2.3. Serological detection of PMTV in Spongospora subterranea
through TAS-ELISA
TAS-ELISA was done as described previously (Torrance et al.,
1992; Arif et al., 1994). Leaf and root samples (1 g/5 ml) and
tuber tissues (1 g/ml) were extracted in extraction buffer [0.01 M
phosphate buffered saline (PBS) containing 0.05% Tween-20
and 0.1–0.2% skimmed milk powder (EveryDay, Nestlé Pakistan,
Lahore, Pakistan)]. Samples were added to microtitre plates
(NUNC Immunoplate II) pre-coated with polyclonal anti-PMTV
immunoglobulin (IgG) diluted 1:500 and monoclonal anti-PMTV
IgG (1:1000) with coating buffer pH 9.6. For the virus detection in
zoospores, preparation were obtained by air drying scabby potato
peels and incubating 0.1–0.2 g of cystosori in 10 ml of sterile distilled
water (SDW) at 12–15 ◦C for 7–10 days. The germinated
zoospore suspensions were filtered through fine plastic mesh to
remove debris. Between c. 1 × 107 and 6 × 107 zoospores per ml
were present in the suspensions. The zoospores were centrifuged
at 800 g for 5 min, re-suspended in 2 ml extraction buffer, frozen at
−70 ◦C for 20 min, then thawed on ice and used in TAS-ELISA.