Pathogenicity resulting from mutation at the b locus of Ustilago maydis

This paper explores the genetic basis of the ability of the fungus, Ustilago maydis, to induce neoplastic galls in the corn plant (Zea mays). Pathogenic mutants of U. maydis were produced by ultraviolet irradiation of cultures of nonpathogenic diploids homozygous at the b locus. The mutants formed smaller neoplasms, produced fewer teliospores, and showed higher frequencies of meiotic failure and lower rates of basidiospore survival than did the wild-type fungus.