Use of molecular markers for monitoring fungi involved in stalk rot of corn.

Separate genes conferring antibiotic drag resistance have been inserted into Fusarium graminearum and Fusarium moniliforme. These organisms are associated with stalk rot of corn, a disease of uncertain cause. Antibiotic resistant fungi were obtained by developing a gene transfer system using whole cells as recipients for DNA. Hygromycin B and benomyl-resistant colonies were isolated by treating fungal tissue with lithium acetate and adding plasmid vectors containing the respective genes which give drug resistance. The DNA was stably integrated into the fungal chromosome. Following plant inoculation, disease symptoms developed and the isolates were recovered on selective medium. In each case, these fungi retained the transformed phenotype, although extensive rearrangements and/or deletions occurred. Specific molecular tagging allows detailed studies of this interaction and should be of general use in situations involving complex multiple pathogen diseases.