Genetics of Gibberella fujikuroi. II. Natural occurrence and significance of heterokaryosis in sorghum isolates

Abstract

Of all the stalk rot fungi, Gibberella fujikuroi (Sawada) Wollenw. (anamorph stage Fusarium moniliforme Sheld.) was most frequently isolated from naturally infected, symptomless sorghum plants. Phenotypically distinct isolates of G. fujikuroi were recovered. This variability is ascribed to heterokaryosis. The homokaryotic components of the most frequently recovered heterokaryons found at a given growth stage were identified on the basis of colony color, texture, growth rate, and sporulation. Nuclear ratios were determined to confirm the presence and stability of heterokaryons. Natural and laboratory-induced heterokaryons were compared on synthetic and natural media, prepared from plant tissue, for stability and other attributes. The occurrence of different heterokaryons at different growth stages suggests genetic adaptation and a possible role of heterokaryosis in generating and maintaining natural variability in this fungus.