Variation among isolates of Fusarium lateritium from sweetpotato for pathogenicity and vegetative compatibility

Isolates (132) of Fusarium lateritium from sweetpotato and from other hosts (20) were compared for pathogenicity to sweetpotato vines and vegetative compatibility grouping (VCG) using complementation among nitrate nonutilizing (nit) mutants. Isolates from sweetpotato were either nonpathogenic or fell into one of two pathotypes: the chlorotic leaf distortion (CLD) pathotype, which induced all symptoms of CLD, or the epiphytic mycelial growth pathotype, which produced the typical epiphytic, systemic mycelial growth but did not induce chlorosis. With one possible exception, isolates from other hosts were nonpathogenic to sweetpotato. All isolates from sweetpotato produced nit mutants, and 44 VCGs were identified. Only 16 of 20 isolates from other hosts could be induced to produce nit mutants, only 10 of these were self-compatible, and none of these were compatible with any other isolate. Sweetpotato isolates from the United States appeared less diverse by VCG analysis than isolates from Africa.