Five speakers took a closer look at the subject recently during a knowledge session on ultra-sensitive detection techniques at Naktuinbouw. Do the techniques offer opportunities or risks, was the question addressed by Maaike Bruinsma of NVWA, Sven Berendsen of Rijk Zwaan, Harrie Koenraadt of Naktuinbouw, René van der Vlugt of WUR and Harry Vennema of RIVM.
Molecular detection techniques have helped enormously in testing vegetable seeds for the absence of diseases, Sven shared on behalf of breeding company Rijk Zwaan. Those tests are needed is the for international trade. Indirect techniques do not distinguish between viruses that can cause infection and non-infectious 'enviromental' RNA, causing unnecessary rejection of seed lots. He lamented.
'Shouldn't direct methods, such as plant pathogenicity indicator tests that detect only infectious virus, be relied on more in risk analysis?', was a question he asked. Besides historical data, this could possibly be substantiated with digital PCR to determine the presence or absence of fully genomic RNA in a sample.
With the emergence of High Throughput Sequencing (HTS) techniques, it is now possible to 'detect' a multitude of viruses in plants and plant material, René shared on behalf of WUR. Often, these viruses go unnoticed because they do not cause symptoms. But such discoveries do raise all kinds of questions about the possible phytosanitary risks. In a sub-project PPS Phytosanitary Important for the Netherlands, research was carried out into the viruses occurring in non-European tuberous plants. On the example of Mashua (Tropaeolum tuberosum), those virus findings are discussed, as well as important follow-up questions.
Economics and politics
Both speakers had an eye for the economic side of the virus issue (not rejecting seeds unnecessarily) and specifically René also for the tension between scientists and policymakers. "A virologist takes into account how pathogenic and infectious a new virus is. A policymaker goes more for ruling out any risk and places a new virus on the quarantine list for safety reasons." As happened with ToBRFV, for example. Meanwhile, the Netherlands is keen to get rid of that Q status, now that the virus is now widespread anyway. Q status was also already under discussion in the US.
"It is important to find a balance between these two extremes," René thinks. "To keep it workable, we need to decide with experts which viruses we will investigate further. One approach here could be to look specifically at possible risks on frequently traded crops with high economic importance," he suggests in a pre-publication of an interview for Naktuinbouw magazine Buitenstebinnen.
Source: Naktuinbouw