esterase, hexose kinase, and malate dehydrogenase of the enzymes assayed. Fungi often have limited variability among isozyme pr ofiles, and this is especially true for fungi that have host specialization such as biotrophs or fungi with formae speciales designations. Optimum gro wth temperature, colony color, and pycnidiospore production were also measu red. All isolates had an optimum temperature of 28 to 31 degrees C for colo ny growth on acidified potato dextrose agar. Colony color and pycnidiospore production were variable over the course of several experiments, indicatin g that these phenotypes are poor genetic markers.