Jg. Van Der Beek et al., A pathotype system to describe intraspecific variation in pathogenicity ofMeloidogyne chitwoodi, J NEMATOL, 31(4), 1999, pp. 386-392
Tests of eight Dutch Meloidogyne chitwoodi isolates to the differential set
for host races 1 and 2 in M. chitwoodi provided no evidence for the existe
nce of host race 2 in the Netherlands. The data showed deviations from expe
cted reactions on the differential hosts; which raised doubts of the useful
ness of the host race classification in M. chitwoodi. The term "pathotype"
is proposed for groups of isolates of one Meloidogyne sp. that exhibit the
same level of pathogenicity on genotypes of one host species. We recommend
that the pathotype classification be applied in pathogen-host relationships
when several genotypes of a Meloidogyne sp. are tested on several genotype
s of one host species. Three pathotypes of M. chitwoodi were identified on
Solanum bulbocastanum, suggesting at least two different genetic factors fo
r virulence and resistance in the pathogen and the host species, respective
ly. The occurrence of several virulence factors in M. chitwoodi will compli
cate the successful application of resistance factors from S. bulbocastanum
for developing resistant potato cultivars.