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The purpose of this study is to determine the cause of a
previously undignosed wilt of asparagus bean ( Vigna
sesquipedalis ) and its primary inoculum in fields. Based on
completion of Kock's Postulates, this disease was proved to be
caused by Fusarium oxysporum f. sp. tracheiphilum ( Fot ) in
Taiwan. The fungus ( isolate F42 from Taiwan ) had the same
reactions as Fot race 3 ( isolate T-89-15 from U. S. A. )when
inoculated to the differential varieties of cowpea ( Vigna
sinensis ). Both isolates were pathonic to the susceptible
variery ''BE-5'' , whereas they can not attack the resistant
variety ''BE-88'' , in the greenhouse inoculation tests. Moreover,
their cultural characteristics were quite similar on potato
dextrose agar ( PDA ) . Therefore, Taiwanese Fot ( isolate F42 )
was identified as race 3. The optimum temperature and pH value
for mycelial growth of the pathogen were 28 ℃ and 7 on PDA,
respectively. Howere , the optimum temperature for the disease
development was 32 ℃by root-prunning inoculation metd. The
isolates were made from rhizosphere soils collected from many
asparagus bean fields on pentachloronitrobenzene ( PCNB )
medium and resulted that Fot was only found in fields Tachia and
Likang I that had continously cropped asparagus bean and had
Fusarium wilt for years. The soil samples from other fields that
were new to asparagus bean failed to yield Fot. Especially,
Fusarium wilt of asparagus bean occurred in field Likang III
that never had asparagus bean before and the cultivation was
managed by ooding method. The disease rates were 23, 8 and 11 ％
at early, middle and late growth stages of asparagus bean,
reapectively, which was not different significantly according to
the stastistical analysis. Moreover, 8 - 20 ％of Fot isolated
from seeds by placing on Komada selective medium or from
seedlings grown in pathogen-free soil in greenhouse, but none
was obtained from surface-disinfected seeds in these
experiments. All evidences were in favor of seed transmission of
this disease in Taiwan. In more advce experiments, unrippening
pods were removed from diseased plants and isolations were made
from their pedicel, funicle, vascular, pulp and seeds. For was
found in pulp, vascular and seeds but not in pedicel and
funicle. Moreover, out of 350 seeds, only 1 % yielded Fot.
Resistant screenings of 21 asparagus bean varieties/lines to Fot
by using root-pruning inoculation method indicated that lines
''14-3'', ''20-4'' and ''80-10'' had disease severity less than 13.3.
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