Comparison of tissue blot immunoassay and reverse transcription polymerase chain reaction assay for virus-testing pulse crops from a South-Eastern Australia survey

Abstract

A virus survey of field pea (Pisum sativum) and faba bean (Vicia faba) crops in southern NSW and Victoria in October, 2006, provided the opportunity to compare the diagnostic results of a large number of field samples using reverse transcription polymerase chain reaction (RT-PCR) to the accepted reference test of tissue blot immunoassay (TBIA). One hundred unbiased plant samples from each of 21 field pea and three faba bean crops from NSW and ten field pea crops from Victoria were tested for Alfalfa mosaic virus (AMV), Bean yellow mosaic virus (BYMV), Cucumber mosaic virus (CMV), Pea seed-borne mosaic virus (PSbMV), Bean leafroll virus (BLRV) and Beet western yellows virus (BWYV) by TBIA. PSbMV was present at high levels (32–77 %) in 12 out of 21 field pea crops sampled from NSW. BLRV was present at high levels (28–42 %) in faba bean crops from NSW. In Victorian field pea crops, BWYV was most prevalent (4–28 %). Other viruses tested for were present at low incidences or absent. The seed to seedling transmission rate of PSbMV in the field pea seedlots used to sow six of the surveyed NSW pea crops, determined by TBIA, ranged from 0 to 23 % and had a clear effect on the level of PSbMV in the field. Test results for PSbMV and BLRV using TBIA were compared with results using RT-PCR and compared favourably in giving similar estimates of infection incidence and low costs (both less than A$1.00 per sample) for detecting these two viruses. It is concluded that TBIA is the preferred technique to get a precise estimate of infection incidence, while RT-PCR is particularly useful to test bulk samples for the presence of viruses with a low incidence and provides an alternative if antiserum is not available.