Monitoring current season potato leafroll virus movement with an immunosorbent direct tissue blotting assay

A direct tissue blotting assay (DTBA) was used to track the movement of potato leafroll virus (PLRV) from newly infected foliage to the tubers. Plant and tuber characteristics were recorded to assess plant growth stage at inoculation and PLRV effect on yield. Russet Burbank potatoes were planted at different times in 1991 and 1992 to provide plants of different maturities which were then inoculated using PLRV carrying aphids. Aphids were allowed to feed two to three days after which an insecticide was applied. Stems and tubers were tested periodically for PLRV with DTBA after inoculation. Indexed tubers were grown out and ELISA tested in the greenhouse the following winter to confirm results of summer serological tests. Plant age affected percentages more consistently than did inoculation date. When plants approximately 43 days from planting were inoculated at different dates, early inoculation produced a higher percentage of infected plants. Conversely, when plants approximately 62 days from planting were inoculated at different dates, late inoculation resulted in a higher percentage of infected plants. However, early inoculation of young plants resulted in the highest infection percentages. Tuber size and yield were negatively affected by higher percentages of leafroll regardless of the stage of growth at inoculation. DTBA is best used for detecting PLRV in foliage of plants grown from infected tubers (i.e. secondary PLRV). DTBA is less accurate for detecting primary PLRV.