Detection of Potato Leaf Roll Virus in Intact Sprout Disks by Enzyme-linked Immunosorbent Assay

Potato leaf roll virus (PLRV) was detected by enzyme-linked immunosorbent assay (ELISA) when intact sprout, stem or leaf tissue disks were substituted for leaf or tuber extracts as test samples. Absorbance (A₄₀₅) values increased with increasing number of disks per plate well. Readings with sprout disks were significantly higher than those with disks cut from other plant tissues or with tuber sap. A₄₀₅ values obtained by using 7 or 5 sprout disks per well were near the maximum oneobtained with leaf sap. PLRV was slightly more efficiently detected by ELISA in light sprout disks than in etiolated sprout ones. When ten out of 34 healthy tubers were replaced by PLRV-infected ones in the tuber indexing test, the diseased samples werereliably detected with 5 etiolated sprout disks per well. The sprout disk sampling technique should be useful for qualitative evaluation of PLRV infection in sprouted potato tubers without necessity to wound them and using sprouts not long enough for maceration.