sample preparation in strip test. This was different from our previous
report on strip test for Sugarcane mosaic virus in corn which
expressed good reactivity with sap made from ELISA-carbonate
extraction buffer (Chiemsombat et al., 2009). Nario et al. (2007)
found that 0.1 M citrate buffer, pH 7.0 was the best grinding
buffer for Satsuma dwarf virus (SDV) strip test, and the additive used
in ELISA extraction buffer can cause undesirable coagulation of the
colloidal gold. The optimal time for reading test line was 3e5 min in
our test conditions. The result obtained with ELISA end-point sap
dilution at 1:10204 suggested cut off time for visual reading at
13.19 min (Table 3). Reading of test line by eyes varied among reports
between 10 and 15 min preferably not exceed 15 min (Drygin
et al., 2011). In addition, to verify the test strip efficacy and practical
usage, sap from 76 passion fruit plants in the open field of Pangda
Station were used in virus diagnosis by the strip. Most of them (73
in 76 plants) exhibited positive red test line, confirming of being
infected by TeMV. Ten plant samples were also used for parallel
testing of ELISA and the strip and result obtained showed 100%
correlation of the two methods.
In conclusion, we have isolated and identified the potyvirus
associated with passion fruit severe mosaic and fruit woodiness
disease in Thailand as a strain of Telosma mosaic virus (TeMV). We
were able to develop a sensitive rapid strip test kit for virus diagnosis,
and this work provided efficient production of virus-free
planting stocks for farmers.