During a survey of root diseases of pea in Denmark, a new genetic vari
ant of Fusarium oxysporum f.sp. pisi was isolated from vining peas in
two widely separated geographical regions. In terms of pathogenicity o
n a set of differential pea lines, the Danish isolated closely resembl
ed a race 6 isolate from the United States. DNA extracts of the isolat
es: restricted with the endonuclease HindIII, then probed with a homol
ogous repetitive genomic fragment from the plasmid pDG106 by the South
ern hybridization technique, gave a unique 'fingerprint' pattern disti
nctly different from the American race 6 and all other known races. Wh
en probed with pDG312, containing a homologous ribosomal repeat unit,
the pattern obtained for the Danish isolates-was indistinguishable fro
m races 1, 5 and 6 but distinctly different from 2A and 2B. The Danish
isolates represent a separate vegetative compatibility group because
they are compatible with each other but incompatible with the other kn
own races. In pigmentation the new variant resembled races 1, 5 and 6
for the first 8-12 days, after which it began to secrete a dark purple
pigment resembling that of race 2A and 2B. Until an additional line i
n the host differentials can separate the new genetic variant it shoul
d be considered a subgroup of F. oxysporum f. sp. pisi race 6.