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Host-Specific Forms of Trichometasphaeria turcica in Relation to Homokaryons and Heterokaryons in Nature. O. R. Masias, Former Graduate Student, and R. R. Bergquist, Assistant Plant Pathologist, Plant Pathology Department, College of Tropical Agriculture, University of Hawaii, Honolulu 96822. Phytopathology 64:436-438.

Trichometasphaeria turcica (Helminthosporium turcicum) isolates from nature pathogenic to only one host species of corn, sorghum, or johnson grass were homokaryons.  T. turcicaisolates from nature pathogenic to both corn and sorghum were heterokaryons, with one exception wich is postulated to be a recombinant from a heterokaryon.  Heterokaryon analysis suggests physiological distinctness of genes that condition pathogenicity to each host species.  Genes which conditioned pathogenicity to corn and sorghum functioned in an additive manner in a heterokaryon.  No evidence for recessiveness or dominance was detected in heterokaryons pathogenic to more than one host.