A. Purwantara et al., BIOASSAY AND BAITING METHODS FOR DETERMINING OCCURRENCE OF RACES OF PHYTOPHTHORA-CLANDESTINA IN SOIL, Australian journal of experimental agriculture, 36(7), 1996, pp. 815-822
The method currently used for determining races of Phytophthora clande
stina requires isolation of pure cultures of the pathogen and testing
of their pathogenicity on a range of differential cultivars. To date,
the pathogen has not been isolated directly from soil and isolation of
the pathogen from naturally infected seedlings is laborious. A bioass
ay involving the planting of differential cultivars in soil samples in
small planting trays was developed to identify races of P. clandestin
a in soil. The specific faces of the pathogen in the soil were determi
ned by assessing the disease severity and the extent of sporulation of
the pathogen on the roots of the differential cultivars. A more rapid
baiting method using cotyledons of differential cultivars in flooded
soil samples was also developed to determine the presence of different
races in the samples. Both bioassays were used to confirm the presenc
e of race 0 and race 1 in separate paddocks at Rutherglen, northern Vi
ctoria, over 4 seasons. The presence in field soil of another root rot
pathogen of subterranean clover, Aphanomyces euteiches, was also dete
cted using these techniques.