In article <199604171049.LAA25410 at caird.scri.sari.ac.uk>,
djones at SCRI.SARI.AC.UK (D Jones) says:
> I'd be really interested to see the preliminary results you
>refer to. Was the comparison done on dormant tubers, or on tubers on
>which dormancy had been broken? Also what were the comparative
>the two techniques? In my experience with molecular techniques, even
>labour costs are taken into account, the cost compared to ELISA can be
>prohibitive. Seeing as ultimately the cost of any test is bourne by the
>grower and farmers are notoriously 'careful with there money' this is an
>important consideration. Any one else have any views?
You are welcome to see the preliminary results - in fact if you'd like an
off-print please let me know. The work was carried out using purified
virus and viral RNA rather than tuber material, however that will be the
next stage. The paper reports a 10-fold increase in sensitivity over
ELISA. We have since increased that to 100-fold and believe that there is
further room for improvement.
You are absolutely correct, IMO, to identify cost as the key criterion in
agricultural diagnostics. For many purposes it just doesn't make sense at
the moment to use nucleic-acid based techniques when cheaper ones do
the job just as well.
However, post harvest tuber testing in potatoes may be an exception,
because of the high costs of the existing method. for example, greenhouse
space for 6-8 weeks is a significant overhead - especially with a high
throughput of samples. The grower is also inconvenienced by the long
wait to discover whether his crop is of a good enough standard to be sold
as seed or whether it must be sold as ware. For that reason they may be
willing to pay a slightly higher price for a faster test, if given the choice.
Once the method is optimised and a direct comparison made with ELISA
on tests on dormant tubers, then we will be able to compare costs. All I
can say at the moment is that I expect the costs to be in the same
'ballpark'. The capacity of the LCR method to dispence with the costs
associated with electrophoresis willl be a help here.
Dr Kevin O'Donnell
Diagnostics and Molecular Biology